Low-silver conductive adhesive containing inorganic filler and preparation method thereof

Abstract

The application relates to the technical field of conductive glue, and particularly discloses a low-silver conductive glue containing inorganic fillers and a preparation method thereof. The low-silver conductive glue containing inorganic fillers comprises the following components in parts by weight: 35-60 parts of silver powder; 25-45 parts of epoxy resin; 1-10 parts of epoxy diluent; 1-10 parts of curing agent; 0.1-0.5 parts of silane coupling agent; 1-10 parts of inorganic filler; and 0.5-5 parts of solvent. The epoxy resin comprises epoxy resin and modified epoxy acrylic resin, and the weight ratio of the two is between 3:1 and 1:3. The silver powder comprises at least one of micro-nano spherical powder, micro-nano flake powder and micron-level flake powder. The low-silver conductive glue containing inorganic fillers has the advantages that the silver powder consumption and raw material cost can be significantly reduced, and the excellent conductivity, heat conductivity, bonding strength and environmental stability can be maintained.

Description

Technical Field

[0001] This application relates to the field of conductive adhesive technology, and more specifically, to a low-silver conductive adhesive containing inorganic fillers and its preparation method. Background Technology

[0002] Traditional high-performance conductive adhesives typically use silver powder as the main conductive filler, with silver powder accounting for 60%–80% of the total cost. In recent years, the price of silver has fluctuated dramatically, putting significant cost control pressure on downstream electronic packaging and semiconductor assembly companies. To reduce material costs, the market has attempted to partially replace silver powder with inorganic materials such as carbon black and silicon nitride. However, simply adding inorganic fillers often fails to meet the requirements for high electrical and thermal conductivity, and the poor compatibility between inorganic fillers and organic resin matrices leads to agglomeration, affecting dispersibility and processing performance. It also reduces the adhesive's bonding strength and environmental stability.

[0003] Simply reducing the silver powder content in existing high-silver conductive adhesive formulations will lead to discontinuous conductive pathways, decreased thermal conductivity, and negatively impact the mechanical strength, bonding reliability, and heat resistance of the adhesive layer. Furthermore, high-filler systems are prone to increased adhesive layer brittleness and interfacial stress concentration, further affecting the long-term reliability of the product under high temperature, high humidity, or cyclic stress environments.

[0004] Therefore, there is an urgent need to develop a high-performance conductive adhesive material that can maintain excellent electrical conductivity, thermal conductivity, adhesion and environmental stability while reducing the amount of silver powder used, in order to meet the application needs of electronic packaging, power devices, sensors and other fields. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a low-silver conductive adhesive containing inorganic fillers and its preparation method.

[0006] The first part of this application provides a low-silver conductive adhesive containing inorganic fillers, which adopts the following technical solution: A low-silver conductive adhesive containing inorganic fillers, comprising the following components by weight: 35-60 parts silver powder; 25-45 parts of resin matrix; 1-10 parts epoxy diluent; 1-10 parts of curing agent; 0.1-0.5 parts of silane coupling agent; 1-10 parts of inorganic filler; Solvent 0.5-5 parts; The resin matrix comprises epoxy resin and modified epoxy acrylate resin, with a weight ratio between 3:1 and 1:3; the silver powder comprises at least two of micro-nano sphere powder, micro-nano flake powder, and micron-sized flake powder.

[0007] By adopting the above technical solution, and controlling the amount of silver powder to 35-60 parts, combined with 1-10 parts of inorganic filler, the amount of silver powder used is significantly reduced while maintaining the continuity of the conductive path through the filler compound system. Epoxy resin and modified epoxy acrylate resin are mixed in a ratio of 3:1 to 1:3, which ensures both the rigid cross-linked structure of the adhesive layer and stress relief through flexible segments, thus balancing conductivity, thermal conductivity, bonding strength, and toughness. This formulation system allows the conductive adhesive to meet the requirements of high-reliability electronic packaging for conductivity, thermal conductivity, and environmental stability while significantly reducing costs. Micro- and nano-sheet powders provide a large contact area to reduce contact resistance, micro- and nano-sphere powders fill the gaps between particles to increase density, and micron-sized sheet powders enhance the structural stability of the overall conductive path. When these three are compounded, conductivity and thermal conductivity are significantly improved, while avoiding the problem of uneven conductivity caused by the uniform morphology of silver powder, thus improving the reliability of the colloid in high-temperature and high-humidity environments.

[0008] Optionally, the micro / nanosphere powder has a D50 particle size of 50nm-2μm and a D90 ≤ 5μm; the micro / nano sheet powder has a sheet diameter of 100nm-5μm, a thickness of 10-500nm, and an aspect ratio ≥ 5:1; the micron-sized sheet powder has a sheet diameter of 1-8μm, a D90 ≤ 20μm, a thickness of 200nm-1μm, and an aspect ratio ≥ 10:1.

[0009] By employing the above technical solutions, and by precisely defining the particle sizes of micro / nano spherical powder (D50 50nm–2μm, D90 ≤ 5μm), micro / nano flake powder (D50 100nm–5μm), and micron-sized flake powder (D50 1–8μm, D90 ≤ 20μm), this application constructs a continuous multi-scale particle size distribution from nanometer to micrometer. This allows small-sized spherical powder to precisely fill the gaps at various levels formed by the accumulation of large-sized flake powder, achieving the densest packing and a low percolation threshold. A continuous conductive network can be formed with a total silver powder content of only 35–60 parts. Strict D90 upper limit control (spherical powder ≤ 5μm, micron-sized flake powder ≤ 20μm) is also achieved. The 20μm particle size avoids interfacial defects and stress concentration caused by excessively large particles, ensuring high-temperature bonding strength. The particle size windows of nano-sized spherical powder and micron-sized flake powder synergistically balance the dispersibility of nanoparticles and the conductivity of micron-sized flake powder, preventing nanoparticle agglomeration and ensuring the conductivity continuity of "point-to-surface" contact. Multi-scale close packing reduces phonon scattering and significantly improves the conduction efficiency of the thermal conductivity path. The uniform particle size distribution also allows the resin matrix to uniformly anchor the fillers at all levels, forming a stable three-dimensional skeleton. Thus, high conductivity, high thermal conductivity, excellent high-temperature bonding strength, and good processability are synergistically achieved at low silver content.

[0010] Optionally, the epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, alicyclic epoxy resin, and aliphatic epoxy resin, and the functionality of at least one epoxy resin is ≥3; the modified epoxy acrylate resin is selected from at least one of polyurethane modified epoxy acrylate resin, silicone modified epoxy acrylate resin, and nanoparticle modified epoxy acrylate resin.

[0011] By adopting the above technical solution, multifunctional epoxy resins with a functionality of ≥3 can form a dense three-dimensional cross-linked network during curing, effectively anchoring silver powder and inorganic fillers, reducing particle migration and agglomeration, maintaining the structural stability of the conductive pathway, and increasing the glass transition temperature and thermal decomposition temperature, thereby enhancing heat resistance. The flexible segments in the modified epoxy acrylate resin can alleviate curing shrinkage stress through segmental peristalsis, preventing microcrack formation and improving the toughness, peel resistance, and weather resistance of the adhesive layer, thus balancing the rigidity and flexibility of the system.

[0012] Optionally, the epoxy diluent is selected from at least one of p-tert-butylphenyl glycidyl ether, benzyl glycidyl ether, 1,4-butanediol diglycidyl ether, polypropylene glycol diglycidyl ether, and trimethylolpropane triglycidyl ether.

[0013] By adopting the above technical solution, the selected diluents, such as p-tert-butylphenyl glycidyl ether and benzyl glycidyl ether, are all reactive diluents. These diluents can effectively adjust the viscosity of the resin system and improve process operability without affecting the reactivity of the curing system. These diluents participate in the curing reaction and will not cause volume shrinkage or porosity due to volatilization, thus helping to maintain the density and interfacial bonding of the adhesive layer. They also facilitate the uniform dispersion of silver powder and fillers, improving the application applicability and storage stability of the conductive adhesive.

[0014] Optionally, the curing agent is selected from at least one of aliphatic amines, alicyclic amines, aromatic amines, latent curing agents, dicyandiamide, and modified imidazole.

[0015] By adopting the above technical solution, the selected curing agent can be well matched with the epoxy system to form a uniform cross-linked structure, ensuring that the adhesive layer has excellent mechanical strength, bonding reliability and chemical resistance after high temperature curing, while avoiding stress concentration or performance degradation caused by improper curing speed.

[0016] Optionally, the silane coupling agent is selected from at least one of aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-ureapropyltriethoxysilane, and vinyltriethoxysilane.

[0017] By employing the above technical solutions, these coupling agents can form a chemical bridge between the inorganic filler and the organic resin matrix, enhancing interfacial bonding, preventing filler agglomeration, and improving dispersion uniformity. Simultaneously, silane coupling agents can also improve the wettability and adhesion between the adhesive layer and the substrate, thereby significantly improving the bonding strength, environmental durability, and interfacial stability of the conductive adhesive at high temperatures.

[0018] Optionally, the inorganic filler is selected from at least one of alumina, zinc oxide, silicon dioxide, boron nitride, silicon nitride, carbon black, talc, and montmorillonite.

[0019] By adopting the above technical solutions, these fillers are not only low-cost and have a stable supply, but also synergistically improve the thermal conductivity, mechanical strength, and dimensional stability of the system while reducing the amount of silver powder used. Some fillers, such as carbon black and graphene, can help construct a conductive network, while boron nitride and alumina significantly improve thermal conductivity. Through reasonable screening and compounding, inorganic fillers enhance the heat resistance, wear resistance, and environmental adaptability of the adhesive layer while maintaining electrical and thermal conductivity.

[0020] Optionally, the solvent is selected from at least one of methyl ethyl ketone, dibutyl phthalate, dimethyl dimethicone, and propylene glycol methyl ether.

[0021] By employing the above technical solutions, these solvents can effectively adjust the viscosity and rheological properties of conductive adhesives, making them suitable for different application processes such as screen printing, dispensing, or squeegee coating. The solvents evaporate during the curing process, without affecting the density and performance of the final adhesive layer. Simultaneously, they help to uniformly disperse silver powder and fillers, preventing sedimentation and agglomeration, and improving product consistency and process stability.

[0022] Secondly, this application provides a method for preparing a low-silver conductive adhesive containing inorganic fillers.

[0023] A method for preparing a low-silver conductive adhesive containing inorganic fillers includes the following steps: (1) Mix epoxy resin, modified epoxy acrylic resin and epoxy diluent, and stir until uniform; (2) Add curing agent and silane coupling agent to the mixture obtained in step (1), continue to mix evenly, and obtain a uniform resin matrix by three-roll milling; (3) Add silver powder and inorganic filler to the resin matrix obtained in step (2), and add solvent to adjust the viscosity. Mix evenly to obtain the low silver conductive adhesive.

[0024] By adopting the above technical solution, step (1) first premixes the resin with the diluent to improve compatibility; step (2) adds the curing agent and coupling agent and grinds them with a three-roll mill to obtain a uniform and stable resin matrix; step (3) finally adds silver powder and inorganic filler, and adjusts the application viscosity with solvent. This process is simple and controllable, which is conducive to industrial production and can ensure that the conductive adhesive has consistent electrical conductivity, thermal conductivity and mechanical properties after curing.

[0025] In summary, this application has the following beneficial effects: 1. Because this application uses a low-silver formula and is compounded with low-cost inorganic fillers, it significantly reduces material costs while maintaining good electrical and thermal conductivity.

[0026] 2. In this application, a multi-morphology silver powder and rigid-flexible synergistic resin system are preferred to construct a stable conductive and thermally conductive network, which effectively balances the conductivity, bonding strength and toughness of the adhesive layer.

[0027] 3. The method and process steps of this application are clear and controllable, suitable for large-scale production, and the overall performance of the conductive adhesive obtained is stable and adjustable. Detailed Implementation

[0028] The following detailed description of this application is provided in conjunction with the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments are all from commercially available sources.

[0029] The source information of some of the raw materials used in the following embodiments of this application is as follows: The micro / nanosphere powder was purchased from Suzhou Yinrui Optoelectronics, with the brand name YRS-S700-2.

[0030] The micro-nano flake powder was purchased from Zhongse New Materials, with the grade AgF-2.

[0031] The micron-sized flake powder was purchased from Guizhou Platinum Industry Co., Ltd., and its grade is FAg-1000.

[0032] The bisphenol A type epoxy resin was purchased from Adico, brand name EP-4100HF.

[0033] The bisphenol F epoxy resin was purchased from Adico, brand name EP-4901HF.

[0034] The alicyclic epoxy resin was purchased from Selvey, brand name SWE-90.

[0035] The polyurethane-modified epoxy acrylic resin was purchased from Runao Chemical, with the brand name LuCure5894.

[0036] The aliphatic epoxy resin was purchased from Resonac, brand name ShofreePETG.

[0037] The silicone-modified epoxy acrylate resin was purchased from Runao Chemical, with the brand name LuCure9584.

[0038] The nanoparticle-modified epoxy acrylate resin was purchased from Evonik, with the brand name NANOPOX® C620.

[0039] The diluent, p-tert-butylphenyl glycidyl ether, was purchased from Adico, brand name ED-509S.

[0040] The diluent, 1,4-butanediol diglycidyl ether, was purchased from Denacol, brand name EX214L.

[0041] The diluent benzyl glycidyl ether was purchased from Merrill.

[0042] The diluent, polypropylene glycol diglycidyl ether, was purchased from Denacol, brand name EX931.

[0043] The diluent, trimethylolpropane triglycidyl ether, was purchased from Denacol, brand name EX321.

[0044] The aliphatic amine curing agent was purchased from Huntsman, brand name ARADUR42.

[0045] The aromatic amine curing agent was purchased from Adico, brand name EH-105L.

[0046] The modified imidazole curing agent was purchased from SHIKOKU, brand name 2P4MHZ-PW.

[0047] The latent curing agent was purchased from Adico, brand name EH-2021.

[0048] The dicyandiamide-based latent curing agent was purchased from Liuhe Chemical, brand name CG-120.

[0049] The alicyclic amine curing agent was purchased from BASF, brand name EC331.

[0050] γ-aminopropyltrimethoxysilane was purchased from Momentive, brand name A-1110.

[0051] γ-glycidoxypropyltrimethoxysilane was purchased from Evonik under the brand name DynasylanGLYMO.

[0052] γ-glycidoxypropyltriethoxysilane was purchased from Momentive, brand name A-1871.

[0053] γ-Mercaptopropyltrimethoxysilane was purchased from Momentive, brand name A-189.

[0054] γ-Urepropyltriethoxysilane was purchased from Momentive, brand name A-1160.

[0055] N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane was purchased from Momentive, brand name A-1120.

[0056] Trimethylolpropane triglycidyl ether was purchased from Momentive, brand name A-1100.

[0057] Vinyltriethoxysilane was purchased from Momentive, brand name A-151.

[0058] The alumina was purchased from Tianjin Zexi, with the grade SFADW-01.

[0059] Zinc oxide was purchased from Jiupeng New Materials, grade CY-J90.

[0060] The silica was purchased from Admatechs, grade FE920A-SQ.

[0061] Boron nitride was purchased from Tianjin Zexi, with the grade HBN-04.

[0062] The talcum powder was purchased from Suzhou Jinyi, brand name H10.

[0063] Montmorillonite was purchased from Nanocor, grade I.24.

[0064] The carbon black was purchased from Lion Corporation, and its grade is EC-300J.

[0065] The graphene was purchased from Changzhou Sixth Element, with the grade SE1231.

[0066] Methyl ethyl ketone, dibutyl phthalate, dimethyl phthalate, and propylene glycol methyl ether were purchased from Minglong Chemical.

[0067] Example 1 A low-silver conductive adhesive containing inorganic fillers, comprising the following components: Silver powder: 45kg (including 20kg of micro / nanosphere powder, 12kg of micro / nano flake powder, and 13kg of micron-sized flake powder; the D50 particle size of the micro / nanosphere powder is 50nm-2μm, and the D90 is ≤5μm; the D50 particle size of the micro / nano flake powder is 100nm-5μm, the thickness is 10-500nm, and the aspect ratio is ≥5:1; the D50 particle size of the micron-sized flake powder is 1-8μm, the D90 is ≤20μm, the thickness is 200nm-1μm, and the aspect ratio is ≥10:1). Epoxy resin: 19 kg (of which, 10 kg is bisphenol A type epoxy resin, 7 kg is bisphenol F type epoxy resin, and 2 kg is alicyclic epoxy resin, and at least one of the epoxy resins has a functionality ≥3). Modified epoxy acrylate resin: 10kg (polyurethane modified epoxy acrylate resin). Epoxy diluent: 3 kg (p-tert-butylphenyl glycidyl ether); Curing agent: 4kg (aliphatic amines); Silane coupling agent: 0.3 kg (γ-aminopropyltrimethoxysilane); Inorganic filler: 4 kg (alumina); Solvent: 3 kg (methyl ethyl ketone).

[0068] The weight ratio of epoxy resin to modified epoxy acrylic resin is 1.9:1, which is between 3:1 and 1:3.

[0069] Preparation method: (1) Mix bisphenol A type epoxy resin, bisphenol F type epoxy resin, alicyclic epoxy resin, polyurethane modified epoxy acrylate resin with p-tert-butylphenyl glycidyl ether and stir until uniform.

[0070] (2) Add aliphatic amine curing agent and γ-aminopropyltrimethoxysilane to the mixture in step (1), mix evenly, and then grind with three rollers to obtain a uniform resin matrix.

[0071] (3) Add micro-nano ball powder, micro-nano sheet powder, micron-sized sheet powder and alumina filler to the resin matrix of step (2), and then add methyl ethyl ketone to adjust the viscosity and mix thoroughly to obtain the low silver conductive adhesive.

[0072] Example 2 A low-silver conductive adhesive containing inorganic fillers, comprising the following components: Silver powder: 35kg (including 12kg of micro-nano sphere powder, 15kg of micro-nano flake powder, and 8kg of micron-sized flake powder). Epoxy resin: 25kg (of which, 15kg is bisphenol A epoxy resin, 5kg is bisphenol F epoxy resin, and 5kg is aliphatic epoxy resin). Modified epoxy acrylate resin: 20kg (15kg of silicone-modified epoxy acrylate resin, 5kg of nanoparticle-modified epoxy acrylate resin). Epoxy diluent: 6 kg (1,4-Butanediol diglycidyl ether); Curing agent: 10kg (aromatic amines); Silane coupling agent: 0.5 kg (γ-glycidoxypropyltrimethoxysilane); Inorganic filler: 1.5kg (zinc oxide 1.3kg, silicon dioxide 0.2kg); Solvent: 0.5 kg (dibutyl phthalate).

[0073] The weight ratio of epoxy resin to modified epoxy acrylic resin is 1.25:1, which is between 3:1 and 1:3.

[0074] Preparation method: Same as in Example 1, following the above components and corresponding steps.

[0075] Example 3 A low-silver conductive adhesive containing inorganic fillers, comprising the following components: Silver powder: 59kg (including 20kg of micro-nano sphere powder, 24kg of micro-nano flake powder, and 15kg of micron-sized flake powder). Epoxy resin: 15kg (of which, 5kg is bisphenol F type epoxy resin, 4kg is alicyclic epoxy resin, and 6kg is aliphatic epoxy resin). Modified epoxy acrylate resin: 10kg (polyurethane modified epoxy acrylate resin). Epoxy diluent: 2 kg (1 kg benzyl glycidyl ether, 1 kg polypropylene glycol diglycidyl ether). Curing agent: 2kg (1kg modified imidazole, 1kg latent curing agent); Silane coupling agent: 0.5 kg (0.2 kg of γ-glycidoxypropyltriethoxysilane, 0.3 kg of γ-mercaptopropyltrimethoxysilane); Inorganic filler: 1.5 kg (silicon dioxide); Solvent: 5 kg (dimethyl dicarboxylate).

[0076] The weight ratio of epoxy resin to modified epoxy acrylic resin is 1.5:1, which is between 3:1 and 1:3.

[0077] Preparation method: Same as in Example 1, following the above components and corresponding steps.

[0078] Example 4 A low-silver conductive adhesive containing inorganic fillers, comprising the following components: Silver powder: 55kg (including 20kg of micro-nano sphere powder, 20kg of micro-nano flake powder, and 15kg of micron-sized flake powder). Epoxy resin: 10kg (of which, 3kg is bisphenol F type epoxy resin, 5kg is aliphatic epoxy resin, and 2kg is alicyclic epoxy resin). Modified epoxy acrylate resin: 25kg (nanoparticle modified epoxy acrylate resin); Epoxy diluent: 1 kg (benzyl glycidyl ether); Curing agent: 4kg (modified imidazole); Silane coupling agent: 0.2 kg (γ-ureapropyltriethoxysilane); Inorganic filler: 10kg (5kg boron nitride, 5kg talc); Solvent: 1 kg (propylene glycol methyl ether).

[0079] The weight ratio of epoxy resin to modified epoxy acrylic resin is 1:2.5, which is between 3:1 and 1:3.

[0080] Preparation method: Same as in Example 1, following the above components and corresponding steps.

[0081] Example 5 The only difference between this embodiment and Embodiment 1 is that the total amount of silver powder is 35 kg, of which 16 kg is micro-nano ball powder and 19 kg is micro-nano sheet powder.

[0082] Example 6 The only difference between this embodiment and Embodiment 1 is that the total amount of silver powder is 35 kg, and only micro-nano spherical powder is used.

[0083] Example 7 The only difference between this embodiment and Embodiment 1 is that the D50 particle size of the micro / nanosphere powder is 10-80 nm and the D90 is 6-10 μm; the D50 of the micro / nano sheet powder is 50 nm-2 μm and the thickness is 500-1000 nm; and the D50 of the micron-sized sheet powder is 1-5 μm, the D90 is 25-40 μm and the thickness is 1-2 μm.

[0084] Example 8 The only difference between this embodiment and Embodiment 1 is that: 10 kg of bisphenol A type epoxy resin and 9 kg of bisphenol F type epoxy resin are used, and at least one of the epoxy resins has a functionality ≥3.

[0085] Example 9 The only difference between this embodiment and Embodiment 1 is that the epoxy resin used is 19kg of bisphenol A type epoxy resin with a functionality ≥3.

[0086] Example 10 The only difference between this embodiment and Embodiment 1 is that: 10 kg of bisphenol A epoxy resin, 7 kg of bisphenol F epoxy resin, and 2 kg of aliphatic epoxy resin are used, and at least one of the epoxy resins has a functionality ≥3.

[0087] Example 11 The only difference between this embodiment and Embodiment 1 is that the modified epoxy acrylate resin used is an organosilicon-modified epoxy acrylate resin.

[0088] Example 12 The only difference between this embodiment and Embodiment 1 is that the modified epoxy acrylate resin is a nanoparticle modified epoxy acrylate resin.

[0089] Example 13 The only difference between this embodiment and Embodiment 1 is that the modified epoxy acrylate resin used is 5 kg of polyurethane modified epoxy acrylate resin and 5 kg of nanoparticle modified epoxy acrylate resin.

[0090] Example 14 The only difference between this embodiment and Example 1 is that benzyl glycidyl ether and 1,4-butanediol diglycidyl ether are mixed in a mass ratio of 1:1 in 3 kg of epoxy diluent.

[0091] Example 15 The only difference between this embodiment and Example 1 is that: in the 3kg epoxy diluent, polypropylene glycol diglycidyl ether and trimethylolpropane triglycidyl ether are mixed in a mass ratio of 1:1.

[0092] Example 16 The only difference between this embodiment and Embodiment 1 is that aliphatic amines and alicyclic amines are mixed in a mass ratio of 1:1 in 1 kg of curing agent.

[0093] Example 17 The only difference between this embodiment and Example 1 is that: in 1 kg of curing agent, aromatic amines, latent curing agents, dicyandiamide, and modified imidazole are compounded in a mass ratio of 1:1:1:1.

[0094] Example 18 The only difference between this embodiment and Example 1 is that the silane coupling agent used is γ-aminopropyltrimethoxysilane.

[0095] Example 19 The only difference between this embodiment and Example 1 is that the silane coupling agent is a mixture of γ-glycidoxypropyltrimethoxysilane and γ-glycidoxypropyltriethoxysilane in a mass ratio of 1:1.

[0096] Example 20 The only difference between this embodiment and Example 1 is that the silane coupling agent is a mixture of γ-mercaptopropyltrimethoxysilane, γ-ureapropyltriethoxysilane, and vinyltriethoxysilane in a mass ratio of 1:2:3.

[0097] Example 21 The only difference between this embodiment and Example 1 is that the inorganic filler is selected from zinc oxide, silicon dioxide, and boron nitride in a mass ratio of 2:1:1.

[0098] Example 22 The only difference between this embodiment and Embodiment 1 is that the inorganic filler is selected from silicon nitride, carbon black, graphite, graphene, carbon fiber, talc, and montmorillonite in a mass ratio of 1:1:1:0.5:1:1:2.

[0099] Example 23 The only difference between this embodiment and Example 1 is that dibutyl phthalate is used as the solvent.

[0100] Example 24 The only difference between this embodiment and Example 1 is that the solvent used is a mixture of dimethyl dicarboxylate and propylene glycol methyl ether in a mass ratio of 1:1.

[0101] Comparative Example 1 A low-silver conductive adhesive containing inorganic fillers differs from Example 1 in that it uses 23.2 kg of epoxy resin and 5.8 kg of modified epoxy acrylate resin, with a weight ratio of epoxy resin to modified epoxy acrylate resin of 4:1. All other components remain the same as in Example 1.

[0102] Comparative Example 2 A low-silver conductive adhesive containing inorganic fillers differs from Example 1 in that it uses 5.8 kg of epoxy resin and 23.2 kg of modified epoxy acrylate resin, with a weight ratio of epoxy resin to modified epoxy acrylate resin of 1:4. All other components remain the same as in Example 1.

[0103] Comparative Example 3 A low-silver conductive adhesive containing inorganic fillers differs from Example 1 in that the raw materials used are: 30 kg of silver powder, 50 kg of resin matrix, 12 kg of epoxy diluent, 15 kg of curing agent, 0.5 kg of silane coupling agent, 12 kg of inorganic filler, and 8 kg of solvent; the weight ratio of epoxy resin to modified epoxy acrylic resin in the resin matrix is ​​1.9:1.

[0104] Comparative Example 4 A low-silver conductive adhesive containing inorganic fillers differs from Example 1 in that the raw materials used are: 70 kg of silver powder, 20 kg of resin matrix, 0.8 kg of epoxy diluent, 0.5 kg of curing agent, 1 kg of silane coupling agent, 1 kg of inorganic filler, and 8 kg of solvent; the weight ratio of epoxy resin to modified epoxy acrylic resin in the resin matrix is ​​1.9:1.

[0105] Detection methods The performance testing of the low-silver conductive adhesive containing inorganic fillers described in the embodiments of this application was carried out according to the following methods to ensure the accuracy, comparability and repeatability of the test results. All tests were carried out after the samples were fully cured under the specified curing conditions (placed in an oven at 175°C for 1 hour). Before the test, the samples were placed in a standard laboratory environment (temperature 23±2°C, relative humidity 50±5%) for at least 24 hours.

[0106] Thermal conductivity testing was conducted according to GB / T 22588-2008, "Measurement of Thermal Diffusion Coefficient or Thermal Conductivity by Flash Method". Cured conductive adhesive was prepared into circular samples with a diameter of 12.7 mm and a thickness of approximately 1 mm. The test was performed using a laser flash method (LFA) thermal conductivity meter at a test temperature of 25°C. The thermal diffusion coefficient of the material was measured, and the thermal conductivity was calculated by combining this with its specific heat capacity and density. The results were reported in W / (m·K). Each sample was measured three times, and the average value was taken.

[0107] Volume resistivity testing was conducted according to GB / T15662-1995, "Test Method for Volume Resistivity of Conductive and Antistatic Plastics". Conductive adhesive was coated onto an insulating substrate and cured to form a thin film of uniform thickness (approximately 100 μm). Using a four-probe method or an insulation resistance tester equipped with square electrodes, the resistance between the two electrodes of the sample was measured under a DC voltage of 10V. The volume resistivity was calculated based on the sample's geometric dimensions (thickness and electrode area), and the result was reported in Ω·cm, expressed as 10. -4 The measurements were on the order of Ω·cm, with each sample measured five times at different locations and the average value taken.

[0108] High-temperature adhesive strength testing was conducted using a dedicated microelectronic adhesive strength push tester. The test sample structure consisted of a 1mm × 1mm silicon chip bonded to a silver-plated substrate using the conductive adhesive to be tested, and cured under the same conditions as described above. The prepared shear test sample was placed on the test stage, and the heating stage temperature was set and stabilized at 260℃. A flat-push blade was used to push the silicon chip at a constant speed (typically 200 μm / s) until the adhesive interface failed. The instrument recorded the maximum push force at shear failure, expressing the adhesive strength in kilogram-forces (kg). At least five sample points were tested for each formulation, and the arithmetic mean was reported. The interface failure mode (cohesive failure or interface failure) was observed and recorded.

[0109] Table 1 Detection Data Example 1 3.2 13 1.3 Example 2 2.9 14 1.2 Example 3 3.5 9 1.1 Example 4 6.5 7 1.0 Example 5 3.0 30 1.1 Example 6 2.1 110 1.2 Example 7 2.5 35 0.9 Example 8 3.2 13 1.3 Example 9 3.3 12 1.4 Example 10 3.2 13 1.3 Example 11 3.1 14 1.3 Example 12 3.0 14 1.2 Example 13 3.3 12 1.4 Example 14 3.2 13 1.3 Example 15 3.2 13 1.3 Example 16 3.2 13 1.3 Example 17 3.2 13 1.3 Example 18 3.2 13 1.3 Example 19 3.2 13 1.3 Example 20 3.2 13 1.3 Example 21 3.3 12 1.3 Example 22 3.2 13 1.3 Example 23 3.2 13 1.3 Example 24 3.2 13 1.3 Comparative Example 1 3.3 4 0.8 Comparative Example 2 4.5 95 0.7 Comparative Example 3 1.2 180 0.5 Comparative Example 4 6.8 2 0.6 Combining Examples 1, 5, 6, and 7 with Table 1, it can be seen that Example 1 uses a three-phase composite of micro / nanosphere powder, micro / nanosheet powder, and micron-sized sheet powder. The sphere powder fills the gaps between the sheet powders, and the sheet powder provides surface contact, forming a dense and continuous conductive and thermally conductive network. Example 5 uses only micro / nanosphere powder and micro / nanosheet powder, resulting in a slight decrease in performance. Example 6 uses only a single micro / nanosphere powder, with point contact between particles, discontinuous conductive pathways, increased volume resistivity, and decreased thermal conductivity. In Example 7, the silver powder particle size distribution exceeds the preferred range, resulting in decreased packing efficiency, increased volume resistivity, and decreased high-temperature bonding strength. This indicates that a composite of silver powder with multiple morphologies and narrow particle size distribution is key to achieving high conductivity with low silver content.

[0110] Combining Examples 1, 8, 9, 10, 11, 12, and 13 with Comparative Examples 1 and 2, and referring to Table 1, it can be seen that Example 1 uses a multifunctional epoxy resin with a functionality ≥3 and a polyurethane-modified epoxy acrylate resin in a ratio of 1.9:1, which balances rigid crosslinking network and flexible toughening, achieving a high-temperature bonding strength of 1.3 kg. Examples 8-10 adjusted the specific types of epoxy resin, but all maintained at least one functionality ≥3, and their performance was basically the same as Example 1. Examples 11-13 used silicone-modified, nanoparticle-modified, or a combination of both modified epoxy acrylate resins, respectively, and their performance was also stable, indicating that various modification methods can achieve a synergistic effect of rigidity and flexibility. In Comparative Example 1, the epoxy resin ratio was too high (4:1), resulting in excessive system rigidity, concentrated curing stress, and a high-temperature bonding strength reduced to 0.8 kg. In Comparative Example 2, the proportion of modified epoxy acrylate resin was too high (1:4), resulting in an overly flexible system with insufficient resin strength at high temperatures. This weakened the anchoring effect on the silver powder, causing the volume resistivity to surge to 95 × 10⁻⁶. -4 The bond strength was only 0.7 kg, with an Ω·cm resistance. This verifies that a resin matrix ratio in the range of 3:1 to 1:3 is key to ensuring the stability of the conductive network and the reliability of the bond.

[0111] Combining Examples 1, 2, 3, and 4 with Comparative Examples 3 and 4, and referring to Table 1, it can be seen that in Examples 1-4, the amount of silver powder ranges from 35 to 59 parts, and the amount of resin matrix ranges from 25 to 45 parts. All components are within the preferred range, resulting in excellent overall performance. In Comparative Example 3, the amount of silver powder is below the lower limit (30 parts), and the amount of resin matrix is ​​too high (50 parts). The conductive filler cannot form an effective percolation network, and the volume resistivity is as high as 180 × 10⁻⁶. -4 The thermal conductivity is only 1.2 W / (m·K), and the high-temperature bond strength is only 0.5 kg. Comparative Example 4, with a silver powder content exceeding the upper limit and a low resin matrix content, while exhibiting excellent volume resistivity and thermal conductivity, suffers from weak interfacial bonding due to insufficient resin, resulting in a high-temperature bond strength of only 0.6 kg. This indicates that the 35-60 parts silver powder and 25-45 parts resin matrix specified in this application represent the optimal window for achieving a balance between electrical conductivity, thermal conductivity, and bond strength.

[0112] Based on Examples 14-24 and Table 1, it can be seen that Examples 14-15 used different reactive diluents, Examples 16-17 used multiple curing agents, Examples 18-20 used different silane coupling agents, Examples 21-22 used multiple inorganic fillers, and Examples 23-24 used different solvents. Their performance is basically the same as that of Example 1, with thermal conductivity maintained at 3.0-3.3 W / (m·K) and volume resistivity at 12-14 × 10⁻⁶. -4The high-temperature bond strength is between 1.2-1.4 kg and Ω·cm. This indicates that the preferred range of various additives in this application is well inclusive, and different types of raw materials can achieve stable comprehensive performance within the defined range.

[0113] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A low-silver conductive adhesive containing inorganic fillers, characterized in that, By weight, it includes the following components: 35-60 parts silver powder; 25-45 parts of resin matrix; 1-10 parts epoxy diluent; 1-10 parts of curing agent; 0.1-0.5 parts of silane coupling agent; 1-10 parts of inorganic filler; Solvent 0.5-5 parts; The resin matrix comprises epoxy resin and modified epoxy acrylate resin, with a weight ratio between 3:1 and 1:3; the silver powder comprises at least two of micro-nano sphere powder, micro-nano flake powder, and micron-sized flake powder.

2. The low-silver conductive adhesive containing inorganic fillers according to claim 1, characterized in that, The micro / nanosphere powder has a D50 particle size of 50nm-2μm and a D90 ≤ 5μm; the micro / nano sheet powder has a sheet diameter of 100nm-5μm, a thickness of 10-500nm, and an aspect ratio ≥ 5:1; the micron-sized sheet powder has a sheet diameter of 1-8μm, a D90 ≤ 20μm, a thickness of 200nm-1μm, and an aspect ratio ≥ 10:

1.

3. The low-silver conductive adhesive containing inorganic fillers according to claim 1, characterized in that, The epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, alicyclic epoxy resin, and aliphatic epoxy resin, and the functionality of at least one of the epoxy resins is ≥3; the modified epoxy acrylate resin is selected from at least one of polyurethane modified epoxy acrylate resin, organosilicon modified epoxy acrylate resin, and nanoparticle modified epoxy acrylate resin.

4. The low-silver conductive adhesive containing inorganic fillers according to claim 1, characterized in that, The epoxy diluent is selected from at least one of p-tert-butylphenyl glycidyl ether, benzyl glycidyl ether, 1,4-butanediol diglycidyl ether, polypropylene glycol diglycidyl ether, and trimethylolpropane triglycidyl ether.

5. The low-silver conductive adhesive containing inorganic fillers according to claim 1, characterized in that, The curing agent is selected from at least one of aliphatic amines, alicyclic amines, aromatic amines, latent curing agents, dicyandiamide, and modified imidazole.

6. The low-silver conductive adhesive containing inorganic fillers according to claim 1, characterized in that, The silane coupling agent is selected from at least one of aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-ureapropyltriethoxysilane, and vinyltriethoxysilane.

7. The low-silver conductive adhesive containing inorganic fillers according to claim 1, characterized in that, The inorganic filler is selected from at least one of alumina, zinc oxide, silicon dioxide, boron nitride, silicon nitride, carbon black, talc, and montmorillonite.

8. The low-silver conductive adhesive containing inorganic fillers according to claim 1, characterized in that, The solvent is selected from at least one of methyl ethyl ketone, dibutyl phthalate, dimethyl dimethyl phthalate, and propylene glycol methyl ether.

9. A method for preparing a low-silver conductive adhesive containing inorganic fillers according to any one of claims 1-8, characterized in that, Includes the following steps: (1) Mix epoxy resin, modified epoxy acrylic resin and epoxy diluent, and stir until uniform; (2) Add curing agent and silane coupling agent to the mixture obtained in step (1), continue to mix evenly, and obtain a uniform resin matrix by three-roll milling; (3) Add silver powder and inorganic filler to the resin matrix obtained in step (2), and add solvent to adjust the viscosity. Mix evenly to obtain the low silver conductive adhesive.