Silver colloid, preparation method thereof and semiconductor device

Abstract

The invention belongs to the technical field of electronic packaging materials, and particularly relates to silver colloid, a preparation method thereof and a semiconductor device. The silver colloid comprises silver particles, epoxy resin, a curing agent and a coupling agent; wherein the curing agent comprises phenolic resin and a thiol curing agent, and the thiol curing agent contains at least two sulfydryl groups. The sulfydryl of the thiol curing agent reacts with part of epoxy groups before phenolic hydroxyl groups of phenolic resin at a low temperature, a silver powder network is preliminarily stabilized through the bonding effect of the sulfydryl and the silver powder, and an initial cross-linked network with toughness is formed. After the temperature is continuously increased, the phenolic resin reacts with the remaining epoxy groups, and a main body curing reaction is started to construct a high-strength and high-crosslinking-density three-dimensional network, so that the structural strength and the heat resistance are improved. And the compact three-dimensional network can more stably wrap the silver powder particles stacked at high density, so that the quality of a conductive path under high silver content is ensured, and the mechanical bonding strength of an adhesive layer is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of electronic packaging materials technology, specifically relating to a silver paste, its preparation method, and semiconductor devices. Background Technology

[0002] As electronic devices evolve towards miniaturization, high density, and high power, traditional tin-lead solder, due to its lead content, high melting point, and high thermal stress, can no longer meet the demands of advanced packaging for environmental friendliness, reliability, and fine-pitch interconnects. Conductive silver paste, with its low-temperature curing, lead-free environmental friendliness, and good process compatibility, is widely used in chip mounting, power modules, and LED packaging. However, conventional thermosetting conductive silver paste, limited by its organic resin matrix, suffers from poor thermal stability, insufficient thermal conductivity, and susceptibility to aging under high-temperature and high-humidity environments, making it unsuitable for high-reliability packaging requirements.

[0003] To enhance performance, semi-sintered silver paste has emerged. Its silver content typically exceeds 85 wt%, and at 150–250°C, it forms "sintering necks" through atomic diffusion between silver particles, constructing a highly conductive and thermally conductive three-dimensional network. Simultaneously, it retains a small amount of resin to provide wettability, flexibility, and stress buffering. This material combines excellent electrical / thermal properties, high thermal stability, and good processability, and is considered an important direction for next-generation interconnect materials.

[0004] However, in the die bonding process, semi-sintered silver paste often exhibits "resin bleeding out" (RBO): resin components migrate outward along the edge of the adhesive dot, forming an organic contamination zone that affects subsequent wire bonding, sealing, and other processes, and may even cause short circuits or bonding failures. The RBO problem is particularly severe in high-density packaging, becoming a major bottleneck for industrial applications. Currently, the industry has attempted to mitigate the resin bleeding problem by optimizing the resin system viscosity, controlling the morphology and particle size distribution of silver powder, and introducing thixotropic agents or surface modifiers. However, these methods often sacrifice the rheological properties, sintering density, or electrical and thermal conductivity of the paste while suppressing RBO, making it difficult to achieve synergistic performance optimization. Summary of the Invention

[0005] The purpose of this application is to provide a silver paste and its preparation method, as well as a semiconductor device, which aims to solve to some extent the problem that existing silver pastes sacrifice the rheological properties, sintering density, or electrical and thermal conductivity of the paste while suppressing RBO.

[0006] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows: In a first aspect, this application provides a silver paste, which is a semi-sintered silver paste, comprising the following components: Silver microparticles, epoxy resin, curing agent, and coupling agent; The curing agent includes phenolic resin and thiol curing agent, wherein the thiol curing agent contains at least two mercapto groups.

[0007] In some possible implementations, the mass percentage of each component in the silver paste is as follows: Silver microparticles 85%~90%, epoxy resin 1%~5%, curing agent 1%~3%, coupling agent 0.1%~0.5%; The mass ratio of the phenolic resin to the thiol curing agent is (3~8):1.

[0008] In some possible implementations, the phenolic resin is selected from at least one of linear phenolic resin, o-cresol phenolic resin, trifunctional phenolic resin, bisphenol A phenolic resin, special biphenyl phenolic resin, XYLOK aralkyl phenolic resin, and phenol-formaldehyde phenolic resin.

[0009] In some possible implementations, the thiol curing agent is selected from at least one of difunctional polythiols, trifunctional polythiols, tetrafunctional polythiols, and hexafunctional polythiols.

[0010] In some possible implementations, the coupling agent is selected from at least one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β-aminoethyl-γ-aminopropyltrimethoxysilane, and 2-(3,4-epoxycyclohexane)ethyltrimethoxysilane.

[0011] In some possible implementations, the phenolic resin is selected from at least one of linear phenolic resin, o-cresol phenolic resin, cresol-formaldehyde resin, xylenol-formaldehyde resin, and linear naphthol-formaldehyde resin.

[0012] In some possible implementations, the thiol curing agent is selected from at least one of bis(2-mercaptoethyl) ether, polyethylene glycol dithiol, trimethylolpropane tris(3-mercaptopropionic acid) ester, and pentaerythritol tetrakis(3-mercaptopropionic acid) ester.

[0013] In some possible implementations, the silver particles include silver nanoparticles and silver micron-sized particles, wherein the mass ratio of silver nanoparticles to silver micron-sized particles is 1:(1~4).

[0014] In some possible implementations, the epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, alicyclic epoxy resin, and multifunctional epoxy resin.

[0015] In some possible implementations, the particle size of the nano-silver powder is 80~300nm, and the particle size of the micron-silver powder is 1~5μm.

[0016] In some possible implementations, the shape of the micron-sized silver powder includes at least one of spherical, near-spherical, microcrystalline, flake, and rod-shaped.

[0017] In some possible implementations, the epoxy resin is selected from at least one of bisphenol A epoxy resin, bisphenol F type epoxy resin, and alicyclic epoxy resin.

[0018] In some possible implementations, the silver paste further includes the following components in weight percentage: Diluent 6%~8%.

[0019] In some possible implementations, the diluent includes at least one of phenyl glycidyl ether, o-tolyl glycidyl ether, butyl glycidyl ether, octyl glycidyl ether, benzyl glycidyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, dipropylene glycol methyl ether, and dipropylene glycol methyl ether acetate.

[0020] Secondly, this application provides a method for preparing silver paste, comprising the following steps: Phenolic resin and diluent are mixed and thoroughly mixed to obtain the first mixture. Epoxy resin, thiol curing agent and coupling agent are added to the first mixture and mixed until homogeneous to obtain an organic carrier. The organic carrier was mixed with silver microparticles and ground to obtain silver paste.

[0021] Thirdly, this application provides a semiconductor device encapsulated using silver paste as described above or silver paste obtained by the preparation method described above.

[0022] The silver paste provided in the first aspect of this application, during the curing process, involves the mercapto groups of the thiol curing agent reacting with some epoxy groups at lower temperatures before the phenolic hydroxyl groups of the phenolic resin. This initial reaction, through bonding with the silver powder, stabilizes the silver powder network and forms an initial, relatively resilient cross-linked network. As the temperature continues to rise, the phenolic resin reacts with the remaining epoxy groups, initiating the main curing reaction and constructing a high-strength, high-crosslink density three-dimensional network. This provides the final structural strength and heat resistance for the entire system. The dense three-dimensional network can more firmly coat the densely stacked silver powder particles, thus ensuring the quality of the conductive pathways under high silver content and significantly improving the mechanical bonding strength of the adhesive layer.

[0023] The silver paste preparation method provided in the second aspect of this application firstly involves premixing a high molecular weight phenolic resin with a diluent. The diluent effectively reduces the inherent high viscosity, promoting full swelling and dissolution to form a homogeneous first mixture. Subsequently, epoxy resin, a polythiol curing agent, and a coupling agent are sequentially introduced into this system to avoid local crosslinking or uneven dispersion caused by direct blending, ensuring high compatibility and stability of the functional components within the organic carrier (including the curing system and the interface modifier). Finally, the optimized organic carrier is mixed and ground with nano / micro composite silver particles to achieve efficient wetting, uniform dispersion, and deagglomeration of silver powder. Simultaneously, the advantages of stepwise crosslinking of thiol and phenolic resin and dense sintering of silver particles are synergistically utilized during the subsequent curing-sintering process, effectively suppressing resin exudation at high silver content while ensuring excellent electrical and thermal conductivity and encapsulation reliability.

[0024] The semiconductor device provided in the third aspect of this application, such as a semiconductor device that may include a metal substrate and a chip, uses the silver paste described in any of the foregoing embodiments as the interconnect or encapsulation bonding material between the chip and the metal substrate. Its core advantages are: the silver paste can form a highly conductive, highly thermally conductive and dense silver network under low-temperature sintering conditions of 150-250°C. At the same time, the optimized organic carrier system effectively suppresses resin exudation, avoiding contamination or reliability risks to subsequent wire bonding, molding and other processes. In addition, it has excellent thermal stability, mechanical bonding strength and stress buffering ability, which can significantly improve the long-term reliability of semiconductor devices under harsh conditions such as high temperature, high humidity and thermal cycling. Detailed Implementation

[0025] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0026] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0027] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0028] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0029] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0030] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as µg, mg, g, or kg.

[0031] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0032] In a first aspect, this application provides a silver paste comprising the following components: Silver microparticles, epoxy resin, curing agent, and coupling agent; The curing agent includes phenolic resin and thiol curing agent, and the thiol curing agent contains at least two mercapto groups.

[0033] The silver paste provided in the first aspect of this application, during the curing process, involves the mercapto groups of the thiol curing agent reacting with some epoxy groups at lower temperatures before the phenolic hydroxyl groups of the phenolic resin. This initial reaction, through bonding with the silver powder, stabilizes the silver powder network and forms an initial, relatively resilient cross-linked network. As the temperature continues to rise, the phenolic resin reacts with the remaining epoxy groups, initiating the main curing reaction and constructing a high-strength, high-crosslink density three-dimensional network, providing the final structural strength and heat resistance for the entire system. This dense three-dimensional network more firmly encapsulates the densely stacked silver powder particles, ensuring the quality of the conductive pathways under high silver content and significantly improving the mechanical bonding strength of the adhesive layer. In this system, the high molecular weight phenolic resin helps form a cohesive matrix, reducing the possibility of low-molecular-weight migration and thus inhibiting the formation of RBO (reactive oxygen species).

[0034] By synergistically introducing high molecular weight phenolic resin and multi-thiol curing agents, a stepwise "low-temperature-high-temperature" crosslinking network is constructed in the epoxy resin system: the thiol curing agent, through the strong interfacial interaction between its thiol groups and silver particles, not only effectively reduces the system viscosity, improves the silver filling rate and wettability, but also rapidly forms a tough initial network at low temperatures, inhibiting resin exudation; subsequently, the phenolic resin completes the construction of a rigid skeleton with high crosslinking density at high temperatures, ensuring excellent thermal stability and mechanical strength. This design significantly improves rheological properties, sintering density, and RBO resistance while maintaining high electrical / thermal conductivity, achieving synergistic optimization of several key performance characteristics required for high-reliability packaging.

[0035] In the silver paste of this application embodiment, multiple thiol groups of the multi-thiol curing agent can react simultaneously with multiple epoxy groups and the surface of silver particles, which not only significantly improves the crosslinking density and network stability, but also forms a "bridging" effect between silver powders, strengthening the three-dimensional conductive network structure. At the same time, the multifunctionality allows it to build a denser and more cohesive initial crosslinking network at low temperature, more effectively anchoring resin components and significantly inhibiting resin exudation (RBO). In addition, the multi-thiol structure helps maintain the rheological stability of the colloidal material under high silver filling conditions and further enhances the interfacial bonding and sintering density, thereby achieving a synergistic improvement in conductivity, mechanical strength and process reliability.

[0036] In the silver paste of this application embodiment, the coupling agent has a molecular structure containing functional groups, such as thiol, amino, and carboxyl groups, at one end that can chemically adsorb or coordinate with the silver surface, while the other end can covalently bond with the epoxy resin or curing agent. Through this "bridging" effect, the coupling agent effectively improves the dispersion stability of highly filled silver powder in the resin, reduces agglomeration, and promotes close contact and atomic diffusion between silver particles during sintering, thereby enhancing the continuity and density of the conductive / thermal conductive network; thus improving the adhesive strength, resistance to damp heat aging, and overall mechanical reliability of the adhesive layer, and further suppressing delamination, cracking, and RBO.

[0037] In some possible implementations, the mass percentage of each component in the silver paste is as follows: Silver microparticles 85%~90%, epoxy resin 1%~5%, curing agent 1%~3%, coupling agent 0.1%~0.5%; The mass ratio of phenolic resin to thiol curing agent is (3~8):1.

[0038] In the silver paste of this application embodiment, silver microparticles with a mass percentage of 85%~90% ensure excellent electrical and thermal conductivity, laying the foundation for the formation of an effective sintering network; epoxy resin with a mass percentage of 1%~5% provides the necessary adhesion and film-forming ability while avoiding excessive organic phases that weaken sintering performance; phenolic resin with a mass percentage of 1%~3% and a mass ratio of phenolic resin to thiol curing agent of (3~8):1, with phenolic resin as the main curing agent and a higher proportion, forms a rigid three-dimensional network with high cross-linking density and high heat resistance at high temperature, effectively anchoring silver particles and inhibiting resin migration, thereby significantly alleviating the RBO phenomenon; thiol curing agent with a smaller proportion, whose multi-thiol structure can strongly interact with the silver surface, reacts rapidly at low temperature, reduces system viscosity, improves silver powder wettability, and constructs an initial flexible network, improving the processability and toughness of the colloid; coupling agent with a mass percentage of 0.1%~0.5% further enhances the interfacial bonding force between inorganic silver powder and organic resin, promotes the formation of sintering necks, and improves overall bonding reliability.

[0039] Specifically, the mass percentage of silver microparticles can be any typical but non-limiting point value or a range between any two points, such as 85%, 86%, 87%, 88%, 89%, or 90%; the mass percentage of epoxy resin can be any typical but non-limiting point value or a range between any two points, such as 1%, 2%, 3%, 4%, or 5%; the mass percentage of curing agent can be any typical but non-limiting point value or a range between any two points, such as 1%, 2%, or 3%; and the mass percentage of coupling agent can be any typical but non-limiting point value or a range between any two points, such as 0.1%, 2%, 3%, 4%, or 0.5%. The mass ratio of phenolic resin to thiol curing agent can be 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, etc., and is not limited to these.

[0040] In some possible implementations, the phenolic resin is selected from at least one of linear phenolic resin, o-cresol phenolic resin, trifunctional phenolic resin, bisphenol A phenolic resin, special biphenyl phenolic resin, XYLOK aralkyl phenolic resin, and phenol-formaldehyde phenolic resin.

[0041] The aforementioned phenolic resins are all beneficial for optimizing the curing behavior and final properties of silver paste, improving crosslinking density and thermal stability, effectively inhibiting resin exudation, and enhancing high-temperature mechanical strength.

[0042] In some possible implementations, the thiol curing agent is selected from at least one of difunctional polythiols, trifunctional polythiols, tetrafunctional polythiols, and hexafunctional polythiols.

[0043] The aforementioned thiol curing agents not only form a network with higher crosslinking density with epoxy resin, enhancing the cohesiveness and thermal stability of the colloid and effectively inhibiting resin exudation, but also achieve more uniform silver powder dispersion, stronger interface anchoring, and more efficient low-temperature pre-crosslinking through strong interactions between multiple thiol groups and the surface of silver particles. At the same time, with the increase of functionality, their ability to "bridge" silver particles is enhanced, which helps to build continuous and dense conductive pathways under high filling conditions, and synergizes with phenolic resin to achieve gradient curing, taking into account process flowability, sintering density, and final mechanical reliability.

[0044] In some possible implementations, the coupling agent is selected from at least one of γ-aminopropyltriethoxysilane (KH-550), γ-glycidoxypropyltrimethoxysilane (KH-560 / DL-171), γ-methacryloyloxypropyltrimethoxysilane (KH-570), γ-mercaptopropyltriethoxysilane (KH-580), N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane (KH-602), N-β-aminoethyl-γ-aminopropyltrimethoxysilane (KH-792), and 2-(3,4-epoxycyclohexane)ethyltrimethoxysilane (A-186).

[0045] In some possible implementations, the phenolic resin is selected from at least one of linear phenolic resin, o-cresol phenolic resin, cresol-formaldehyde resin, xylenol-formaldehyde resin, and linear naphthol-formaldehyde resin, but is not limited thereto.

[0046] In some possible implementations, the thiol curing agent is selected from, but is not limited to, at least one of bis(2-mercaptoethyl) ether, polyethylene glycol dithiol, trimethylolpropane tris(3-mercaptopropionic acid) ester, and pentaerythritol tetrakis(3-mercaptopropionic acid) ester, and is not limited thereto.

[0047] In some possible implementations, the silver particles include silver nanoparticles and silver microparticles, wherein the mass ratio of silver nanoparticles to silver microparticles is 1:(1~4).

[0048] Specifically, micron-sized silver powder, acting as the main framework, provides excellent conductive pathways and a low specific surface area, helping to control system viscosity and maintain a high filling rate. Nano-sized silver powder fills the gaps between micron-sized particles, and at lower temperatures, its high surface energy facilitates atomic diffusion, promoting sintering neck formation and accelerating the construction of a three-dimensional conductive / thermal network. The synergistic effect of both not only improves sintering density and electrothermal performance but also optimizes the rheological properties and printability of the paste, while further suppressing resin exudation without significantly increasing organic content. The mass ratio of nano-sized silver powder to micron-sized silver powder can be 1:1, 1:2, 1:3, or 1:4.

[0049] In some possible implementations, the epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, alicyclic epoxy resin, and multifunctional epoxy resin.

[0050] The epoxy resins mentioned above not only provide good adhesion and moderate reactivity, but also increase crosslinking density, enhance the cohesive force of the adhesive layer, effectively inhibit resin exudation, and improve mechanical strength.

[0051] In some possible implementations, the particle size of nano silver powder is 80~300nm, and the particle size of micron silver powder is 1~5μm.

[0052] Specifically, the particle size of nano-silver powder can be any typical but non-limiting point value or a range between any two points, such as 80nm, 100nm, 150nm, 200nm, 250nm, and 300nm; the particle size of micron-sized silver powder can be any typical but non-limiting point value or a range between any two points, such as 1μm, 2μm, 3μm, 4μm, and 5μm. In this case, micron-sized silver powder, as a conductive framework, provides low specific surface area and good flowability, avoiding excessively high system viscosity; while nano-silver powder, with its high specific surface area and high surface energy, promotes interparticle atomic diffusion and sintering neck formation at lower temperatures, filling the gaps between micron-sized particles and improving the density and electrical / thermal conductivity of the adhesive layer.

[0053] In some possible implementations, the shape of the micron-sized silver powder includes at least one of the following: spherical, near-spherical, microcrystalline, flake, rod-shaped, and not limited thereto.

[0054] In some possible implementations, the epoxy resin is selected from at least one of bisphenol A epoxy resin, bisphenol F type epoxy resin, and alicyclic epoxy resin, but is not limited thereto.

[0055] In some possible implementations, the silver paste also includes the following components by weight percentage: Diluent 6%~8%.

[0056] Specifically, in this embodiment, a diluent with a mass percentage of 6% to 8% is introduced into the silver paste to effectively adjust the viscosity of the system without significantly sacrificing the final performance, thereby improving the processing fluidity and printability under high silver filling.

[0057] In some possible implementations, the diluent includes at least one of phenyl glycidyl ether, o-tolyl glycidyl ether, butyl glycidyl ether, octyl glycidyl ether, benzyl glycidyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, dipropylene glycol methyl ether, and dipropylene glycol methyl ether acetate.

[0058] The above-mentioned diluent can reduce the initial viscosity of epoxy resin and high molecular weight phenolic resin mixture, making it easier to evenly disperse silver powder and fully wet the substrate, and adapt to the requirements of precision packaging processes such as dispensing or printing; at the same time, during the curing and sintering process, the diluent can gradually volatilize or participate in the reaction, avoiding excessive residual organic matter from affecting the sintering density.

[0059] Secondly, this application provides a method for preparing silver paste, comprising the following steps: S10. Mix the phenolic resin with the diluent until homogeneous to obtain the first mixture. S20. Add epoxy resin, thiol curing agent and coupling agent to the first mixture and mix well to obtain an organic carrier. S30. Mix the organic carrier with silver microparticles and grind them to obtain silver paste.

[0060] The silver paste preparation method provided in the second aspect of this application involves first premixing a high molecular weight phenolic resin with a diluent. The diluent effectively reduces the inherent high viscosity, promoting full swelling and dissolution to form a uniform first mixture. Subsequently, epoxy resin, a multi-thiol curing agent, and a coupling agent are sequentially introduced into this system to avoid local crosslinking or uneven dispersion caused by direct blending, ensuring high compatibility and stability of the functional components (including the curing system and interface modifier) ​​within the organic carrier. Finally, the optimized organic carrier is mixed and ground with nano / micro composite silver particles to achieve efficient wetting, uniform dispersion, and deagglomeration of silver powder. Simultaneously, the advantages of stepwise crosslinking of thiol and phenolic resin and dense sintering of silver particles are synergistically utilized in the subsequent curing-sintering process, effectively suppressing resin exudation at high silver content while ensuring excellent electrical conductivity, thermal conductivity, and encapsulation reliability.

[0061] In some possible implementations, in step S10, the mixing of phenolic resin and diluent can be carried out under conditions of heating to 90°C and mechanical stirring to promote the dissolution and uniform dispersion of high molecular weight phenolic resin.

[0062] In some possible implementations, in step S20, if the phenolic resin and diluent are mixed under heating conditions, the first mixture can be cooled to room temperature before adding the epoxy resin, thiol curing agent, and coupling agent, followed by mechanical stirring. This is to avoid premature curing reactions or component degradation caused by high temperatures, ensuring the stability and effective synergy of each functional component.

[0063] In step S20, the mechanical stirring speed is 500-800 rpm and the time is 10-30 min.

[0064] In some possible implementations, in step S30, a non-invasive planetary mixer can be used to mix the silver microparticles and the organic carrier in a specific ratio, followed by grinding using a three-roll mill.

[0065] In some embodiments, the method for preparing silver paste in this embodiment further includes the following steps: S40, the silver paste obtained from S30 is further degassed under vacuum using a non-invasive planetary mixer.

[0066] The raw materials involved in the above-mentioned silver paste preparation method, such as silver microparticles, epoxy resin, phenolic resin, thiol curing agent, coupling agent, diluent, etc., are the same as the corresponding components and functions in the silver paste of the aforementioned embodiments. For relevant details, please refer to the above-mentioned embodiments, which will not be repeated here.

[0067] Thirdly, this application provides a semiconductor device encapsulated with silver paste obtained by the above-described silver paste or the above-described preparation method.

[0068] The semiconductor device provided in the third aspect of this application uses the silver paste described in any of the aforementioned embodiments as a chip interconnect or encapsulation bonding material. Its core advantage lies in the fact that the silver paste can form a highly conductive, highly thermally conductive, and dense silver network under low-temperature sintering conditions of 150-250°C. At the same time, the optimized organic carrier system effectively suppresses resin exudation, avoiding contamination or reliability risks to subsequent wire bonding, molding, and other processes. In addition, it has excellent thermal stability, mechanical bonding strength, and stress buffering capacity, which can significantly improve the long-term reliability of semiconductor devices under harsh conditions such as high temperature, high humidity, and thermal cycling.

[0069] To enable those skilled in the art to clearly understand the above-described implementation details and operations of this application, and to demonstrate the significant improvement in the performance of the silver paste and its preparation method in the embodiments of this application, the above technical solutions are illustrated below through multiple embodiments.

[0070] Example 1 A silver paste comprising the following components in weight percentages: The composition includes 88% silver microparticles, 2.8% epoxy resin, 1.6% phenolic resin, 0.4% thiol curing agent, 0.2% coupling agent, and 7% diluent. Among them, the silver microparticles include nano-silver powder and micron-silver powder in a mass ratio of 30:58. The average particle size of the nano-silver powder is 120nm, and the average particle size of the micron-silver powder is 3µm. The epoxy resin is bisphenol A type epoxy resin, the thiol curing agent is bifunctional polythiol, the coupling agent is KH560, and the diluent is butyl glycidyl ether.

[0071] Its preparation method includes the following steps: (1) Heat the phenolic resin and diluent in a glass container to 90°C, stir until fully dissolved, cool to room temperature, add epoxy resin, thiol curing agent and coupling agent in proportion, and mechanically stir at room temperature for 20 min to obtain organic carrier; (2) Add the silver microparticles and the organic carrier obtained in step (1) into the material cup in proportion, mix them using a non-interventional planetary mixer, and then further disperse them evenly using a three-roll mill.

[0072] (3) Further vacuum degassing was performed using a non-interventional planetary mixer to obtain silver paste.

[0073] Example 2 A silver paste, which differs from Example 1 in that it contains 1.75% phenolic resin and 0.25% thiol curing agent.

[0074] Example 3 A silver paste, which differs from Example 1 in that: the phenolic resin is o-cresol phenolic resin, and the thiol curing agent is trifunctional polythiol.

[0075] Example 4 A silver paste, which differs from Example 2 in that: the phenolic resin is o-cresol resin and the thiol curing agent is trifunctional polythiol.

[0076] Example 5 A silver paste, which differs from Example 3 in that the ratio of phenolic resin to thiol curing agent is 11:1.

[0077] Example 6 A silver paste, which differs from Example 3 in that the ratio of phenolic resin to thiol curing agent is 1:1.

[0078] Comparative Example 1 A silver paste, which differs from Example 1 in that it does not include a phenolic resin curing agent.

[0079] Comparative Example 2 A silver paste, which differs from Example 1 in that it does not contain a thiol curing agent.

[0080] To verify the advancements of the silver paste and its preparation method in this application, the RBO diffusion distance was measured using a high-power microscope, the maximum force required for the chip to detach from the substrate was measured using a push-pull force tester, and the resistivity performance was tested using a four-probe tester.

[0081] The components, dosages, and test results of the silver paste provided in Examples 1-4 and Comparative Examples 1-2 are shown in Table 1 below.

[0082] Table 1

[0083] The data in Table 1 show that: Comparative Example 1, which only added a thiol-based curing agent and no phenolic curing agent, exhibited severe RBO (Residual Bonding Occurrence); Comparative Example 2, which only added a phenolic curing agent and no thiol-based curing agent, did not show RBO, but its chip push-off strength and conductivity were poor. Combining Comparative Examples 1 and 2, it is evident that thiol-based curing agents and phenolic resins have an irreplaceable synergistic effect in the semi-sintered silver paste system, and a single curing agent cannot simultaneously meet the comprehensive performance requirements of suppressing RBO, achieving high bond strength, and providing excellent conductivity.

[0084] In Examples 1 and 3, the ratio of phenolic curing agent to thiol curing agent was 4:1, which significantly suppressed RBO while maintaining high silver content, chip push, and conductivity. In Examples 2 and 4, the ratio of phenolic curing agent to thiol curing agent was 7:1, achieving complete suppression of RBO while also maintaining high silver content, chip push, and conductivity. In Example 5, the ratio of phenolic curing agent to thiol curing agent was 11:1, and no RBO occurred, but chip push and conductivity were poor. In Example 6, the ratio of phenolic curing agent to thiol curing agent was 1:1, and severe RBO occurred. Combining Examples 1-5, it can be seen that the mass ratio of phenolic resin to thiol curing agent has a decisive influence on the overall performance of semi-sintered silver paste. There exists an optimal ratio window (3:1~8:1), within which effective suppression of RBO and high chip push and high conductivity can be achieved synergistically; an imbalance in the ratio will lead to performance degradation.

[0085] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of protection of this application is limited to these examples; within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of one or more embodiments of this application as described above, which are not provided in detail for the sake of brevity.

[0086] One or more embodiments in this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments in this application should be included within the protection scope of this application.

Claims

1. A silver paste for encapsulating semiconductor devices, characterized in that, It includes the following components: Silver microparticles, epoxy resin, curing agent, and coupling agent; The curing agent includes phenolic resin and thiol curing agent, wherein the thiol curing agent contains at least two mercapto groups.

2. The silver paste according to claim 1, characterized in that, The mass percentage of each component in the silver paste is as follows: Silver microparticles 85%~90%, epoxy resin 1%~5%, curing agent 1%~3%, coupling agent 0.1%~0.5%; The mass ratio of the phenolic resin to the thiol curing agent is (3~8):

1.

3. The silver paste according to claim 2, characterized in that, The phenolic resin is selected from at least one of linear phenolic resin, o-cresol phenolic resin, trifunctional phenolic resin, bisphenol A phenolic resin, special biphenyl phenolic resin, XYLOK aralkyl phenolic resin, and phenol-formaldehyde phenolic resin. And / or, the thiol curing agent is selected from at least one of difunctional polythiols, trifunctional polythiols, tetrafunctional polythiols, and hexafunctional polythiols; And / or, the coupling agent is selected from at least one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β-aminoethyl-γ-aminopropyltrimethoxysilane, and 2-(3,4-epoxycyclohexane)ethyltrimethoxysilane.

4. The silver paste according to claim 2, characterized in that, The phenolic resin is selected from at least one of linear phenolic resin, o-cresol phenolic resin, cresol-formaldehyde resin, xylenol-formaldehyde resin, and linear naphthol-formaldehyde resin; And / or, the thiol curing agent is selected from at least one of bis(2-mercaptoethyl) ether, polyethylene glycol dithiol, trimethylolpropane tris(3-mercaptopropionic acid) ester, and pentaerythritol tetrakis(3-mercaptopropionic acid) ester.

5. The silver paste according to any one of claims 1 to 4, characterized in that, The silver particles include silver nanoparticles and silver micron-sized particles, wherein the mass ratio of silver nanoparticles to silver micron-sized particles is 1:(1~4); And / or, the epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, alicyclic epoxy resin, and multifunctional epoxy resin.

6. The silver paste according to claim 5, characterized in that, The nano-silver powder has a particle size of 80~300nm, and the micron-silver powder has a particle size of 1~5μm; And / or, the shape of the micron-sized silver powder includes at least one of spherical, near-spherical, microcrystalline, flake, and rod-shaped; And / or, the epoxy resin is selected from at least one of bisphenol A epoxy resin, bisphenol F type epoxy resin, and alicyclic epoxy resin.

7. The silver paste according to claim 1, characterized in that, The silver paste also includes the following components in weight percentage: Diluent 6%~8%.

8. The silver paste according to claim 7, characterized in that, The diluent includes at least one of phenyl glycidyl ether, o-tolyl glycidyl ether, butyl glycidyl ether, octyl glycidyl ether, benzyl glycidyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, dipropylene glycol methyl ether, and dipropylene glycol methyl ether acetate.

9. A method for preparing silver paste as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Phenolic resin and diluent are mixed and thoroughly mixed to obtain the first mixture. Epoxy resin, thiol curing agent and coupling agent are added to the first mixture and mixed until homogeneous to obtain an organic carrier. The organic carrier was mixed with silver microparticles and ground to obtain silver paste.

10. A semiconductor device, characterized in that, Encapsulation using silver paste as described in claims 1-8 or the preparation method described in claim 9.

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