阅读说明：本技术 焊锡粒子、导电材料、焊锡粒子的保管方法、导电材料的保管方法、导电材料的制造方法、连接结构体及连接结构体的制造方法 (Solder particle, conductive material, method for storing solder particle, method for storing conductive material, method for producing conductive material, connection structure, and method for produci) 是由 宋士辉 定永周治郎 山中雄太 伊藤将大 斋藤谕 于 2018-12-20 设计创作，主要内容包括：本发明提供一种焊锡粒子,其具有焊锡粒子主体、以及配置于所述焊锡粒子主体的外表面上的氧化被膜,所述焊锡粒子的粒径为1μm以上且15μm以下,将所述焊锡粒子在空气氛围下以120℃加热10小时时,加热前的所述氧化被膜的平均厚度与加热后的氧化被膜的平均厚度之比为2/3以下。(The present invention provides a solder particle having a solder particle body and an oxide film disposed on an outer surface of the solder particle body, wherein the solder particle has a particle diameter of 1 μm or more and 15 μm or less, and when the solder particle is heated at 120 ℃ for 10 hours in an air atmosphere, a ratio of an average thickness of the oxide film before heating to an average thickness of the oxide film after heating is 2/3 or less.)

1. A solder particle comprising a solder particle body and an oxide film disposed on the outer surface of the solder particle body,

the solder particles have a particle size of 1 to 15 [ mu ] m,

when the solder particles are heated at 120 ℃ for 10 hours in an air atmosphere, the ratio of the average thickness of the oxide film before heating to the average thickness of the oxide film after heating is 2/3 or less.

2. The solder particle according to claim 1, wherein an absolute value of a heat generation amount at 200 ℃ or higher is 100mJ/mg or higher.

3. A conductive material comprising a thermosetting component and a plurality of solder particles, wherein,

the solder particle has a solder particle body and an oxide film disposed on an outer surface of the solder particle body,

the solder particles have a particle size of 1 to 15 [ mu ] m,

when the solder particles are heated at 120 ℃ for 10 hours in an air atmosphere, the ratio of the average thickness of the oxide film before heating to the average thickness of the oxide film after heating is 2/3 or less.

4. The conductive material of claim 3 having a viscosity of 10Pa at 25 ℃_·s is more than and 600Pa_·s is less than or equal to.

5. The conductive material according to claim 3 or 4, wherein a thixotropic index obtained by dividing a viscosity measured using an E-type viscometer at 25 ℃ and 0.5rpm by a viscosity measured using an E-type viscometer at 25 ℃ and 5rpm is 1.1 or more and 5 or less.

6. The conductive material according to any one of claims 3 to 5, wherein an absolute value of a heat generation amount of the solder particles at 200 ℃ or higher is 100mJ/mg or higher.

7. The conductive material according to any one of claims 3 to 6, which is a conductive paste.

8. A method for storing solder particles according to claim 1 or 2, wherein,

placing the solder particles in a storage container and storing in an inert gas atmosphere, or placing the solder particles in a storage container and storing at 1 × 10²Vacuum storage is performed under the condition of Pa or less.

9. A method for storing a conductive material according to any one of claims 3 to 7, wherein,

placing the conductive material in a storage container and storing the conductive material at-40 ℃ to 10 ℃; or placing the conductive material in a storage container and storing the conductive material in an inert gas atmosphere.

10. A method for producing a conductive material, comprising a mixing step of mixing a thermosetting component and a plurality of solder particles to obtain a conductive material,

the manufacturing method of the conductive material obtains the following conductive material: the solder particles have a solder particle body and an oxide film disposed on the outer surface of the solder particle body, the solder particles have a particle diameter of 1 [ mu ] m or more and 15 [ mu ] m or less, and when the solder particles are heated at 120 ℃ for 10 hours in an air atmosphere, the ratio of the average thickness of the oxide film before heating to the average thickness of the oxide film after heating is 2/3 or less.

11. The method for producing a conductive material according to claim 10, further comprising a storage step of storing the solder particles,

said custodyThe step (a) is a step of storing the solder particles in a storage container in an inert gas atmosphere, or a step of storing the solder particles in a storage container in an atmosphere of 1 × 10²A step of storing the glass in vacuum under a condition of Pa or less,

the solder particles are stored through the storage step.

12. A connection structure body is provided with:

a first member to be connected having a first electrode on the surface thereof,

A second connection object member having a second electrode on the surface thereof, and

a connecting portion for connecting the first connection object member and the second connection object member,

the material of the connecting part contains the solder particles according to claim 1 or 2,

the first electrode and the second electrode are electrically connected by a solder portion in the connecting portion.

13. A connection structure body is provided with:

a first member to be connected having a first electrode on the surface thereof,

A second connection object member having a second electrode on the surface thereof, and

a connecting portion for connecting the first connection object member and the second connection object member,

the material of the connecting part is the conductive material according to any one of claims 3 to 7,

the first electrode and the second electrode are electrically connected by a solder portion in the connecting portion.

14. A method for manufacturing a connection structure, comprising the steps of:

a step of disposing a conductive material containing the solder particles according to claim 1 or 2 on a surface of a first member to be connected having a first electrode on the surface,

a step of disposing a second connection target member having a second electrode on a surface thereof on a surface of the conductive material opposite to the first connection target member side, and making the first electrode and the second electrode face each other, and

and a step of forming a connection portion for connecting the first connection object member and the second connection object member from the conductive material by heating the conductive material to a temperature equal to or higher than a melting point of the solder particles, and electrically connecting the first electrode and the second electrode via a solder portion in the connection portion.

15. A method of manufacturing a connection structure, comprising:

the step of disposing the conductive material according to any one of claims 3 to 7 on the surface of a first member to be connected having a first electrode on the surface thereof,

a step of disposing a second connection target member having a second electrode on a surface thereof on a surface of the conductive material opposite to the first connection target member side, and making the first electrode and the second electrode face each other, and

and a step of forming a connection portion for connecting the first connection target member and the second connection target member from the conductive material by heating the conductive material to a temperature equal to or higher than a melting point of the solder particles, and electrically connecting the first electrode and the second electrode with a solder portion in the connection portion.

Technical Field

The present invention relates to solder particles that can be used for electrical connection between electrodes, and a method for storing the solder particles. The present invention also relates to a conductive material containing the solder particles, a method for storing the conductive material, and a method for producing the conductive material. The present invention also relates to a connection structure using the solder particles or the conductive material, and a method for manufacturing the connection structure.

Background

Anisotropic conductive materials such as anisotropic conductive pastes and anisotropic conductive films are widely known. The anisotropic conductive material has conductive particles dispersed in a binder. As the conductive particles, solder particles are widely used.

The anisotropic conductive material is used to obtain various connection structures. Examples of the connection by the anisotropic conductive material include connection between a flexible printed circuit board and a glass substrate (fog (film on glass)), connection between a semiconductor chip and a flexible printed circuit board (cof (chip on film)), connection between a semiconductor chip and a glass substrate (cog (chip glass)), and connection between a flexible printed circuit board and a glass epoxy substrate (fob (film on board)).

When the electrodes of the flexible printed circuit board and the electrodes of the glass epoxy resin substrate are electrically connected to each other through the anisotropic conductive material, for example, the anisotropic conductive material containing conductive particles is disposed on the glass epoxy resin substrate. Then, the flexible printed circuit board core is laminated, and heated and pressed. In this way, the anisotropic conductive material is cured, and the electrodes are electrically connected by the conductive particles, thereby obtaining a connection structure.

As an example of the anisotropic conductive material, patent document 1 listed below describes an anisotropic conductive material containing conductive particles and a resin component that does not cure at the melting point of the conductive particles. Specific examples of the conductive particles include metals such as tin (Sn), indium (In), bismuth (Bi), silver (Ag), copper (Cu), zinc (Zn), lead (Pb), cadmium (Cd), gallium (Ga), and thallium (Tl), and alloys of these metals.

Patent document 1 describes that the electrodes are electrically connected by the following steps: a resin heating step of heating the anisotropic conductive resin to a temperature higher than the melting point of the conductive particles and at which the resin component does not complete curing, and a resin component curing step of curing the resin component. Patent document 1 describes that the mounting is performed using a temperature Profile (temperature Profile) shown in fig. 8 of patent document 1. In patent document 1, conductive particles are melted in a resin component that has been cured at a heating temperature of an anisotropic conductive resin.

Patent document 2 discloses a solderThe material comprises a solder layer and a coating layer for coating the surface of the solder layer. The solder layer is made of a metal material composed of an alloy having a Sn content of 40% or more, or a metal material having a Sn content of 100%. The coating layer is made of SnO film and SnO₂A membrane. The SnO film is formed on the outer surface side of the solder layer. The SnO₂The film is formed on the outer surface side of the SnO film. The thickness of the coating layer is more than 0nm and less than 4.5 nm.

Disclosure of Invention

Problems to be solved by the invention

In recent years, fine pitches of wirings of printed wiring boards and the like have been advanced in the industry. As for conductive materials containing solder particles or conductive particles having solder on the surface thereof, miniaturization and reduction in particle size of solder particles or conductive particles having solder on the surface thereof have been advanced with the fine pitch of wiring.

When the solder particles and the like are made smaller in size, the following may occur: when conducting connection using a conductive material, it is difficult to efficiently aggregate solder particles or the like between upper and lower electrodes to be connected. In particular, the following are present: when the conductive material is heated and cured, the viscosity of the conductive material increases until the solder particles and the like are sufficiently transferred to the electrodes, and the solder particles and the like remain in the electrode-free regions. As a result, the following may occur: it is not possible to sufficiently improve the reliability of conduction between electrodes to be connected and the reliability of insulation between adjacent electrodes that cannot be connected.

Further, as the particle size of the solder particles or the like becomes smaller, the surface area of the solder particles or the like increases, and therefore the content of the oxide film on the surface of the solder particles or the like also increases. If an oxide film is present on the surface of solder particles or the like, the solder particles or the like cannot be efficiently aggregated on the electrode, and therefore, measures such as increasing the content of flux in the conductive material have been required for conventional conductive materials. However, if the content of the flux in the conductive material is increased, there are cases where: the flux reacts with a thermosetting component in the conductive material, and the storage stability of the conductive material is lowered or the heat resistance of a cured product of the conductive material is lowered. In addition, if the content of the flux in the conductive material is increased, there are cases where: voids are generated in the cured product of the conductive material, or poor curing of the conductive material is generated.

In the conventional conductive material, it is difficult to satisfy all of the requirements such as improvement of solder cohesiveness at the time of conductive connection, improvement of storage stability of the conductive material, and improvement of heat resistance of a cured product of the conductive material.

The purpose of the present invention is to provide solder particles and a method for storing solder particles, which can effectively improve the cohesiveness of solder during conductive connection. Further, the present invention aims to provide a conductive material containing the solder particles, a method for storing the conductive material, and a method for producing the conductive material. Another object of the present invention is to provide a connection structure using the solder particles or the conductive material, and a method for manufacturing the connection structure.

Means for solving the problems

According to a broader aspect of the present invention, there is provided a solder particle including a solder particle body and an oxide film disposed on an outer surface of the solder particle body, wherein a particle diameter of the solder particle is 1 μm or more and 15 μm or less, and a ratio of an average thickness of the oxide film before heating to an average thickness of the oxide film after heating is 2/3 or less when the solder particle is heated at 120 ℃ for 10 hours in an air atmosphere.

In a specific embodiment of the solder particle of the present invention, the absolute value of the heat generation amount at 200 ℃ or higher is 100mJ/mg or higher.

According to a broader aspect of the present invention, there is provided a conductive material including a thermosetting component and a plurality of solder particles, wherein the solder particles have a solder particle main body and an oxide film disposed on an outer surface of the solder particle main body, the solder particles have a particle diameter of 1 μm or more and 15 μm or less, and when the solder particles are heated at 120 ℃ for 10 hours in an air atmosphere, a ratio of an average thickness of the oxide film before heating to an average thickness of the oxide film after heating is 2/3 or less.

In a specific embodiment of the conductive material of the present invention, the viscosity at 25 ℃ is 10Pa · s or more and 600Pa · s or less.

In a specific embodiment of the conductive material of the present invention, a thixotropic index obtained by dividing a viscosity measured at 25 ℃ and 0.5rpm with an E-type viscometer by a viscosity measured at 25 ℃ and 5rpm with an E-type viscometer is 1.1 or more and 5 or less.

In a specific embodiment of the conductive material of the present invention, the absolute value of the heat generation amount of the solder particles at 200 ℃ or higher is 100mJ/mg or higher.

In a specific aspect of the conductive material of the present invention, the conductive material is a conductive paste.

According to a broad aspect of the present invention, there is provided a method for storing solder particles, wherein the solder particles are stored in a storage container in an inert gas atmosphere, or the solder particles are stored in a storage container in a state of 1 × 10²Vacuum storage is performed under the condition of Pa or less.

According to a broader aspect of the present invention, there is provided a method for storing a conductive material, wherein the conductive material is stored in a storage container at-40 ℃ to 10 ℃; or placing the conductive material in a storage container and storing the conductive material in an inert gas atmosphere.

According to a broad aspect of the present invention, there is provided a method for producing a conductive material, including a mixing step of mixing a thermosetting component and a plurality of solder particles to obtain a conductive material, the method for producing a conductive material comprising: the solder particles have a solder particle body and an oxide film disposed on the outer surface of the solder particle body, the solder particles have a particle diameter of 1 [ mu ] m or more and 15 [ mu ] m or less, and when the solder particles are heated at 120 ℃ for 10 hours in an air atmosphere, the ratio of the average thickness of the oxide film before heating to the average thickness of the oxide film after heating is 2/3 or less.

In a specific embodiment of the method for producing a conductive material according to the present invention, the method further comprises a storage step of storing the solder particles, wherein the storage step is a step of storing the solder particles in a storage container in an inert gas atmosphere, or a step of storing the solder particles in a storage container in an atmosphere of 1 × 10²And a step of storing the solder particles in vacuum under a condition of Pa or less, wherein the solder particles are stored through the storage step.

According to a broader aspect of the present invention, there is provided a connection structure including: the solder particles are contained in a material of the connection portion, and the first electrode and the second electrode are electrically connected by the solder portion in the connection portion.

According to a broader aspect of the present invention, there is provided a connection structure including: the first connection object member having a first electrode on a surface thereof, the second connection object member having a second electrode on a surface thereof, and the connection portion connecting the first connection object member and the second connection object member, wherein the connection portion is made of the conductive material, and the first electrode and the second electrode are electrically connected by a solder portion in the connection portion.

According to a broad aspect of the present invention, there is provided a method for manufacturing a connection structure, comprising: the method for manufacturing a printed circuit board includes a step of disposing a conductive material containing the solder particles on a surface of a first connection object member having a first electrode on a surface thereof, a step of disposing a second connection object member having a second electrode on a surface thereof opposite to the first connection object member and facing the first electrode and the second electrode, and a step of forming a connection portion for connecting the first connection object member and the second connection object member from the conductive material by heating the conductive material to a melting point of the solder particles or more, and electrically connecting the first electrode and the second electrode via a solder portion in the connection portion.

According to a broader aspect of the present invention, there is provided a method for manufacturing a connection structure, including: the method for manufacturing a printed circuit board includes a step of disposing the conductive material on a surface of a first connection object member having a first electrode on a surface thereof, a step of disposing a second connection object member having a second electrode on a surface thereof opposite to the first connection object member on a surface thereof, and a step of forming a connection portion for connecting the first connection object member and the second connection object member from the conductive material by heating the conductive material to a melting point of the solder particles or more, and electrically connecting the first electrode and the second electrode via a solder portion in the connection portion.

ADVANTAGEOUS EFFECTS OF INVENTION

The solder particle of the present invention has a solder particle body and an oxide film disposed on an outer surface of the solder particle body. In the solder particles of the present invention, the solder particles have a particle size of 1 μm or more and 15 μm or less. In the solder particles of the present invention, when the solder particles are heated at 120 ℃ for 10 hours in an air atmosphere, the ratio of the average thickness of the oxide film before heating to the average thickness of the oxide film after heating is 2/3 or less. The solder particles of the present invention have the above technical features, and therefore, the solder cohesiveness at the time of conductive connection can be effectively improved.

The conductive material of the present invention contains a thermosetting component and a plurality of solder particles. In the conductive material of the present invention, the solder particle has a solder particle body and an oxide film disposed on an outer surface of the solder particle body. In the conductive material of the present invention, the solder particles have a particle size of 1 μm or more and 15 μm or less. In the conductive material of the present invention, when the solder particles are heated at 120 ℃ for 10 hours in an air atmosphere, the ratio of the average thickness of the oxide film before heating to the average thickness of the oxide film after heating is 2/3 or less. The conductive material of the present invention has the above technical features, and therefore, the solder cohesiveness at the time of conductive connection can be effectively improved.

The method for producing a conductive material of the present invention includes a mixing step of mixing a thermosetting component and a plurality of solder particles to obtain a conductive material. In the method for producing a conductive material of the present invention, the solder particles have a solder particle body and an oxide film disposed on an outer surface of the solder particle body. In the method for producing a conductive material of the present invention, the solder particles have a particle size of 1 μm to 15 μm. In the method for producing a conductive material of the present invention, the following conductive material is obtained: when the solder particles are heated at 120 ℃ for 10 hours in an air atmosphere, the ratio of the average thickness of the oxide film before heating to the average thickness of the oxide film after heating is 2/3 or less. The method for producing a conductive material of the present invention has the above-described technical features, and therefore, solder cohesiveness at the time of conductive connection can be effectively improved.

Drawings

Fig. 1 is a cross-sectional view schematically showing a connection structure obtained by using a conductive material according to an embodiment of the present invention.

Fig. 2(a) to (c) are cross-sectional views illustrating respective steps of an example of a method for manufacturing a connection structure using a conductive material according to an embodiment of the present invention.

Fig. 3 is a cross-sectional view showing a modification of the connection structure.

Fig. 4 is a cross-sectional view showing an example of solder particles that can be used for the conductive material.

Fig. 5 is a diagram for explaining the cohesiveness of solder particles.

Detailed Description

The present invention will be described in detail below.

(solder particles)

The solder particle of the present invention has a solder particle body and an oxide film disposed on an outer surface of the solder particle body. In the solder particles of the present invention, the solder particles have a particle size of 1 μm or more and 15 μm or less. In the solder particles of the present invention, when the solder particles are heated at 120 ℃ for 10 hours in an air atmosphere, the ratio of the average thickness of the oxide film before heating to the average thickness of the oxide film after heating is 2/3 or less.

The solder particles of the present invention have the above technical features, and therefore, the solder cohesiveness at the time of conductive connection can be effectively improved.

Compared with the conventional conductive material containing solder particles having a particle size of about 35 μm, the conductive material containing solder particles having a particle size of 10 μm or less has the following problems: in the case of conductive connection, solder particles cannot be efficiently aggregated between upper and lower electrodes to be connected. The present inventors have made diligent studies to solve the problems, and as a result, have found that the reasons for the problems are: as the solder particles become smaller in size, the oxide film present on the surface of the solder particles becomes relatively thick; and the content of the oxide film existing on the surface of the solder particle is increased due to the increase of the surface area of the solder particle. Further, the present inventors have made diligent studies to solve the above problems and, as a result, have found that: the oxide film present on the surface of the solder particle can be controlled to have a specific thickness, thereby solving the above-mentioned problems. In the present invention, the solder particles are reduced in particle size, but the movement of the solder particles to the electrodes is sufficiently performed, so that the solder can be effectively aggregated between the electrodes to be connected, and the conduction reliability and the insulation reliability can be improved.

Fig. 5 is a diagram for explaining the cohesiveness of solder particles. Fig. 5 is a view showing how solder particles under each condition (4 seed diameters and whether the thickness of the oxide film is controlled) are heated and whether or not the solder particles are aggregated is checked.

The solder particles in fig. 5, in which the thickness of the oxide film is not controlled, can be understood as follows: the smaller the particle size of the solder particles, the less the solder particles are aggregated. The reason for this is that: as the solder particles become smaller in size, the oxide film present on the surface of the solder particles becomes relatively thick; and increasing the content of the oxide film existing on the surface of the solder particle due to the increase in the surface area of the solder particle.

With respect to the solder particles in which the thickness of the oxide film was not controlled, it was confirmed that, with respect to the solder particles having a particle size of 35 μm: the solder particles are agglomerated and 1 large solder agglomerate is formed. The solder particles having a particle size of 10 μm were aggregated to form solder aggregates, but the unagglomerated solder particles were observed around the solder aggregates. With respect to solder particles having particle diameters of 2 μm and 5 μm, it was confirmed that: no solder particles are aggregated and no solder aggregate is formed.

On the other hand, with respect to the solder particles of fig. 5 in which the thickness of the oxide film is controlled, it was confirmed that: regardless of the particle size of the solder particles, the solder particles aggregated to form 1 large solder aggregate. It can be understood that: in order to improve the cohesiveness of the solder particles, it is important to control the oxide film present on the surface of the solder particles to a specific thickness.

In the present invention, the oxide film present on the surface of the solder particles is controlled to have a specific thickness, so that the solder particles can be efficiently aggregated on the electrode, and therefore, it is not necessary to excessively increase the content of the flux in the conductive material. As a result, the reaction between the thermosetting component in the conductive material and the flux can be effectively suppressed, and the storage stability of the conductive material can be effectively improved.

In addition, the melting point (activation temperature) of the flux in the conductive material is often lower than Tg of the thermosetting component in the conductive material, and the following tendency is present: the more the content of the flux in the conductive material becomes, the more the heat resistance of the cured product of the conductive material is reduced. The present invention can effectively improve the heat resistance of a cured product of an electrically conductive material because it is not necessary to excessively increase the content of a flux in the electrically conductive material. In addition, according to the present invention, since it is not necessary to excessively increase the content of the flux in the conductive material, it is possible to effectively suppress the occurrence of voids in a cured product of the conductive material and to effectively suppress the occurrence of poor curing of the conductive material.

The present invention has the above-described technical features, and therefore can satisfy all of the requirements of improving solder cohesiveness at the time of conductive connection, improving storage stability of a conductive material, and improving heat resistance of a cured product of the conductive material.

In the present invention, the oxide film present on the surface of the solder particle is controlled to a specific thickness, which contributes greatly to the above-described effects.

The solder particle has a solder particle body and an oxide film disposed on an outer surface of the solder particle body. The central part and the outer surface of the solder particle main body are both formed by solder. The solder particle body is a particle in which the central part and the outer surface are both solder. The oxide film is formed by oxidizing the outer surface of the solder particle body with oxygen in the air. The oxide film contains tin oxide or the like. Generally, commercially available solder particles have an oxide film on their outer surface, which is oxidized by oxygen in the air.

When conductive particles including base particles made of a material other than solder and solder portions disposed on the surfaces of the base particles are used instead of the solder particles, the conductive particles are less likely to be accumulated on the electrodes. Further, since the conductive particles have low solder bondability with each other, the conductive particles moving to the electrodes tend to easily move to the outside of the electrodes, and the effect of suppressing positional displacement between the electrodes tends to be low.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. In the following drawings, the size, thickness, shape, and the like may be different from the actual size, thickness, shape, and the like for convenience of illustration.

Fig. 4 is a cross-sectional view showing an example of solder particles that can be used for the conductive material.

The solder particle 21 shown in fig. 4 includes a solder particle body 22 and an oxide film 23 disposed on the outer surface of the solder particle body 22. The solder particle body 22 is in contact with the oxide film 23. The entire solder particle body 22 is formed of solder. The solder particle main body 22 is not a core-shell particle, and does not have a base material particle in the core. The central portion and the outer surface of the solder particle body 22 are formed of solder.

The solder is preferably a metal having a melting point of 450 ℃ or lower (low-melting-point metal). The solder particles are preferably metal particles having a melting point of 450 ℃ or lower (low-melting-point metal particles). The low-melting-point metal particles are particles containing a low-melting-point metal. The low-melting metal is a metal having a melting point of 450 ℃ or lower. The melting point of the low-melting metal is preferably 300 ℃ or lower, more preferably 160 ℃ or lower. The solder particles are preferably low melting point solder having a melting point of less than 150 ℃.

The melting point of the solder particles can be determined by Differential Scanning Calorimetry (DSC). Examples of a Differential Scanning Calorimetry (DSC) device include "EXSTAR DSC 7020" manufactured by SII corporation.

In addition, the solder particles preferably contain tin. The content of tin in 100 wt% of the metal contained in the solder particles is preferably 30 wt% or more, more preferably 40 wt% or more, further preferably 70 wt% or more, and particularly preferably 90 wt% or more. If the tin content in the solder particles is not less than the lower limit, the connection reliability between the solder portion and the electrode is further improved.

The content of tin can be measured using a high-frequency inductively coupled plasma emission spectrometer ("ICP-AES" manufactured by horiba ltd.), a fluorescent X-ray analyzer ("EDX-800 HS" manufactured by shimadzu ltd.), or the like.

By using the solder particles, the solder is melted and bonded to the electrodes, and the solder is solidified to form solder portions that conduct the electrodes. For example, since the solder portion and the electrode are easily in surface contact rather than point contact, the connection resistance becomes low. Further, the use of the solder particles increases the bonding strength between the solder portion and the electrode, and as a result, the solder portion and the electrode are less likely to be peeled off, and the conduction reliability and the connection reliability are further improved.

The metal constituting the solder particles is not particularly limited. The metal is preferably tin, or an alloy containing tin. Examples of the alloy include tin-silver alloy, tin-copper alloy, tin-silver-copper alloy, tin-bismuth alloy, tin-zinc alloy, and tin-indium alloy. The metal is preferably tin, a tin-silver alloy, a tin-silver-copper alloy, a tin-bismuth alloy, or a tin-indium alloy, in view of excellent wettability to the electrode. More preferably, tin-bismuth alloy and tin-indium alloy.

The solder particles are prepared according to JIS Z3001: for the term of fusion bonding, a filler having a liquidus of 450 ℃ or less is preferred. The composition of the solder particles includes, for example, a metal component containing zinc, gold, silver, lead, copper, tin, bismuth, indium, and the like. Preferably, tin-indium type (117 ℃ eutectic) or tin-bismuth type (139 ℃ eutectic) having a low melting point and no lead is used. That is, the solder particles preferably contain no lead, and preferably contain tin and indium or tin and bismuth.

In order to further improve the bonding strength between the solder portion and the electrode, the solder particles may include metals such as nickel, copper, antimony, aluminum, zinc, iron, gold, titanium, phosphorus, germanium, tellurium, cobalt, bismuth, manganese, chromium, molybdenum, and palladium. In addition, from the viewpoint of further improving the bonding strength between the solder portion and the electrode, the solder particles preferably contain nickel, copper, antimony, aluminum, or zinc. From the viewpoint of further improving the bonding strength between the solder portion and the electrode, the content of these metals for improving the bonding strength is preferably 0.0001 wt% or more and preferably 1 wt% or less among 100 wt% of the solder particles.

In the solder particles of the present invention, the solder particles have a particle size of 1 μm or more and 15 μm or less. The solder particles preferably have a particle size of 1 μm or more, more preferably 2 μm or more, and preferably 10 μm or less, more preferably 5 μm or less. When the particle diameter of the solder particles is not less than the lower limit and not more than the upper limit, the solder cohesiveness at the time of conductive connection can be further effectively improved. The solder particles preferably have a particle size of 2 μm or more and 5 μm or less.

The particle size of the solder particles is preferably an average particle size, and is preferably a number average particle size. The particle size of the solder particles was determined as follows: for example, arbitrary 50 solder particles are observed by an electron microscope or an optical microscope, and the average value of the particle diameters of the solder particles is calculated or the particle size distribution is measured by laser diffraction. The particle size of 1 solder particle was determined as a circle equivalent diameter in observation by an electron microscope or an optical microscope. In observation by an electron microscope or an optical microscope, the average particle diameter by circle equivalent diameter of arbitrary 50 solder particles is substantially equal to the average particle diameter by sphere equivalent diameter. In the laser diffraction particle size distribution measurement, the particle size of each solder particle is determined as a spherical equivalent diameter. The average particle diameter of the solder particles is preferably calculated by laser diffraction particle size distribution measurement.

The coefficient of variation (CV value) of the particle diameter of the solder particles is preferably 5% or more, more preferably 10% or more, and preferably 40% or less, more preferably 30% or less. When the coefficient of variation of the particle size of the solder particles is not less than the lower limit and not more than the upper limit, the solder can be more uniformly arranged on the electrode. However, the CV value of the particle diameter of the solder particles may be less than 5%.

The coefficient of variation (CV value) can be determined as follows.

CV value (%) - (ρ/Dn) × 100

ρ: standard deviation of particle size of solder particles

Dn: average value of solder particle diameter

The shape of the solder particles is not particularly limited. The solder particles may have a spherical shape or a shape other than a spherical shape such as a flat shape.

In the solder particles of the present invention, when the solder particles are heated at 120 ℃ for 10 hours in an air atmosphere, the ratio (average thickness A/average thickness B) of the average thickness (average thickness A) of the oxide film before heating to the average thickness (average thickness B) of the oxide film after heating is 2/3 or less. The ratio (average thickness a/average thickness B) is preferably 1/2 or less. The lower limit of the ratio (average thickness a/average thickness B) is not particularly limited. The ratio (average thickness a/average thickness B) may be 1/100 or more, 1/50 or more, or 1/10 or more. If the ratio (average thickness a/average thickness B) is not more than the upper limit, solder cohesiveness at the time of conductive connection can be further effectively improved. When the ratio (average thickness a/average thickness B) is not more than the upper limit, the storage stability of the conductive material can be further effectively improved, and the heat resistance of the cured product of the conductive material can be further effectively improved. When the ratio (average thickness a/average thickness B) is not more than the upper limit, the conductive material can be preferably used for applications of the conductive material. When the ratio (average thickness a/average thickness B) is not less than the lower limit, the handling of the conductive material containing the solder particles can be further effectively improved. Further, by setting the ratio (average thickness a/average thickness B) to the lower limit or more and the upper limit or less, the fusibility of the surface of the solder particles during heating can be appropriately controlled, and therefore it is considered that the solder cohesiveness during conductive connection is further effectively increased.

Since the solder particle of the present invention has the oxide film before heating controlled to a specific thickness (the oxide film is relatively thin), the solder particle can satisfy the above ratio (average thickness a/average thickness B) by heating at 120 ℃ for 10 hours in an air atmosphere to increase the thickness of the oxide film. The conventional solder particles have a relatively thick oxide film before heating, and therefore have insufficient margin for oxidation, and even when heated at 120 ℃ for 10 hours in an air atmosphere, the thickness of the oxide film does not increase so much, and the ratio (average thickness a/average thickness B) is not satisfied.

The average thickness of the oxide film before heating (average thickness A) is preferably 1nm or more, more preferably 2nm or more, and preferably 5nm or less, more preferably 4nm or less. When the average thickness of the oxide film before heating (average thickness a) is not less than the lower limit and not more than the upper limit, the solder cohesiveness at the time of conductive connection can be more effectively improved. When the average thickness of the oxide film before heating (average thickness a) is not less than the lower limit and not more than the upper limit, the storage stability of the conductive material can be more effectively improved, and the heat resistance of the cured product of the conductive material can be more effectively improved. When the average thickness of the oxide film before heating (average thickness a) is not less than the lower limit, the present invention can be applied to the use of a conductive material.

The average thickness of the oxide film before heating (average thickness a) can be determined, for example, by observing the cross section of the solder particle using a transmission electron microscope. The average thickness of the oxide film before heating (average thickness a) can be calculated from the average thickness of the oxide film in 10 arbitrarily selected portions, for example.

The ratio of the average thickness (average thickness a) of the oxide film before heating to the particle diameter of the solder particles (average thickness a/particle diameter of solder particles) is preferably 0.0001 or more, more preferably 0.0005 or more, even more preferably 0.001 or more, and preferably 0.01 or less, more preferably 0.008 or less, and even more preferably 0.005 or less. If the ratio (average thickness a/particle diameter of solder particles) is not less than the lower limit and not more than the upper limit, the solder cohesiveness at the time of conductive connection can be more effectively improved. When the ratio (average thickness a/particle diameter of solder particles) is not less than the lower limit and not more than the upper limit, the storage stability of the conductive material can be more effectively improved, and the heat resistance of the cured product of the conductive material can be more effectively improved.

The content of the oxide film in 100 vol% of the solder particles is preferably 0.1 vol% or more, more preferably 0.5 vol% or more, and preferably 10 vol% or less, more preferably 8 vol% or less, and further preferably 5 vol% or less. When the content of the oxide film is not less than the lower limit and not more than the upper limit, the solder cohesiveness at the time of conductive connection can be further effectively improved. When the content of the oxide film is not less than the lower limit and not more than the upper limit, the storage stability of the conductive material can be further effectively improved, and the heat resistance of a cured product of the conductive material can be further effectively improved.

The content of the oxide film can be calculated from the weight of the solder particles before and after the oxide film is removed.

The absolute value of the heat generation amount of the solder particles at 200 ℃ or higher is preferably 100mJ/mg or higher, more preferably 200mJ/mg or higher, and is preferably 400mJ/mg or lower, more preferably 300mJ/mg or lower. The absolute value of the amount of heat generated by the solder particles at 200 ℃ or higher is considered to vary depending on the thickness of the oxide film on the surface of the solder particles. When the absolute value of the heat generation amount at 200 ℃ or higher is not less than the lower limit and not more than the upper limit, the solder cohesiveness at the time of conductive connection can be further effectively improved.

The amount of heat generated by the solder particles at 200 ℃ or higher can be determined by Differential Scanning Calorimetry (DSC). Examples of a Differential Scanning Calorimetry (DSC) device include "EXSTAR DSC 7020" manufactured by SII corporation.

The solder particles can be obtained by, for example, subjecting commercially available solder particles to acid treatment. The thickness of the oxide film present on the surface of the solder particle is preferably controlled by the acid treatment. As commercially available solder particles, "DS 10" manufactured by Mitsui Metal mining, Inc., "ST-5" manufactured by Mitsui Metal mining, Inc., and "ST-2" manufactured by Mitsui Metal mining, Inc., can be mentioned. Examples of the acid used for the acid treatment include organic acids.

(method of storing solder particles)

The method for storing solder particles of the present invention is preferably a method for storing the solder particles, the solder particles are preferably stored by the method for storing solder particles of the present invention, the solder particles are preferably stored in a storage container in an inert gas atmosphere, or the solder particles are stored in a storage container in an inert gas atmosphere of 1 × 10²Vacuum storage under Pa or below。

The method of storing the solder particles may be a cold storage or a freezing storage, from the viewpoint of further effectively improving the solder cohesiveness at the time of conductive connection.

However, the solder particles of the present invention can be stored in a storage container at 10 ℃ to 50 ℃ for example. The solder particles of the present invention may be stored at 10 ℃ to 45 ℃ or lower, at 20 ℃ to 25 ℃ or higher, at 40 ℃ to 30 ℃ or lower. The solder particles are preferably stored at or below room temperature, and preferably stored at less than room temperature.

In order to store the solder particles under the temperature condition, a constant temperature bath or the like may be used. Preferably, the storage container containing the solder particles is stored in a thermostatic bath set to the preferred temperature condition.

From the viewpoint of further effectively improving the solder cohesiveness at the time of conductive connection, it is preferable that the solder particles are stored in a storage container in an inert gas atmosphere.

Examples of the inert gas include argon gas and nitrogen gas.

From the viewpoint of further effectively improving the solder cohesiveness at the time of conductive connection, it is preferable that the solder particles are placed in a storage container in a range of 0.8 × 10²Vacuum storage is performed under Pa or less, and more preferably 0.5 × 10²Vacuum storage is performed under the condition of Pa or less.

In order to store the solder particles under the vacuum condition, it is preferable to store the solder particles in the storage container under reduced pressure by using a vacuum pump or the like.

The storage container is not particularly limited as long as it can be stored in a refrigerated storage, a frozen storage, or a vacuum storage. From the viewpoint of further effectively improving the solder cohesiveness at the time of conductive connection, the storage container is preferably a container capable of preventing permeation of oxygen, and is preferably a container having good sealing properties. The storage container may be an aluminum bag.

From the viewpoint of further effectively improving the solder cohesiveness at the time of conductive connection, it is preferable to control the oxygen concentration in the storage container. From the viewpoint of further effectively improving solder cohesiveness at the time of conductive connection, the oxygen concentration in the storage container is preferably 200ppm or less, more preferably 100ppm or less. Examples of a method for controlling the oxygen concentration in the storage container include a method of replacing the storage container with nitrogen gas.

The oxygen concentration in the storage container can be determined using an oxygen concentration meter. Examples of the oxygen concentration meter include "XO-326 IIsA" manufactured by New NewCosmos Electric Co., Ltd.

(conductive Material and method for producing conductive Material)

The conductive material of the present invention contains a thermosetting component and a plurality of solder particles. In the conductive material of the present invention, the solder particle has a solder particle body and an oxide film disposed on an outer surface of the solder particle body. In the conductive material of the present invention, the solder particles have a particle size of 1 μm or more and 15 μm or less. In the conductive material of the present invention, when the solder particles are heated at 120 ℃ for 10 hours in an air atmosphere, the ratio of the average thickness of the oxide film before heating to the average thickness of the oxide film after heating is 2/3 or less.

The method for producing a conductive material of the present invention includes a mixing step of mixing a thermosetting component and a plurality of solder particles to obtain a conductive material. In the method for producing a conductive material of the present invention, the solder particles have a solder particle body and an oxide film disposed on an outer surface of the solder particle body. In the method for producing a conductive material of the present invention, the solder particles have a particle size of 1 μm to 15 μm. In the method for producing a conductive material of the present invention, the following conductive material is obtained: when the solder particles are heated at 120 ℃ for 10 hours in an air atmosphere, the ratio of the average thickness of the oxide film before heating to the average thickness of the oxide film after heating is 2/3 or less.

In the conductive material of the present invention and the method for producing the conductive material of the present invention, solder particles are used. The solder particles are preferably the solder particles. The conductive material of the present invention and the method for producing a conductive material of the present invention preferably use the solder particles.

The conductive material of the present invention and the method for producing a conductive material of the present invention have the above-described technical features, and therefore, solder cohesiveness at the time of conductive connection can be effectively improved.

Compared with a conventional conductive material containing solder particles having a particle size of about 35 μm, a conductive material containing solder particles having a particle size of 10 μm or less has the following problems: in the case of conductive connection, solder particles cannot be efficiently aggregated between upper and lower electrodes to be connected. The inventors of the present invention have made diligent studies to solve the technical problems, and as a result, have found that the reasons for the problems are: as the solder particles become smaller in size, the oxide film present on the surface of the solder particles becomes relatively thick; and increasing the content of the oxide film existing on the surface of the solder particle due to the increase in the surface area of the solder particle. As a result of diligent research directed toward solving the above problems, the inventors of the present invention found that: the oxide film present on the surface of the solder particles can be controlled to have a specific thickness, thereby solving the above-mentioned problems. In the present invention, the solder particles are made smaller in size, but the movement of the solder particles to the electrodes is sufficiently performed, so that the solder can be effectively aggregated between the electrodes to be connected, and the conduction reliability and the insulation reliability can be improved.

In the present invention, the oxide film present on the surface of the solder particles is controlled to have a specific thickness, so that the solder particles can be efficiently aggregated on the electrode, and therefore, the content of the flux in the conductive material does not need to be excessively increased. As a result, the reaction between the thermosetting component in the conductive material and the flux can be effectively suppressed, and the storage stability of the conductive material can be effectively improved.

In addition, there is a tendency that: the melting point (activation temperature) of the flux in the conductive material is often lower than the Tg of the thermosetting component in the conductive material, and the heat resistance of the cured product of the conductive material decreases as the content of the flux in the conductive material increases. The present invention can effectively improve the heat resistance of a cured product of an electrically conductive material because it is not necessary to excessively increase the content of a flux in the electrically conductive material. In addition, according to the present invention, since it is not necessary to excessively increase the content of the flux in the conductive material, it is possible to effectively suppress the occurrence of voids in a cured product of the conductive material and to effectively suppress the occurrence of poor curing of the conductive material.

The present invention has the above-described technical features, and therefore can satisfy all of the requirements of improving solder cohesiveness at the time of conductive connection, improving storage stability of a conductive material, and improving heat resistance of a cured product of the conductive material.

In the present invention, the oxide film present on the surface of the solder particle is controlled to a specific thickness, which contributes greatly to the effect described above.

In addition, the present invention can prevent the positional deviation between the electrodes. In the present invention, when the second connection target member is superposed on the first connection target member having the conductive material arranged on the upper surface thereof, even in a state where the alignment of the electrode of the first connection target member and the electrode of the second connection target member is shifted, the shift can be corrected to connect the electrodes to each other (self-alignment effect).

From the viewpoint of further effectively improving solder cohesiveness at the time of conductive connection, the conductive material is preferably in a liquid state at 25 ℃, and is preferably a conductive paste.

From the viewpoint of further effectively improving the solder cohesiveness at the time of conductive connection, the viscosity (η 25 Pa · s or more (5rpm)) of the conductive material at 25 ℃ and 5rpm is preferably 10Pa · s or more, more preferably 30Pa · s or more, further preferably 50Pa · s or more, and particularly preferably 100Pa · s or more, from the viewpoint of further effectively improving the solder cohesiveness at the time of conductive connection, the viscosity (η 25(5rpm)) of the conductive material at 25 ℃ and 5rpm is preferably 600Pa · s or less, more preferably 400Pa · s or less, further preferably 300Pa · s or less, and more preferably 250Pa · s or less, and particularly preferably 200Pa · s or less, and the viscosity (η 25(5rpm)) can be appropriately adjusted depending on the kind and the mixing amount of the mixed component.

The viscosity (η 25(5rpm)) can be measured, for example, using an E-type viscometer ("TVE 22L" manufactured by Toyobo industries, Ltd.) at 25 ℃ and 5 rpm.

From the viewpoint of further effectively improving the solder cohesiveness at the time of conductive connection, the viscosity (η 20(5rpm)) of the conductive material under the conditions of 20 ℃ and 5rpm is preferably 10Pa · s or more, more preferably 30Pa · s or more, and preferably 600Pa · s or less, more preferably 400Pa · s or less, and the viscosity (η 20(5rpm)) can be appropriately adjusted depending on the kind of the mixed component and the mixing amount.

The viscosity (η 20(5rpm)) can be measured, for example, using an E-type viscometer ("TVE 22L" manufactured by Toyobo industries, Ltd.) at 20 ℃ and 5 rpm.

From the viewpoint of further effectively improving the solder cohesiveness at the time of conductive connection, the viscosity (η 25(0.5rpm)) of the conductive material measured at 25 ℃ and 0.5rpm with an E-type viscometer is preferably 50Pa · s or more, more preferably 100Pa · s or more, and preferably 400Pa · s or less, more preferably 300Pa · s or less, and the viscosity (η 25(0.5rpm) may be appropriately adjusted depending on the kind and the mixing amount of the components to be mixed.

From the viewpoint of further effectively improving the solder cohesiveness at the time of conductive connection, the viscosity (η 25(5rpm)) of the conductive material measured at 25 ℃ and 5rpm with an E-type viscometer is preferably 50Pa · s or more, more preferably 100Pa · s or more, and preferably 250Pa · s or less, more preferably 200Pa · s or less, and the viscosity (η 25(5rpm)) can be appropriately adjusted depending on the kind and the amount of the mixed component.

Examples of the E-type viscometer include "TVE 22L" manufactured by eastern industries co.

The thixotropic index (η 25(0.5rpm)/η 25(5rpm)) obtained by dividing the viscosity of the electrically conductive material measured at 25 ℃ and 0.5rpm by the viscosity of the electrically conductive material measured at 25 ℃ and 5rpm with an E-type viscometer is preferably 1.1 or more, more preferably 1.5 or more, the thixotropic index (η 25(0.5rpm)/η 25(5rpm)) obtained by dividing the viscosity of the electrically conductive material measured at 25 ℃ and 0.5rpm with an E-type viscometer by the viscosity of the electrically conductive material measured at 25 ℃ and 5rpm with an E-type viscometer is preferably 5 or less, more preferably 4 or less, further preferably 3 or less, and if the thixotropic index (η 25(0.5rpm)/η 25(5rpm)) is the lower limit or more and the upper limit or less, the solder cohesiveness at the time of electrically conductive connection can be more effectively improved.

The conductive material can be used as a conductive paste, a conductive film, and the like. The conductive paste is preferably an anisotropic conductive paste, and the conductive film is preferably an anisotropic conductive film. The conductive material is preferably a conductive paste from the viewpoint of further effectively improving solder cohesiveness at the time of conductive connection. The conductive material may be suitably used for electrical connection of the electrodes. The conductive material is preferably a circuit connecting material.

The method for producing a conductive material of the present invention preferably further comprises a storage step of storing the solder particles, wherein the storage step is preferably a step of storing the solder particles in a storage container in an inert gas atmosphere, and in the method for producing a conductive material of the present invention, the storage step is preferably a step of storing the solder particles in a storage container in a state where the solder particles are stored in the storage container at 1 × 10²And a step of storing the glass in vacuum under a condition of Pa or less. In the method for producing a conductive material according to the present invention, the solder particles are preferably solder particles stored through the storage step.

The method of storing the solder particles may be a cold storage or a freezing storage, from the viewpoint of further effectively improving the solder cohesiveness at the time of conductive connection.

However, the solder particles of the present invention may be stored in a storage container at 10 ℃ to 50 ℃ in a storage container, for example. The solder particles of the present invention may be stored at 10 ℃ to 45 ℃ inclusive, at 20 ℃ to 25 ℃ inclusive, at 40 ℃ to 30 ℃ inclusive. The solder particles are preferably stored at or below room temperature, and preferably stored at less than room temperature.

In the method for producing a conductive material according to the present invention, the solder particles are preferably the solder particles. In the method for producing a conductive material of the present invention, the solder particles may be solder particles stored by the method for storing solder particles.

In the mixing step, a method of mixing the thermosetting component and the solder particles may use a previously known dispersion method, and is not particularly limited. As a method of dispersing the solder particles in the thermosetting component, the following method can be mentioned. A method of adding the solder particles to the thermosetting component and then kneading and dispersing the solder particles by a planetary mixer or the like. A method in which the solder particles are uniformly dispersed in water or an organic solvent using a homogenizer or the like, and then added to the thermosetting component and kneaded and dispersed using a planetary mixer or the like. A method of diluting the thermosetting component with water, an organic solvent, or the like, then adding the solder particles, and kneading and dispersing the solder particles with a planetary mixer or the like.

In the mixing step, the oxygen concentration is preferably controlled so that the solder particles are not excessively oxidized, from the viewpoint of further effectively improving the solder cohesiveness at the time of conductive connection. As a method for controlling the oxygen concentration, a method of performing the mixing step in a nitrogen atmosphere may be mentioned. The oxygen concentration in the mixing step is preferably 200ppm or less, more preferably 100ppm or less, from the viewpoint of further effectively improving solder cohesiveness at the time of conductive connection.

The oxygen concentration in the mixing step can be determined using an oxygen concentration meter. Examples of the oxygen concentration meter include "XO-326 IIsA" manufactured by NewCosmos Electric Co., Ltd.

The content of the solder particles is preferably 30 wt% or more, more preferably 50 wt% or more, and preferably 80 wt% or less, more preferably 70 wt% or less, in 100 wt% of the conductive material. When the content of the solder particles is not less than the lower limit and not more than the upper limit, the solder can be more effectively disposed on the electrode, and the conduction reliability can be more effectively improved. From the viewpoint of further effectively improving the conduction reliability, the content of the solder particles is preferably large.

(method of storing conductive Material)

The method for storing the conductive material of the present invention is preferably a method for storing the conductive material. The conductive material is preferably stored by the method for storing a conductive material of the present invention.

From the viewpoint of further effectively improving the solder cohesiveness at the time of conductive connection, it is preferable that the conductive material is stored in a storage container at a temperature of-40 ℃ to 10 ℃; or placing the conductive material in a storage container and storing the conductive material in an inert gas atmosphere.

The conductive material may be stored in a refrigerated or frozen state from the viewpoint of further effectively improving the solder cohesiveness at the time of conductive connection.

However, the conductive material of the present invention may be stored at 10 ℃ to 45 ℃ inclusive, at 20 ℃ to 25 ℃ inclusive, at 40 ℃ to 30 ℃ inclusive. The conductive material of the present invention can be stored at-20 ℃ or higher, can be stored at-10 ℃ or higher, can be stored at 50 ℃ or lower, and can be stored at 10 ℃ or lower. The conductive material is preferably stored at room temperature or lower, and preferably stored at a temperature lower than room temperature.

In order to store the conductive material under the temperature condition, a refrigerator, a freezer, a constant temperature bath, or the like can be used. Preferably, the storage container containing the conductive material is stored in a thermostatic bath set to the preferred temperature condition.

From the viewpoint of further effectively improving the solder cohesiveness at the time of conductive connection, it is preferable that the conductive material is stored in a storage container in an inert gas atmosphere.

Examples of the inert gas include argon gas and nitrogen gas.

From the viewpoint of further effectively improving the solder cohesiveness at the time of conductive connection, it is preferable that the conductive material is stored in a storage container at 0.8 × 10²Vacuum storage is performed under Pa or less, and more preferably 0.5 × 10²Vacuum storage is performed under the condition of Pa or less.

In order to store the conductive material under the vacuum condition, it is preferable to store the conductive material in the storage container under reduced pressure by using a vacuum pump or the like.

The storage container is not particularly limited as long as it can be stored in a refrigerated or frozen state. From the viewpoint of further effectively improving the solder cohesiveness at the time of conductive connection, the storage container is preferably a container capable of preventing permeation of oxygen, and is preferably a container having good sealing properties. The storage container may be an aluminum bag.

From the viewpoint of further effectively improving the solder cohesiveness at the time of conductive connection, it is preferable to control the oxygen concentration in the storage container. From the viewpoint of further effectively improving solder cohesiveness at the time of conductive connection, the oxygen concentration in the storage container is preferably 200ppm or less, more preferably 100ppm or less. Examples of a method for controlling the oxygen concentration in the storage container include a method of replacing the storage container with nitrogen gas.

The oxygen concentration in the storage container can be determined using an oxygen concentration meter. Examples of the oxygen concentration meter include "XO-326 IIsA" manufactured by NewCosmos Electric Co., Ltd.

Other details of the conductive material will be described below.

(thermosetting component)

The thermosetting component is not particularly limited. The thermosetting component may include a thermosetting compound curable by heating and a thermosetting agent.

(thermosetting component: thermosetting compound)

Examples of the thermosetting compound include oxetane compounds, epoxy compounds, episulfide compounds, (meth) acrylic compounds, phenol compounds, amino compounds, unsaturated polyester compounds, polyurethane compounds, organosilicon compounds, polyimide compounds, and the like. From the viewpoint of further improving the curability and viscosity of the conductive material, further effectively improving the conduction reliability, and further effectively improving the insulation reliability, the epoxy compound or the episulfide compound is preferable, and the epoxy compound is more preferable. The thermosetting component preferably contains an epoxy compound. The thermosetting component preferably contains an epoxy compound and a curing agent. The thermosetting component may be used in 1 kind, or 2 or more kinds may be used in combination.

The epoxy compound is a compound having at least 1 epoxy group. As the epoxy compound, there can be mentioned: bisphenol a type epoxy compounds, bisphenol F type epoxy compounds, bisphenol S type epoxy compounds, phenol novolac type epoxy compounds, biphenyl novolac type epoxy compounds, biphenol type epoxy compounds, resorcinol type epoxy compounds, naphthalene type epoxy compounds, fluorene type epoxy compounds, benzophenone type epoxy compounds, phenol aralkyl type epoxy compounds, naphthol aralkyl type epoxy compounds, dicyclopentadiene type epoxy compounds, anthracene type epoxy compounds, epoxy compounds having an adamantane skeleton, epoxy compounds having a tricyclodecane skeleton, naphthyl ether type epoxy compounds, epoxy compounds having a triazine nucleus in the skeleton, and the like. The epoxy compounds can be used alone in 1 kind, also can be combined with more than 2 kinds.

The epoxy compound is preferably an aromatic epoxy compound such as a resorcinol type epoxy compound, a naphthalene type epoxy compound, a biphenyl type epoxy compound, a benzophenone type epoxy compound, or a phenol novolac type epoxy compound. The melting temperature of the epoxy compound is preferably equal to or lower than the melting point of the solder. The melting temperature of the epoxy compound is preferably 100 ℃ or lower, more preferably 80 ℃ or lower, and still more preferably 40 ℃ or lower. By using the preferable epoxy compound, the viscosity is high at the stage of bonding the members to be connected, and when acceleration is applied due to an impact of conveyance or the like, positional displacement of the first member to be connected and the second member to be connected can be suppressed. Further, the viscosity can be greatly reduced by the heat at the time of curing, and the solder cohesiveness at the time of conductive connection can be further effectively improved.

The thermosetting component preferably contains a thermosetting compound having a isocyanuric skeleton from the viewpoint of further effectively improving the heat resistance of the cured product.

The thermosetting compound having a isocyanuric skeleton includes triallylisocyanurate type epoxy compounds, and TEPIC series (TEPIC-G, TEPIC-S, TEPIC-SS, TEPIC-HP, TEPIC-L, TEPIC-PAS, TEPIC-V L, TEPIC-UC) manufactured by Nissan chemical industries, Ltd.

The content of the thermosetting compound is preferably 20% by weight or more, more preferably 40% by weight or more, further preferably 50% by weight or more, and preferably 99% by weight or less, more preferably 98% by weight or less, further preferably 90% by weight or less, and particularly preferably 80% by weight or less, in 100% by weight of the conductive material. When the content of the thermosetting compound is not less than the lower limit and not more than the upper limit, the solder cohesiveness at the time of conductive connection can be more effectively improved, and the heat resistance of a cured product of the conductive material can be more effectively improved. From the viewpoint of further effectively improving the impact resistance, it is preferable that the content of the thermosetting compound is large.

The content of the epoxy compound is preferably 20% by weight or more, more preferably 40% by weight or more, further preferably 50% by weight or more, and preferably 99% by weight or less, more preferably 98% by weight or less, further preferably 90% by weight or less, and particularly preferably 80% by weight or less, in 100% by weight of the conductive material. When the content of the epoxy compound is not less than the lower limit and not more than the upper limit, the solder cohesiveness at the time of conductive connection can be further effectively improved, and the heat resistance of a cured product of the conductive material can be further effectively improved. From the viewpoint of further improving the impact resistance, it is preferable that the content of the epoxy compound is large.

(thermosetting component: thermosetting agent)

The thermosetting agent is not particularly limited. The thermosetting agent thermally cures the thermosetting compound. Examples of the thermal curing agent include thiol curing agents such as imidazole curing agents, amine curing agents, phenol curing agents, and polythiol curing agents, phosphonium salts, acid anhydride curing agents, thermal cation initiators (thermal cation curing agents), and thermal radical generators. The heat-curing agent may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

The thermal curing agent is preferably an imidazole curing agent, a thiol curing agent, or an amine curing agent, from the viewpoint that the conductive material can be cured more rapidly at low temperature. In addition, the thermosetting agent is preferably a latent thermosetting agent in view of improving storage stability when the thermosetting compound is mixed with the thermosetting agent. The latent heat-curing agent is preferably a latent imidazole curing agent, a latent thiol curing agent, or a latent amine curing agent. The thermosetting agent may be coated with a polymer such as a polyurethane resin or a polyester resin.

The imidazole curing agent is not particularly limited. Examples of the imidazole curing agent include: 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2, 4-diamino-6- [2 '-methylimidazolyl- (1') ] -ethyl-s-triazine and 2, 4-diamino-6- [2 '-methylimidazolyl- (1') ] -ethyl-s-triazine isocyanurate trimer adduct, 2-phenyl-4, 5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-dihydroxymethylimidazole, 2-phenyl-4-benzyl-5-hydroxymethylimidazole, 2-p-tolyl-4-methyl-5-hydroxymethylimidazole, and imidazole compounds such as 2-m-tolyl-4-methyl-5-hydroxymethylimidazole, 2-m-tolyl-4, 5-dihydroxymethylimidazole and 2-p-tolyl-4, 5-dihydroxymethylimidazole in which the hydrogen at the 5-position of 1H-imidazole is substituted with a hydroxymethyl group and the hydrogen at the 2-position is substituted with a phenyl group or a tolyl group.

The thiol curing agent is not particularly limited. Examples of the thiol curing agent include trimethylolpropane tri-3-mercaptopropionate, pentaerythritol tetra-3-mercaptopropionate, and dipentaerythritol hexa-3-mercaptopropionate.

The amine curing agent is not particularly limited. As the amine curing agent, there may be mentioned: hexamethylenediamine, octamethylenediamine, decamethylenediamine, 3, 9-bis (3-aminopropyl) -2,4,8, 10-tetraspiro [5.5] undecane, bis (4-aminocyclohexyl) methane, m-phenylenediamine, diaminodiphenylsulfone, and the like.

The phosphonium salt is not particularly limited. As described aboveSalts, which may be mentioned: tetra-n-butyl bromideTetra-n-butylO-O diethyl dithiophosphate, methyltributylDimethyl phosphate, tetra-n-butylBenzotriazole, and their use as a medicament,Tetra-n-butylTetrafluoroborate and tetra-n-butylTetraphenylborate, and the like.

The acid anhydride curing agent is not particularly limited, and any acid anhydride can be widely used as long as it is used as a curing agent for a thermosetting compound such as an epoxy compound. Examples of the acid anhydride curing agent include: and bifunctional acid anhydride curing agents such as phthalic anhydride, tetrahydrophthalic anhydride, trialkyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylbutenyl tetrahydrophthalic anhydride, phthalic acid derivative anhydrides, maleic anhydride, nadic anhydride, methylnadic anhydride, glutaric anhydride, succinic anhydride, glycerol bistrimellitic anhydride monoacetate, and ethylene glycol bistrimellitic anhydride, trifunctional acid anhydride curing agents such as trimellitic anhydride, and tetrafunctional or more acid anhydride curing agents such as pyromellitic anhydride, benzophenone tetracarboxylic anhydride, methylcyclohexene tetracarboxylic anhydride, and polyazelaic anhydride.

The thermal cationic initiator (thermal cationic curing agent) is not particularly limited. As the thermal cationic initiator (thermal cationic curing agent), iodine may be mentionedCation-like curing agent and oxygenCation-like curing agents and sulfonium cation-like curing agents. As the above iodineExamples of the cation-like curing agent include bis (4-t-butylphenyl) iodideHexafluorophosphates, and the like. As the above oxygenCationic curing agent, e.g., trimethyl oxideTetrafluoroborates, and the like. Examples of the sulfonium cationic curing agent include tri-p-tolylsulfonium hexafluorophosphate and the like.

The thermal radical generator is not particularly limited. Examples of the thermal radical generator include azo compounds and organic peroxides. Examples of the azo compound include Azobisisobutyronitrile (AIBN). Examples of the organic peroxide include di-tert-butyl peroxide and methyl ethyl ketone peroxide.

The reaction initiation temperature of the thermosetting agent is preferably 50 ℃ or higher, more preferably 70 ℃ or higher, further preferably 80 ℃ or higher, and preferably 250 ℃ or lower, more preferably 200 ℃ or lower, further preferably 150 ℃ or lower, and particularly preferably 140 ℃ or lower. If the reaction initiation temperature of the thermosetting agent is not lower than the lower limit and not higher than the upper limit, the solder can be more effectively disposed on the electrode. The reaction initiation temperature of the thermosetting agent is particularly preferably 80 ℃ or higher and 140 ℃ or lower.

From the viewpoint of more efficiently disposing solder on the electrode, the reaction initiation temperature of the thermosetting agent is preferably higher than the melting point of solder in the solder particles, more preferably higher by 5 ℃ or more, and even more preferably higher by 10 ℃ or more.

The reaction initiation temperature of the thermal curing agent means a temperature at which the rise of the exothermic peak in the DSC starts.

The content of the thermosetting agent is not particularly limited. The content of the thermosetting agent is preferably 0.01 parts by weight or more, more preferably 1 part by weight or more, and preferably 200 parts by weight or less, more preferably 100 parts by weight or less, and further preferably 75 parts by weight or less, relative to 100 parts by weight of the thermosetting compound. When the content of the thermosetting agent is not less than the lower limit, the conductive material can be easily cured sufficiently. When the content of the thermosetting agent is not more than the upper limit, the residual thermosetting agent that does not participate in curing is less likely to remain after curing, and the heat resistance of the cured product is further increased.

(flux)

The conductive material may include a flux. By using the flux, the solder can be further effectively disposed on the electrode. The flux is not particularly limited. As the flux, flux generally used for soldering or the like can be used.

Examples of the flux include: zinc chloride, a mixture of zinc chloride and an inorganic halide, a mixture of zinc chloride and an inorganic acid, a molten salt, phosphoric acid, a derivative of phosphoric acid, an organic halide, hydrazine, an amine compound, an organic acid, rosin, or the like. The flux can be used alone in 1 kind, and can also be used in combination in more than 2 kinds.

Examples of the molten salt include ammonium chloride. Examples of the organic acid include lactic acid, citric acid, stearic acid, glutamic acid, and glutaric acid. Examples of the rosin include activated rosin and non-activated rosin. The flux is preferably an organic acid having 2 or more carboxyl groups, or rosin. The soldering flux can be organic acid with more than 2 carboxyl groups, and can also be rosin. By using an organic acid or rosin having 2 or more carboxyl groups, the conduction reliability between electrodes is further improved.

Examples of the organic acid having 2 or more carboxyl groups include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid.

As the amine compound, there may be mentioned: cyclohexylamine, dicyclohexylamine, benzylamine, benzhydrylamine, imidazole, benzimidazole, phenylimidazole, carboxybenzimidazole, benzotriazole, carboxybenzotriazole, and the like.

The rosin is rosin containing abietic acid as main component. Examples of the rosin include abietic acid and acrylic acid-modified rosin. The flux is preferably rosin, more preferably abietic acid. By using the preferable flux, the reliability of conduction between electrodes is further improved.

The activation temperature (melting point) of the flux is preferably 50 ℃ or more, more preferably 70 ℃ or more, further preferably 80 ℃ or more, and preferably 200 ℃ or less, more preferably 190 ℃ or less, more preferably 160 ℃ or less, further preferably 150 ℃ or less, and more preferably 140 ℃ or less. When the active temperature of the flux is not lower than the lower limit and not higher than the upper limit, the flux effect can be more effectively exhibited, and the solder can be more uniformly arranged on the electrode. The activation temperature (melting point) of the flux is preferably 80 ℃ or higher and 190 ℃ or lower. The activation temperature (melting point) of the flux is particularly preferably 80 ℃ or higher and 140 ℃ or lower.

Examples of the flux having an activation temperature (melting point) of 80 ℃ or higher and 190 ℃ or lower include: succinic acid (melting point 186 ℃ C.), glutaric acid (melting point 96 ℃ C.), adipic acid (melting point 152 ℃ C.), pimelic acid (melting point 104 ℃ C.), dicarboxylic acid such as suberic acid (melting point 142 ℃ C.), benzoic acid (melting point 122 ℃ C.), malic acid (melting point 130 ℃ C.), and the like.

The flux preferably has a boiling point of 200 ℃ or lower.

From the viewpoint of more effectively disposing solder on the electrode, the melting point of the flux is preferably higher than the melting point of solder in the solder particles, more preferably higher by 5 ℃ or more, and even more preferably higher by 10 ℃ or more.

From the viewpoint of more effectively disposing solder on the electrode, the melting point of the flux is preferably higher than the reaction start temperature of the thermosetting agent, more preferably higher by 5 ℃ or more, and still more preferably higher by 10 ℃ or more.

The flux may be dispersed in a conductive material or may be attached to the surface of the solder particles.

The flux has a melting point higher than that of the solder, and thus solder particles can be effectively aggregated in the electrode portion. The reason for this is that: when heat is applied at the time of bonding, when the electrode formed on the connection target member is compared with the portion of the connection target member around the electrode, the thermal conductivity of the electrode portion is higher than that of the portion of the connection target member around the electrode, and thus the temperature of the electrode portion is increased rapidly. At a stage exceeding the melting point of the solder particles, the solder particles are dissolved inside, but the oxide film formed on the surface does not reach the melting point (activation temperature) of the flux and is not removed. In this state, since the temperature of the electrode portion reaches the melting point (activation temperature) of the flux first, the oxide film on the surface of the solder particles moving to the electrode is preferentially removed, and the solder particles can be wet-diffused to the surface of the electrode. This can effectively agglomerate the solder particles on the electrode.

The flux is preferably a flux that releases cations upon heating. By using the flux which releases cations by heating, the solder can be further efficiently arranged on the electrode.

The thermal cation initiator (thermal cation curing agent) can be used as the flux that releases cations by heating.

The flux is preferably a salt of an acid compound and a basic compound from the viewpoint of more effectively disposing solder on the electrode, from the viewpoint of more effectively improving insulation reliability, and from the viewpoint of more effectively improving conduction reliability.

The acid compound is preferably an organic compound having a carboxyl group. Examples of the acid compound include aliphatic carboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, citric acid, malic acid, cyclic aliphatic carboxylic acids such as cyclohexylcarboxylic acid, 1, 4-cyclohexyldicarboxylic acid, aromatic carboxylic acids such as isophthalic acid, terephthalic acid, trimellitic acid, and ethylenediaminetetraacetic acid. The acid compound is preferably glutaric acid, cyclohexylcarboxylic acid, or adipic acid from the viewpoint of more effectively disposing solder on the electrode, from the viewpoint of more effectively improving insulation reliability, and from the viewpoint of more effectively improving conduction reliability.

The base compound is preferably an organic compound having an amine group. As the base compound, there can be mentioned: diethanolamine, triethanolamine, methyldiethanolamine, ethyldiethanolamine, cyclohexylamine, dicyclohexylamine, benzylamine, benzhydrylamine, 2-methylbenzylamine, 3-methylbenzylamine, 4-tert-butylbenzylamine, N-methylbenzylamine, N-ethylbenzylamine, N-phenylbenzylamine, N-tert-butylbenzylamine, N-isopropylbenzylamine, N-dimethylbenzylamine, an imidazole compound, and a triazole compound. The alkali compound is preferably benzylamine from the viewpoint of more effectively disposing solder on the electrode, from the viewpoint of more effectively improving insulation reliability, and from the viewpoint of more effectively improving conduction reliability.

The content of the flux is preferably 0.5 wt% or more, and preferably 30 wt% or less, and more preferably 25 wt% or less, of 100 wt% of the conductive material. The conductive material may include a flux. When the content of the flux is not less than the lower limit and not more than the upper limit, the oxide film is further less likely to be formed on the surfaces of the solder and the electrode, and the oxide film formed on the surfaces of the solder and the electrode can be further effectively removed.

(Filler)

The conductive material of the present invention may contain a filler. The filler may be an organic filler or an inorganic filler. By including the filler in the conductive material, the solder can be uniformly condensed on the entire electrode of the substrate.

The conductive material preferably does not contain the filler, or contains the filler at 5 wt% or less. In the case of using the thermosetting compound, the solder is more likely to move to the electrode as the content of the filler is smaller.

The content of the filler is preferably 0 wt% (not contained) or more, and preferably 5 wt% or less, more preferably 2 wt% or less, and further preferably 1 wt% or less, in 100 wt% of the conductive material. If the content of the filler is not less than the lower limit and not more than the upper limit, the solder can be more effectively disposed on the electrode.

(other Components)

The conductive material may contain various additives such as fillers, extenders, softeners, plasticizers, thixotropic agents, leveling agents, polymerization catalysts, curing catalysts, colorants, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, lubricants, antistatic agents, and flame retardants, as needed.

(connecting structure and method for manufacturing connecting structure)

The connection structure of the present invention includes: a first connection object member having a first electrode on a surface thereof; a second connection object member having a second electrode on a surface thereof; and a connecting portion that connects the first connection target member and the second connection target member. In the connection structure of the present invention, the material of the connection portion includes the solder particles. In the connection structure of the present invention, the material of the connection portion is the conductive material. In the connection structure of the present invention, the first electrode and the second electrode are electrically connected by a solder portion in the connection portion.

The method for manufacturing a connection structure of the present invention includes the steps of: the conductive material is disposed on the surface of the first connection target member having the first electrode on the surface thereof, using the conductive material containing the solder particles or the conductive material. The method for manufacturing a connection structure of the present invention includes the steps of: a second member to be connected having a second electrode on a surface thereof is disposed on a surface of the conductive material opposite to the first member to be connected, and the first electrode and the second electrode are opposed to each other. The method for manufacturing a connection structure of the present invention includes the steps of: the conductive material is heated to a temperature equal to or higher than a melting point of the solder particles, whereby a connection portion for connecting the first connection target member and the second connection target member is formed of the conductive material, and the first electrode and the second electrode are electrically connected by a solder portion in the connection portion.

In the connection structure and the method for manufacturing the connection structure according to the present invention, since the specific solder particles or the specific conductive material is used, the solder particles can be efficiently arranged on the electrode, the solder particles can be easily gathered between the first electrode and the second electrode, and the solder particles can be efficiently aggregated on the electrode (wire). In addition, a part of the solder particles is not easily arranged in a region (gap) where no electrode is formed, and the amount of the solder particles arranged in the region where no electrode is formed can be greatly reduced. Therefore, the conduction reliability between the first electrode and the second electrode can be improved. Furthermore, electrical connection between laterally adjacent electrodes that should not be connected can be prevented, and insulation reliability can be improved.

In addition, in order to efficiently dispose solder on the electrode and to greatly reduce the amount of solder disposed in a region where no electrode is formed, it is preferable to use a conductive paste instead of the conductive film.

The thickness of the solder portion between the electrodes is preferably 10 μm or more, more preferably 20 μm or more, and preferably 100 μm or less, more preferably 80 μm or less. The solder wetting area on the surface of the electrode (the area of the contact solder in 100% of the exposed area of the electrode) is preferably 50% or more, more preferably 70% or more, and preferably 100% or less.

In the method for manufacturing a connection structure according to the present invention, it is preferable that the conductive material is weighted by the weight of the second member to be connected without applying pressure in the step of disposing the second member to be connected and the step of forming the connection portion. In the method for manufacturing a connection structure according to the present invention, it is preferable that in the step of disposing the second connection object member and the step of forming the connection portion, a pressure force exceeding the weight of the second connection object member is not applied to the conductive material. In these cases, the uniformity of the solder amount can be further improved in the plurality of solder portions. Further, the thickness of the solder portion can be further effectively increased, and a large number of solder particles can be easily collected between the electrodes, and the solder particles can be further effectively arranged on the electrodes (wires). In addition, a part of the plurality of solder particles is not easily arranged in a region (gap) where no electrode is formed, and the amount of solder in the solder particles arranged in the region where no electrode is formed can be further reduced. Therefore, the reliability of conduction between the electrodes can be further improved. Further, electrical connection between laterally adjacent electrodes that should not be connected can be prevented, and insulation reliability can be further improved.

In addition, if a conductive paste is used instead of the conductive film, the thickness of the connecting portion and the solder portion can be easily adjusted by the amount of the conductive paste applied. On the other hand, the conductive film has the following problems: in order to change or adjust the thickness of the connection portion, it is necessary to prepare conductive films having different thicknesses or to prepare conductive films having a specific thickness. In addition, the conductive film tends to be as follows: as compared with a conductive paste, the melting viscosity of a conductive film cannot be sufficiently reduced at the melting temperature of solder, and the aggregation of solder particles is easily inhibited.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

Fig. 1 is a cross-sectional view schematically showing a connection structure obtained by using a conductive material according to an embodiment of the present invention.

The connection structure 1 shown in fig. 1 includes a first connection object member 2, a second connection object member 3, and a connection portion 4 for connecting the first connection object member 2 and the second connection object member 3. The connection portion 4 is formed of the conductive material. In the present embodiment, the conductive material includes a thermosetting compound, a thermosetting agent, and solder particles. In this embodiment, a conductive paste is used as a conductive material.

The connection portion 4 includes a solder portion 4A in which a plurality of solder particles are aggregated and bonded to each other, and a cured product portion 4B in which a thermosetting compound is thermally cured.

The first connection target member 2 has a plurality of first electrodes 2a on a surface (upper surface). The second connection target member 3 has a plurality of second electrodes 3a on a front surface (lower surface). The first electrode 2a and the second electrode 3a are electrically connected by the solder portion 4A. Therefore, the first connection object member 2 and the second connection object member 3 are electrically connected by the solder portion 4A. In the connection portion 4, no solder particles are present in a region (the portion of the cured product portion 4B) different from the solder portion 4A collected between the first electrode 2a and the second electrode 3 a. In a region (the portion of the cured product 4B) different from the solder portion 4A, there are no solder particles separated from the solder portion 4A. If the amount is small, solder particles may be present in a region (the portion of the cured product 4B) different from the solder portion 4A collected between the first electrode 2a and the second electrode 3 a.

As shown in fig. 1, in the connection structure 1, a plurality of solder particles are aggregated between the first electrode 2a and the second electrode 3a, and after the plurality of solder particles are melted, the melt of the solder particles wets and spreads on the surface of the electrodes, and then solidifies to form the solder portion 4A. Therefore, the connection area between the solder portion 4A and the first electrode 2a and between the solder portion 4A and the second electrode 3a is increased. That is, by using the solder particles, the contact area between the solder portion 4A and the first electrode 2a and the contact area between the solder portion 4A and the second electrode 3a become larger than in the case of using conductive particles whose conductive outer surfaces are made of metal such as nickel, gold, or copper. This improves the conduction reliability and connection reliability of the connection structure 1. In the case where the flux is contained in the conductive material, the flux is generally gradually deactivated by heating.

In the connection structure 1 shown in fig. 1, all of the solder portions 4A are located in the facing region between the first electrode 2a and the second electrode 3 a. In the connection structure 1X of the modification shown in fig. 3, only the connection portion 4X is different from the connection structure 1 shown in fig. 1. The connection portion 4X has a solder portion 4XA and a cured product portion 4 XB. In the connection structure 1X, most of the solder portion 4XA is located in the region facing the first electrode 2a and the second electrode 3a, and a part of the solder portion 4XA protrudes to the side from the region facing the first electrode 2a and the second electrode 3 a. The solder portion 4XA extending from the facing region of the first electrode 2a and the second electrode 3a to the side is a part of the solder portion 4XA and is not solder particles separated from the solder portion 4 XA. In the present embodiment, the amount of solder particles separated from the solder portion can be reduced, and the solder particles separated from the solder portion can be present in the cured product portion.

When the amount of solder particles used is reduced, the connection structure 1 can be easily obtained. When the amount of the solder particles used is increased, the connection structure 1X can be easily obtained.

In the connection structures 1 and 1X, when only the facing portions of the first electrode 2a and the second electrode 3a are viewed in the lamination direction of the first electrode 2a, the connection portions 4 and 4X, and the second electrode 3a, the solder portions 4A and 4XA in the connection portions 4 and 4X are preferably arranged in 50% or more of 100% of the area of the facing portions of the first electrode 2a and the second electrode 3 a. By satisfying the above-described preferable mode with solder portions 4A and 4XA in connection portions 4 and 4X, conduction reliability can be further improved.

When only the facing portion of the first electrode and the second electrode is viewed in the lamination direction of the first electrode, the connection portion, and the second electrode, the solder portion in the connection portion is preferably disposed in 50% or more of 100% of the area of the facing portion of the first electrode and the second electrode. When only the facing portion of the first electrode and the second electrode is viewed in the lamination direction of the first electrode, the connection portion, and the second electrode, the solder portion in the connection portion is more preferably disposed in 60% or more of 100% of the area of the facing portion of the first electrode and the second electrode. When only the facing portion of the first electrode and the second electrode is viewed in the lamination direction of the first electrode, the connection portion, and the second electrode, it is more preferable that the solder portion in the connection portion is disposed in 70% or more of 100% of the area of the facing portion of the first electrode and the second electrode. When only the facing portion of the first electrode and the second electrode is viewed in the lamination direction of the first electrode, the connection portion, and the second electrode, it is particularly preferable that the solder portion in the connection portion is disposed in 80% or more of 100% of the area of the facing portion of the first electrode and the second electrode. When only the facing portion of the first electrode and the second electrode is viewed in the lamination direction of the first electrode, the connection portion, and the second electrode, it is most preferable that the solder portion in the connection portion is disposed in 90% or more of 100% of the area of the facing portion of the first electrode and the second electrode. The solder portion in the connection portion satisfies the preferable aspect, and the conduction reliability can be further improved.

When only the facing portion of the first electrode and the second electrode is viewed in a direction perpendicular to the stacking direction of the first electrode, the connection portion, and the second electrode, it is preferable that 60% or more of the solder portion in the connection portion is arranged in the facing portion of the first electrode and the second electrode. When only the facing portion of the first electrode and the second electrode is observed in a direction perpendicular to the stacking direction of the first electrode, the connection portion, and the second electrode, it is more preferable that 70% or more of the solder portion in the connection portion is arranged in the facing portion of the first electrode and the second electrode. When only the facing portion of the first electrode and the second electrode is viewed in the direction perpendicular to the stacking direction of the first electrode, the connection portion, and the second electrode, it is more preferable that 90% or more of the solder portion in the connection portion is arranged in the facing portion of the first electrode and the second electrode. When only the facing portion of the first electrode and the second electrode is viewed in the direction perpendicular to the stacking direction of the first electrode, the connection portion, and the second electrode, it is particularly preferable that 95% or more of the solder portion in the connection portion is arranged in the facing portion of the first electrode and the second electrode. When only the facing portion of the first electrode and the second electrode is viewed in a direction perpendicular to the stacking direction of the first electrode, the connection portion, and the second electrode, it is most preferable that 99% or more of the solder portion in the connection portion is arranged in the facing portion of the first electrode and the second electrode. The solder portion in the connection portion satisfies the preferable aspect, and the conduction reliability can be further improved.

Next, an example of a method for manufacturing the connection structure 1 using the conductive material according to the embodiment of the present invention will be described with reference to fig. 2.

First, the first connection target member 2 having the first electrode 2a on the front surface (upper surface) is prepared. Next, as shown in fig. 2a, the conductive material 11 including the thermosetting component 11B and the plurality of solder particles 11A is disposed on the surface of the first member to be connected 2 (first step). The conductive material 11 used contains a thermosetting compound and a thermosetting agent as the thermosetting component 11B.

A conductive material 11 is disposed on the surface of the first connection target member 2 on which the first electrode 2a is provided. After the conductive material 11 is disposed, the solder particles 11A are disposed on the first electrodes 2a (lines) and on the regions (gaps) where the first electrodes 2a are not formed.

The method of disposing the conductive material 11 is not particularly limited, and coating by a dispenser, screen printing, spraying by an ink jet apparatus, and the like can be mentioned.

In addition, a second connection target member 3 having a second electrode 3a on the front surface (lower surface) is prepared. Next, as shown in fig. 2(b), the second member to be connected 3 is disposed on the surface of the conductive material 11 on the opposite side of the conductive material 11 from the first member to be connected 2, among the conductive materials 11 on the surface of the first member to be connected 2 (second step). On the surface of the conductive material 11, the second connection target member 3 is arranged from the second electrode 3a side. At this time, the first electrode 2a and the second electrode 3a are opposed to each other.

Next, the conductive material 11 is heated to the melting point of the solder particles 11A or higher (third step). The conductive material 11 is preferably heated to a temperature equal to or higher than the curing temperature of the thermosetting component 11B (thermosetting compound). During this heating, the solder particles 11A existing in the region where no electrode is formed are gathered between the first electrode 2a and the second electrode 3a (self-aggregation effect). When the conductive paste is used without using the conductive film, the solder particles 11A are more effectively collected between the first electrode 2a and the second electrode 3 a. The solder particles 11A are melted and bonded to each other. In addition, the thermosetting component 11B is thermally cured. As a result, as shown in fig. 2(c), the connection portion 4 connecting the first connection object member 2 and the second connection object member 3 is formed of the conductive material 11. The connecting portion 4 is formed by the conductive material 11, the solder portion 4A is formed by bonding the plurality of solder particles 11A, and the cured product portion 4B is formed by thermosetting the thermosetting component 11B. If the solder particles 11A move sufficiently, the temperature can be kept constant from the start of the movement of the solder particles 11A that are not positioned between the first electrode 2a and the second electrode 3a until the completion of the movement of the solder particles 11A between the first electrode 2a and the second electrode 3 a.

In the present embodiment, it is preferable that the second step and the third step are not pressurized. In this case, the weight of the second connection target member 3 is applied to the conductive material 11. Therefore, the solder particles 11A are more effectively collected between the first electrode 2a and the second electrode 3a when the connection portion 4 is formed. When the pressure is applied in at least one of the second step and the third step, the tendency of the solder particles 11A to aggregate and the action between the first electrode 2a and the second electrode 3a to be inhibited increases.

In the present embodiment, since the pressurization is not performed, when the first connection object member 2 and the second connection object member 3 are superposed on each other, even in a state where the alignment of the first electrode 2a and the second electrode 3a is shifted, the shift can be corrected, and the first electrode 2a and the second electrode 3a can be connected (self-alignment effect). This is because: in the case of the molten solder that has condensed and melted between the first electrode 2a and the second electrode 3a and the molten solder that has condensed and melted between the first electrode 2a and the second electrode 3a, the solder between the first electrode 2a and the second electrode 3a is energetically stabilized when the area of contact with other components of the conductive material is minimized, and therefore, a force that becomes an aligned connection structure that is a connection structure of the minimum area is exerted. In this case, it is desirable that the conductive material is not cured and that the viscosity of the components of the conductive material other than the solder particles is sufficiently low under the conditions of the temperature and the time.

The viscosity (η mp) of the conductive material at the melting point of the solder particles is preferably 50 pas or less, more preferably 10 pas or less, further preferably 1 pas or less, and preferably 0.1 pas or more, more preferably 0.2 pas or more, the viscosity (η mp) is the upper limit or less, the solder particles can be efficiently agglomerated, and the viscosity (η mp) is the lower limit or more, the voids of the connection portion can be suppressed, and the conductive material can be suppressed from overflowing to the outside of the connection portion.

The viscosity (η mp) of the conductive material at the melting point of the solder particles can be used

STRESSTECH (manufactured by REO L OGICA) under the conditions of strain control of 1rad, frequency of 1Hz, temperature rise rate of 20 ℃/min, and measurement temperature range of 25 to 200 ℃ (wherein the upper temperature limit is set to the melting point of the solder particles when the melting point of the solder particles exceeds 200 ℃), and the viscosity of the solder particles at the melting point (. degree. C.) is evaluated from the measurement results.

In this manner, the connection structure 1 shown in fig. 1 is obtained. The second step and the third step may be performed continuously. After the second step, the obtained laminate of the first connection target member 2, the conductive material 11, and the second connection target member 3 may be moved to a heating unit to perform the third step. In order to perform the heating, the laminate may be disposed on a heating member, or the laminate may be disposed in a heated space.

The heating temperature in the third step is preferably 140 ℃ or higher, more preferably 160 ℃ or higher, and preferably 450 ℃ or lower, more preferably 250 ℃ or lower, and further preferably 200 ℃ or lower.

Examples of the heating method in the third step include: a method of heating the entire connection structure to a temperature not lower than the melting point of the solder particles and not lower than the curing temperature of the thermosetting component by using a reflow furnace or an oven; and a method of locally heating only the connection portion of the connection structure.

Examples of the tool used in the method of locally heating include a hot plate, a hot air gun for applying hot air, a soldering iron, and an infrared heater.

When the heating plate is used to locally heat, it is preferable that the upper surface of the heating plate is formed of a metal having high thermal conductivity directly below the connecting portion, and a material having low thermal conductivity such as a fluororesin is used in a portion which is not preferably heated.

The first member to be connected and the second member to be connected are not particularly limited, and specific examples thereof include electronic components such as semiconductor chips, semiconductor packages, L ED chips, L ED packages, capacitors, diodes, and the like, and electronic components such as resin films, printed boards, flexible flat cables, rigid-flexible boards, glass epoxy boards, glass boards, and the like.

Preferably, at least one of the first connection target member and the second connection target member is a resin film, a flexible printed board, a flexible flat cable, or a rigid flexible board. Preferably, the second member to be connected is a resin film, a flexible printed board, a flexible flat cable, or a rigid flexible board. Resin films, flexible printed boards, flexible flat cables, and rigid flexible boards have high flexibility and are relatively lightweight. When a conductive film is used for connection of such members to be connected, solder particles tend to be less likely to gather on the electrodes. In contrast, by using the conductive paste, solder particles are effectively collected on the electrodes even when a resin film, a flexible printed circuit board, a flexible flat cable, or a flex-rigid substrate is used, and thus the reliability of conduction between the electrodes can be sufficiently improved. When a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible board is used, the effect of improving the reliability of the electrical connection between the electrodes can be more effectively obtained because the pressing is not performed as compared with the case where another connection target member such as a semiconductor chip is used.

Examples of the electrode provided in the connection target member include metal electrodes such as a gold electrode, a nickel electrode, a tin electrode, an aluminum electrode, a copper electrode, a molybdenum electrode, a silver electrode, an SUS electrode, and a tungsten electrode. When the member to be connected is a flexible printed circuit board, the electrode is preferably a gold electrode, a nickel electrode, a tin electrode, a silver electrode, or a copper electrode. When the member to be connected is a glass substrate, the electrode is preferably an aluminum electrode, a copper electrode, a molybdenum electrode, a silver electrode, or a tungsten electrode. When the electrode is an aluminum electrode, the electrode may be formed of aluminum alone or may be formed by laminating an aluminum layer on the surface of a metal oxide layer. Examples of the material of the metal oxide layer include indium oxide doped with a metal element having a valence of 3, zinc oxide doped with a metal element having a valence of 3, and the like. The metal element having a valence of 3 includes Sn, Al, Ga, and the like.

In the connection structure of the present invention, the first electrode and the second electrode are preferably provided in an array or on the outer periphery. When the first electrode and the second electrode are arranged in an array or on the outer periphery, the effects of the present invention can be more effectively exhibited. The array is a structure in which electrodes are arranged in a lattice shape on a surface on which the electrodes of the connection target member are arranged. The outer periphery is a structure in which an electrode is disposed on the outer periphery of the member to be connected. In the case of the structure in which the electrodes are arranged in a comb shape, the solder particles may be agglomerated in a direction perpendicular to the comb, whereas in the array or the outer peripheral structure, the solder particles need to be agglomerated uniformly over the entire surface on which the electrodes are arranged. Therefore, the solder amount tends to become uneven in the conventional method, and the method of the present invention can more effectively exhibit the effects of the present invention.

The present invention will be specifically described below with reference to examples and comparative examples. The present invention is not limited to the following examples.

Thermosetting component (thermosetting compound):

thermosetting compound 1: "D.E.N-431" manufactured by Dow chemical Co., Ltd., epoxy resin

Thermosetting compound 2: "JeR 152" manufactured by Mitsubishi chemical corporation, epoxy resin

Thermosetting component (thermosetting agent):

thermal curing agent 1: BF3-MEA manufactured by Tokyo chemical industry Co., Ltd, boron trifluoride-monoethylamine complex

Thermal curing agent 2: "2 PZ-CN" manufactured by four chemical industries, Ltd., 1-cyanoethyl-2-phenylimidazole

Solder particles:

solder particles 1: sn42Bi58 solder particles, melting point 138 ℃, particle size: 10 μm, average thickness of oxide film: 3nm

Solder particles 2: sn42Bi58 solder particles, melting point 138 ℃, particle size: 5 μm, average thickness of oxide film: 5nm

Solder particles 3: sn42Bi58 solder particles, melting point 138 ℃, particle size: 2 μm, average thickness of oxide film: 2nm

Solder particles 4: sn42Bi58 solder particles, melting point 138 ℃, particle size: 10 μm, average thickness of oxide film: 6nm

Solder particles 5: sn42Bi58 solder particles, melting point 138 ℃, particle size: 5 μm, average thickness of oxide film: 12nm

Solder particles 6: sn42Bi58 solder particles, melting point 138 ℃, particle size: 2 μm, average thickness of oxide film: 4nm

Flux:

flux 1: "Pentamethylglutarate" having a melting point of 108 deg.C

The preparation method of the soldering flux 1 comprises the following steps:

a glass bottle was charged with 24g of water as a reaction solvent and 13.212g of glutaric acid (Wako pure chemical industries, Ltd.) and dissolved at room temperature until a uniform solution was obtained. Thereafter, 10.715g of benzylamine (Wako pure chemical industries, Ltd.) was added thereto and stirred for about 5 minutes to obtain a mixed solution. Placing the obtained mixed solution in a refrigerator at 5-10 ℃ for evening. The precipitated crystals were separated by filtration, washed with water, and vacuum-dried to obtain flux 1.

(examples 1 to 6 and comparative examples 1 to 6)

(1) Production of conductive Material (Anisotropic conductive paste)

The components shown in tables 1 and 2 were mixed in the amounts shown in tables 1 and 2 to obtain conductive materials (anisotropic conductive pastes).

(2) Production of connection Structure (L/S: 100 μm/100 μm)

Using the conductive material (anisotropic conductive paste) just produced, a connection structure was produced as follows.

A glass epoxy substrate (FR-4 substrate) (first connection object member) was prepared in which L/S was 100 μm/100 μm and a copper electrode pattern (thickness of copper electrode 12 μm) having an electrode length of 3mm was formed on the upper surface, and a flexible printed substrate (second connection object member) was prepared in which L/S was 100 μm/100 μm and a copper electrode pattern (thickness of copper electrode 12 μm) having an electrode length of 3mm was formed on the lower surface.

The overlapping area of the glass epoxy resin substrate and the flexible printed circuit board was set to 1.5cm × 3mm, and the number of electrodes connected was set to 75 pairs.

On the upper surface of the glass epoxy substrate, a conductive material (anisotropic conductive paste) layer was formed by applying a conductive material (anisotropic conductive paste) which had just been prepared onto the electrode of the glass epoxy substrate by screen printing using a metal mask so as to have a thickness of 100 μm. Next, the flexible printed circuit board was laminated on the upper surface of the conductive material (anisotropic conductive paste) layer so that the electrodes were opposed to each other. At this time, no pressurization is performed. The weight of the flexible printed board is applied to the conductive material (anisotropic conductive paste) layer. The conductive material (anisotropic conductive paste) layer was heated from this state to a temperature at which the solder melted after 5 seconds from the start of the temperature rise. Then, the conductive material (anisotropic conductive paste) layer was cured at a temperature of 160 ℃ 15 seconds after the start of the temperature increase, thereby obtaining a connection structure. During heating, no pressurization is performed.

(evaluation)

(1) Particle diameter of solder particles and average thickness of oxide film

The particle size of the solder particles was measured by using a laser diffraction particle size distribution measuring apparatus ("L A-920" manufactured by horiba, Ltd.).

The solder particles were heated at 120 ℃ for 10 hours in an air atmosphere. The cross section of the solder particles before heating or the solder particles after heating was observed using a transmission electron microscope, and the average thickness of the oxide film before heating (average thickness a) and the average thickness of the oxide film after heating (average thickness B) were calculated from the average value of the thicknesses of the oxide films at 10 arbitrarily selected portions.

From the measurement results of the particle size of the solder particles and the average thickness (average thickness a) of the oxide film of the solder particles before heating, the ratio of the average thickness (average thickness a) of the oxide film of the solder particles before heating to the particle size of the solder particles (average thickness a/particle size of the solder particles) was calculated. Further, from the measurement results of the average thickness (average thickness a and average thickness B) of the oxide film of the solder particles before and after heating, the ratio (average thickness a/average thickness B) of the average thickness (average thickness a) of the oxide film of the solder particles before heating to the average thickness (average thickness B) of the oxide film of the solder particles after heating was calculated.

(2) Content of oxide film in 100 vol% of solder particle

The content of the oxide film in 100 vol% of the solder particles was calculated from the weight of the solder particles before and after the oxide film removal.

(3) Absolute value of heat generation amount of solder particles at 200 ℃ or higher

The amount of heat generated from the solder particles at 200 ℃ or higher was measured using a Differential Scanning Calorimetry (DSC) apparatus ("EXSTARDSC 7020" manufactured by SII corporation).

(4) Viscosity of conductive Material at 25 ℃ (η 25(5rpm))

The viscosity (η 25(5rpm)) of the conductive material at 25 ℃ of the obtained conductive material (anisotropic conductive paste) was measured at 25 ℃ and 5rpm using an E-type viscometer ("TVE 22L" manufactured by eastern mechanical industries, inc.).

(5) Thixotropic index

The viscosity (η 25(0.5rpm)) of the obtained conductive material (anisotropic conductive paste) was measured at 25 ℃ and 0.5rpm using an E-type viscometer ("TVE 22L" manufactured by eastern industries) and the viscosity (η 25(5rpm)) of the obtained conductive material (anisotropic conductive paste) was measured at 25 ℃ and 5rpm using an E-type viscometer ("TVE 22L" manufactured by eastern industries).

From the measurement results, a thixotropic index (η 25(0.5rpm)/η 25(5rpm)) was calculated, which was obtained by dividing the viscosity of the conductive material (anisotropic conductive paste) measured at 25 ℃ and 0.5rpm using an E-type viscometer by the viscosity of the conductive material (anisotropic conductive paste) measured at 25 ℃ and 5rpm using an E-type viscometer.

(6) Precision of solder placement on electrodes (solder cohesiveness)

In the obtained connection structure, when only the mutually facing portions of the first electrode and the second electrode were observed in the lamination direction of the first electrode, the connection portion, and the second electrode, the ratio X of the area of the connection portion where the solder portion was arranged in the area of the mutually facing portion of the first electrode and the second electrode was evaluated in 100%. The placement accuracy (solder cohesiveness) of the solder on the electrode was determined by the following criteria.

[ determination criteria for the placement accuracy (solder cohesiveness) of solder on electrodes ]

○○, the ratio X is more than 70%

○, the ratio X is more than 60% and less than 70%

△, the ratio X is more than 50% and less than 60%

× the ratio X is less than 50%

(7) Conduction reliability between upper and lower electrodes

In the obtained connection structure (n is 15 pieces), the connection resistance at each connection point between the upper and lower electrodes was measured by a four-terminal method, and the average value of the connection resistance was calculated.

[ determination criterion of conduction reliability ]

○○ average value of connection resistance is less than 50m omega

○ average value of connection resistance is more than 50m omega and less than 70m omega

△ average value of connection resistance is more than 70m omega and less than 100m omega

× mean value of connection resistance is larger than 100m omega or bad connection is generated

(8) Reliability of insulation between laterally adjacent electrodes

After the obtained connection structure (n: 15) was left for 100 hours in an environment of 85 ℃ and 85% humidity, 5V was applied between the laterally adjacent electrodes, and the resistance value was measured at 25 sites. The insulation reliability was determined by the following criteria.

[ criterion for determining insulation reliability ]

○○ average value of connection resistance is 10⁷Omega or more

○ average value of connection resistance is 10⁶Omega is more than or equal to 10⁷Ω

△ average value of connection resistance is 10⁵Omega is more than or equal to 10⁶Ω

× average value of connection resistance is less than 10⁵Ω

The results are shown in tables 1 and 2 below.

TABLE 1

[ Table 2]

The same tendency was observed in the case of using a flexible printed circuit board, a resin film, a flexible flat cable, and a flex-rigid board.

Description of the marks

1,1X … connection structure

2 … first connection object member

2a … first electrode

3 … second connection object part

3a … second electrode

4,4X … junction

4A,4XA … solder part

Cured 4B,4XB … product

11 … conductive material

11A … solder particles

11B … Heat curing Components

21 … solder particles

22 … solder particle body

23 … oxidized film