Nano-silver sintering type conductive adhesive for microelectronic packaging and preparation method thereof
By using a mixture of silver nanowires and ultrafine silver powder in conductive adhesives, and optimizing the formulation and preparation process, the problem of low thermal conductivity of conductive adhesives was solved, resulting in a significant improvement in both electrical and thermal conductivity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHENZHEN NO 1 FINE CHEM CO LTD
- Filing Date
- 2022-01-17
- Publication Date
- 2026-07-03
AI Technical Summary
The existing conductive adhesive has low thermal conductivity, which leads to unstable contact resistance.
A mixture of silver nanowires and ultrafine silver powder was used as a conductive filler. By optimizing the raw material ratio and preparation method, a conductive path was formed, thereby improving electrical and thermal conductivity.
The volume resistivity of the conductive adhesive was reduced to 0.30-0.79×10-4Ω·cm, and the thermal conductivity was increased to 9.7-14.9W·m-1·k-1, thus improving its electrical conductivity.
Smart Images
Figure BDA0003474473700000051 
Figure BDA0003474473700000061 
Figure BDA0003474473700000062
Abstract
Description
Technical Field
[0001] This application relates to the field of conductive adhesive technology, and in particular to a nano-silver sintered conductive adhesive for microelectronic packaging and its preparation method. Background Technology
[0002] Conductive adhesives, also known as conductive adhesives, are adhesives that possess both conductive and adhesive functions. The working principle of conductive adhesives is based on the molecular framework structure formed after the polymer cures, providing both mechanical and adhesive properties. Simultaneously, the conductive particles are bonded together by the adhesive effect of the base resin, creating conductive pathways and achieving a conductive connection between the bonded materials.
[0003] Conductive adhesives are mostly used in the assembly of semiconductor integrated circuits, with applications primarily including wafer bonding, flip-chip interconnection, and surface mounting. Currently, conductive adhesives generally consist of a base resin, conductive fillers, and additives. Compared to metal solder paste technology, conductive adhesives have advantages such as being environmentally friendly and requiring fewer processing steps; however, their lower thermal conductivity can easily lead to unstable contact resistance. Summary of the Invention
[0004] To improve the thermal conductivity of conductive adhesives, this application provides a nano-silver sintered conductive adhesive for microelectronic packaging and its preparation method.
[0005] In a first aspect, this application provides a nano-silver sintered conductive adhesive for microelectronic packaging, which adopts the following technical solution: A nano-silver sintered conductive adhesive for microelectronic packaging, comprising the following raw materials in parts by weight: 15-65 parts epoxy resin, 2-10 parts latent curing agent, 1-5 parts toughening agent, 5-15 parts diluent, 0.01-2 parts additive, and 25-90 parts silver powder, wherein the silver powder is a mixture of nano-silver wires and ultrafine nano-silver powder.
[0006] By adopting the above technical solution, the nano-silver sintered conductive adhesive of this application, through the synergistic effect between the raw materials, reduces the volume resistivity and increases the thermal conductivity of the conductive adhesive, thereby improving the conductivity of the conductive adhesive. Specifically, the volume resistivity is 0.30-0.79×10⁻⁶. -4 Ω·cm, thermal conductivity 9.7-14.9 W·m -1 ·k -1 .
[0007] Epoxy resin is the base component of conductive adhesives, acting as an adhesive to enhance bond strength and improve adhesion to various materials. Latent curing agents are single-component systems added to epoxy resin that exhibit certain storage stability at room temperature but rapidly cure under conditions of heat, light, humidity, or pressure. Using latent curing agents in conductive adhesive raw materials allows for rapid curing under specific conditions, increasing the curing rate. Cured epoxy resin has low elongation and high brittleness; when the bonded area is subjected to external force, cracks easily form and propagate rapidly, leading to adhesive layer cracking and weak adhesion. Toughening agents, applied to conductive adhesive raw materials, increase the toughness of the epoxy resin, reduce post-curing cracking, and improve bond strength. Diluents are used as solvents.
[0008] Silver powder, used as a conductive filler in conductive adhesives, forms conductive pathways within the adhesive, thus imparting conductivity. Furthermore, the silver powder is a mixture of silver nanowires and ultrafine silver powder. The silver nanowires increase the contact area with other raw materials, creating more conductive pathways and improving the thermal and electrical conductivity of the conductive adhesive. However, due to the large specific surface area of silver nanowires, mixing them with epoxy resin can easily lead to excessive viscosity, affecting flowability and hindering the mixing of various raw materials. Ultrafine silver powder reduces viscosity, increases flowability, facilitates uniform mixing of raw materials, and improves the conductivity of the conductive adhesive. Adding ultrafine silver powder also reduces costs. Through the synergistic effect between silver nanowires and ultrafine silver powder, the preparation of conductive adhesives is facilitated, and both the electrical and thermal conductivity of the conductive adhesive can be improved.
[0009] As a preferred embodiment, it comprises the following raw materials in parts by weight: 25-50 parts epoxy resin, 5-8 parts latent curing agent, 2-4 parts toughening agent, 6-12 parts diluent, 0.08-1.6 parts additive, and 40-75 parts silver powder.
[0010] By adopting the above technical solution and optimizing the weight ratio of epoxy resin, latent curing agent, toughening agent, diluent, additives, and silver powder, the conductivity and thermal conductivity of the conductive adhesive can be further improved.
[0011] Preferably, the amount of silver nanowires added is 30-70% of the silver powder.
[0012] When the amount of silver nanowires added is too small, insufficient sintering will occur during sintering at 300℃, resulting in the inability to form a conductive network and conductive channels, thus affecting the conductivity of the conductive adhesive. When the amount of silver nanowires added is too large, the sintering temperature needs to be increased to above 300℃, even approaching the softening and melting points of silver; otherwise, good reliable adhesion and the formation of a conductive network cannot be achieved. Furthermore, epoxy resin will quickly carbonize above 300℃, losing its adhesive strength and affecting the adhesion of the conductive adhesive. By adopting the above technical solution, when the amount of silver nanowires added is within the above range, not only can the conductive adhesive maintain good adhesive strength with the material, but the conductivity and thermal conductivity of the conductive adhesive can also be improved, thus enhancing its overall conductivity.
[0013] Preferably, the silver nanowires are silver nanowires with a diameter of 20-200 nm and a length of 2-3 μm, and the ultrafine silver nanoparticles have a particle size of 0.1-10 μm.
[0014] Furthermore, the silver nanowires are silver nanowires with a diameter of 40-60 nm and a length of 2-3 μm, and the ultrafine silver nanoparticles have a particle size of 0.1-10 μm and are in one or more of the following forms: flake-like, linear, or dendritic.
[0015] By adopting the above technical solution, the diameter and length of the silver nanowires and the particle size of the ultrafine silver nanoparticles can be limited, which can further improve the conductivity of the conductive adhesive.
[0016] Preferably, the silver nanowires are prepared using the following method:
[0017] S1: Add silver nitrate to ethylene glycol solution and stir until homogeneous to obtain solution A; add sodium chloride and polyvinylpyrrolidone to ethylene glycol solution and stir until homogeneous to obtain solution B; take ethylene glycol, heat to a temperature of 160-180℃, and add solution A and solution B to ethylene glycol to obtain solution C; stir until solution C turns grayish-white, then stop heating;
[0018] S2: Wash solution C with acetone using ultrasound, centrifuge, remove the solid, wash, and dry to obtain silver nanowires.
[0019] Furthermore, the silver nanowires are prepared using the following method:
[0020] S1: Add silver nitrate to an ethylene glycol solution and stir for 30-40 minutes to obtain solution A; add sodium chloride and polyvinylpyrrolidone to an ethylene glycol solution and stir for 50-60 minutes to obtain solution B; take ethylene glycol, heat it to 160-180℃, and add solution A and solution B to the ethylene glycol to obtain solution C. Stir until solution C turns grayish-white, then stop heating; wherein, the volume of ethylene glycol solution added to each 1g of silver nitrate is 58.5-59.1mL, the molecular weight of polyvinylpyrrolidone is 40000, the volume of ethylene glycol solution added to each 1g of polyvinylpyrrolidone is 0.81-0.85mL, the mass fraction of the ethylene glycol solution is 40-50%, the weight ratio of polyvinylpyrrolidone to sodium chloride is 1:(0.005-0.007), and the weight ratio of solution A, solution B, and ethylene glycol is (70-90):(70-90):(100-120);
[0021] S2: Wash solution C with acetone using ultrasonication at 300-350W, centrifuge at 3000-4000r / min for 10-20min, remove the solid, wash with 70-80% ethanol solution 8-10 times, and then dry the solid at 60-70℃ for 30-40min to obtain silver nanowires; wherein, the amount of acetone added is 720-900mL.
[0022] By employing the above technical solution, using ethylene glycol solution as a solvent, which has a relatively high dielectric constant, silver nitrate and polyvinylpyrrolidone can be dissolved. Then, acetone is used for washing, followed by centrifugation, and the solid is removed and dried to obtain silver nanowires. This preparation method can produce silver nanowires with a high yield.
[0023] Preferably, the silver nanowires are pretreated by the following method before use: glutaric acid is placed in an ethanol solution, stirred evenly, the silver nanowires are added, ultrasonically dispersed, the solid is removed, washed, and dried to obtain the pretreated silver nanowires.
[0024] Furthermore, the silver nanowires are pretreated before use by the following method: glutaric acid is placed in a 70-80% ethanol solution and stirred for 30-50 minutes. The silver nanowires are then added and ultrasonically dispersed at 300-350W for 10-30 minutes. The solid is then removed, washed 3-5 times with a 70-80% ethanol solution, and vacuum dried for 25-35 minutes to obtain the pretreated silver nanowires. The volume of ethanol solution added to each 1g of glutaric acid is 10-20mL, and the weight ratio of glutaric acid to silver nanowires is 1:(1.2-2.0).
[0025] By employing the above technical solution, the large surface area of silver nanowires makes them prone to aggregation, hindering their dispersion in the conductive adhesive and resulting in only localized conductive pathways. This, in turn, affects the stability of the contact resistance. Pre-treating the silver nanowires using the above method improves their dispersibility, allowing them to function better in the conductive adhesive and further enhancing its electrical and thermal conductivity.
[0026] Preferably, the epoxy resin is one or more of the following: glycidyl ether type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, aliphatic epoxy resin, and linear aliphatic epoxy compound.
[0027] Preferably, the latent curing agent is one or more of the following: dicyandiamide, diaminodiphenyl sulfone, organic hydrazide, acid anhydride, imidazole, ammonium-blocked Lewis acid salt, boron trifluoride-amine complex, oxoboron heterocyclic boron-amine complex, imidazole-metal salt complex, and cyclic amide.
[0028] Preferably, the toughening agent is one or more of the following: polysulfide rubber, urethane prepolymer, polyacrylic acid copolymer, core-shell polyacrylic acid particles, carboxyl-terminated butadiene-acrylonitrile rubber, aromatic amide butadiene-acrylonitrile rubber block copolymer, polybutadiene rubber, thermoplastic polyethersulfone (PES), and thermoplastic nylon.
[0029] By adopting the above technical solution and limiting the epoxy resin, latent curing agent, and toughening agent, the conductive adhesive can exhibit better electrical and thermal conductivity.
[0030] Secondly, this application provides a method for preparing a nano-silver sintered conductive adhesive for microelectronic packaging, using the following technical solution:
[0031] A nano-silver sintered conductive adhesive for microelectronic packaging includes the following steps:
[0032] Mix epoxy resin, toughening agent, diluent, additives, and silver powder, stir evenly, melt, then add latent curing agent, stir evenly, and cure at 140-160℃ for 1-3 hours to obtain conductive adhesive.
[0033] Furthermore, a nano-silver sintered conductive adhesive for microelectronic packaging includes the following steps:
[0034] Mix epoxy resin, toughening agent, diluent, additives, and silver powder, stir for 1-2 hours, melt at 130-140℃, add latent curing agent, stir for 40-50 minutes, and cure at 140-160℃ for 1-3 hours to obtain conductive adhesive.
[0035] By adopting the above technical solution, the epoxy resin is first dried to remove the moisture in the epoxy resin, which reduces the formation of cracks after the conductive adhesive and the material are bonded. Then, other raw materials are mixed and cured to obtain conductive adhesive. This makes it easier for the raw materials to be mixed more evenly, and makes it easier for the conductive adhesive to exhibit better conductivity and thermal conductivity.
[0036] In summary, this application includes at least one of the following beneficial technical effects:
[0037] 1. Because this application uses a mixture of silver nanowires and ultrafine silver powder as the raw material for conductive adhesive, it not only reduces costs but also increases the fluidity of the conductive adhesive. Furthermore, through the synergistic effect between the two, it can improve the electrical and thermal conductivity of the conductive adhesive, achieving a volume resistivity of 0.30 × 10⁻⁶. -4 Ω·cm, with a thermal conductivity of 14.9 W·m. -1 ·k -1 .
[0038] 2. In this application, a glutaric acid ethanol solution is preferably used to pretreat the silver nanowires before use. This reduces the specific surface energy of the silver nanowires, minimizes their agglomeration, and facilitates more uniform dispersion of the nanowires in the conductive adhesive. This allows the silver nanowires to function better, thereby improving the conductivity and thermal conductivity of the conductive adhesive, achieving a volume resistivity of 0.30 × 10⁻⁶. -4 Ω·cm, with a thermal conductivity of 14.9 W·m. -1 ·k -1 . Detailed Implementation
[0039] The following provides a more detailed description of this application in conjunction with specific details.
[0040] raw material
[0041] The epoxy resin is hydrogenated bisphenol A alicyclic glycidyl ether type epoxy resin, selected from Shenzhen Longdi Chemical Co., Ltd.; the latent curing agent is dicyandiamide, selected from Henan Mingzhixin Chemical Products Co., Ltd.; the toughening agent is polysulfide rubber CAS63148-67-4, selected from Hubei Dongcao Chemical Technology Co., Ltd.; the diluent is non-reactive diluent n-butanol, selected from Jinan Fangxu Chemical Co., Ltd.; the additive is isooctyl alcohol, selected from Aite (Shandong) New Materials Co., Ltd.; the molecular weight of polyvinylpyrrolidone is 40,000, selected from Jinan Hongwang Chemical Co., Ltd.; and the mass fraction of the ethylene glycol solution is 45%.
[0042] Preparation Example
[0043] Preparation Example 1
[0044] A type of silver nanowire, prepared by the following method:
[0045] S1: Silver nitrate is added to an ethylene glycol solution and stirred for 35 minutes to obtain solution A; sodium chloride and polyvinylpyrrolidone are added to an ethylene glycol solution and stirred for 55 minutes to obtain solution B; ethylene glycol is heated to 170°C, and solutions A and B are added to the ethylene glycol to obtain solution C. The mixture is stirred until solution C turns grayish-white, and then heating is stopped; wherein, the volume of ethylene glycol solution added to each 1g of silver nitrate is 58.8mL, the molecular weight of polyvinylpyrrolidone is 40000, the volume of ethylene glycol solution added to each 1g of polyvinylpyrrolidone is 0.83mL, the weight ratio of polyvinylpyrrolidone to sodium chloride is 1:0.006, and the weight ratio of solution A, solution B, and ethylene glycol is 80:80:110;
[0046] S2: Wash solution C with 810 mL of acetone using ultrasonication at 330 W, centrifuge at 3500 r / min for 15 min, remove the solid, wash it 9 times with 75% ethanol solution, and then dry the solid at 65℃ for 35 min to obtain silver nanowires.
[0047] Example
[0048] Example 1
[0049] A nano-silver sintered conductive adhesive for microelectronic packaging, the raw material ratio of which is shown in Table 1.
[0050] The silver nanowires in the silver powder were prepared using Preparation Example 1. The epoxy resin was hydrogenated bisphenol A alicyclic glycidyl ether type epoxy resin, the latent curing agent was dicyandiamide, the toughening agent was polysulfide rubber CAS63148-67-4, the diluent was non-reactive diluent n-butanol, and the additive was isooctanol.
[0051] A nano-silver sintered conductive adhesive for microelectronic packaging includes the following steps:
[0052] Epoxy resin, toughening agent, diluent, additives, and silver powder are mixed and stirred for 1.5 hours. The mixture is then melted at 135°C. A latent curing agent is added, and the mixture is stirred for 45 minutes. Finally, the mixture is cured at 150°C for 2 hours to obtain a conductive adhesive.
[0053] Examples 2-5
[0054] A nano-silver sintered conductive adhesive for microelectronic packaging differs from Example 1 in that the raw material ratio of the conductive adhesive is different, as shown in Table 1.
[0055] Table 1. Dosage of each raw material in the conductive adhesives of Examples 1-5 (unit: kg)
[0056]
[0057]
[0058] Examples 6-9
[0059] A nano-silver sintered conductive adhesive for microelectronic packaging differs from Example 5 in that the raw material ratio of the conductive adhesive is different, as shown in Table 2.
[0060] Table 2. Dosage of each raw material in the conductive adhesives of Examples 6-9 (unit: kg)
[0061]
[0062] Examples 10-13
[0063] A nano-silver sintered conductive adhesive for microelectronic packaging differs from Example 7 in that the raw material ratio of the conductive adhesive is different, as shown in Table 3.
[0064] Table 3. Dosage of each raw material in the conductive adhesives of Examples 10-13 (unit: kg)
[0065]
[0066] Example 14
[0067] A nano-silver sintered conductive adhesive for microelectronic packaging differs from Example 11 in that the nano-silver wires in the silver powder of the conductive adhesive raw material are pretreated by the following method before use:
[0068] Glutaric acid was placed in a 75% ethanol solution and stirred for 40 min. Silver nanowires were then added and ultrasonically dispersed at 325 W for 20 min. The solid was removed, washed four times with a 75% ethanol solution, and vacuum dried for 30 min to obtain pretreated silver nanowires. The volume of ethanol solution added to each 1 g of glutaric acid was 15 mL, and the weight ratio of glutaric acid to silver nanowires was 1:1.6.
[0069] Comparative Example
[0070] Comparative Example 1
[0071] A nano-silver sintered conductive adhesive for microelectronic packaging differs from Example 1 in that the silver powder in the conductive adhesive is replaced by an equal amount of ultrafine nano-silver wires.
[0072] Comparative Example 2
[0073] A nano-silver sintered conductive adhesive for microelectronic packaging differs from Example 1 in that the silver powder in the conductive adhesive is replaced by an equal amount of ultrafine nano-silver powder instead of nano-silver wires.
[0074] Comparative Example 3
[0075] A nano-silver sintered conductive adhesive for microelectronic packaging differs from Example 1 in that no silver powder is added to the conductive adhesive.
[0076] Performance testing
[0077] The conductive adhesives in Examples 1-14 and Comparative Examples 1-3 were subjected to the following performance tests:
[0078] Volume resistivity: The volume resistivity of the conductive adhesive was determined according to GB / T15662-1995 "Test Method for Volume Resistivity of Conductive and Antistatic Plastics". The test results are shown in Table 4.
[0079] Thermal conductivity: The thermal conductivity of the conductive adhesive was measured according to ASTM D5470 "Test of thermal conductivity". The test results are shown in Table 4.
[0080] Table 4 Test Results
[0081]
[0082]
[0083] As shown in Table 4, the nano-silver sintered conductive adhesive of this application, through the synergistic effect between the raw materials, reduces the volume resistivity and increases the thermal conductivity of the conductive adhesive, thereby improving its electrical conductivity. Specifically, the volume resistivity is 0.30-0.79 × 10⁻⁶. -4 Ω·cm, thermal conductivity 9.7-14.9 W·m -1 ·k -1 .
[0084] As can be seen from Example 1 and Comparative Examples 1-3, the volume resistivity in Example 1 is 0.76 × 10⁻⁶. -4 Ω·cm, thermal conductivity 10.1 W·m -1 ·k -1 The results are superior to those of Comparative Examples 1-3, indicating that using silver nanowires and ultrafine rice silver powder in the raw materials of conductive adhesive is more suitable. Through the synergistic effect between the two, the volume resistivity of conductive adhesive can be reduced and the thermal conductivity can be improved, thereby improving the conductivity of conductive adhesive.
[0085] As can be seen from Examples 1-5, the volume resistivity in Example 5 is 0.52 × 10⁻⁶. -4 Ω·cm, thermal conductivity 12.4 W·m -1 ·k -1 The results in Example 5 are superior to those in other embodiments, indicating that the amount of silver powder added to the raw materials of the conductive adhesive is more suitable, which can reduce the volume resistivity of the conductive adhesive, increase the thermal conductivity, and thus improve the conductivity of the conductive adhesive.
[0086] As can be seen from Examples 6-9, the volume resistivity in Example 7 is 0.41 × 10⁻⁶. -4 Ω·cm, thermal conductivity 13.7 W·m -1 ·k -1 This is superior to other embodiments, indicating that the weight ratio of silver nanowires and ultrafine silver powder in the silver powder in Example 7 is more suitable, which can reduce the volume resistivity of the conductive adhesive, improve the thermal conductivity, and improve the conductivity of the conductive adhesive.
[0087] As can be seen from Examples 10-13, apart from silver powder, the amount of other raw materials in the conductive adhesive has little effect on the conductivity of the conductive adhesive.
[0088] Combining Examples 11 and 14, it can be seen that the volume resistivity in Example 14 is 0.30 × 10⁻⁶. -4 Ω·cm, thermal conductivity 14.9 W·m -1 ·k -1 This is superior to Example 11, indicating that pretreatment of the silver nanowires before use can improve the conductivity of the conductive adhesive, reduce the volume resistivity of the conductive adhesive, and improve the thermal conductivity.
[0089] The embodiments described above are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.
Claims
1. A nano-silver sintered conductive adhesive for microelectronic packaging, characterized in that: It comprises the following raw materials in parts by weight: 30 parts epoxy resin, 6 parts latent curing agent, 3 parts toughening agent, 10 parts diluent, 1.2 parts additives, 45 parts nano silver wire, and 45 parts ultrafine nano silver powder. The silver nanowires were prepared using the following method: S1: Add silver nitrate to ethylene glycol solution and stir until homogeneous to obtain solution A; add sodium chloride and polyvinylpyrrolidone to ethylene glycol solution and stir until homogeneous to obtain solution B; take ethylene glycol, heat to a temperature of 160-180℃, and add solution A and solution B to ethylene glycol to obtain solution C; stir until solution C turns grayish-white, then stop heating; S2: Wash solution C with acetone using ultrasonication, centrifuge, remove the solid, wash, and dry to obtain silver nanowires; The weight ratio of polyvinylpyrrolidone to sodium chloride is 1:(0.005-0.007); The silver nanowires are silver nanowires with a diameter of 20-200 nm and a length of 2-3 μm, and the ultrafine silver nanoparticles have a particle size of 0.1-10 μm. The silver nanowires were pretreated using the following method before use: glutaric acid was placed in a 75% ethanol solution and stirred for 40 minutes. The silver nanowires were then added and ultrasonically dispersed at 325W for 20 minutes. The solid was removed, washed four times with a 75% ethanol solution, and vacuum dried for 30 minutes to obtain the pretreated silver nanowires. The volume of ethanol solution added to each 1g of glutaric acid was 15mL, and the weight ratio of glutaric acid to silver nanowires was 1:1.
6. The epoxy resin is a hydrogenated bisphenol A alicyclic glycidyl ether type epoxy resin, and the latent curing agent is dicyandiamide. The toughening agent is polysulfide rubber CAS63148-67-4; The preparation method of the nano-silver sintered conductive adhesive for microelectronic packaging includes the following steps: Mix epoxy resin, toughening agent, diluent, additives, and silver powder, stir evenly, melt, then add latent curing agent, stir evenly, and cure at 140-160℃ for 1-3 hours to obtain conductive adhesive.