阅读说明：本技术 复合颗粒、磁芯和电子部件 (Composite particle, magnetic core, and electronic component ) 是由 山下保英 寺尾耕太郎 桥本晋亮 于 2021-04-26 设计创作，主要内容包括：本发明提供一种直流重叠特性和耐压高、且抑制高温环境下的耐压的降低的电感元件等电子部件、该电子部件中使用的磁芯和构成该磁芯的复合颗粒。复合颗粒具有：大颗粒,其具有磁性；小颗粒,其直接或间接地附着于大颗粒的表面且平均粒径比大颗粒小；相互缓冲膜,其至少覆盖位于绕大颗粒周围存在的小颗粒之间的大颗粒的表面。将大颗粒的平均粒径设为R、将小颗粒的平均粒径设为r、且将相互缓冲膜的平均厚度设为t时,(r/R)为0.0012以上且0.025以下,(t/r)为大于0且0.7以下,r为12nm以上且100nm以下。(The invention provides an electronic component such as an inductance component, which has high DC superposition characteristics and high withstand voltage and suppresses the decrease of withstand voltage under high-temperature environment, a magnetic core used in the electronic component, and composite particles constituting the magnetic core. The composite particle has: large particles having magnetic properties; small particles which are directly or indirectly attached to the surface of the large particles and have a smaller average particle size than the large particles; and a mutual buffer film covering at least the surface of the large particles positioned between the small particles existing around the large particles. When the average particle size of the large particles is R, the average particle size of the small particles is R, and the average thickness of the buffer films is t, (R/R) is 0.0012 to 0.025 inclusive, (t/R) is greater than 0 to 0.7 inclusive, and R is 12nm to 100nm inclusive.)

1. A composite particle, comprising:

large particles having magnetic properties;

small particles directly or indirectly attached to the surface of the large particles and having a smaller average particle size than the large particles; and

a mutual buffer film covering at least the surface of the large particles located between the small particles existing around the large particles,

when the average particle size of the large particles is R, the average particle size of the small particles is R, and the average thickness of the mutually buffer films is t,

(R/R) is 0.0012 to 0.025 inclusive,

(t/r) is more than 0 and 0.7 or less,

r is 12nm or more and 100nm or less.

2. The composite particle according to claim 1, characterized in that:

the small particles are non-magnetic and insulating.

3. The composite particle according to claim 1, characterized in that:

the small particles contain at least one selected from the group consisting of titanium oxide, aluminum oxide, magnesium oxide, zinc oxide, bismuth oxide, yttrium oxide, calcium oxide, silicon oxide, and ferrite.

4. The composite particle according to claim 1, characterized in that:

the small particles are SiO₂And (3) granules.

5. The composite particle according to claim 1, characterized in that:

the mutual buffer film is obtained by a sol-gel reaction in which a precursor of a metal alkoxide and one or both of non-metal alkoxides are combined.

6. The composite particle according to claim 1, characterized in that:

the mutual buffer film has non-magnetic properties and insulating properties.

7. The composite particle according to claim 1, characterized in that:

the mutual buffer film is tetraethoxysilane.

8. The composite particle according to claim 4, wherein:

the mutual buffer film is tetraethoxysilane.

9. A magnetic core having a cross section or a surface on which the composite particle according to any one of claims 1 to 8 can be observed.

10. An electronic component having the magnetic core of claim 9.

Technical Field

The present invention relates to an electronic component such as an inductance component, and relates to a magnetic core used in the electronic component and composite particles constituting the magnetic core.

Background

Magnetic cores obtained by compression molding magnetic particles and a binder are used in electronic components such as inductance components. In particular, in order to impart rust resistance and insulation to the metal magnetic particles, a coating having a thickness of about 10 to 100nm is applied to the surface of the metal magnetic particles.

For example, in patent document 1, a phosphate coating layer is formed on the surface of an Fe-based soft magnetic powder particle, and a silica-based insulating coating film is formed on the outer side thereof.

In addition, the soft magnetic powder of patent document 2 has: a powder body portion containing Fe and further containing Al, Si, or the like; oxide coating of Al, Si or the like; an oxide coating film of B.

However, there are problems as follows: an electronic component having a magnetic core produced using magnetic particles having a conventional coating film has insufficient direct current superposition characteristics and withstand voltage, and has a significant reduction in withstand voltage under a high-temperature environment.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2017-188678

Patent document 2: japanese laid-open patent publication No. 2009-10180

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide an electronic component such as an inductance component having high dc superimposition characteristics and withstand voltage and suppressing a decrease in withstand voltage in a high-temperature environment, a magnetic core used in the electronic component, and composite particles constituting the magnetic core.

Means for solving the problems

In order to achieve the above object, the composite particle of the present invention has:

large particles having magnetic properties;

small particles which are attached directly or indirectly to the surface of the large particles and have an average particle size smaller than that of the large particles; and

a mutual buffer film covering at least the surfaces of the large particles positioned between the small particles existing around the large particles,

when the average particle size of the large particles is represented by R, the average particle size of the small particles is represented by R, and the average thickness of the mutual buffer film is represented by t,

(R/R) is 0.0012 to 0.025 inclusive,

(t/r) is more than 0 and 0.7 or less,

the r is 12nm to 100 nm.

The present inventors have found that, by adopting the above-described structure for the composite particles of the present invention, electronic parts such as inductance components and the like having magnetic cores formed by using the composite particles have high dc superposition characteristics and high withstand voltage, and also have high magnetic permeability, and thus the decrease in withstand voltage under high-temperature environments is suppressed.

It is considered that, by the composite particles of the present invention having the above-described structure, the large particles are less likely to contact each other even when molding is performed at high pressure. This is because the small particles function as spacers between the large particles. Thus, it is considered that a predetermined distance can be formed between the large particles, and the distance between the large particles can be made constant or longer. It is considered that by setting the distance between the large particles to be equal to or greater than a certain value, the large particles can be prevented from contacting each other even when molding is performed at high pressure, and the withstand voltage can be improved while preventing the decrease in volume resistivity.

In addition, by preventing large particles from contacting each other, concentration of a magnetic field can be prevented, and thus generation of magnetic saturation can be prevented. This is considered to improve the dc superimposition characteristics.

Further, it is considered that the surface of the large particles is covered with the mutually cushioning film, and therefore, the small particles on the surface of the large particles can be prevented from moving along the surface of the large particles during molding. Thus, it is considered that when molding is performed at high pressure, the reliability of the small particles functioning as spacers between large particles is further improved. Further, it is considered that the surface of the large particle is covered with the mutual buffer film to further prevent the magnetic field from concentrating, thereby further improving the dc superimposition characteristics.

In addition, the composite particle of the present invention can be molded at a high pressure by adopting the above-described structure. Therefore, the magnetic permeability can be improved.

In the present invention, the average thickness of the buffer films is set within a predetermined range, so that high magnetic permeability can be ensured and the manufacturing cost can be reduced.

In the present invention, the distance between the large particles can be made constant or longer by the small particles, and therefore, the decrease in withstand voltage in a high-temperature environment can be suppressed.

The composite particles of the present invention preferably have non-magnetic properties and insulating properties.

In the composite particle of the present invention, the above-mentioned small particles may contain at least one selected from the group consisting of titanium oxide, aluminum oxide, magnesium oxide, zinc oxide, bismuth oxide, yttrium oxide, calcium oxide, silicon oxide, and ferrite.

The above-mentioned small particles of the composite particles of the present invention may be SiO₂And (3) granules.

SiO₂The particles have the advantage of being inexpensive. In addition, SiO₂The particles have a lattice volume of particle size from a few nm to a few 100 nm. And, SiO₂The particles tend to have a narrow particle size distribution, and therefore, can serve as uniform spacers between the particles.

The composite particles of the present invention preferably have a nonmagnetic and insulating mutual buffer film.

In the molded article of the present invention, the mutual buffer film can be obtained by a sol-gel reaction in which a precursor of a metal alkoxide and one or both of nonmetal alkoxides are combined.

The above-mentioned mutual buffer film of the composite particle of the present invention may be Tetraethoxysilane (TEOS).

In the present invention, the mutual buffer film is TEOS, which can further improve the withstand voltage. In addition, TEOS has the advantage of low material cost. Further, by using TEOS as the mutual buffer film, the thickness of the mutual buffer film can be adjusted by the temperature, time, or the amount of TEOS added.

The magnetic core of the present invention has a cross section or a surface on which the composite particles can be observed.

The electronic component of the present invention has the composite particles.

Drawings

Fig. 1 is a schematic cross-sectional view of a composite particle according to an embodiment of the present invention.

Fig. 2 is a cross-sectional view of an inductance component according to an embodiment of the present invention.

Fig. 3 is a schematic cross-sectional view of a magnetic core according to an embodiment of the present invention.

Detailed Description

[ first embodiment ]

< composite particles >

As shown in fig. 1, in the composite particle 12 of the present embodiment, small particles 16 having a smaller average particle diameter than the large particles 14 are directly or indirectly attached to the surface of the large particles 14. That is, the small particles 16 may be directly attached to the surface of the large particles 14, the small particles 16 may be indirectly attached to the surface of the large particles 14 through an after-mentioned mutual buffer film 18, and the other small particles 16 may be attached to the surface of the large particles 14 through 1 or more small particles 16.

In addition, in the present embodiment, the mutual buffer film 18 covers at least the surface of the large particles 14 positioned between the small particles 16 existing around the large particles 14. Further, the mutual buffer film 18 may cover the surface of the large particles 14 between the small particles 16 existing around the large particles 14, and also cover the surface of the small particles 16.

< Large particle >

The large particles 14 in this embodiment have magnetic properties. The large particles 14 in the present embodiment are preferably metal magnetic particles or ferrite particles, more preferably metal magnetic particles, and further preferably contain Fe.

As the metal magnetic particles containing Fe, specifically, there can be exemplified: pure iron, carbonyl Fe, Fe-based alloy, Fe-Si-based alloy, Fe-Al-based alloy, Fe-Ni-based alloy, Fe-Si-Al-based alloy, Fe-Si-Cr-based alloy, Fe-Co-based alloy, Fe-based amorphous alloy, Fe-based nanocrystalline alloy, and the like.

Examples of the ferrite particles include ferrite particles of Ni-Cu system and the like.

In the present embodiment, a plurality of large particles 14 of the same material may be used as the large particles 14, or a plurality of large particles 14 of different materials may be mixed and formed. For example, a plurality of Fe-based alloy particles as the large particles 14 and a plurality of Fe — Si-based alloy particles as the large particles 14 may be used in combination.

The average particle diameter (R) of the large particles 14 of the present embodiment is preferably 400nm or more and 100000nm or less, and more preferably 3000nm or more and 30000nm or less. When the average particle diameter (R) of the large particles 14 is large, the permeability tends to be higher.

When the large particles 14 are composed of 2 or more kinds of large particles 14 made of different materials, the average particle size of the large particles 14 made of a certain material and the average particle size of the large particles 14 made of another material may be different from each other as long as they are within the above range.

Examples of the different material include a case where the elements constituting the metal or the alloy are different from each other, a case where the elements constituting the metal or the alloy are the same, and a case where the composition thereof is different from each other.

< Small particles >

The small particles 16 in this embodiment are smaller than the large particles 14. In the present embodiment, when the average particle diameter of the large particles 14 is R and the average particle diameter of the small particles 16 attached to the large particles 14 is R, (R/R) is 0.0012 or more and 0.025 or less, preferably 0.002 or more and 0.015 or less.

The average particle diameter (r) of the small particles 16 is 12nm to 100nm, preferably 12nm to 60 nm.

In the cross section of the composite particle 12, the length of the circumference of the large particle 14 is L, and as shown in fig. 1, the intervals between 2 small particles 16 adjacent to each other on the circumference of the large particle 14 are a1 and a2 … …. In this case, the coating ratio of the small particles 16 with respect to the large particles 14 is expressed as { L- (a1+ a2 … …) }/L. In the present embodiment, the coating rate of the small particles 16 with respect to the large particles 14 is preferably 30% or more and 100% or less.

The number of small particles 16 attached to the large particles 14 is not particularly limited. In the case where the cross section of the composite particle 12 is observed at a substantially diameter portion of the large particles 14, preferably 6 or more small particles 16 are observed, and more preferably 12 or more are observed.

In the present embodiment, the material of the small particles 16 is not particularly limited, but preferably has non-magnetic properties and insulating properties, and more preferably is SiO, for example₂Particles, TiO₂Particles of Al₂O₃Particles, SnO₂Particles, MgO particles, Bi₂O₃Particles, Y₂O₃Particles made of metal oxide or ferrite such as particles and/or CaO particles, and more preferably SiO₂And (3) granules.

In the present embodiment, as the small particles 16, a plurality of small particles 16 having the same material may be used, or a plurality of small particles 16 having different materials may be mixed together.

In addition, the D90 of the small particles 16 of the present embodiment is preferably smaller than the D10 of the large particles 14.

Here, D10 is the particle diameter of the particles whose cumulative frequency is 10% counted from the smaller particle diameter.

D90 is the particle size of particles whose cumulative frequency is 90% counted from the smaller particle size.

The D10 content of the large particles 14 can be measured by a particle size distribution measuring instrument such as a Laser diffraction particle size distribution measuring instrument HELOS (japan Laser, ltd.). D90 of the small particles 16 can be measured by a wet particle size distribution measuring instrument Zetasizer Nano ZS (Spectris corporation) or the like.

In the case where the small particles 16 are composed of 2 or more kinds of small particles 16 of different materials, the average particle diameter of the small particles 16 composed of a certain material and the average particle diameter of the small particles 16 composed of another material may be different.

< mutual buffer film >

In the present embodiment, the mutual buffer film 18 covers at least the surface of the large particles 14 located between the small particles 16 existing around the large particles 14.

In the present embodiment, when the average particle diameter of the small particles 16 is defined as r and the average thickness of the mutual buffer film 18 is defined as t, (t/r) is greater than 0 and 0.7 or less, preferably 0.1 or more and 0.5 or less.

The material of the mutual buffer film 18 of the present embodiment is not particularly limited, but it preferably has non-magnetic properties and insulating properties, and more preferably can impart rust prevention to the large particles 14. The mutual buffer film 18 of the present embodiment is preferably formed by a sol-gel method, and is preferably obtained by a sol-gel reaction in which one or both of a precursor of a metal alkoxide and a non-metal alkoxide are combined.

Examples of the precursor of the metal alkoxide include aluminate, titanate and zirconate, and examples of the non-metal alkoxide include alkoxysilanes and alkoxyborates, for example, Tetramethoxysilane (TMOS) and Tetraethoxysilane (TEOS). As the alkoxy group in the alkoxysilanes, an ethyl group, a methoxy group, a propoxy group, a butoxy group or other long-chain hydrocarbon alkoxy group can be used.

Specific examples of the material of the buffer film 18 of the present embodiment include TEOS, magnesium oxide, glass, resin, and phosphate such as zinc phosphate, calcium phosphate, or iron phosphate. The material of the mutual buffer film 18 of the present embodiment is preferably TEOS. This can further improve the withstand voltage.

The average thickness (t) of the buffer film 18 of the present embodiment is preferably greater than 0nm and not greater than 70nm, and more preferably not less than 5nm and not greater than 20 nm. Further, the average thickness of the mutual buffer film 18 is preferably smaller than the average particle diameter of the small particles 16. The thinner the thickness of the mutual buffer film 18, the higher the magnetic permeability tends to be, and the manufacturing cost can be reduced.

For example, when the mutual buffer film 18 is TEOS, the average thickness of the mutual buffer film 18 can be adjusted by changing the reaction time and reaction temperature between the large particles 14 and the mutual buffer film raw material liquid described later, or by changing the concentration of TEOS in the mutual buffer film raw material liquid.

< inductive element >

The composite particles 12 in the present embodiment can be used as particles constituting the magnetic core 6 of the inductance element 2 shown in fig. 2, for example. As shown in fig. 2, an inductance component 2 according to an embodiment of the present invention includes a winding portion 4 and a magnetic core 6. In the winding portion 4, the conductor 5 is wound in a coil shape. The magnetic core 6 is composed of particles and a binder.

As shown in fig. 3, the magnetic core 6 is formed by compressing, for example, the composite particles 12 and the binder 20. The magnetic core 6 is fixed in a predetermined shape by bonding the large particles 14 to each other with the adhesive 20 interposed therebetween. In fig. 3, the mutual buffer film 18 is not shown for simplicity, but in the composite particle 12 of fig. 3, the mutual buffer film 18 also covers at least the surface of the large particles 14 located between the small particles 16 existing around the large particles 14.

In the present embodiment, at least a part of the magnetic core 6 (for example, the central portion 6a1 of the magnetic core 6) may be constituted by the predetermined composite particles 12 shown in fig. 1, for example.

The predetermined composite particle 12 shown in fig. 1 is preferably 10 mass% to 99.5 mass% when the total amount of the particles constituting at least a part of the magnetic core 6 (for example, the central portion 6a1 of the magnetic core 6), the other particles, and the binder 20 is 100 mass%.

Here, the other particles are particles other than the predetermined composite particles 12 and the binder 20, particles having a composition different from that of the predetermined composite particles 12, particles in which the mutual buffer film 18 is not formed, and the like. Examples of the other particles include pure iron, carbonyl Fe, Fe-based alloys, Fe-Si-based alloys, Fe-Al-based alloys, Fe-Ni-based alloys, Fe-Si-Al-based alloys, Fe-Si-Cr-based alloys, Fe-Co-based alloys, Fe-based amorphous alloys, and Fe-based nanocrystalline alloys.

As the resin constituting the binder 20 of the magnetic core 6, a known resin can be used. Specifically, the following can be exemplified: epoxy resins, phenol resins, polyimide resins, polyamideimide resins, silicone resins, melamine resins, urea resins, furan resins, alkyd resins, unsaturated polyester resins, diallyl phthalate resins, and the like, with epoxy resins being preferred. The resin that serves as the binder of the magnetic core 6 may be a thermosetting resin or a thermoplastic resin, but is preferably a thermosetting resin.

By adopting the above-described structure, the composite particles 12 of the present embodiment are less likely to contact with each other even when molded at high pressure. As shown in fig. 3, this is because 1 or more small particles 16 smaller than the large particles 14 exist as spacers between the large particles 14. This enables a predetermined distance to be formed between the large particles 14, and the distance between the large particles 14 can be set to be constant or longer.

Further, "1 or more small particles 16 having a smaller particle size than the large particles 14 are present as spacers between the large particles 14" means: there are more than 1 small particle 16 attached directly or indirectly to the surface of one large particle 14 of the adjacent 2 large particles 14, and also attached directly or indirectly to the surface of another large particle 14. In addition, it also means: there are 1 or more small particles 16 directly or indirectly attached to the surface of one large particle 14 among the adjacent 2 large particles 14, and also directly or indirectly attached to the surface of another large particle 14 via other small particles 16.

For example, in fig. 3, in the spacer region 22 surrounded by the broken line, small particles 16 having a smaller particle size than the large particles 14 are present as spacers between the large particles 14.

Further, as shown in fig. 1, the surface of the large particles 14 is covered with the mutual buffer film 18, whereby the small particles 16 on the surface of the large particles 14 can be prevented from moving along the surface of the large particles 14 at the time of molding. This can further improve the reliability of the small particles 16 functioning as spacers between the large particles 14 when molded at high pressure. The mutual buffer film 18 of the present embodiment preferably covers the surfaces of each of the large particles 14 and the small particles 16 continuously, but does not necessarily need to be continuous.

As shown in fig. 3, the small particles 16 smaller than the large particles 14 are present as spacers between the large particles 14, so that a predetermined distance can be formed between the large particles 14 and the distance between the large particles 14 can be kept constant or longer. Therefore, even if the molding is performed at a high pressure, the large particles 14 are hard to contact with each other, and therefore, the large particles are prevented from being aggregated, the volume resistivity is increased, and the withstand voltage is increased.

In addition, by preventing large particles from contacting each other, concentration of a magnetic field can be prevented, and thus occurrence of magnetic saturation can be prevented. This is considered to improve the dc superimposition characteristics.

As described above, in the composite particle 12 of the present embodiment, since the small particles 16 and the mutual buffer film 18 adhering to the surface of the large particle 14 are less likely to be peeled off, the magnetic field concentration can be further prevented, and the occurrence of magnetic saturation can be further suppressed. As a result, the magnetic core 6 using such composite particles 12 tends to have higher dc superposition characteristics.

Also, by changing the average particle diameter of the small particles 16 attached to the surface of the large particles 14, the distance between the large particles 14 can be maintained as targeted and constantly. As a result, desired dc superimposition characteristics, withstand voltage, and magnetic permeability can be obtained, and the dc superimposition characteristics, withstand voltage, and magnetic permeability, which are product characteristics, can be stably adjusted.

In addition, the composite particle 12 of the present embodiment can be molded at a high pressure by adopting the above-described structure. Therefore, the magnetic permeability can be improved.

Further, by setting the average thickness of the mutual buffer films 18 within a predetermined range, high magnetic permeability can be secured, and manufacturing cost can be reduced.

In the present embodiment, since the distance between the large particles 14 is constant or longer by the small particles 16, the decrease in withstand voltage in a high-temperature environment can be suppressed. For example, the inductance element 2 is required to have a heat resistant temperature of 150 ℃ or higher in the vehicle-mounted application. In contrast, since the inductance element 2 having the cross section or the surface where the composite particles 12 of the present embodiment can be observed can suppress the decrease in withstand voltage even in a high-temperature environment as described above, it can be suitably used for the in-vehicle application having a heat resistant temperature of 150 ℃.

< method for producing composite particles >

Large particles 14 and small particles 16 are prepared such that the small particles 16 are attached to the surface of the large particles 14. The method for attaching the small particles 16 to the surface of the large particles 14 is not particularly limited, and for example, the small particles 16 may be attached to the surface of the large particles 14 by electrostatic adsorption, the small particles 16 may be attached to the surface of the large particles 14 by mechanochemical method, the small particles 16 may be attached to the surface of the large particles 14 by a method for depositing the small particles 16 on the surface of the large particles 14 by synthesis, or the small particles 16 may be attached to the large particles 14 via an organic material such as a resin.

In the present embodiment, it is preferable that the small particles 16 are attached to the surface of the large particles 14 by electrostatic adsorption. This is because, in the case of electrostatic adsorption, the small particles 16 can be attached to the surface of the large particles 14 by low energy. Compared to the mechanochemical method, electrostatic adsorption enables the small particles 16 to adhere to the surface of the large particles 14 by low energy, and thus strain of the particles is less likely to be generated, and thus magnetic core loss can be reduced. In addition, in the electrostatic adsorption, since the large particles 14 and the small particles 16 are charged oppositely and then adsorbed, there is an advantage that the amount of the small particles 16 attached to the large particles 14 can be easily controlled.

Next, the mutual buffer film 18 is formed on the large particles 14 to which the small particles 16 are attached. The method for forming the mutual buffer film 18 is not particularly limited, and for example, the large particles 14 to which the small particles 16 are attached are immersed in a solution in which a compound constituting the mutual buffer film 18, a precursor thereof, or the like is dissolved, or the solution is sprayed to the large particles 14 to which the small particles 16 are attached. Next, the large particles 14 and the small particles 16 to which the solution is attached are subjected to heat treatment or the like. This enables the formation of the mutual buffer film 18 on the large particles 14 and the small particles 16.

Specifically, the mutual buffer film 18 can be formed on the large particles 14 and the small particles 16 by the following method. First, large particles 14 to which small particles 16 are attached and a raw material liquid of a mutually buffered membrane are mixed.

Here, the raw material liquid of the buffer film is a liquid containing components constituting the buffer film 18. In the present embodiment, for example, when the mutual buffer film 18 is TEOS, a solution containing TEOS, water, ethanol, and hydrochloric acid can be used as the mutual buffer film raw material solution.

The mixed liquid of the large particles 14 with the small particles 16 attached and the raw material liquid of the mutual buffer membrane is heated in a closed pressure container, and the TEOS wet gel is obtained through sol-gel reaction. The heating temperature is not particularly limited, but is, for example, 20 to 80 ℃. The heating time is also not particularly limited, and is 5 to 10 hours. And further heating the TEOS wet gel at 65-75 ℃ for 5-24 hours to obtain dry gel, namely the composite particles 12.

< method for manufacturing magnetic core >

In the present embodiment, the magnetic core 6 is manufactured using the composite particles 12 described above.

As shown in fig. 2, the hollow coil formed by winding the above-described composite particles 12 and the conductor (wire) 5 a predetermined number of times is filled in a mold and compression-molded to obtain a molded body in which the coil is embedded. The compression method is not particularly limited, and the compression may be performed in one direction, or may be performed isotropically by WIP (Warm Isostatic pressing), CIP (Cold Isostatic pressing), or the like, but is preferably performed isotropically. This can achieve rearrangement of the large particles 14 and the small particles 16 and densification of the internal structure.

The large particles 14 and the small particles 16 are fixed by heat treatment of the obtained molded body, and the magnetic core 6 having a predetermined shape in which a coil is embedded is obtained. Such a magnetic core 6 has a coil embedded therein, and therefore functions as a coil-type electronic component such as the inductance element 2.

[ second embodiment ]

The present embodiment is the same as the composite particle 12 of the first embodiment except for the following. Although not shown, in the present embodiment, at least a part of the surface of the large particles 14 has a coating layer. The large particles 14 of the present embodiment can be prevented from being oxidized by having a coating layer in the manufacturing process of the magnetic core 6 shown in fig. 2. Further, by having the coating layer, a layer having non-magnetic properties and insulating properties can be provided on the surface of the large particles 14, and as a result, magnetic properties (dc superimposition properties and withstand voltage) can be improved.

The material of the coating layer is not particularly limited, and examples thereof include: TEOS, magnesium oxide, glass, resin, or phosphate such as zinc phosphate, calcium phosphate, or iron phosphate, TEOS is preferred. This can maintain the withstand voltage higher.

The coating covering the surface of the large particles 14 may cover at least a part of the surface of the large particles 14, but preferably covers the entire surface. Moreover, the coating may cover the surface of the large particles 14 continuously or may cover the surface of the large particles 14 intermittently.

Further, all of the large particles 14 may be uncoated, and for example, 50% or more of the large particles 14 may be coated.

In the case where the large particles 14 have a coating layer as in the present embodiment, the value described as the average particle diameter (R) of the large particles 14 in the first embodiment is understood to include a coating layer in the particle diameter of the large particles 14.

Similarly, in the case where the large particles 14 have a coating layer as in the present embodiment, the content described as D10 of the large particles 14 in the first embodiment is understood to include a coating layer in the particle size of the large particles 14.

The method for forming a coating layer on the surface of the large particles 14 is not particularly limited, and a known method can be used. For example, the coating layer can be formed by subjecting the large particles 14 to wet treatment.

Specifically, the large particles 14 are immersed in a solution in which a compound constituting the coating layer, a precursor thereof, or the like is dissolved, or the solution is sprayed to the large particles 14. Next, the large particles 14 to which the solution has adhered are subjected to heat treatment or the like. Thereby enabling the formation of a coating on the large particles 14.

With the composite particles 12 of the present embodiment having the above-described structure, even if the large particles are pressed against each other and deformed to cause peeling of the coating layer and cracking in the coating layer, the large particles 14 are less likely to contact each other. As shown in fig. 3, this is because small particles 16 smaller than the large particles 14 exist as spacers between the large particles 14. This enables a predetermined distance to be formed between the large particles 14, and the distance between the large particles 14 can be set to be constant or longer.

In this way, peeling and cracking of the insulating coating layer can be prevented, so that a decrease in volume resistivity can be further prevented, and the withstand voltage can be further improved.

In addition, the coating layer functions as a nonmagnetic layer, thereby making the dc bias characteristic more favorable. In the present embodiment, peeling and cracking of the coating layer can be prevented, and therefore, the dc superimposition characteristics tend to be higher.

In the present embodiment, since the large particles 14 and the coating layer have different linear expansion coefficients in a high-temperature environment, even if peeling or cracking occurs in the coating layer, the distance between the large particles 14 can be made constant or longer by the small particles 16, and therefore, a decrease in withstand voltage can be suppressed.

[ third embodiment ]

This embodiment is the same as the first embodiment except for the following. That is, although TEOS is used as the mutual buffer film 18 in the first embodiment, the mutual buffer film 18 is made of resin in the present embodiment. The method for forming the mutual buffer film in the present embodiment is not particularly limited. An example of a method of forming the mutual buffer film in the present embodiment is as follows.

The large particles 14 with the small particles 16 attached thereto and the resin-soluble solution in which the resin is dissolved are mixed to generate a first solution.

Next, a resin-insoluble solution is added to the first solution to produce a second solution. Here, the resin-insoluble solution is a solution that is insoluble in the resin dissolved in the previous step and soluble in the resin-soluble solution.

The second solution is generated by adding the resin-insoluble solution to the first solution, and the resin-soluble solution is dissolved in the resin-insoluble solution. Therefore, the resin dissolved in the resin-soluble solution can be deposited as the buffer film 18.

Next, the second solution is dried. This allows the precipitated mutual buffer film 18 (resin) to adhere to the surface of the large particles 14, and composite particles 12 in which the mutual buffer film 18 (resin) adheres to the surface of the large particles 14 can be obtained.

While the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments at all, and can be modified in various ways within the scope of the present invention.

For example, although the structure of the air-core coil in which the wound conductor 5 is embedded in the core 6 having a predetermined shape is shown as the inductance element 2 in fig. 2, the structure is not particularly limited, and any structure may be used as long as the conductor is wound on the surface of the core having a predetermined shape.

Further, as the shape of the core, the following can be exemplified: FT type, ET type, EI type, UU type, EE type, EER type, UI type, drum type, ring type, pot type, cup type, etc.

In addition, although the composite particles 12 used in the magnetic core 6 have been described above, the composite particles 12 of the present invention can be used not only in the magnetic core 6 but also in other electronic components including particles, for example, electronic components formed using dielectric paste, electrode paste, or the like, magnets including magnetic powder, lithium ion batteries, all solid state lithium batteries, or magnetic shielding sheets.

When the composite particles 12 of the present embodiment are used as dielectric particles of a dielectric paste, examples of the material of the large particles 14 include barium titanate, calcium titanate, strontium titanate, and the like, and examples of the material of the small particles 16 include silicon, a rare earth element, an alkaline earth metal, and the like.

When the composite particles 12 of the present embodiment are used as electrode particles of an electrode paste, examples of the material of the large particles 14 include Ni, Cu, Ag, Au, an alloy thereof, and carbon.

Examples

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

(example 1)

Large particles 14 are prepared, to which small particles 16 are attached to the surface by electrostatic adsorption.

The material of the large particles 14 is Fe, and the average particle size is 4000 nm.

The material of the small particles 16 is SiO₂The average particle size is shown in Table 1.

Next, a raw material liquid of a mutually buffered film containing TEOS, water, ethanol, and hydrochloric acid is prepared and mixed with large particles 14 to which small particles 16 are attached.

Here, the ratio of the average particle diameter r of the small particles 16 to the thickness t of the mutual buffer film, i.e., (t/r), is as shown in table 1, and the thickness of the mutual buffer film 18 is adjusted. Specifically, the thickness of the buffer film 18 is adjusted by adjusting the amount of the buffer film raw material liquid to be added, and the heating temperature and heating time described later.

The mixed liquid of the large particles 14 to which the small particles 16 are attached and the raw material liquid of the mutual buffer film is heated in a closed pressure vessel to obtain a TEOS wet gel. The heating temperature was set at 50 ℃ and the heating time was set at 8 hours. The wet gel of TEOS was further heated at about 100 ℃ for 1 week to obtain composite particles 12.

The epoxy resin was weighed so that the solid content of the epoxy resin was 3 parts by mass with respect to 100 parts by mass of the thus-obtained composite particles 12, and the composite particles 12 and the epoxy resin were mixed and stirred to produce particles.

The obtained pellets were charged in a mold having a predetermined ring shape and molded at a molding pressure of 6t/cm²The pressure of (3) was increased to obtain a molded body of a magnetic core. The molded article of the magnetic core thus produced was subjected to a heat curing treatment at 200 ℃ for 4 hours in the air to obtain a toroidal core (outer diameter 17mm, inner diameter 10 mm).

A copper wire was wound around the ring core in 32 turns to produce a sample.

The obtained sample was evaluated by applying a dc current from 0, setting the value (ampere) of the current flowing when the inductance (μ H) with respect to the current 0 was decreased to 80% as Idc1, and using the value of Idc 1. The case where Idc1 was 30.0A or more was evaluated as "a", the case where Idc1 was 20.0A or more and less than 30.0A was evaluated as "B", and the case where Idc1 was less than 20.0A was evaluated as "C". The results are shown in table 2.

A voltage was applied between the terminal electrodes of the obtained sample using a DC POWER SUPPLY and LCR meter made by KEYSIGHT, and the voltage when a current of 0.5mA was passed was set to a withstand voltage. The voltage resistance was evaluated as "A" when it exceeded 2.0kV, "B" when it was 1kV or more and less than 2.0kV, "C" when it was less than 1 kV. The results are shown in table 2.

The permeability of the obtained sample was measured by an LCR meter (LCR 428A, manufactured by HP). The magnetic permeability of 25 or more was evaluated as "a", the magnetic permeability of 20 or more and less than 25 was evaluated as "B", and the magnetic permeability of less than 20 was evaluated as "C". The results are shown in table 2.

The obtained sample was cut. The average thickness (t) of the cross buffer film 18 was measured by observing the portion of the core 6 on the cut surface with a Scanning Transmission Electron Microscope (STEM), and was 30 nm. In addition, the average coating rate of the small particles 16 in the same cross section with respect to the large particles 14 was 50%.

[ Table 1]

[ Table 2]

(example 2)

A sample was prepared and dc superposition characteristics, withstand voltage, and magnetic permeability were measured in the same manner as in example 1, except that the average particle size of the large particles 14 was 10000nm and the average particle size of the small particles 16 was as described in table 3. The results are shown in table 4.

[ Table 3]

[ Table 4]

From tables 1 to 4, it was confirmed that when (R/R) was 0.0012 or more and 0.025 or less, (t/R) was more than 0 and 0.7 or less, and R was 12nm or more and 100nm or less (sample numbers 3 to 7 and 13 to 16), the permeability ratio R was 200nm or more, and that when (R/R) was 0.030 or more (sample numbers 1, 2, and 11) was good.

From tables 1 to 4, it was confirmed that when (R/R) was 0.0012 or more and 0.025 or less, (t/R) was more than 0 and 0.7 or less, and R was 12nm or more and 100nm or less (sample numbers 3 to 7 and 13 to 16), the dielectric breakdown ratio R was 9nm or less, and that when t/R was 0.889 or more (sample numbers 8 and 17) was good.

(example 3)

The average particle diameter (R) of the large particles 14 was 4000nm, and the average thicknesses (t) of the small particles 16 and the mutual buffer film 18 were changed as shown in tables 5 and 7. In addition, the average thickness of the mutually buffered film 18 is adjusted by changing the reaction time of the mutually buffered film raw material liquid with respect to the large particles 14. Except for this, a sample was produced in the same manner as in example 1. The thickness and magnetic permeability of the mutual buffer film 18 were measured for the obtained sample in the same manner as in example 1.

The pressure resistance before heating (atmosphere at room temperature) and the pressure resistance after heating (atmosphere temperature 175 ℃ C.) were measured for the obtained samples in the same manner as in example 1. Further, the sample was left at 175 ℃ for 48 hours or more, then returned to room temperature, and the pressure resistance after heating was measured in an atmosphere of room temperature. In the present invention, the withstand voltage before heating is 2.0kV or more and the withstand voltage after heating is 1kV or more is evaluated as "a", the withstand voltage before heating is 1.8kV or more and less than 2.0kV, the withstand voltage after heating is 1kV or more is evaluated as "B", and the withstand voltage after heating is less than 1kV is evaluated as "C". The results are shown in tables 6 and 8.

[ Table 5]

[ Table 6]

[ Table 7]

[ Table 8]

From tables 5 to 8, it was confirmed that the permeability ratios of the case where R is 200nm (sample number 21) and the case where t/R is 0.83 (sample number 41) are higher in the cases where (R/R) is 0.0012 to 0.025 inclusive, (t/R) is greater than 0 to 0.7 inclusive, and R is 12nm to 100nm inclusive (sample numbers 22 to 26, 42 to 49).

Further, it can be confirmed from tables 5 to 8 that when (R/R) is 0.0012 to 0.025 inclusive, (t/R) is greater than 0 to 0.7 inclusive, and R is 12nm to 100nm inclusive (sample numbers 22 to 26, 42 to 49), a decrease in withstand voltage under a high-temperature environment can be suppressed as compared with when R is 9nm or less (sample numbers 27 to 35) and when (t/R) is 0 (sample number 50).

Description of the symbols

2 an inductance element; 4 winding parts; 5 a conductor; 6 magnetic cores; 6a1 center portion of magnetic core; 12 composite particles; 14 large particles; 16 small particles; 18 a mutual buffer film; 20 of a resin; 22 spacer regions.