阅读说明：本技术 焊膏和焊膏的制备方法 (Solder paste and method for producing solder paste ) 是由 陈显平 钱靖 李显东 檀春健 陶璐琪 喻佳兵 袁敏 李秋梅 李万杰 张旭 吴灵美 于 2019-11-27 设计创作，主要内容包括：本发明提供了一种焊膏和焊膏的制备方法,焊膏的组分包括：金属纳米颗粒、氧化石墨烯、抗坏血酸、分散剂、增稠剂和触变剂；其中,金属纳米颗粒包括纳米铜颗粒；金属纳米颗粒所占质量百分比的份数为75至85,氧化石墨烯所占质量百分比的份数为5至10,抗坏血酸所占质量百分比的份数为3至8,分散剂所占质量百分比的份数为2至8,增稠剂所占质量百分比的份数为2至8,触变剂所占质量百分比的份数为2至8。金属纳米颗粒具备了抗氧化性,可以有效地改善焊料层整体的导热、导电性能；少量其他纳米金属和还原氧化石墨烯对烧结后的焊料层缺陷能够进行有效的填充,减少焊料层整体的孔隙率,从而进一步提高焊料层整体的导电、散热和连接性能。(The invention provides a soldering paste and a preparation method thereof, and the components of the soldering paste comprise: metal nanoparticles, graphene oxide, ascorbic acid, a dispersant, a thickener, and a thixotropic agent; wherein the metal nanoparticles comprise nano-copper particles; the metal nano-particles account for 75 to 85 mass percent, the graphene oxide accounts for 5 to 10 mass percent, the ascorbic acid accounts for 3 to 8 mass percent, the dispersant accounts for 2 to 8 mass percent, the thickening agent accounts for 2 to 8 mass percent, and the thixotropic agent accounts for 2 to 8 mass percent. The metal nano particles have oxidation resistance, and can effectively improve the overall heat conduction and electric conduction of the solder layer; a small amount of other nano-metals and reduced graphene oxide can effectively fill the defects of the sintered solder layer, so that the overall porosity of the solder layer is reduced, and the overall conductivity, heat dissipation and connection performance of the solder layer are further improved.)

1. A solder paste, characterized in that the composition of the solder paste comprises:

metal nanoparticles, graphene oxide, ascorbic acid, a dispersant, a thickener, and a thixotropic agent;

wherein the metal nanoparticles comprise nano-copper particles;

the metal nanoparticles account for 75-85 parts by mass, the graphene oxide accounts for 5-10 parts by mass, the ascorbic acid accounts for 3-8 parts by mass, the dispersant accounts for 2-8 parts by mass, the thickener accounts for 2-8 parts by mass, and the thixotropic agent accounts for 2-8 parts by mass.

2. A solder paste according to claim 1, wherein the metal nanoparticles further comprise:

nano nickel particles and/or nano silver particles.

3. A solder paste according to claim 2, wherein the mass ratio of the nano copper particles to the nano nickel particles is 7: 1 to 7: 16, the mass ratio of the nano copper particles to the nano silver particles is 7: 1.

4. a solder paste according to claim 2,

the diameter of the nano copper particles is more than or equal to 30 nanometers and less than or equal to 80 nanometers;

the diameter of the nano nickel particles is more than or equal to 10 nanometers and less than or equal to 30 nanometers;

the diameter of the nano silver particles is more than or equal to 10 nanometers and less than or equal to 30 nanometers.

5. The solder paste according to any one of claims 1 to 4,

the dispersant is stearic acid or triethylhexylphosphoric acid; and/or

The thickening agent is phenolic resin; and/or

The thixotropic agent is polyvinyl alcohol.

6. A solder paste according to any one of claims 1 to 4, wherein a solid content accounts for 80% or more by mass in the solder paste.

7. A method for preparing a solder paste, comprising:

mixing ascorbic acid, graphene oxide and metal nanoparticles to obtain a first mixed solution;

drying the first mixed solution to obtain mixed powder;

mixing a thickening agent, a thixotropic agent, a dispersing agent and the mixed powder to obtain a second mixed solution;

drying the second mixed solution to obtain the soldering paste;

wherein the metal nanoparticles comprise nano-copper particles, and further comprising: nano nickel particles and/or nano silver particles.

8. The method for preparing a solder paste according to claim 7, wherein the step of mixing ascorbic acid, graphene oxide and metal nanoparticles to obtain a first mixed solution specifically comprises:

dissolving the ascorbic acid into pure water, and adding glacial acetic acid to obtain a third mixed solution;

magnetically stirring the third mixed solution for 15 to 20 minutes;

ultrasonically dispersing the third mixed solution for 1 to 5 minutes to obtain a reducing ascorbic acid aqueous solution;

mixing the reductive ascorbic acid aqueous solution, the graphene oxide and the metal nanoparticles to obtain a fourth mixed solution;

magnetically stirring the fourth mixed solution for 15 to 30 minutes;

ultrasonically dispersing the fourth mixed solution for 20 to 60 minutes to obtain the first mixed solution.

9. The method of preparing a solder paste according to claim 8, wherein before the step of mixing the aqueous reducing ascorbic acid solution, the graphene oxide, and the metal nanoparticles to obtain a fourth mixed solution, the method further comprises:

soaking the nano-copper particles in an acidic solution;

centrifugally separating the nano-copper particles after the soaking time reaches a preset time;

washing the nano-copper particles with pure water 3 to 5 times;

ultrasonically cleaning the nano-copper particles for 1 to 2 times by using ethanol;

and drying the nano copper particles in vacuum.

10. The method for preparing solder paste according to claim 7, wherein the step of mixing the thickener, the thixotropic agent, the dispersant and the mixed powder to obtain a second mixed solution specifically comprises:

mixing a thickener, a thixotropic agent, a dispersant and the mixed powder;

adding the mixed thickener, thixotropic agent, dispersant and mixed powder into ethanol;

ultrasonically dispersing and mechanically stirring the mixed thickener, the thixotropic agent, the dispersant, the mixed powder and the ethanol to obtain the second mixed solution.

Technical Field

The invention relates to the technical field of device welding, in particular to a soldering paste and a preparation method of the soldering paste.

Background

With the continuous improvement of the power density of the power device, the thermal reliability of the device becomes a difficult problem to be solved urgently in the field of power semiconductors. The device packaging mainly comprises two parts of electrical interconnection and plastic molding, wherein the electrical interconnection is the key point for directly influencing the normal work of the chip. Compared with a bonding lead on the upper surface of the chip, the contact area between the solder layer between the lower surface of the chip and the substrate and the chip is larger, and the heat conduction performance of the solder layer directly influences the performance and reliability of the chip. Therefore, finding a soldering material with excellent thermal, electrical and mechanical properties and a low melting point has been a hot research in the field of packaging technology.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art or the related art.

To this end, a first aspect of the present invention is to provide a solder paste.

In a second aspect of the present invention, a method for preparing a solder paste is provided.

In view of the above, a first aspect of the present invention provides a solder paste, the composition of which comprises: metal nanoparticles, graphene oxide, ascorbic acid, a dispersant, a thickener, and a thixotropic agent; wherein the metal nanoparticles comprise nano-copper particles; the metal nano-particles account for 75 to 85 mass percent, the graphene oxide accounts for 5 to 10 mass percent, the ascorbic acid accounts for 3 to 8 mass percent, the dispersant accounts for 2 to 8 mass percent, the thickening agent accounts for 2 to 8 mass percent, and the thixotropic agent accounts for 2 to 8 mass percent.

In the technical scheme, a solder paste is defined, and the components of the solder paste are specified. The solder paste comprises metal nanoparticles, graphene oxide, ascorbic acid, a dispersing agent, a thickening agent and a thixotropic agent. Specifically, the metal nanoparticles include nano-copper particles. By adding the graphene oxide and the small-particle-size metal nanoparticles, the graphene oxide can coat the metal nanoparticles, so that the metal nanoparticles in the soldering paste have oxidation resistance, and hydrogen and ascorbic acid can simultaneously react with the graphene oxide in the sintering process to generate hexagonal reduced graphene oxide, so that the overall heat conduction and electric conduction performance of the soldering paste layer can be effectively improved; meanwhile, the defects of the solder layer after the sintering of the nano copper can be effectively filled by a small amount of other nano metals and the reduced graphene oxide, and the overall porosity of the solder layer is reduced, so that the overall conductivity, heat dissipation and connection performance of the solder layer are further improved. In addition, the overall thermal expansion coefficient of the soldering paste can be effectively reduced by adding the graphene oxide, so that the thermal expansion coefficients of the soldering paste and the chip are more matched, and the stress transfer between the chip and the soldering flux layer is reduced.

Further, the proportion of each component in the solder paste is specifically limited. Wherein, the mass percentage of the metal nano particles in the soldering paste is 75 to 85; the mass percentage of the graphene oxide in the soldering paste is 5-10; the mass percentage of the ascorbic acid in the soldering paste is 3 to 8; the mass percentage of the dispersant in the solder paste is 2 to 8; the mass percentage of the thickening agent in the soldering paste is 2 to 8; the mass percentage of the thixotropic agent in the solder paste is 2 to 8. Through the specific proportion of each component, the overall heat conduction and electric conduction performance of the solder layer are effectively improved, the overall porosity of the solder layer is reduced, the overall heat dissipation performance and connection performance of the solder layer are improved, and the stress transfer between the chip and the solder layer is reduced.

In addition, the solder paste in the above technical solution provided by the present invention may further have the following additional technical features:

in the above technical solution, preferably, the solder paste according to claim 1, the metal nanoparticles further include: nano nickel particles and/or nano silver particles.

In the technical scheme, the metal nanoparticles are specifically limited. In the metal nano-particles, the nano-copper particles are essential metal nano-particles, and the rest metal nano-particles can be selected from nano-nickel particles and/or nano-silver particles. The metal nano copper particles have excellent heat conductivity and electric conductivity, the cost of the metal nano copper particles is low, and the cost of the soldering paste can be reduced on the premise of ensuring the performance of the soldering paste by selecting the metal nano copper particles. Through adding the nano nickel particles or the nano silver particles except the nano copper particles into the soldering paste, the nano nickel particles, the nano silver particles and the graphene oxide can effectively fill the defects of the nano copper layer in the sintering process by means of the reduced graphene oxide reduced in the graphene oxide sintering process, so that the transmission path is increased in the microcosmic aspect, and the overall conductivity, heat dissipation performance and mechanical strength of the soldering flux layer are enhanced in the macroscopic aspect.

In any of the above technical solutions, preferably, the mass ratio of the nano copper particles to the nano nickel particles is 7: 1 to 7: 16, the mass ratio of the nano copper particles to the nano silver particles is 7: 1.

in the technical scheme, the previous technical scheme is adopted, and the proportion of the metal nanoparticles is specifically limited. When the nano nickel particles are selected, the mass ratio of the nano copper particles to the nano nickel particles is 7: 1 to 7: 16. when the nano silver particles are selected, the mass ratio of the nano copper particles to the nano silver particles is 7: 1. through the quality ratio of injecing between the different kinds of metal nanoparticle, can guarantee that heat conductivity, electric conductivity and the mechanical connection nature of soldering paste are reliable and stable, in addition, can also reduce the manufacturing cost of product under the prerequisite of guarantee performance to promote the long time competitiveness of soldering paste.

In any of the above technical solutions, preferably, the diameter of the nano-copper particle is greater than or equal to 30 nanometers and less than or equal to 80 nanometers; the diameter of the nano nickel particles is more than or equal to 10 nanometers and less than or equal to 30 nanometers; the diameter of the nano silver particles is more than or equal to 10 nanometers and less than or equal to 30 nanometers.

In the technical scheme, the particle size of the metal nanoparticles is specifically limited. Wherein the diameter of the nano copper particles is more than or equal to 30 nanometers and less than or equal to 80 nanometers; the diameter of the nano nickel particles is more than or equal to 10 nanometers and less than or equal to 30 nanometers; the diameter of the nano silver particles is more than or equal to 10 nanometers and less than or equal to 30 nanometers. By limiting the diameter range of the metal nano-particles, the particle structure in the soldering paste can be optimized, and the stable and reliable performance of the soldering paste is ensured.

In any of the above embodiments, preferably, the dispersant is stearic acid or triethylhexylphosphoric acid; and/or the thickener is a phenolic resin; and/or the thixotropic agent is polyvinyl alcohol.

In the technical scheme, the types of the selected dispersing agent, the thickening agent and the thixotropic agent are specifically limited. Wherein stearic acid or triethyl hexyl phosphoric acid is selected as a dispersing agent, and the dispersing agent can uniformly disperse liquid particles and solid particles which are difficult to dissolve in liquid, thereby effectively preventing the metal nano particles from settling and coagulating to form stable suspension. Phenolic resin is selected as a thickening agent, and the thickening agent can enhance the paste viscosity and consistency of the soldering paste, so that the soldering paste can be kept in a uniform and stable suspension state. The polyvinyl alcohol is selected as the thixotropic agent, so that the thixotropy of the soldering paste can be improved, the consistency of the soldering paste is reduced when the soldering paste is sheared, and the consistency is increased when the shearing is stopped, so that the soldering paste can be more suitable for connecting a chip and a soldering flux layer, the defects of the soldering flux layer are effectively filled, and the heat conductivity and the electric conductivity of the soldering paste are further improved.

In any of the above technical solutions, preferably, the mass percentage of the solid component in the solder paste is greater than or equal to 80%.

In the technical scheme, the solid-liquid ratio in the soldering paste is specifically limited, and all solid components in the prepared soldering paste account for more than or equal to 80% by mass. Through the solid component and the liquid component mass ratio of injecing in the soldering paste, guaranteed the stability and the reliability of soldering paste, avoid appearing because of the soldering paste inefficacy or the impaired technical problem of welding effect that the inside solid-liquid ratio of soldering paste arouses, and then realize promoting the technical effect of product stability and reliability.

A second aspect of the present invention provides a method for producing a solder paste, the method comprising: mixing ascorbic acid, graphene oxide and metal nanoparticles to obtain a first mixed solution; drying the first mixed solution to obtain mixed powder; mixing a thickening agent, a thixotropic agent, a dispersing agent and mixed powder to obtain a second mixed solution; drying the second mixed solution to obtain soldering paste; wherein, the metal nanoparticle includes nanometer copper particle, still includes: nano nickel particles and/or nano silver particles.

In the technical scheme, in the preparation process of the soldering paste, firstly, ascorbic acid, graphene oxide and metal nanoparticles are mixed together to form a first mixed solution, then, the first mixed solution is dried to remove liquid in the first mixed solution to obtain mixed powder, then, a thickening agent, a thixotropic agent, a dispersing agent and the mixed powder are mixed together to form a second mixed solution, and finally, the second mixed solution is dried to remove redundant liquid in the second mixing, so that the soldering paste defined by the application is obtained. Specifically, the metal nanoparticles include copper nanoparticles, and further include: nano nickel particles and/or nano silver particles. Through mixing into graphite oxide in the soldering paste, make graphite oxide can carry out the cladding to metal nanoparticle, metal nanoparticle in the messenger soldering paste has possessed the oxidation resistance, through adding nano-nickel granule or nano-silver granule except that nano-copper granule in to the soldering paste, make nano-nickel granule, nano-silver granule and graphite oxide can effectively fill the defect on nanometer copper layer with the help of the reduction oxidation graphite oxide that reduces into in the graphite oxide sintering process in the sintering process, thereby increase transmission path in the microcosmic, reinforcing whole electric conductivity, heat dispersion and the mechanical strength of solder layer in the macroscopical.

In any of the above technical solutions, preferably, the step of mixing ascorbic acid, graphene oxide, and metal nanoparticles to obtain a first mixed solution specifically includes: dissolving ascorbic acid in pure water, and adding glacial acetic acid to obtain a third mixed solution; magnetically stirring the third mixed solution for 15 to 20 minutes; ultrasonically dispersing the third mixed solution for 1 to 5 minutes to obtain a reducing ascorbic acid aqueous solution; mixing a reducing ascorbic acid aqueous solution, graphene oxide and metal nanoparticles to obtain a fourth mixed solution; magnetically stirring the fourth mixed solution for 15 to 30 minutes; and ultrasonically dispersing the fourth mixed solution for 20 to 60 minutes to obtain a first mixed solution.

In the technical scheme, the step of mixing ascorbic acid, graphene oxide and metal nanoparticles to obtain a first mixed solution is specifically limited. The method comprises the following steps: firstly, dissolving ascorbic acid in deionized pure water, and then adding a proper amount of glacial acetic acid to adjust the overall pH value of the solution to obtain a third mixed solution; secondly, magnetically stirring the third mixed solution for 15 to 20 minutes, and then ultrasonically dispersing the third mixed solution for 1 to 5 minutes to obtain a uniformly dispersed reductive ascorbic acid aqueous solution; finally, mixing the reducing ascorbic acid aqueous solution, the graphene oxide and the metal nanoparticles together to obtain a fourth mixed solution, magnetically stirring the fourth mixed solution for 15-30 minutes, and ultrasonically dispersing the fourth mixed solution for 20-60 minutes to obtain the first mixed solution.

In any of the above technical solutions, preferably, before the step of mixing the reducing ascorbic acid aqueous solution, the graphene oxide, and the metal nanoparticles to obtain the fourth mixed solution, the preparation method further includes: soaking the nano-copper particles in an acidic solution; centrifugally separating nano copper particles after the soaking time reaches a preset time; washing the nano-copper particles with pure water for 3 to 5 times; ultrasonically cleaning the nano-copper particles by using ethanol for 1 to 2 times; and (4) drying the nano copper particles in vacuum.

In the technical scheme, before the step of mixing the reducing ascorbic acid aqueous solution, the graphene oxide and the metal nanoparticles, the nano-copper particles are subjected to a deoxidation treatment. The method comprises the following steps: firstly, pouring powder of nano-copper particles into an acidic solution to dissolve oxides and impurities on the nano-copper particles through the acidic solution, and centrifugally separating the nano-copper particles through a centrifugal separator after the nano-copper particles are soaked for a preset time; and then, washing the nano-copper particles for 3 to 5 times by using deionized pure water, then ultrasonically washing the nano-copper particles for 1 to 2 times by using absolute ethyl alcohol, and finally drying the nano-copper particles in vacuum to obtain pure and impurity-free nano-copper particle powder.

In any of the above technical solutions, preferably, the step of mixing the thickener, the thixotropic agent, the dispersant and the mixed powder to obtain the second mixed solution specifically includes: mixing a thickening agent, a thixotropic agent, a dispersing agent and mixed powder; adding the mixed thickener, thixotropic agent, dispersant and mixed powder into ethanol; ultrasonically dispersing and mechanically stirring and mixing the thickening agent, the thixotropic agent, the dispersing agent, the mixed powder and the ethanol to obtain a second mixed solution.

In this embodiment, the step of mixing the thickener, the thixotropic agent, the dispersant and the mixed powder to obtain the second mixed solution is specifically defined. The method comprises the following steps: firstly, mixing a thickening agent, a thixotropic agent, a dispersing agent and mixed powder together in proportion, and then adding the mixed thickening agent, thixotropic agent, dispersing agent and mixed powder into absolute ethyl alcohol; thereafter, the step of ultrasonic dispersion-mechanical stirring-ultrasonic dispersion is performed on the mixed thickener, thixotropic agent, dispersant, mixed powder and ethanol to obtain a second mixed solution.

Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

fig. 1 shows a flowchart of a method of manufacturing a solder paste according to an embodiment of the present invention;

fig. 2 shows a flowchart of a method for producing a solder paste according to another embodiment of the present invention;

fig. 3 shows a flowchart of a method of manufacturing a solder paste according to still another embodiment of the present invention;

fig. 4 is a flowchart showing a method of manufacturing a solder paste according to still another embodiment of the present invention;

fig. 5 is a schematic flow chart showing a method for producing a solder paste according to still another embodiment of the present invention;

fig. 6 illustrates a schematic view of a package structure of a solder paste provided according to an embodiment of the present invention;

fig. 7 shows a microscopic view of a solder paste provided according to an embodiment of the present invention;

fig. 8 shows a schematic view of nano-copper particles in a solder paste provided according to an embodiment of the invention as shown in fig. 5;

fig. 9 shows a schematic view of other nano-metal particles in a solder paste provided according to an embodiment of the invention as shown in fig. 5;

fig. 10 shows a microscopic view of a solder paste provided according to another embodiment of the present invention.

Wherein, the correspondence between the reference numbers and the part names in fig. 6 to 10 is:

1 soldering paste, 10 nano-copper particles, 12 other metal nano-particles, 14 graphene oxide, 16 reduced graphene oxide, 3 chips and 5 copper substrates.

Detailed Description

In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings. It should be noted that the embodiments and features of the embodiments of the present application may be combined with each other without conflict.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described herein, and therefore the scope of the present invention is not limited by the specific embodiments disclosed below.

A solder paste and a method of preparing the solder paste according to some embodiments of the present invention are described below with reference to fig. 1 to 10.

In an embodiment of the first aspect of the present invention, there is provided a solder paste, the composition of which includes: metal nanoparticles, graphene oxide, ascorbic acid, a dispersant, a thickener, and a thixotropic agent; wherein the metal nanoparticles comprise nano-copper particles; the metal nano-particles account for 75 to 85 mass percent, the graphene oxide accounts for 5 to 10 mass percent, the ascorbic acid accounts for 3 to 8 mass percent, the dispersant accounts for 2 to 8 mass percent, the thickening agent accounts for 2 to 8 mass percent, and the thixotropic agent accounts for 2 to 8 mass percent.

In this embodiment, a solder paste is defined, and the composition of the solder paste is specified. The solder paste comprises metal nanoparticles, graphene oxide, ascorbic acid, a dispersing agent, a thickening agent and a thixotropic agent. Specifically, the metal nanoparticles include nano-copper particles. By adding the graphene oxide and the small-particle-size metal nanoparticles, the graphene oxide can coat the metal nanoparticles, so that the metal nanoparticles in the soldering paste have oxidation resistance, and hydrogen and ascorbic acid can simultaneously react with the graphene oxide in the sintering process to generate hexagonal reduced graphene oxide, so that the overall heat conduction and electric conduction performance of the soldering paste layer can be effectively improved; meanwhile, the defects of the solder layer after the sintering of the nano copper can be effectively filled by a small amount of other nano metals and the reduced graphene oxide, and the overall porosity of the solder layer is reduced, so that the overall conductivity, heat dissipation and connection performance of the solder layer are further improved. In addition, the overall thermal expansion coefficient of the soldering paste can be effectively reduced by adding the graphene oxide, so that the thermal expansion coefficients of the soldering paste and the chip are more matched, and the stress transfer between the chip and the soldering flux layer is reduced.

Further, the proportion of each component in the solder paste is specifically limited. Wherein, the mass percentage of the metal nano particles in the soldering paste is 75 to 85; the mass percentage of the graphene oxide in the soldering paste is 5-10; the mass percentage of the ascorbic acid in the soldering paste is 3 to 8; the mass percentage of the dispersant in the solder paste is 2 to 8; the mass percentage of the thickening agent in the soldering paste is 2 to 8; the mass percentage of the thixotropic agent in the solder paste is 2 to 8. Through the specific proportion of each component, the overall heat conduction and electric conduction performance of the solder layer are effectively improved, the overall porosity of the solder layer is reduced, the overall heat dissipation performance and connection performance of the solder layer are improved, and the stress transfer between the chip and the solder layer is reduced.

In an embodiment of the present invention, further, according to the solder paste of claim 1, the metal nanoparticles further comprise: nano nickel particles and/or nano silver particles.

In this embodiment, the metal nanoparticles are specifically defined. In the metal nano-particles, the nano-copper particles are essential metal nano-particles, and the rest metal nano-particles can be selected from nano-nickel particles and/or nano-silver particles. The metal nano copper particles have excellent heat conductivity and electric conductivity, the cost of the metal nano copper particles is low, and the cost of the soldering paste can be reduced on the premise of ensuring the performance of the soldering paste by selecting the metal nano copper particles. Through adding the nano nickel particles or the nano silver particles except the nano copper particles into the soldering paste, the nano nickel particles, the nano silver particles and the graphene oxide can effectively fill the defects of the nano copper layer in the sintering process by means of the reduced graphene oxide reduced in the graphene oxide sintering process, so that the transmission path is increased in the microcosmic aspect, and the overall conductivity, heat dissipation performance and mechanical strength of the soldering flux layer are enhanced in the macroscopic aspect.

In one embodiment of the present invention, further, the mass ratio of the nano copper particles to the nano nickel particles is 7: 1 to 7: 16, the mass ratio of the nano copper particles to the nano silver particles is 7: 1.

in this embodiment, the above technical solution is adopted, and the ratio of the metal nanoparticles is specifically limited. When the nano nickel particles are selected, the mass ratio of the nano copper particles to the nano nickel particles is 7: 1 to 7: 16. when the nano silver particles are selected, the mass ratio of the nano copper particles to the nano silver particles is 7: 1. through the quality ratio of injecing between the different kinds of metal nanoparticle, can guarantee that heat conductivity, electric conductivity and the mechanical connection nature of soldering paste are reliable and stable, in addition, can also reduce the manufacturing cost of product under the prerequisite of guarantee performance to promote the long time competitiveness of soldering paste.

In one embodiment of the present invention, further, the diameter of the nano-copper particle is greater than or equal to 30 nanometers and less than or equal to 80 nanometers; the diameter of the nano nickel particles is more than or equal to 10 nanometers and less than or equal to 30 nanometers; the diameter of the nano silver particles is more than or equal to 10 nanometers and less than or equal to 30 nanometers.

In this embodiment, the particle diameter in the metal nanoparticles is specifically defined. Wherein the diameter of the nano copper particles is more than or equal to 30 nanometers and less than or equal to 80 nanometers; the diameter of the nano nickel particles is more than or equal to 10 nanometers and less than or equal to 30 nanometers; the diameter of the nano silver particles is more than or equal to 10 nanometers and less than or equal to 30 nanometers. By limiting the diameter range of the metal nano-particles, the particle structure in the soldering paste can be optimized, and the stable and reliable performance of the soldering paste is ensured.

In one embodiment of the present invention, further, the dispersant is stearic acid or triethylhexylphosphoric acid; and/or the thickener is a phenolic resin; and/or the thixotropic agent is polyvinyl alcohol.

In this example, the kinds of the dispersing agent, the thickening agent and the thixotropic agent selected are specifically defined. Wherein stearic acid or triethyl hexyl phosphoric acid is selected as a dispersing agent, and the dispersing agent can uniformly disperse liquid particles and solid particles which are difficult to dissolve in liquid, thereby effectively preventing the metal nano particles from settling and coagulating to form stable suspension. Phenolic resin is selected as a thickening agent, and the thickening agent can enhance the paste viscosity and consistency of the soldering paste, so that the soldering paste can be kept in a uniform and stable suspension state. The polyvinyl alcohol is selected as the thixotropic agent, so that the thixotropy of the soldering paste can be improved, the consistency of the soldering paste is reduced when the soldering paste is sheared, and the consistency is increased when the shearing is stopped, so that the soldering paste can be more suitable for connecting a chip and a soldering flux layer, the defects of the soldering flux layer are effectively filled, and the heat conductivity and the electric conductivity of the soldering paste are further improved.

In one embodiment of the present invention, further, the solid content accounts for 80% or more by mass of the solder paste.

In this embodiment, the solid-liquid ratio in the solder paste is specifically defined, and the mass percentage of all solid components in the prepared solder paste is greater than or equal to 80%. Through the solid component and the liquid component mass ratio of injecing in the soldering paste, guaranteed the stability and the reliability of soldering paste, avoid appearing because of the soldering paste inefficacy or the impaired technical problem of welding effect that the inside solid-liquid ratio of soldering paste arouses, and then realize promoting the technical effect of product stability and reliability.

As shown in fig. 1, in an embodiment of a second aspect of the present invention, there is provided a method of manufacturing a solder paste, the method of manufacturing a solder paste including:

step S102, mixing ascorbic acid, graphene oxide and metal nanoparticles to obtain a first mixed solution;

step S104, drying the first mixed solution to obtain mixed powder;

step S106, mixing a thickening agent, a thixotropic agent, a dispersing agent and mixed powder to obtain a second mixed solution;

and step S108, drying the second mixed solution to obtain the soldering paste.

Wherein, the metal nanoparticle includes nanometer copper particle, still includes: nano nickel particles and/or nano silver particles.

In this embodiment, in the preparation process of the solder paste, the ascorbic acid, the graphene oxide and the metal nanoparticles are mixed together to form a first mixed solution, then the first mixed solution is subjected to a drying treatment to remove the liquid in the first mixed solution to obtain a mixed powder, then the thickener, the thixotropic agent, the dispersant and the mixed powder are mixed together to form a second mixed solution, and finally the second mixed solution is subjected to a drying treatment to remove the excessive liquid in the second mixing, so as to obtain the solder paste defined in the present application. Specifically, the metal nanoparticles include copper nanoparticles, and further include: nano nickel particles and/or nano silver particles. Through mixing into graphite oxide in the soldering paste, make graphite oxide can carry out the cladding to metal nanoparticle, metal nanoparticle in the messenger soldering paste has possessed the oxidation resistance, through adding nano-nickel granule or nano-silver granule except that nano-copper granule in to the soldering paste, make nano-nickel granule, nano-silver granule and graphite oxide can effectively fill the defect on nanometer copper layer with the help of the reduction oxidation graphite oxide that reduces into in the graphite oxide sintering process in the sintering process, thereby increase transmission path in the microcosmic, reinforcing whole electric conductivity, heat dispersion and the mechanical strength of solder layer in the macroscopical.

In an embodiment of the present invention, further, as shown in fig. 2, a method for preparing a solder paste includes:

step S202, dissolving ascorbic acid in pure water, and adding glacial acetic acid to obtain a third mixed solution;

step S204, magnetically stirring the third mixed solution for 15 to 20 minutes;

step S206, ultrasonically dispersing the third mixed solution for 1 to 5 minutes to obtain a reducing ascorbic acid aqueous solution;

step S208, mixing a reducing ascorbic acid aqueous solution, graphene oxide and metal nanoparticles to obtain a fourth mixed solution;

step S210, magnetically stirring the fourth mixed solution for 15 to 30 minutes;

step S212, ultrasonically dispersing the fourth mixed solution for 20-60 minutes to obtain a first mixed solution;

step S214, drying the first mixed solution to obtain mixed powder;

step S216, mixing a thickening agent, a thixotropic agent, a dispersing agent and mixed powder to obtain a second mixed solution;

step S218, drying the second mixed solution to obtain a solder paste.

In this embodiment, the step of mixing ascorbic acid, graphene oxide, and metal nanoparticles to obtain a first mixed solution is specifically defined. The method comprises the following steps: firstly, dissolving ascorbic acid in deionized pure water, and then adding a proper amount of glacial acetic acid to adjust the overall pH value of the solution to obtain a third mixed solution; secondly, magnetically stirring the third mixed solution for 15 to 20 minutes, and then ultrasonically dispersing the third mixed solution for 1 to 5 minutes to obtain a uniformly dispersed reductive ascorbic acid aqueous solution; finally, mixing the reducing ascorbic acid aqueous solution, the graphene oxide and the metal nanoparticles together to obtain a fourth mixed solution, magnetically stirring the fourth mixed solution for 15-30 minutes, and ultrasonically dispersing the fourth mixed solution for 20-60 minutes to obtain the first mixed solution.

In an embodiment of the present invention, further, as shown in fig. 3, a method for preparing a solder paste includes:

step S302, dissolving ascorbic acid in pure water, and adding glacial acetic acid to obtain a third mixed solution;

step S304, magnetically stirring the third mixed solution for 15 to 20 minutes;

s306, ultrasonically dispersing the third mixed solution for 1 to 5 minutes to obtain a reducing ascorbic acid aqueous solution;

step S308, soaking the nano-copper particles in an acid solution;

step S310, centrifugally separating out nano-copper particles after the soaking time reaches a preset time;

step S312, washing the nano-copper particles for 3 to 5 times by using pure water;

step S314, ultrasonically cleaning the nano-copper particles for 1 to 2 times by using ethanol;

step S316, drying the nano-copper particles in vacuum;

step S318, mixing the reducing ascorbic acid aqueous solution, the graphene oxide and the metal nanoparticles to obtain a fourth mixed solution;

step S320, magnetically stirring the fourth mixed solution for 15 to 30 minutes;

step S322, ultrasonically dispersing the fourth mixed solution for 20-60 minutes to obtain a first mixed solution;

step S324, drying the first mixed solution to obtain mixed powder;

step S326, mixing a thickening agent, a thixotropic agent, a dispersing agent and mixed powder to obtain a second mixed solution;

step S328, drying the second mixed solution to obtain a solder paste.

In this embodiment, the nano-copper particles are subjected to a deoxidation treatment before the step of mixing the reducing ascorbic acid aqueous solution, the graphene oxide, and the metal nano-particles. The method comprises the following steps: firstly, pouring powder of nano-copper particles into an acidic solution to dissolve oxides and impurities on the nano-copper particles through the acidic solution, and centrifugally separating the nano-copper particles through a centrifugal separator after the nano-copper particles are soaked for a preset time; and then, washing the nano-copper particles for 3 to 5 times by using deionized pure water, then ultrasonically washing the nano-copper particles for 1 to 2 times by using absolute ethyl alcohol, and finally drying the nano-copper particles in vacuum to obtain pure and impurity-free nano-copper particle powder.

In an embodiment of the present invention, further, as shown in fig. 4, a method for preparing a solder paste includes:

step S402, mixing ascorbic acid, graphene oxide and metal nanoparticles to obtain a first mixed solution;

step S404, drying the first mixed solution to obtain mixed powder;

step S406, mixing a thickening agent, a thixotropic agent, a dispersing agent and mixed powder;

step S408, adding the mixed thickener, thixotropic agent, dispersant and mixed powder into ethanol;

step S410, ultrasonically dispersing and mechanically stirring and mixing the thickening agent, the thixotropic agent, the dispersing agent, the mixed powder and the ethanol to obtain a second mixed solution;

step S412, drying the second mixed solution to obtain a solder paste.

In this example, the step of mixing the thickener, the thixotropic agent, the dispersant and the mixed powder to obtain the second mixed solution is specifically defined. The method comprises the following steps: firstly, mixing a thickening agent, a thixotropic agent, a dispersing agent and mixed powder together in proportion, and then adding the mixed thickening agent, thixotropic agent, dispersing agent and mixed powder into absolute ethyl alcohol; thereafter, the step of ultrasonic dispersion-mechanical stirring-ultrasonic dispersion is performed on the mixed thickener, thixotropic agent, dispersant, mixed powder and ethanol to obtain a second mixed solution.

In the first embodiment of the present invention, as shown in fig. 5 and 6, the present invention will be described in detail in conjunction with a specific method of adding a small amount of nano silver having a particle size of 10 to 30nm to a solder paste 1:

the method comprises the following steps: measuring an ascorbic acid solution, placing ascorbic acid and glacial acetic acid in a reaction beaker, dissolving in deionized water, magnetically stirring for 5min, ultrasonically dispersing for 10min, and preparing a reducing agent solution.

Step two: according to the mass ratio of the reducing agent solution to the nano copper of 5: 1, weighing nano copper, and dissolving the nano copper in a reducing agent solution.

Step three: according to the mass ratio of nano copper to graphene oxide of 10: 1, weighing graphene oxide, and dissolving the graphene oxide in a reducing agent solution.

Step four: according to the mass ratio of nano copper to nano silver of 5: 1, weighing nano silver, and dissolving the nano silver in a reducing agent solution.

Step five: and magnetically stirring the reducing agent solution for 15min, and performing ultrasonic treatment for 10min to obtain a uniformly dispersed solution.

Step six: vacuum drying at room temperature for 2 hours to obtain the mixed powder of the ascorbic acid, a small amount of nano silver and the nano copper coated by the graphene oxide.

Step seven: mixing the mixed powder obtained in the step six with stearic acid, phenolic resin and polyvinyl alcohol according to the mass ratio of 16: 2: 2: 1 and mixing.

Step eight: vacuum drying is carried out for 0.5 hour at room temperature, and the graphene oxide-containing soldering paste 1 with the solid mass ratio of more than 80% is obtained.

Step nine: a square solder paste 1 having a thickness of 80 μm and a size of 13.5mm × 13.5mm was printed on the copper substrate 5 by screen printing, and a chip 3 having the same size was precisely placed on the solder layer.

Step ten: placing a sample piece to be sintered in a hot press, vertically applying a pressure of 0.5MPa, introducing hydrogen with a gas flow rate of 12ml/min and helium with a gas flow rate of 88ml/min, heating to 140 ℃ for sintering for 20min, then heating to 280 ℃ for sintering for 30min, and then cooling to obtain the sintered sample piece, wherein the shear strength of a solder layer is more than 8.5MPa, and the overall thermal resistance is less than 0.2K/W.

In a second embodiment of the present invention, as shown in fig. 5 and 6, the present embodiment describes the present invention in detail in conjunction with a specific method of adding a small amount of nano nickel having a particle size of 10 to 30nm to a solder paste 1:

the method comprises the following steps: measuring an ascorbic acid solution, placing ascorbic acid and glacial acetic acid in a reaction beaker, dissolving in deionized water, magnetically stirring for 5min, ultrasonically dispersing for 10min, and preparing a reducing agent solution.

Step two: according to the mass ratio of the reducing agent solution to the nano copper of 5: 1, weighing nano copper, and dissolving the nano copper in a reducing agent solution.

Step three: according to the mass ratio of nano copper to graphene oxide of 10: 1, weighing graphene oxide, and dissolving the graphene oxide in a reducing agent solution.

Step four: according to the mass ratio of nano copper to nano nickel of 5: 1, weighing nano nickel, and dissolving the nano nickel in a reducing agent solution.

Step five: and magnetically stirring the reducing agent solution for 15min, and performing ultrasonic treatment for 10min to obtain a uniformly dispersed solution.

Step six: vacuum drying at room temperature for 2 hours to obtain the mixed powder of the ascorbic acid, a small amount of nano nickel and the nano copper coated by the graphene oxide.

Step seven: mixing the mixed powder obtained in the step six with stearic acid, phenolic resin and polyvinyl alcohol according to the mass ratio of 16: 2: 2: 1 and mixing.

Step eight: vacuum drying is carried out for 0.5 hour at room temperature, and the graphene oxide-containing soldering paste 1 with the solid mass ratio of more than 80% is obtained.

Step nine: a square solder paste 1 with the thickness of 80 microns and the size of 13.5mm × 13.5mm is printed on the copper substrate 5 by screen printing, and a chip 3 with the same size is accurately placed on the solder layer, and the packaging structure is shown in fig. 3.

Step ten: placing a sample piece to be sintered in a hot press, vertically applying pressure of 0.5MPa, introducing hydrogen with gas flow rate of 15ml/min and helium with gas flow rate of 85ml/min, heating to 140 ℃ for sintering for 20min, heating to 280 ℃ for sintering for 30min, and cooling to obtain the sintered sample piece, wherein the shear strength of a solder layer is more than 10MPa, and the overall thermal resistance is less than 0.22K/W.

In the third embodiment of the present invention, as shown in fig. 5 and 6, the present embodiment describes the present invention in detail in conjunction with a specific method of adding a small amount of nano silver-nano nickel mixed powder (mass ratio 1: 1) having a particle size of 10 to 30nm to the solder paste 1:

the method comprises the following steps: measuring an ascorbic acid solution, placing ascorbic acid and glacial acetic acid in a reaction beaker, dissolving in deionized water, magnetically stirring for 5min, ultrasonically dispersing for 10min, and preparing a reducing agent solution.

Step two: according to the mass ratio of the reducing agent solution to the nano copper of 5: 1, weighing nano copper, and dissolving the nano copper in a reducing agent solution.

Step three: according to the mass ratio of nano copper to graphene oxide of 10: 1, weighing graphene oxide, and dissolving the graphene oxide in a reducing agent solution.

Step four: according to the mass ratio of nano copper to nano silver-nano nickel mixture of 5: 1, weighing the nano silver-nano nickel mixture, and dissolving the mixture in a reducing agent solution.

Step five: and magnetically stirring the reducing agent solution for 15min, and performing ultrasonic treatment for 10min to obtain a uniformly dispersed solution.

Step six: vacuum drying at room temperature for 2 hours to obtain the mixed powder of ascorbic acid, a small amount of nano silver-nano nickel mixture and nano copper coated by graphene oxide.

Step seven: mixing the mixed powder obtained in the step six with stearic acid, phenolic resin and polyvinyl alcohol according to the mass ratio of 16: 2: 2: 1 and mixing.

Step eight: vacuum drying is carried out for 0.5 hour at room temperature, and the graphene oxide-containing soldering paste 1 with the solid mass ratio of more than 80% is obtained.

Step nine: a square solder paste 1 with the thickness of 80 microns and the size of 13.5mm × 13.5mm is printed on the copper substrate 5 by screen printing, and a chip 3 with the same size is accurately placed on the solder layer, and the packaging structure is shown in fig. 3.

Step ten: placing a sample piece to be welded in a hot press, vertically applying 5MPa pressure, introducing hydrogen with the gas flow rate of 25ml/min and helium with the gas flow rate of 75ml/min, heating to 140 ℃ for sintering for 20min, then heating to 300 ℃ for sintering for 30min, and then cooling to obtain the sintered sample piece, wherein the shear strength of a solder layer is greater than 28MPa, and the overall thermal resistance is less than 0.19K/W.

In the fourth embodiment of the present invention, as shown in fig. 7, the nano-copper particles 10 are uniformly dispersed in the solder paste 1 in a state where the solder paste 1 is not used (sintered), and the other metal nano-particles 12 are filled in the gaps between the nano-copper particles 10.

As shown in fig. 8, the exterior of the nano-copper particle 10 is wrapped with graphene oxide 14.

As shown in fig. 9, the other metal nanoparticles 12 are externally wrapped with graphene oxide 14.

As shown in fig. 10, after the soldering paste 1 completes the connection (sintering) of the chip, the graphene oxide outside the nano-copper particles 10 and the other metal nano-particles 12 is sintered into granular reduced graphene oxide 16.

In the present invention, the terms "mounting," "connecting," "fixing," and the like are used in a broad sense, for example, "connecting" may be a fixed connection, a detachable connection, or an integral connection; "coupled" may be direct or indirect through an intermediary. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the description herein, the description of the terms "one embodiment," "some embodiments," "specific embodiments," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.