Liquid metal microcapsule modified pressureless sintering silver paste and preparation method thereof

Abstract

The invention belongs to the field of electronic packaging, and particularly relates to liquid metal microcapsule modified pressureless sintering silver paste and a preparation method thereof. The pressureless sintering silver paste is prepared from the following raw materials in parts by mass: 90 to 95 parts of silver powder filler, 2 to 4 parts of liquid metal microcapsules, 2.3 to 5.5 parts of organic solvent, 0.20 to 0.27 part of dispersing agent, 0.05 to 0.08 part of rheological agent and 0.25 to 0.35 part of defoaming agent. The mixed powder of the flaky micron silver powder and the spherical nano silver powder is adopted, so that the sintering temperature of the silver paste can be remarkably reduced, and the sintering bonding strength of the silver paste can be improved. After being sintered, the pressureless sintered silver paste prepared by the method is high in shear strength, high in thermal conductivity and good in thermal mechanical fatigue performance, is suitable for packaging high-power devices, and has a relatively high practical value.

Description

Technical Field

[0001] This invention belongs to the field of electronic packaging, and particularly relates to a liquid metal microcapsule modified pressureless sintering silver paste and its preparation method. Background Technology

[0002] Pressureless sintering silver paste is a novel interconnect material used in electronic packaging. It primarily consists of micro / nano silver particles, organic carriers, and additives. It can be sintered at low temperatures (150-250℃) without external pressure, forming a dense silver layer with high electrical and thermal conductivity. Its core principle is the metallurgical bonding between particles achieved through spontaneous diffusion and necking growth driven by the surface energy of the silver particles. Compared to traditional tin-based solders and pressure-sintered silver paste, pressureless sintering silver paste avoids the risk of mechanical damage to chips caused by high pressure, while possessing higher thermal and electrical conductivity, making it a key material for the packaging of third-generation semiconductors and high-power devices.

[0003] Domestic and international research on pressureless sintering silver paste mainly focuses on innovation in silver powder systems. Patent US20210327321A1 proposes a composite of flake and spherical silver powder, achieving 97% density at 180℃ and increasing shear strength to 45MPa. Patent CN202311563835.3 discloses a method for preparing surface-modified nano-silver powder and silver paste; the nano-silver paste using nano-silver powder as raw material, after sintering at 200℃, achieves a shear strength of 40MPa when bonded to a chip. However, existing pressureless sintering silver pastes have significant shortcomings in thermomechanical fatigue, primarily due to the mismatch in thermal expansion coefficients between the paste and the packaging substrate material. Silver has a thermal expansion coefficient of 19ppm / K, while commonly used substrates such as silicon carbide (SiC, 4ppm / K) and aluminum nitride (AlN, 4.5ppm / K) have much lower coefficients, leading to high shear stress at the interface during temperature cycling (-55℃ to 175℃), ultimately causing delamination failure. Therefore, improving the thermomechanical fatigue properties of pressureless sintered silver paste is a key issue that must be addressed when applying pressureless sintered silver paste to the packaging of third-generation semiconductors and high-power devices. Summary of the Invention

[0004] To address the aforementioned issues, the purpose of this application is to provide a liquid metal microcapsule-modified pressureless sintering silver paste. This pressureless sintering silver paste contains a certain amount of liquid metal microcapsules, and the carboxyl polyurethane shell has excellent thermoelastic properties. The liquid metal inside can fill the cracks between the encapsulation interfaces after the microcapsules rupture, thereby significantly improving the service life of the pressureless sintering silver paste.

[0005] To achieve the above objectives, this application provides a liquid metal microcapsule-modified pressureless sintering silver paste, which is composed of the following raw materials in parts by weight: 90-95 parts silver powder filler, 2-4 parts liquid metal microcapsules, 2.3-5.5 parts organic solvent, 0.20-0.27 parts dispersant, 0.05-0.08 parts rheology modifier, and 0.25-0.35 parts defoamer.

[0006] The liquid metal microcapsules are prepared by the following steps: S1. Liquid metal emulsification: Sodium dodecyl sulfate is dissolved in deionized water, eutectic Ga-In-Sn liquid metal is added, and emulsification is performed to form a liquid metal emulsion; S2. Microencapsulation polymerization reaction: Take the above liquid metal emulsion and add poly(1,4-butanediol adipate), stir, then add isophorone diisocyanate and dibutyltin dilaurate, adjust the pH to alkaline, react for 2-4 hours, then add dimethylolpropionic acid and react for 2-3 hours to obtain the reaction solution. S3. Microcapsule solidification: Heat the reaction solution from step S2 to 55-65℃, stir, centrifuge, collect the microcapsules, wash, and dry to obtain liquid metal microcapsules.

[0007] Furthermore, the silver powder filler is composed of micron-sized silver powder and nano-sized silver powder, with a weight ratio of 8-9:1-2.

[0008] Furthermore, the micron-sized silver powder is in the form of flakes with a size of 20-100 μm, and the nano-sized silver powder is in the form of spheres with a size of 5-20 nm.

[0009] Furthermore, the organic solvent is at least one selected from ethylene glycol ethyl ether, propylene glycol butyl ether, butyl carbitol, tripropylene glycol, polyethylene glycol, ethyl acetate, butyl acetate, xylene, and di-tert-butylphenol.

[0010] Furthermore, the dispersant is one of polyvinylpyrrolidone, sodium dodecyl sulfate, and polyethylene glycol.

[0011] Furthermore, the rheology modifier is one of polyvinyl butyral, ethyl cellulose, and polyamide wax.

[0012] Furthermore, the defoamer is one of polydimethylsiloxane, polyether, and mineral oil.

[0013] A method for preparing liquid metal microcapsule-modified pressureless sintering silver paste includes the following steps: A1. Take an organic solvent, and add the dispersant, rheology modifier and defoamer to the organic solvent in sequence and mix evenly to obtain an organic carrier; A2. Add silver powder filler to the organic carrier and stir to obtain a mixed solution; A3. Add liquid metal microcapsules to the mixed solution and mix evenly to obtain liquid metal microcapsule modified pressureless sintering silver paste.

[0014] In summary, this application has the following beneficial effects: (1) The present invention uses a mixture of flake-shaped micron silver powder and spherical nano silver powder, which can not only significantly reduce the sintering temperature of silver paste, but also improve the sintering bonding strength of silver paste.

[0015] (2) This invention introduces core-shell structured liquid metal microcapsules (the core is a Ga-In-Sn low-melting-point alloy, and the shell is a carboxyl polyurethane), which endows the material with self-healing function while maintaining the pressureless sintering characteristics. The carboxyl polyurethane shell has excellent thermoelasticity and controllable cracking characteristics. When microcracks are generated in the silver paste layer due to thermomechanical stress, the microcapsule shell softens and cracks upon heating. The released liquid metal rapidly fills the cracks under capillary action and achieves in-situ self-healing through wetting and spreading with the silver substrate. The pressureless sintered silver paste prepared by this invention, after sintering, exhibits high shear strength, high thermal conductivity, and good thermomechanical fatigue performance, making it suitable for packaging high-power devices and possessing significant practical value. Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0017] The raw materials used in the embodiments of this invention are shown below, and all reagents used are analytical grade.

[0018] The average size of the micron-sized silver powder is 30 μm, and the average size of the nano-sized silver powder is 10 nm. 1,4-Butanediol adipate is selected from Shanghai Yuanye Biotechnology Co., Ltd., No. Y68314; isophorone diisocyanate is selected from Shandong Dexin Fine Chemical Co., Ltd., No. D00275; polyvinylpyrrolidone is selected from Shanghai Yuanye Biotechnology Co., Ltd., No. S30269; polyvinyl butyral is selected from Shanghai Yuanye Biotechnology Co., Ltd., No. S30198; ethyl cellulose is selected from Xi'an Kangnuo Chemical Co., Ltd., No. KN0178; polydimethylsiloxane is selected from Nantong Runfeng Petrochemical Co., Ltd., No. RF092529; and polyether is selected from Shanghai Chuangsai Technology Co., Ltd., No. PA74109.

[0019] Example 1 A liquid metal microcapsule-modified pressureless sintering silver paste, the silver paste being composed of silver powder filler, liquid metal microcapsules, organic solvent, dispersant, rheology modifier and defoamer.

[0020] The liquid metal microcapsules are prepared by the following steps: S1. Liquid metal emulsification: Dissolve 0.5g of sodium dodecyl sulfate in 50mL of deionized water, add 10g of eutectic Ga-In-Sn liquid metal, place in a high-speed shear emulsifier at 25℃ for 10 minutes at a speed of 12000rpm, and protect with nitrogen gas throughout the emulsification process to form a liquid metal emulsion. S2. Microencapsulation polymerization reaction: The above liquid metal emulsion was transferred to a three-necked flask, 2g of poly(1,4-butanediol adipate) was added, and the mixture was mechanically stirred at 500 rpm. Then, 5g of isophorone diisocyanate was added, along with 0.1g of dibutyltin dilaurate catalyst. The pH was adjusted to 8 with 0.1M sodium bicarbonate, and the mixture was kept in a constant temperature water bath at 40°C for 3 hours. Then, 2g of dimethylolpropionic acid was added, and the mixture was stirred (at 500 rpm) for 2 hours to obtain the reaction solution. S3. Microcapsule solidification: Heat the reaction solution to 60°C and continue stirring (500 rpm) for 1 hour. Then, place the reaction solution in a centrifuge and centrifuge at 4000 rpm for 10 minutes. Collect the microcapsules and wash them three times with a 1:1 volume ratio ethanol / water mixture. Dry them under vacuum at 40°C for 12 hours to obtain liquid metal microcapsules.

[0021] A method for preparing liquid metal microcapsule-modified pressureless sintering silver paste specifically includes the following steps: A1. Take 1.5 parts of ethylene glycol ethyl ether, 2.0 parts of butyl carbitol, and 2.0 parts of ethyl acetate and mix them evenly. Then add 0.20 parts of polyvinylpyrrolidone, 0.05 parts of polyvinyl butyral, and 0.25 parts of polydimethylsiloxane in sequence and mix evenly to obtain an organic carrier. A2. Take 81 parts of micron-sized silver powder and 9 parts of nano-sized silver powder and add them to the organic carrier, then stir mechanically (1500 rpm for 10 min) to obtain a mixed solution; A3. Add 4 parts of liquid metal microcapsules to the mixed solution, place it in a vacuum degassing gravity mixer and mix evenly. Then, ball mill for 5 minutes at a speed of 2500 rpm to obtain liquid metal microcapsule modified pressureless sintering silver paste.

[0022] Example 2 A liquid metal microcapsule-modified pressureless sintering silver paste, the silver paste being composed of silver powder filler, liquid metal microcapsules, organic solvent, dispersant, rheology modifier and defoamer.

[0023] The liquid metal microcapsules are prepared by the following steps: S1. Liquid metal emulsification: Dissolve 0.5g of sodium dodecyl sulfate in 50mL of deionized water, add 10g of eutectic Ga-In-Sn liquid metal, place in a high-speed shear emulsifier at 25℃ for 10 minutes at a speed of 12000rpm, and protect with nitrogen gas throughout the emulsification process to form a liquid metal emulsion. S2. Microencapsulation polymerization reaction: The above liquid metal emulsion was transferred to a three-necked flask, 2g of poly(1,4-butanediol adipate) was added, and the mixture was mechanically stirred at 500 rpm. Then, 5g of isophorone diisocyanate was added, along with 0.1g of dibutyltin dilaurate catalyst. The pH was adjusted to 8 with 0.1M sodium bicarbonate, and the mixture was kept in a constant temperature water bath at 40°C for 3 hours. Then, 2g of dimethylolpropionic acid was added, and the mixture was stirred (at 500 rpm) for 2 hours to obtain the reaction solution. S3. Microcapsule solidification: Heat the reaction solution to 60°C and continue stirring (500 rpm) for 1 hour. Then, place the reaction solution in a centrifuge and centrifuge at 4000 rpm for 10 minutes. Collect the microcapsules and wash them three times with a 1:1 volume ratio ethanol / water mixture. Dry them under vacuum at 40°C for 12 hours to obtain liquid metal microcapsules.

[0024] A method for preparing liquid metal microcapsule-modified pressureless sintering silver paste specifically includes the following steps: A1. Take 1.3 parts of butyl carbitol and 1.0 parts of ethyl acetate and mix them evenly. Then add 0.27 parts of polyethylene glycol 2000, 0.08 parts of ethyl cellulose and 0.35 parts of polyether in sequence and mix evenly to obtain an organic carrier. A2. Take 76 parts of micron-sized silver powder and 19 parts of nano-sized silver powder and add them to the organic carrier, then stir mechanically (1500 rpm for 10 min) to obtain a mixed solution; A3. Add 2 parts of liquid metal microcapsules to the mixed solution, place them in a vacuum degassing gravity mixer and mix evenly. Then, ball mill for 5 minutes at a speed of 2500 rpm to obtain liquid metal microcapsule modified pressureless sintering silver paste.

[0025] Example 3 A liquid metal microcapsule-modified pressureless sintering silver paste, the silver paste being composed of silver powder filler, liquid metal microcapsules, organic solvent, dispersant, rheology modifier and defoamer.

[0026] The liquid metal microcapsules are prepared by the following steps: S1. Liquid metal emulsification: Dissolve 0.5g of sodium dodecyl sulfate in 50mL of deionized water, add 10g of eutectic Ga-In-Sn liquid metal, place in a high-speed shear emulsifier at 25℃ for 10 minutes at a speed of 12000rpm, and protect with nitrogen gas throughout the emulsification process to form a liquid metal emulsion. S2. Microencapsulation polymerization reaction: The above liquid metal emulsion was transferred to a three-necked flask, 2g of poly(1,4-butanediol adipate) was added, and the mixture was mechanically stirred at 500 rpm. Then, 5g of isophorone diisocyanate was added, along with 0.1g of dibutyltin dilaurate catalyst. The pH was adjusted to 8 with 0.1M sodium bicarbonate, and the mixture was kept in a constant temperature water bath at 40°C for 3 hours. Then, 2g of dimethylolpropionic acid was added, and the mixture was stirred (at 500 rpm) for 2 hours to obtain the reaction solution. S3. Microcapsule solidification: Heat the reaction solution to 60°C and continue stirring (500 rpm) for 1 hour. Then, place the reaction solution in a centrifuge and centrifuge at 4000 rpm for 10 minutes. Collect the microcapsules and wash them three times with a 1:1 volume ratio ethanol / water mixture. Dry them under vacuum at 40°C for 12 hours to obtain liquid metal microcapsules.

[0027] A method for preparing liquid metal microcapsule-modified pressureless sintering silver paste specifically includes the following steps: A1. Take 1.39 parts of ethylene glycol ethyl ether and 2.0 parts of ethyl acetate and mix them evenly. Then add 0.25 parts of polyvinylpyrrolidone, 0.06 parts of polyvinyl butyral and 0.3 parts of polydimethylsiloxane in sequence and mix them evenly to obtain an organic carrier. A2. Take 79.05 parts of micron-sized silver powder and 13.95 parts of nano-sized silver powder and add them to the organic carrier, then stir mechanically (1500 rpm for 10 min) to obtain a mixed solution; A3. Add 3 parts of liquid metal microcapsules to the mixed solution, place them in a vacuum degassing gravity mixer and mix evenly at 2500 rpm for 5 minutes to obtain liquid metal microcapsule modified pressureless sintering silver paste.

[0028] Example 4 A liquid metal microcapsule-modified pressureless sintering silver paste, the silver paste being composed of silver powder filler, liquid metal microcapsules, organic solvent, dispersant, rheology modifier and defoamer.

[0029] The liquid metal microcapsules are prepared by the following steps: S1. Liquid metal emulsification: Dissolve 0.5g of sodium dodecyl sulfate in 50mL of deionized water, add 10g of eutectic Ga-In-Sn liquid metal, place in a high-speed shear emulsifier at 25℃ for 10 minutes at a speed of 12000rpm, and protect with nitrogen gas throughout the emulsification process to form a liquid metal emulsion. S2. Microencapsulation polymerization reaction: The above liquid metal emulsion was transferred to a three-necked flask, 2g of poly(1,4-butanediol adipate) was added, and the mixture was mechanically stirred at 500 rpm. Then, 5g of isophorone diisocyanate was added, along with 0.1g of dibutyltin dilaurate catalyst. The pH was adjusted to 8 with 0.1M sodium bicarbonate, and the mixture was kept in a constant temperature water bath at 40°C for 3 hours. Then, 2g of dimethylolpropionic acid was added, and the mixture was stirred (at 500 rpm) for 2 hours to obtain the reaction solution. S3. Microcapsule solidification: Heat the reaction solution to 60°C and continue stirring (500 rpm) for 1 hour. Then, place the reaction solution in a centrifuge and centrifuge at 4000 rpm for 10 minutes. Collect the microcapsules and wash them three times with a 1:1 volume ratio ethanol / water mixture. Dry them under vacuum at 40°C for 12 hours to obtain liquid metal microcapsules.

[0030] A method for preparing liquid metal microcapsule-modified pressureless sintering silver paste specifically includes the following steps: A1. Take 1.0 part of ethylene glycol ethyl ether and 1.3 parts of ethyl acetate and mix them evenly. Then add 0.27 parts of polyvinylpyrrolidone, 0.08 parts of polyvinyl butyral and 0.35 parts of polydimethylsiloxane in sequence and mix evenly to obtain an organic carrier. A2. Take 85.5 parts of micron-sized silver powder and 9.5 parts of nano-sized silver powder and add them to the organic carrier, then stir mechanically (1500 rpm for 10 min) to obtain a mixed solution; A3. Add 2 parts of liquid metal microcapsules to the mixed solution, place them in a vacuum degassing gravity mixer and mix evenly. Then, ball mill for 5 minutes at a speed of 2500 rpm to obtain liquid metal microcapsule modified pressureless sintering silver paste.

[0031] Example 5 A liquid metal microcapsule-modified pressureless sintering silver paste, the silver paste being composed of silver powder filler, liquid metal microcapsules, organic solvent, dispersant, rheology modifier and defoamer.

[0032] The liquid metal microcapsules are prepared by the following steps: S1. Liquid metal emulsification: Dissolve 0.5g of sodium dodecyl sulfate in 50mL of deionized water, add 10g of eutectic Ga-In-Sn liquid metal, place in a high-speed shear emulsifier at 25℃ for 10 minutes at a speed of 12000rpm, and protect with nitrogen gas throughout the emulsification process to form a liquid metal emulsion. S2. Microencapsulation polymerization reaction: The above liquid metal emulsion was transferred to a three-necked flask, 2g of poly(1,4-butanediol adipate) was added, and the mixture was mechanically stirred at 500 rpm. Then, 5g of isophorone diisocyanate was added, along with 0.1g of dibutyltin dilaurate catalyst. The pH was adjusted to 8 with 0.1M sodium bicarbonate, and the mixture was kept in a constant temperature water bath at 40°C for 3 hours. Then, 2g of dimethylolpropionic acid was added, and the mixture was stirred (at 500 rpm) for 2 hours to obtain the reaction solution. S3. Microcapsule solidification: Heat the reaction solution to 60°C and continue stirring (500 rpm) for 1 hour. Then, place the reaction solution in a centrifuge and centrifuge at 4000 rpm for 10 minutes. Collect the microcapsules and wash them three times with a 1:1 volume ratio ethanol / water mixture. Dry them under vacuum at 40°C for 12 hours to obtain liquid metal microcapsules.

[0033] A method for preparing liquid metal microcapsule-modified pressureless sintering silver paste specifically includes the following steps: A1. Take 2.5 parts of butyl carbitol and 3.0 parts of ethyl acetate and mix them evenly. Then add 0.2 parts of polyethylene glycol 2000, 0.05 parts of ethyl cellulose and 0.25 parts of polyether in sequence and mix evenly to obtain an organic carrier. A2. Take 72 parts of micron-sized silver powder and 18 parts of nano-sized silver powder and add them to the organic carrier, then stir mechanically (1500 rpm for 10 min) to obtain a mixed solution; A3. Add 4 parts of liquid metal microcapsules to the mixed solution, place it in a vacuum degassing gravity mixer and mix evenly. Then, ball mill for 5 minutes at a speed of 2500 rpm to obtain liquid metal microcapsule modified pressureless sintering silver paste.

[0034] Compare with Example 1 The difference between this comparative example and Example 2 is that silver powder filler is used instead of liquid metal microcapsules.

[0035] Compare with Example 2 The difference between this comparative example and Example 2 is that the amount of liquid metal microcapsules used in this comparative example is 5 parts.

[0036] Performance testing Functional tests were performed on the liquid metal microcapsule-modified pressureless sintered silver paste prepared in Examples 1-5 and Comparative Examples 1-2.

[0037] Liquid metal microcapsules modified pressureless sintering silver paste were screen-printed onto the chip surface and sintered at 220℃ for 10 min. Shear strength (MPa) was measured using a push-blade tester, and thermal conductivity (W / m•K) was measured using a laser scintillation method. Thermomechanical fatigue performance was assessed by 1000 cycles of thermal cycling from -55℃ to 175℃, and the presence of cracks was observed. The results are shown in Table 1.

[0038] Table 1

[0039] As shown in Table 1, the liquid metal microcapsule-modified pressureless sintered silver paste prepared in the embodiments of this application exhibits high shear strength, high thermal conductivity, and no cracks were observed during 1000 cycles of thermal cycling from -55°C to 175°C, demonstrating excellent performance, especially Example 2. Compared with Example 2, Comparative Example 1 used silver powder filler instead of liquid metal microcapsules. The test results showed that Comparative Example 1 had low shear strength and cracks appeared during 1000 cycles of thermal cycling from -55°C to 175°C, exhibiting performance inferior to Example 2. This indicates that the addition of liquid metal microcapsules helps improve the performance of pressureless sintered silver paste. Compared with Example 2, the content of liquid metal microcapsules in Comparative Example 2 was increased to 5 parts. The test results showed that the liquid metal microcapsule-modified pressureless sintered silver paste prepared in Comparative Example 2 had relatively low shear strength and thermal conductivity, exhibiting performance inferior to Example 2.

[0040] In summary, the liquid metal microcapsule modified pressureless sintering silver paste prepared in the embodiments of this application has excellent shear resistance and high thermal conductivity, and no cracks appear in 1000 thermal cycling tests from -55°C to 175°C. In particular, the effect of Example 2 is the best, and Example 2 is the preferred embodiment of this application.

[0041] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A liquid metal microcapsule-modified pressureless sintering silver paste, characterized in that, The pressureless sintering silver paste is composed of the following raw materials in parts by weight: 90-95 parts silver powder filler, 2-4 parts liquid metal microcapsules, 2.3-5.5 parts organic solvent, 0.20-0.27 parts dispersant, 0.05-0.08 parts rheology modifier and 0.25-0.35 parts defoamer.

2. The liquid metal microcapsule-modified pressureless sintering silver paste according to claim 1, characterized in that, The liquid metal microcapsules are prepared by the following steps: S1. Liquid metal emulsification: Sodium dodecyl sulfate is dissolved in deionized water, eutectic Ga-In-Sn liquid metal is added, and emulsification is performed to form a liquid metal emulsion; S2. Microcapsule polymerization reaction: Take the above liquid metal emulsion and add poly(1,4-butanediol adipate), stir, then add isophorone diisocyanate and dibutyltin dilaurate, adjust the pH to alkaline, react for 2-4 hours, then add dimethylolpropionic acid to react and obtain the reaction solution. S3. Microcapsule solidification: Heat the reaction solution from step S2 to 55-65℃, stir, centrifuge, collect the microcapsules, wash, and dry to obtain liquid metal microcapsules.

3. The liquid metal microcapsule-modified pressureless sintering silver paste according to claim 1, characterized in that, The silver powder filler is composed of micron-sized silver powder and nano-sized silver powder, with a weight ratio of 8-9:1-2.

4. The liquid metal microcapsule-modified pressureless sintering silver paste according to claim 1, characterized in that, The micron-sized silver powder is in the form of flakes with a size of 20-100 μm, while the nano-sized silver powder is in the form of spheres with a size of 5-20 nm.

5. The liquid metal microcapsule-modified pressureless sintering silver paste according to claim 1, characterized in that, The organic solvent is at least one of ethylene glycol ethyl ether, propylene glycol butyl ether, butyl carbitol, tripropylene glycol, polyethylene glycol, ethyl acetate, butyl acetate, xylene, and di-tert-butylphenol.

6. The liquid metal microcapsule-modified pressureless sintering silver paste according to claim 1, characterized in that, The dispersant is one of polyvinylpyrrolidone, sodium dodecyl sulfate, and polyethylene glycol.

7. The liquid metal microcapsule-modified pressureless sintering silver paste according to claim 1, characterized in that, The rheology modifier is one of polyvinyl butyral, ethyl cellulose, and polyamide wax.

8. The liquid metal microcapsule-modified pressureless sintering silver paste according to claim 1, characterized in that, The defoamer is one of polydimethylsiloxane, polyether, and mineral oil.

9. A method for preparing liquid metal microcapsule-modified pressureless sintering silver paste as described in any one of claims 1-8, characterized in that, Includes the following steps: A1. Take an organic solvent, and add the dispersant, rheology modifier and defoamer to the organic solvent in sequence and mix evenly to obtain an organic carrier; A2. Add silver powder filler to the organic carrier and stir to obtain a mixed solution; A3. Add liquid metal microcapsules to the mixed solution and mix evenly to obtain liquid metal microcapsule modified pressureless sintering silver paste.

Images