Wide-temperature-range low-volatility high-resilience conductive adhesive and preparation method thereof

Abstract

This invention relates to the field of conductive adhesive technology, and more specifically, to a wide-temperature-range, low-volatility, high-resilience conductive adhesive and its preparation method. It comprises the following components in parts by weight: 25-40 parts of a wide-temperature-range, low-volatility, high-resilience silicone resin, 40-65 parts of conductive powder, 0.6-1.7 parts of plasticizer, 0.2-1.2 parts of interface compatibilizer, 1.1-3.8 parts of filler, 2.5-6.8 parts of crosslinking agent, 0.2-0.8 parts of catalyst, and 3-8 parts of solvent. This invention uses methylphenylcyclosiloxane and vinyl-terminated polysiloxane to modify α,ω-dihydroxypolydimethylsiloxane. The resulting conductive adhesive substrate maintains stable elasticity and resilience under wide-temperature alternating environments, effectively overcoming the technical defects of traditional conductive adhesives that are prone to deformation and severe elasticity decay under high or low temperature conditions, ensuring the sealing integrity of independent cavities during long-term service.

Description

Technical Field

[0001] This invention relates to the field of conductive adhesive technology, and more specifically, to a wide-temperature-range, low-volatility, high-resilience conductive adhesive and its preparation method. Background Technology

[0002] As core components of electronic equipment evolve towards higher integration, higher density, miniaturization, and higher reliability, the dense deployment of multi-band, high-power components within limited spaces has led to increasingly prominent internal electromagnetic interference (EMI) problems. Independent cavity isolation design has become a key technological approach for blocking electromagnetic coupling. These components need to operate for extended periods in wide-temperature alternating environments, placing stringent requirements on packaging materials for low release, zero pollution, and high stability. Electromagnetic shielding adhesives, as the core material for electromagnetic shielding and sealing of independent cavities, possess conductive, adhesive, and sealing functions, making them crucial for ensuring electromagnetic isolation within the cavity and the stability of the components.

[0003] However, traditional conductive adhesives have significant shortcomings under wide-temperature cycling conditions: they easily release moisture and harmful gases, causing particle migration, contaminating cavities, and leading to a decline in electromagnetic shielding performance; they also pose risks such as elasticity decay, reduced sealing performance, adhesive overflow, and migration of solid foreign matter. Furthermore, they have poor interface compatibility, making it difficult to simultaneously achieve both conductivity stability and low volatility. Existing improvement technologies have not yet been able to simultaneously solve the comprehensive problems of maintaining elasticity over a wide temperature range, low volatility, electromagnetic shielding, and interface compatibility, thus failing to meet the application requirements of core electronic components in extreme environments. Therefore, developing a conductive adhesive that is low in volatility, stable over a wide temperature range, has good interface compatibility, and reliable conductivity has significant practical implications and engineering application value. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, one aspect of the present invention is to provide a wide-temperature-range, low-volatility, high-resilience conductive adhesive, wherein the conductive adhesive comprises the following components in parts by weight: 25 to 40 parts of wide-temperature-range, low-volatility, high-resilience silicone resin, 40 to 65 parts of conductive powder, 0.6 to 1.7 parts of plasticizer, 0.2 to 1.2 parts of interface compatibilizer, 1.1 to 3.8 parts of filler, 2.5 to 6.8 parts of crosslinking agent, 0.2 to 0.8 parts of catalyst, and 3 to 8 parts of solvent.

[0005] Another objective of this invention is to provide a method for preparing a wide-temperature-range, low-volatility, high-resilience conductive adhesive, the specific steps of which are as follows: S1. Mix α,ω-dihydroxypolydimethylsiloxane with methylphenylcyclosiloxane and vinyl-terminated polysiloxane at a mass ratio of 6.5:2.5:1 and place in a vacuum drying oven. Control the temperature at 85-95℃ and the vacuum degree at -0.08 to -0.09 MPa, and vacuum dry for 2.5-3 hours. Add 0.4-0.6% of tetramethylammonium hydroxide by mass, purge with nitrogen for protection, and react at a constant temperature of 120-130℃ and 0.15-0.25 MPa for 3 hours. After 0-4.5h, methyltriethoxysilane accounting for 1.2-1.8% of the total mass is added to the reaction system, and the reaction is continued at the temperature for 1.5-2.0h. Then the reaction product is cooled to 65-75℃, and an appropriate amount of acetic acid is added to neutralize to pH=6.8-7.2. Finally, vacuum degassing is performed for 1.5-2.0h under vacuum conditions of -0.09~-0.1MPa and temperature of 70-75℃. A small amount of insoluble impurities are removed by filtration to obtain a wide temperature range, low volatility, and high resilience silicone resin. S2. Vacuum disperse the wide-temperature-range low-volatility high-resilience silicone resin, plasticizer, interface compatibilizer, and crosslinking agent in a double planetary mixer for 10-30 minutes, add the filler and vacuum disperse for 15-40 minutes to obtain a mixture; S3. Add solvent and conductive powder to the mixture prepared in S2 and vacuum disperse for 20-30 min. Then add catalyst and vacuum disperse for 10-20 min in a double planetary mixer to obtain a wide-temperature-range, low-volatility, high-resilience conductive adhesive.

[0006] Preferably, the S1 wide-temperature-range low-volatility high-resilience silicone resin structure is as follows: Where m, n, and p represent the degree of polymerization, m ≥ 100, n is 50~80, and p is 20~40.

[0007] Preferably, the molecular weight of the S1 wide-temperature-range low-volatility high-resilience silicone resin is 10,000-50,000.

[0008] Preferably, the plasticizer in S2 is one or a combination of two or more of phenyl silicone oil, dioctyl sebacate, and trioctyl trimellitate.

[0009] Preferably, the interface compatibilizer in S2 is one or a combination of two or more of the following: KH-550, KH-560, KH-171, hexamethyldisilazane (HMDS), phenyltrimethoxysilane, polyether-modified silicone oil, titanate coupling agent, and organosilicon-acrylate block copolymer.

[0010] Preferably, the crosslinking agent in S2 is one or a combination of two or more of tetraethyl orthosilicate, methyltrimethoxysilane, methyltriethoxysilane, and vinyltriethoxysilane; the filler is one or a combination of two or more of silica, alumina, talc, calcium carbonate, kaolin, and mica powder.

[0011] Preferably, the solvent in S3 is one or a combination of two or more of xylene, toluene, isoalkanes, and solvent oil.

[0012] Preferably, the conductive powder in S3 includes silver powder, silver-plated copper powder, silver-plated aluminum powder, carbon black, nickel-plated graphite, nickel powder, and silver-coated nanomaterials.

[0013] Preferably, the catalyst in S3 includes organotin, titanate and its complexes or guanidine alkoxysilane.

[0014] The beneficial effects of this invention are as follows: Excellent wide-temperature stability and resilience: This invention modifies α,ω-dihydroxypolydimethylsiloxane with methylphenylcyclosiloxane and vinyl-terminated polysiloxane. The resulting conductive adhesive substrate can maintain stable elasticity and resilience under wide temperature alternation environment, effectively overcoming the technical defects of traditional conductive adhesives that are prone to deformation and severe elastic decay under high or low temperature conditions, and ensuring the sealing integrity of independent cavities during long-term service.

[0015] Significantly low volatility: Through reasonable molecular structure design and modification path, the conductive adhesive of this invention has extremely low volatile release during wide temperature cycling, which can effectively suppress the volatilization of water vapor and harmful gases and the migration of particles, avoid internal contamination of the cavity and deterioration of electromagnetic protection performance, and meet the stringent requirements of electronic equipment for low release and zero pollution of packaging materials.

[0016] Excellent interface compatibility and process reliability: This conductive adhesive is not prone to adhesive overflow or solid foreign matter migration during curing and service. It has excellent interface compatibility and can form a stable and reliable bonding interface with different substrates, thereby improving the process consistency and long-term reliability of the overall packaging structure.

[0017] Balancing Conductivity Stability and Multiple Performance Characteristics: This invention achieves wide temperature range, low volatility, and high resilience while maintaining excellent conductivity stability. It successfully solves the problem that existing conductive adhesives struggle to balance conductivity with low volatility, wide temperature range stability, and elasticity retention. This achieves a precise balance of multiple performance indicators, meets the service requirements of core electronic equipment components in extreme environments, and ensures long-term stability of the electromagnetic isolation performance of independent cavities.

[0018] In summary, the conductive adhesive prepared by this invention exhibits significant advantages in terms of wide temperature range stability, low volatility, high resilience, interfacial compatibility, and conductivity reliability, and has important engineering application value.

[0019] Additional aspects and advantages of the invention will become apparent from the description which follows, or may be learned by practice of the invention. Attached Figure Description

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This invention relates to a wide-temperature-range, low-volatility, high-resilience resin polymerization process. Detailed Implementation

[0021] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0022] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0023] Example 1 α,ω-dihydroxypolydimethylsiloxane, methylphenylcyclosiloxane, and vinyl-terminated polysiloxane were mixed in a mass ratio of 6.5:2.5:1 and placed in a vacuum drying oven. The temperature was controlled at 85℃ and the vacuum degree at -0.08MPa for 2.5h. Tetramethylammonium hydroxide (0.5% by mass) was added, and nitrogen gas was introduced for protection. The reaction was carried out at a constant temperature of 125℃ and 0.20MPa for 4.0h. Then, methyltriethoxysilane (1.5% by mass) was added to the reaction system, and the reaction was continued at this temperature for 1.5h. The reaction product was then cooled to 70℃, and acetic acid was added to neutralize it to pH=7.1. Finally, the product was degassed under vacuum at -0.08MPa and 75℃ for 2.0h, and filtered to remove a small amount of insoluble impurities.

[0024] 30.46 parts by weight of wide-temperature-range low-volatility high-resilience silicone resin, 0.62 parts by weight of phenyl silicone oil, 0.26 parts by weight of KH-550, and 2.53 parts by weight of methyltrimethoxysilane were vacuum dispersed in a double planetary mixer for 25 min. Then, 1.33 parts by weight of silica were added and vacuum dispersed for 30 min to obtain a mixture. 4.77 parts by weight of isoparaffin and 59.78 parts by weight of silver-plated copper powder were added to the mixture and vacuum dispersed for 25 min. Then, 0.25 parts by weight of organotin catalyst were added and vacuum dispersed in a double planetary mixer for 15 min to obtain a wide-temperature-range low-volatility high-resilience adhesive.

[0025] Example 2 α,ω-dihydroxypolydimethylsiloxane, methylphenylcyclosiloxane, and vinyl-terminated polysiloxane were mixed at a mass ratio of 6:3:1 and placed in a vacuum drying oven. The temperature was controlled at 85℃ and the vacuum degree at -0.08MPa for 2.5h. Tetramethylammonium hydroxide (0.4% by mass) was added, and nitrogen gas was introduced for protection. The reaction was carried out at a constant temperature of 125℃ and 0.20MPa for 4.0h. Then, methyltriethoxysilane (1.2% by mass) was added to the reaction system, and the reaction was continued at this temperature for 1.5h. The reaction product was then cooled to 70℃, and acetic acid was added to neutralize it to pH=7.1. Finally, the mixture was degassed under vacuum at -0.08MPa and 75℃ for 2.0h, and filtered to remove a small amount of insoluble impurities.

[0026] 30.46 parts by weight of wide-temperature-range low-volatility high-resilience silicone resin, 0.62 parts by weight of phenyl silicone oil, 0.26 parts by weight of KH-550, and 2.53 parts by weight of methyltrimethoxysilane were vacuum dispersed in a double planetary mixer for 25 min. Then, 1.33 parts by weight of silica were added and vacuum dispersed for 30 min to obtain a mixture. 4.77 parts by weight of isoparaffin and 59.78 parts by weight of silver-plated copper powder were added to the mixture and vacuum dispersed for 25 min. Then, 0.25 parts by weight of organotin catalyst were added and vacuum dispersed in a double planetary mixer for 15 min to obtain a wide-temperature-range low-volatility high-resilience adhesive.

[0027] Example 3 α,ω-dihydroxypolydimethylsiloxane, methylphenylcyclosiloxane, and vinyl-terminated polysiloxane were mixed at a mass ratio of 7:2:1 and placed in a vacuum drying oven. The temperature was controlled at 85℃ and the vacuum degree at -0.08MPa for 2.5h. Tetramethylammonium hydroxide (0.6% by mass) was added, and nitrogen gas was introduced for protection. The reaction was carried out at a constant temperature of 125℃ and 0.20MPa for 4.0h. Then, methyltriethoxysilane (1.8% by mass) was added to the reaction system, and the reaction was continued at this temperature for 1.5h. The reaction product was then cooled to 70℃, and acetic acid was added to neutralize it to pH=7.1. Finally, the mixture was degassed under vacuum at -0.08MPa and 75℃ for 2.0h, and the mixture was filtered to remove a small amount of insoluble impurities.

[0028] 30.46 parts by weight of wide-temperature-range low-volatility high-resilience silicone resin, 0.62 parts by weight of phenyl silicone oil, 0.26 parts by weight of KH-550, and 2.53 parts by weight of methyltrimethoxysilane were vacuum dispersed in a double planetary mixer for 25 min. Then, 1.33 parts by weight of silica were added and vacuum dispersed for 30 min to obtain a mixture. 4.77 parts by weight of isoparaffin and 59.78 parts by weight of silver-plated copper powder were added to the mixture and vacuum dispersed for 25 min. Then, 0.25 parts by weight of organotin catalyst were added and vacuum dispersed in a double planetary mixer for 15 min to obtain a wide-temperature-range low-volatility high-resilience adhesive.

[0029] Comparative Example 1 30.46 parts by weight of unmodified silicone resin, 0.62 parts by weight of phenyl silicone oil, 0.26 parts by weight of KH-550, and 2.53 parts by weight of methyltrimethoxysilane were vacuum dispersed in a double planetary mixer for 25 min. Then, 1.33 parts by weight of silica were added and vacuum dispersed for 30 min to obtain a mixture. 4.77 parts by weight of isoparaffin and 59.78 parts by weight of silver-plated copper powder were added to the mixture and vacuum dispersed for 25 min. Then, 0.25 parts by weight of organotin catalyst were added and vacuum dispersed in a double planetary mixer for 15 min to obtain adhesive I.

[0030] Comparative Example 2 α,ω-dihydroxypolydimethylsiloxane and methylphenylcyclosiloxane were mixed at a mass ratio of 6:4 and placed in a vacuum drying oven. The temperature was controlled at 85℃ and the vacuum degree at -0.08MPa for 2.5h. Tetramethylammonium hydroxide (0.4% by mass) was added, and nitrogen gas was introduced for protection. The reaction was carried out at a constant temperature of 125℃ and 0.20MPa for 4.0h. Then, methyltriethoxysilane (1.2% by mass) was added to the reaction system, and the reaction was continued at a constant temperature for 1.5h. The reaction product was then cooled to 70℃, and acetic acid was added to neutralize it to pH=7.1. Finally, the product was degassed under vacuum at -0.08MPa and 75℃ for 2.0h. A small amount of insoluble impurities were removed by filtration to obtain modified α,ω-dihydroxypolydimethylsiloxane I.

[0031] 30.46 parts by weight of wide-temperature-range low-volatility high-resilience silicone resin, 0.62 parts by weight of phenyl silicone oil, 0.26 parts by weight of KH-550, and 2.53 parts by weight of methyltrimethoxysilane were vacuum dispersed in a double planetary mixer for 25 min. Then, 1.33 parts by weight of silica were added and vacuum dispersed for 30 min to obtain a mixture. 4.77 parts by weight of isoparaffin and 59.78 parts by weight of silver-plated copper powder were added to the mixture and vacuum dispersed for 25 min. Then, 0.25 parts by weight of organotin catalyst were added and vacuum dispersed in a double planetary mixer for 15 min to obtain wide-temperature-range low-volatility high-resilience adhesive II.

[0032] Comparative Example 3 α,ω-dihydroxypolydimethylsiloxane and vinyl-terminated polysiloxane were mixed at a mass ratio of 7:3 and placed in a vacuum drying oven. The temperature was controlled at 85℃ and the vacuum degree at -0.08MPa for 2.5h. Tetramethylammonium hydroxide (0.6% by mass) was added, and nitrogen gas was introduced for protection. The reaction was carried out at a constant temperature of 125℃ and 0.20MPa for 4.0h. Then, methyltriethoxysilane (1.8% by mass) was added to the reaction system, and the reaction was continued at a constant temperature for 1.5h. The reaction product was then cooled to 70℃, and acetic acid was added to neutralize it to pH=7.1. Finally, the product was degassed under vacuum at -0.08MPa and 75℃ for 2.0h. A small amount of insoluble impurities were removed by filtration to obtain modified α,ω-dihydroxypolydimethylsiloxane II.

[0033] 30.46 parts by weight of wide-temperature-range low-volatility high-resilience silicone resin, 0.62 parts by weight of phenyl silicone oil, 0.26 parts by weight of KH-550, and 2.53 parts by weight of methyltrimethoxysilane were vacuum dispersed in a double planetary mixer for 25 min. Then, 1.33 parts by weight of silica were added and vacuum dispersed for 30 min to obtain a mixture. 4.77 parts by weight of isoparaffin and 59.78 parts by weight of silver-plated copper powder were added to the mixture and vacuum dispersed for 25 min. Then, 0.25 parts by weight of organotin catalyst were added and vacuum dispersed in a double planetary mixer for 15 min to obtain adhesive III.

[0034] Experimental example: By comparing the bonding performance of conductive adhesives with shear strength, the conductive adhesives prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were used to bond silicone rubber strips to aluminum substrates, cured at room temperature for 7 days, and then the shear strength was tested.

[0035] By comparing the conductivity of conductive adhesives with their volume resistivity, volume resistivity test samples were prepared using the conductive adhesives obtained in Examples 1 to 3 and Comparative Examples 1 to 3 above, and then tested.

[0036] By comparing the elasticity retention performance of conductive adhesives during service, test samples were prepared using the conductive adhesives obtained in Examples 1 to 3 and Comparative Examples 1 to 3 above, and rebound rate tests were conducted. Simultaneously, the conductive adhesive test samples were subjected to three cycles at -55℃ to +150℃ according to GJB150.3A-2009 before the rebound rate test was performed.

[0037] By comparing the volatility of conductive adhesives, test samples were prepared using the conductive adhesives obtained in Examples 1 to 3 and Comparative Examples 1 to 3 above, and then tested.

[0038] The shear strength of the samples was determined according to GB / T 7124-2008; Volume resistivity was determined according to GB / T 2439-2001; The rebound rate was determined according to GB / T 20671.2-2006; Volatility was tested according to GB / T 2793-1995.

[0039] The results are shown in Table 1 below: Table 1. Functional performance test data of samples obtained from the examples and comparative examples The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A wide temperature range, low volatile, high resilience, electrically conductive adhesive, characterized in that: The conductive adhesive comprises the following components in parts by weight: 25 to 40 parts of wide-temperature-range low-volatility high-resilience silicone resin, 40 to 65 parts of conductive powder, 0.6 to 1.7 parts of plasticizer, 0.2 to 1.2 parts of interface compatibilizer, 1.1 to 3.8 parts of filler, 2.5 to 6.8 parts of crosslinking agent, 0.2 to 0.8 parts of catalyst, and 3 to 8 parts of solvent.

2. The method for preparing a wide-temperature-range, low-volatility, high-resilience conductive adhesive according to claim 1, characterized in that: The specific steps of the preparation method are as follows: S1. Mix α,ω-dihydroxypolydimethylsiloxane with methylphenylcyclosiloxane and vinyl-terminated polysiloxane at a mass ratio of 6.5:2.5:1 and place in a vacuum drying oven. Control the temperature at 85-95℃ and the vacuum degree at -0.08 to -0.09 MPa, and vacuum dry for 2.5-3 hours. Add 0.4-0.6% of tetramethylammonium hydroxide by mass, purge with nitrogen for protection, and react at a constant temperature of 120-130℃ and 0.15-0.25 MPa for 3 hours. After 0-4.5h, methyltriethoxysilane accounting for 1.2-1.8% of the total mass is added to the reaction system, and the reaction is continued at the temperature for 1.5-2.0h. Then the reaction product is cooled to 65-75℃, and an appropriate amount of acetic acid is added to neutralize to pH=6.8-7.

2. Finally, vacuum degassing is performed for 1.5-2.0h under vacuum conditions of -0.09~-0.1MPa and temperature of 70-75℃. A small amount of insoluble impurities are removed by filtration to obtain a wide temperature range, low volatility, and high resilience silicone resin. S2. Vacuum disperse the wide-temperature-range low-volatility high-resilience silicone resin, plasticizer, interface compatibilizer, and crosslinking agent in a double planetary mixer for 10-30 minutes, add the filler and vacuum disperse for 15-40 minutes to obtain a mixture; S3. Add solvent and conductive powder to the mixture prepared in S2 and vacuum disperse for 20-30 min. Then add catalyst and vacuum disperse for 10-20 min in a double planetary mixer to obtain a wide-temperature-range, low-volatility, high-resilience conductive adhesive.

3. The method for preparing a wide-temperature-range, low-volatility, high-resilience conductive adhesive according to claim 2, characterized in that: The S1 wide-temperature-range low-volatility high-resilience silicone resin structure is as follows: Where m, n, and p represent the degree of polymerization, m ≥ 100, n is 50~80, and p is 20~40.

4. The method for preparing a wide-temperature-range, low-volatility, high-resilience conductive adhesive according to claim 2, characterized in that: The S1 wide-temperature-range low-volatility high-resilience silicone resin has a molecular weight of 10,000-50,000.

5. The method for preparing a wide-temperature-range, low-volatility, high-resilience conductive adhesive according to claim 2, characterized in that: The plasticizer in S2 is one or a combination of two or more of phenyl silicone oil, dioctyl sebacate, and trioctyl trimellitate.

6. The method for preparing a wide-temperature-range, low-volatility, high-resilience conductive adhesive according to claim 2, characterized in that: The interface compatibilizer in S2 is one or a combination of two or more of the following: KH-550, KH-560, KH-171, hexamethyldisilazane, phenyltrimethoxysilane, polyether-modified silicone oil, titanate coupling agent, and organosilicon-acrylate block copolymer.

7. The method for preparing a wide-temperature-range, low-volatility, high-resilience conductive adhesive according to claim 2, characterized in that: The crosslinking agent in S2 is one or a combination of two or more of tetraethyl orthosilicate, methyltrimethoxysilane, methyltriethoxysilane, and vinyltriethoxysilane; the filler is one or a combination of two or more of silica, alumina, talc, calcium carbonate, kaolin, and mica powder.

8. The method for preparing a wide-temperature-range, low-volatility, high-resilience conductive adhesive according to claim 2, characterized in that: The solvent in S3 is one or a combination of two or more of xylene, toluene, isoalkanes, and solvent oil.

9. The method for preparing a wide-temperature-range, low-volatility, high-resilience conductive adhesive according to claim 2, characterized in that: The conductive powder in S3 includes silver powder, silver-plated copper powder, silver-plated aluminum powder, carbon black, nickel-plated graphite, nickel powder, and silver-coated nanomaterials.

10. The method for preparing a wide-temperature-range, low-volatility, high-resilience conductive adhesive according to claim 1, characterized in that: The catalyst in S3 includes organotin, titanate and its complexes, or guanidine-alkoxysilane.

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