Brazing electronic paste and preparation process thereof

Abstract

The invention discloses brazing electronic paste and a preparation process thereof. The brazing electronic paste comprises the following raw materials in parts by mass: 40-60 parts of brazing alloy powder; 20 to 35 parts of nano-scale and micron-scale composite silver powder; 3-8 parts of metal hydride powder; 5-13 parts of an organic carrier; 4 to 8 parts of resin; 1-5 parts of a solvent; comprising the following steps: preparation of nano silver powder: adopting a liquid phase reduction process, accurately controlling the pH value of a solution, the reaction temperature and reactant feeding speed parameters, selecting a dispersing agent, and preparing nano silver powder of which the characteristic structure size is controlled to be 10-500 nanometers to form a two-dimensional form; the preparation method has the beneficial effects that the introduction of the nanoscale silver powder remarkably improves the heat conduction and electric conduction performance of the paste, and meanwhile, the composite arrangement of the nanoscale silver powder and the micron-sized silver powder optimizes the overall performance of the material; and by using the high-temperature-resistant resin and the new-type organic additive, the toughness and the aging resistance of the slurry are enhanced, and the problem of cracking after high and low temperature circulation is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of brazing electronic pastes, and particularly relates to a brazing electronic paste and a preparation process thereof. Background Art

[0002] At present, the thermal interface materials for chip interconnection in semiconductor devices are mainly tin-based brazing alloys. The melting point of metallic tin is 232°C, and the commonly used lead-free soft solders are tin-silver eutectic alloy (Sn / Ag) and tin-silver-copper eutectic alloy (S / Ag / Cu). When used as thermal interface materials, the soft solders melt at 30 - 40°C above the eutectic melting point and undergo a wetting reaction with the interface. The soft solders react with the back metal layer (gold plating or silver plating) between the chip and the substrate to form intermetallic compounds such as AgSn and AuSn, etc., making the interconnection joints after the reaction have good mechanical properties. However, the melting points of Sn / Ag eutectic solder (melting point: 221°C) and Sn / Ag / Cu eutectic solder (melting point: 217°C) are too low, and the service temperature needs to be lower than the melting point. They are suitable for the application environment of existing semiconductor devices but cannot be applied to the chip interconnection of wide-bandgap semiconductors, and cannot give full play to the advantages of high power density of chips such as SiC.

[0003] As a typical high-temperature-resistant encapsulation material, low-temperature sintered silver can achieve encapsulation interconnection at low temperatures (200°C - 300°C) and serve stably for a long time at high temperatures (theoretically up to 700°C), so it has received extensive attention. The process temperature of the sintered silver paste is 180 - 250°C. Sintering necks are formed through atomic diffusion between particles, and then densification is completed through volume shrinkage to form a sintered body. Metallurgical connections are formed between silver particles and the interface through interdiffusion, thereby obtaining good mechanical properties. The sintered body after sintering has good thermal and electrical conductivity and good high-temperature stability, and can meet the requirements of low-temperature connection and high-temperature service of power semiconductor devices such as SiC.

[0004] A brazing electronic paste, a preparation method and an application thereof with the publication number of CN109648221A are prepared from the following raw materials in parts by mass: 50 - 70 parts of brazing alloy powder, 18 - 32 parts of silver powder, 2 - 6 parts of metal hydride powder, 0.01 - 1 part of surface modifier; 7 - 15 parts of organic carrier; including the following steps: mixing the brazing alloy powder, silver powder, metal hydride powder, surface modifier and organic carrier according to the above parts by mass to obtain the brazing electronic paste. Although it solves some problems to a certain extent, it is insufficient in thermal conductivity and toughness and is difficult to meet the high requirements of automotive-grade chip packaging. Summary of the Invention

[0005] The purpose of the present invention is to provide a brazing electronic paste and a preparation process thereof to solve the problems raised in the above background art.

[0006] To achieve the above object, the present invention provides the following technical solutions: A brazing electronic paste, comprising the following raw materials in parts by mass: brazing alloy powder: 40 - 60 parts; nano - and micro - composite silver powder: 20 - 35 parts; metal hydride powder: 3 - 8 parts; organic carrier: 5 - 13 parts; resin: 4 - 8 parts; solvent: 1 - 5 parts.

[0007] As a preferred technical solution of the present invention, the nano - silver powder is prepared by a liquid - phase reduction process, and the characteristic structure size is controlled within 10 - 500 nanometers.

[0008] As a preferred technical solution of the present invention, the resin is a thermosetting or thermoplastic resin, and the number of C atoms in the main carbon chain of the resin ≥ 12.

[0009] As a preferred technical solution of the present invention, the thermosetting resin is one of epoxy resin, polyester resin, and phenolic resin.

[0010] As a preferred technical solution of the present invention, the thermoplastic resin is polycarbonate.

[0011] As a preferred technical solution of the present invention, the solvent is ethylene glycol monoethyl ether acetate, and the organic carrier is prepared by a two - stage co - activation process.

[0012] As a preferred technical solution of the present invention, the metal hydride powder is one of titanium hydride and lanthanum hydride.

[0013] The present invention also discloses a preparation process of the brazing electronic paste, comprising the following steps:

[0014] Preparation of nano - silver powder: Using the liquid - phase reduction process, by precisely controlling the pH value of the solution, reaction temperature, and reactant feeding speed parameters, and selecting a dispersant, nano - silver powder with a characteristic structure size controlled within 10 - 500 nanometers is prepared to form a two - dimensional morphology;

[0015] Preparation of organic carrier: Selecting a thermosetting or thermoplastic resin and a new - type organic additive, and preparing by a two - stage co - activation process;

[0016] Mixing and grinding: Mixing the brazing alloy powder; nano - and micro - composite silver powder; metal hydride powder; organic carrier; resin; solvent; according to the predetermined mass parts, and obtaining a uniformly dispersed brazing electronic paste through a high - speed stirring and grinding device.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] The introduction of nano - silver powder significantly improves the thermal and electrical conductivity of the paste, and at the same time, the composite arrangement with micro - silver powder optimizes the overall performance of the material;

[0019] The use of high-temperature resistant resins and new types of organic additives enhances the toughness and aging resistance of the paste, solving the problem of cracking after high and low temperature cycling.

[0020] The organic carrier prepared by the two-stage co-activation process has excellent dispersibility and long-term storage stability.

[0021] By optimizing the liquid-phase reduction process, the precise preparation of nano-scale silver powder is achieved, improving the thermal conductivity and electrical conductivity of the paste. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a process flow chart of the brazing electronic paste preparation of the present invention.

[0023] Figure 2 It is a schematic diagram of the "interpenetrating network" structure composite organic carrier of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] Embodiment 1

[0026] Please refer to Figure 1 , which is the first embodiment of the present invention. This embodiment provides a brazing electronic paste, including the following raw materials in parts by mass: brazing alloy powder: 40 parts; nano-scale and micro-scale composite silver powder: 20 parts; metal hydride powder: 3 parts; organic carrier: 5 parts; resin: 4 parts; solvent: 1 part; the nano-scale silver powder is prepared by a liquid-phase reduction process, and the characteristic structure size is controlled within 10 nanometers; the resin is a thermosetting or thermoplastic resin, and the main carbon chain C atoms of the resin ≥ 12; the thermosetting resin is epoxy resin; the thermoplastic resin is polycarbonate; the solvent is ethylene glycol monoethyl ether acetate, and the organic carrier is prepared by a two-stage co-activation process; the nano-scale silver powder has a two-dimensional morphology, with a thickness in the nano-scale and a diameter in the micro-scale, and its morphology and stability are controlled by optimizing the dispersant and process parameters. The organic carrier system has excellent aging resistance and can maintain stable performance at a higher working temperature (>300 °C); the metal hydride powder is titanium hydride.

[0027] A preparation process of a brazing electronic paste includes the following steps:

[0028] Preparation of nano silver powder: The liquid-phase reduction process is adopted. By precisely controlling the pH value of the solution, reaction temperature, and reactant feeding speed parameters, and selecting a dispersant, nano silver powder with a characteristic structural size controlled within 10 nanometers is prepared, forming a two-dimensional morphology.

[0029] Preparation of organic carrier: Select a thermosetting or thermoplastic resin and a new-type organic additive, and prepare them through a two-stage co-activation process.

[0030] Mixing and grinding: Mix the brazing alloy powder; nano- and micro-scale composite silver powder; metal hydride powder; organic carrier; resin; solvent; according to the predetermined mass fractions, and obtain a uniformly dispersed brazing electronic paste through a high-speed stirring and grinding device.

[0031] Example 2

[0032] Please refer to Figure 1 , which is the second embodiment of the present invention. This embodiment provides a brazing electronic paste, including the following raw materials by mass fractions: brazing alloy powder: 50 parts; nano- and micro-scale composite silver powder: 28 parts; metal hydride powder: 6 parts; organic carrier: 9 parts; resin: 6 parts; solvent: 3 parts; The nano silver powder is prepared by the liquid-phase reduction process, and the characteristic structural size is controlled within 245 nanometers; the resin is a thermosetting or thermoplastic resin, and the number of C atoms in the main carbon chain of the resin ≥ 12; the thermosetting resin is a polyester resin; the thermoplastic resin is a polycarbonate; the solvent is ethylene glycol monoethyl ether acetate, and the organic carrier is prepared by the two-stage co-activation process; the nano silver powder has a two-dimensional morphology, with a thickness in the nano-scale and a diameter in the micro-scale, and its morphology and stability are controlled by optimizing the dispersant and process parameters. The organic carrier system has excellent anti-aging performance and can maintain stable performance at a relatively high working temperature (>300 °C); the metal hydride powder is lanthanum hydride.

[0033] A preparation process of a brazing electronic paste includes the following steps:

[0034] Preparation of nano silver powder: The liquid-phase reduction process is adopted. By precisely controlling the pH value of the solution, reaction temperature, and reactant feeding speed parameters, and selecting a dispersant, nano silver powder with a characteristic structural size controlled within 10 - 500 nanometers is prepared, forming a two-dimensional morphology.

[0035] Preparation of organic carrier: Select a thermosetting or thermoplastic resin and a new-type organic additive, and prepare them through a two-stage co-activation process.

[0036] Mixing and grinding: Mix the brazing alloy powder; nano- and micro-scale composite silver powder; metal hydride powder; organic carrier; resin; solvent; according to the predetermined mass fractions, and obtain a uniformly dispersed brazing electronic paste through a high-speed stirring and grinding device.

[0037] Example 3

[0038] Please refer to Figure 1 and Figure 2 which is the third embodiment of the present invention. This embodiment provides a brazing electronic paste, comprising the following raw materials in parts by mass: brazing alloy powder: 60 parts; nano- and micro-composite silver powder: 35 parts; metal hydride powder: 8 parts; organic carrier: 13 parts; resin: 8 parts; solvent: 5 parts. The nano-silver powder is prepared by a liquid-phase reduction process, and the characteristic structure size is controlled at 500 nanometers. The resin is a thermosetting or thermoplastic resin, and the number of C atoms in the main carbon chain of the resin is ≥12. The thermosetting resin is phenolic resin. The thermoplastic resin is polycarbonate. The solvent is ethylene glycol monoethyl ether acetate. The organic carrier is prepared by a two-stage co-activation process. The nano-silver powder has a two-dimensional morphology, with a thickness in the nanometer range and a diameter in the micrometer range. Its morphology and stability are controlled by optimizing the dispersant and process parameters. The organic carrier system has excellent anti-aging performance and can maintain stable performance at a relatively high working temperature (>300°C). The metal hydride powder is titanium hydride.

[0039] A preparation process of a brazing electronic paste comprises the following steps:

[0040] Preparation of nano-silver powder: Using a liquid-phase reduction process, by precisely controlling parameters such as the pH value of the solution, reaction temperature, and reactant feeding rate, and selecting a dispersant, nano-silver powder with a characteristic structure size controlled at 500 nanometers is prepared to form a two-dimensional morphology.

[0041] Preparation of organic carrier: Selecting a thermosetting or thermoplastic resin and a new-type organic additive, and preparing it by a two-stage co-activation process.

[0042] Mixing and grinding: Mixing the brazing alloy powder; nano- and micro-composite silver powder; metal hydride powder; organic carrier; resin; solvent; according to the predetermined mass parts, and obtaining a uniformly dispersed brazing electronic paste through a high-speed stirring and grinding device.

[0043] The thermosetting / thermoplastic resin (the number of C atoms in the main carbon chain is ≥12) developed innovatively can form an interpenetrating network polymer during sintering and curing processes, thereby further increasing the compatibility and wettability between the organic carrier and the silver powder, and achieving the effects of toughening and reducing packaging stress. Studying the organic resin polymer, analyzing the influence of its structure on heat resistance, such as the influence of the number of multi-functional groups and the reactivity with the curing agent on Tg. At the same time, studying the correlation between the resin network structure and the decomposition temperature, and developing a modified resin with a high cross-linking density that can form a rigid cured network structure, making it have a high Tg and high heat resistance.

[0044] By adopting a new type of organic additive and developing the preparation process, activation conditions, and post-treatment methods of organic carrier raw materials through a two-stage co-activation production process, the problems of the traditional feeding and pure stress grinding activation production methods, such as easy formation of too wide particle size distribution, easy agglomeration, delamination, and poor storage and thermal stability, are solved, achieving the effect of optimizing the slurry dispersibility and long-term storage stability.

[0045] In the preparation of nano-conductive materials, the appropriate ratio of nano-silver powder and micro-silver powder is considered, and the organic system is selected, so that the conductive paste can be sintered at a low temperature below 200°C, and has excellent thermal conductivity and electrical conductivity, and at the same time has good adhesion to the substrate.

[0046] By introducing specially designed two-dimensional silver nanoparticles (nano-sheets) or silver powder with nanostructures in the slurry to partially replace the micro-silver powder commonly used in conventional resin-based slurries, and matching a suitable organic resin system with good heat resistance; using the above silver powder as the filler of the conductive material, it can form metal-metal bonding connections with micro-silver at low temperatures (<200°C), similar to the metal body, with excellent thermal and electrical conductivity; at 200°C, the nano-silver powder can be melt-sintered, and at the same time, the high-temperature-resistant resin crosslinks to form a three-dimensional network structure, so it becomes a semi-sintered slurry; this new type of nano-silver has the characteristics of high conductivity and high thermal conductivity of bulk silver material after sintering, which can solve the problem of low thermal conductivity of conventional resin-based slurries; at the same time, due to the addition of high-temperature-resistant resin in the sintered silver paste, the problem of insufficient toughness of conventional fully sintered silver paste is solved, which can greatly improve the ability of semiconductor chips to resist thermal stress, enabling them to adapt to a working environment with a higher temperature (>300°C) while having higher reliability; due to the use of nano-scale solid raw materials, the powder is finer and has better operability.

[0047] Experimental verification:

[0048]

[0049] The thermal conductivity is tested by the laser flash method, the toughness is tested by the standard tensile test, the high and low temperature cycle test is cycled 1000 times between -40°C and 150°C, and the storage stability test observes the dispersibility and stability of the slurry at room temperature;

[0050] As can be seen from the table, compared with the patents cited in the background art, the present invention has a significant improvement in the thermal conductivity, which has increased from 80 - 90 W / mK to 120 - 140 W / mK. This is mainly due to the introduction of nano - sized silver powder and its composite arrangement with micro - sized silver powder. At the same time, the toughness has also been significantly improved, and the elongation at break has increased from 5 - 8% to 12 - 18%. This is mainly attributed to the use of high - temperature - resistant resin and new - type organic additives. In addition, the present invention has also solved the problem of cracking after high - low temperature cycling and has longer storage stability. These improvements enable the soldering electronic paste of the present invention to better meet the high requirements of automotive - grade chip packaging.

[0051] Although the embodiments of the present invention have been shown and described, see the detailed description above, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A brazing electronic paste, characterized in that: It comprises raw materials in the following parts by mass: brazing alloy powder: 40 - 60 parts; nano - and micro - composite silver powder: 20 - 35 parts; metal hydride powder: 3 - 8 parts; organic carrier: 5 - 13 parts; resin: 4 - 8 parts; solvent: 1 - 5 parts.

2. The brazing electronic paste according to claim 1, characterized in that: The nano - silver powder is prepared by a liquid - phase reduction process, and the characteristic structure size is controlled within 10 - 500 nanometers.

3. A brazing electronic paste according to claim 1, characterized in that: The resin is a thermosetting or thermoplastic resin, and the number of C atoms in the main carbon chain of the resin is ≥12.

4. The brazing electronic paste according to claim 3, characterized in that: The thermosetting resin is one of epoxy resin, polyester resin, and phenolic resin.

5. A brazing electronic paste according to claim 3, characterized in that: The thermoplastic resin is polycarbonate.

6. A brazing electronic paste according to claim 1, characterized in that: The solvent is carbitol acetate, and the organic carrier is prepared by a two - stage co - activation process.

7. A brazing electronic paste according to claim 1, characterized in that: The metal hydride powder is one of titanium hydride and lanthanum hydride.

8. The preparation process of a brazing electronic paste according to any one of claims 1-7, characterized in that: It includes the following steps: Preparation of nano - silver powder: Using the liquid - phase reduction process, by precisely controlling parameters such as the pH value of the solution, reaction temperature, and reactant feeding rate, and selecting a dispersant, nano - silver powder with a characteristic structure size controlled within 10 - 500 nanometers is prepared to form a two - dimensional morphology; Preparation of organic carrier: Selecting a thermosetting or thermoplastic resin and a new - type organic additive, and preparing it by a two - stage co - activation process; Mixing and grinding: Mixing the brazing alloy powder; nano - and micro - composite silver powder; metal hydride powder; organic carrier; resin; solvent; according to the predetermined parts by mass, and obtaining a uniformly dispersed brazing electronic paste through a high - speed stirring and grinding device.

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