High-temperature-resistant hole-filling silver paste and preparation method and application thereof

Abstract

The invention discloses high-temperature-resistant hole-filling silver paste as well as a preparation method and application thereof, and belongs to the technical field of high polymer materials. The high-temperature-resistant pore-filling silver paste comprises the following raw materials in parts by weight: 88-93 parts of silver powder, 4-11 parts of resin, 1-6 parts of a solvent and 0.1-0.5 part of a silver powder dispersion arrangement auxiliary agent, the resin comprises first resin and second resin, the first resin is selected from a group consisting of maleic anhydride grafted polyolefin thermoplastic resin, maleic anhydride grafted thermoplastic resin, maleic anhydride grafted thermoplastic resin, maleic anhydride grafted thermoplastic resin, maleic anhydride grafted thermoplastic resin, maleic anhydride grafted thermoplastic resin, maleic anhydride grafted thermoplastic resin, maleic anhydride grafted thermoplastic resin, maleic anhydride grafted thermoplastic resin and maleic anhydride grafted thermoplastic resin; and the second resin is selected from glycidyl amine epoxy resin with a benzene ring, wherein the epoxy groups of the glycidyl amine epoxy resin are not less than 3 and are symmetrically distributed. The silver paste has the characteristics of high dispersity, high conductivity and high temperature resistance, continuous and stable discharging can be realized, the interior is compact and uniform and has no crack, collapse or leakage phenomenon after hole filling and curing, the average conductivity is higher than 5.5 kS / mm, the conduction rate is higher than 96%, the conduction rate is not changed after high-temperature heat treatment, and the performance is stable.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and particularly relates to a high-temperature resistant pore-filling silver paste, its preparation method, and its application. Background Technology

[0002] Currently, conductive silver paste is widely used in chip interconnection and packaging in the microelectronics industry due to its excellent conductivity and oxidation resistance. With the rapid development of third-generation semiconductor power devices (silicon carbide and gallium nitride), the reflow soldering process in its production plays a crucial role in efficiency, yield, and reliability. However, traditional conductive silver paste has poor high-temperature resistance. After undergoing a reflow soldering process at 250-300℃, its conductivity and adhesion decrease sharply, eventually leading to cracking or peeling of the silver paste. The main reasons are: First, the resin matrix has insufficient thermal stability. Conventional resins are prone to thermal decomposition or cross-linking failure above 200℃, resulting in the breakage of the conductive network in the silver paste. Second, the interfacial bonding force decreases. The coefficients of thermal expansion (CTE) of resin and silver powder are different. At high temperatures, the volume expansion rate of resin is large while that of silver particles is almost unchanged. This creates voids between the resin and silver particles, weakens the interfacial bonding force, and leads to the interruption of the conductive path, resulting in poor adhesion and reliability. Especially when using silver paste for high-precision hole filling, if the silver paste cannot withstand the reflow soldering process, cracks and voids will appear in the hole, leading to problems such as silver paste falling off and cracking, thus failing to form an effective passage.

[0003] Existing technologies typically employ methods such as adding fillers like glass particles, aluminum nitride, and carbon nanotubes to silver paste to improve its thermal stability, as shown in CN 112037960 A, CN 108922647 A, and CN 117690633 A. Adding glass particles improves the temperature resistance of the silver paste and reduces its resistivity fluctuations. However, adding other fillers to the silver paste reduces its dispersion and conductivity properties, and can easily lead to problems such as needle clogging and uneven material output during direct-write 3D printing, affecting printing accuracy and stability.

[0004] Therefore, developing a conductive silver paste that combines high dispersibility, high conductivity, and high temperature resistance is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The main objective of this invention is to provide a high-temperature resistant pore-filling silver paste, its preparation method, and its application, so as to solve the problem that silver pastes in the prior art are difficult to simultaneously possess high dispersibility, high conductivity, and high temperature resistance.

[0006] In a first aspect, the present invention provides a high-temperature resistant pore-filling silver paste, the raw materials of which, by weight, include: 88-93 parts silver powder, 4-11 parts resin, 1-6 parts solvent and 0.1-0.5 parts silver powder dispersion and arrangement aid, wherein the resin includes a first resin and a second resin, the first resin being selected from a polyolefin thermoplastic resin whose main resin is maleic anhydride grafted, and the second resin being selected from a glycidylamine epoxy resin with ≥3 epoxy groups and symmetrical distribution and containing benzene rings, wherein the mass ratio of the first resin to the second resin is (1-5):1.

[0007] Furthermore, the pore-filling silver paste may also include 1 to 5 parts of curing agent, leveling agent and / or thixotropic agent, etc.

[0008] Furthermore, the surface of the silver powder contains short-chain fatty acids with ≤18 carbon atoms.

[0009] Furthermore, the silver powder dispersion and arrangement aid is selected from at least one of polyhydroxycarboxylic acid esters containing acidic groups, polyhydroxycarboxylic acid amides, and modified polyurea compounds.

[0010] Further, the solvent includes 0.1 to 2 parts of a first solvent and 0.5 to 5 parts of a second solvent, wherein the boiling point of the first solvent is below 160°C and the boiling point of the second solvent is above 190°C; more preferably, the boiling point of the first solvent is between 140 and 160°C and the boiling point of the second solvent is between 190 and 220°C.

[0011] Further, the solvent is selected from any one or more of aliphatic ketones with ≤12 carbon atoms and aliphatic esters with ≤12 carbon atoms; preferably, the first solvent is selected from at least one of cyclohexanone, propylene glycol methyl ether acetate, methyl 2-methoxypropionate, 3,3-dimethoxy-2-butanone, and 2,2-dimethylcyclopentanone, and the second solvent is selected from at least one of isophorone, DBE, ethylene glycol diacetate, and diethylene glycol ethyl ether acetate; more preferably, the solvent includes 0.1 to 1 part cyclohexanone, 0.1 to 1 part isophorone, 0.1 to 1 part DBE, 0.1 to 1 part ethylene glycol diacetate, and 0.1 to 1 part diethylene glycol ethyl ether acetate.

[0012] Furthermore, the silver powder has a spherical or near-spherical morphology and is selected from any one or more of the following: silver powder with a particle size D50 of 200-500 nm, silver powder with a D50 of 500 nm-1 μm, and silver powder with a D50 of 1-3 μm.

[0013] Furthermore, the silver paste is continuously dispensed for more than 24 hours under a printing needle with a 30μm aperture, has an average conductivity higher than 5.5kS / mm, and has a conductivity higher than 96% after heat treatment at 300℃ for 1 hour.

[0014] Furthermore, the pore size of the silver powder filling is 30–200 μm, and it is particularly suitable for filling pores with a diameter of ≤50 μm.

[0015] Secondly, the present invention also provides a method for preparing the above-mentioned high-temperature resistant pore-filling silver paste, the method comprising the following steps:

[0016] Add the resin, silver powder dispersion additive, and silver powder to the solvent in parts by weight and disperse them evenly.

[0017] After the silver paste is dispersed and degassed, the pore-filling silver paste is obtained.

[0018] Furthermore, the preparation method of the high-temperature resistant pore-filling silver paste specifically includes:

[0019] Homogenize the resin and solvent at 1000-1500 rpm for 5 minutes or more; then add the silver powder dispersion and alignment aid, and homogenize at 1000-1500 rpm for 3 minutes or more. Repeat the homogenization process two or more times to ensure that the silver powder dispersion and alignment aid is evenly dispersed; then add the silver powder in three or more batches, homogenizing at 800-1000 rpm for 3 minutes or more after each addition, until all the silver powder has been added.

[0020] Then homogenize the mixed material at 1000-1300 rpm for 3 minutes or more, repeating at least 3 times or more, to further disperse the silver paste.

[0021] The above silver paste was dispersed using a three-roll mill (pitch 80μm / 40μm-20μm / 10μm);

[0022] Continue homogenizing at 1000-1300 rpm for 3 minutes or more, repeating at least 3 times or more, to further disperse the silver paste;

[0023] Filtration process to remove impurities from silver paste;

[0024] The silver paste is placed in a homogenizer, and the air pressure is set to 3-6 kPa, the rotation speed is 1000-1500 rpm, and the time is 5 minutes or more to perform degassing treatment, so as to obtain the hole-filling silver paste for the direct-write 3D printing substrate.

[0025] Thirdly, the present invention also provides the application of the above-mentioned high-temperature resistant hole-filling silver paste in direct-write 3D printing. Specifically, the direct-write 3D printing method can be used to fill holes in a substrate, the substrate including a glass substrate, a silicon substrate or a PCB substrate, etc.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The silver paste has excellent high temperature resistance. Its conductivity remains unchanged after heat treatment at 300℃ for 1 hour and is still higher than 96%. Its performance is stable at high temperature. This feature effectively overcomes the problem that the conductivity and adhesion of traditional silver paste are prone to decline sharply in high temperature environment. It significantly improves the long-term reliability and service life of silver paste under high temperature conditions and provides key material guarantee for precision electronic packaging in high temperature environment.

[0028] (2) The silver paste is suitable for high-precision printing and filling. After the filling is cured, the interior is dense and uniform, without cracks, collapse or leakage. The average conductivity is higher than 5.5 kS / mm and the conductivity is higher than 96%.

[0029] (3) By introducing a silver powder dispersion and arrangement aid containing acidic groups, the dispersion stability of silver powder in the organic phase is significantly improved. The selected aid has good compatibility with silver powder, can fully coat it, and has a good anti-settling effect, which greatly improves the discharge performance and can achieve stable discharge. The optimized slurry can achieve continuous, stable and uniform discharge for more than 24 hours in a 30μm diameter needle, avoiding material breakage and needle blockage caused by particle blockage in the direct writing 3D printing process. Attached Figure Description

[0030] Figure 1 This is a morphology image of the silver paste obtained in Example 1 after filling and curing.

[0031] Figure 2 The image shows the morphology of the silver paste prepared in Example 1 after being treated at 300°C for 1 hour.

[0032] Figure 3 This is a morphology image of the silver paste obtained in Example 4 after filling and curing.

[0033] Figure 4 This is a morphology image of the silver paste prepared in Example 4 after being treated at 300°C for 1 hour.

[0034] Figure 5 This is a morphology image of the silver paste prepared in Comparative Example 3 after filling and curing.

[0035] Figure 6 The image shows the morphology of the silver paste prepared in Comparative Example 3 after being treated at 300℃ for 1 hour.

[0036] Figure 7 This is a morphology image of the silver paste prepared in Comparative Example 4 after filling and curing.

[0037] Figure 8 The image shows the morphology of the silver paste prepared in Comparative Example 4 after being treated at 300℃ for 1 hour. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0039] As described in the background section of this invention, traditional conductive silver pastes have poor high-temperature resistance. After undergoing a reflow soldering process at 250–300°C, both conductivity and adhesion decrease sharply, ultimately leading to cracking or peeling of the silver paste. Existing technologies typically improve thermal stability by adding fillers such as glass particles, aluminum nitride, and carbon nanotubes to the silver paste. However, adding other fillers reduces its dispersibility, which can easily cause problems such as needle clogging and uneven material output during direct-write 3D printing, affecting printing accuracy and stability. Therefore, existing silver pastes struggle to simultaneously achieve good dispersibility, conductivity, and high-temperature resistance.

[0040] To address the aforementioned problems, a first aspect of the present invention provides a high-temperature resistant pore-filling silver paste, the raw materials of which, by weight, comprise: 88-93 parts silver powder, 4-11 parts resin, 1-6 parts solvent, and 0.1-0.5 parts silver powder dispersion and arrangement aid. The resin comprises a first resin and a second resin. The first resin is selected from a polyolefin thermoplastic resin with maleic anhydride grafted as the main resin, and the second resin is selected from a glycidylamine epoxy resin with ≥3 epoxy groups symmetrically distributed and containing benzene rings. The mass ratio of the first resin to the second resin is (1-5):1.

[0041] The specific reasons for choosing the aforementioned second resin are as follows:

[0042] (1) The resin molecule contains multiple epoxy groups, and the number of crosslinking points increases exponentially with the increase of functionality. During the curing process, it can undergo multi-dimensional crosslinking reaction with the curing agent to form a high-density three-dimensional network structure. The three-dimensional network locks the molecular chain through covalent bonds, making it difficult to depolymerize at high temperatures, thus providing extremely strong adhesion and high temperature resistance, and can withstand the 300℃ reflow soldering process. In addition, the higher the degree of crosslinking of the resin, the smaller the coefficient of thermal expansion, the smaller the CTE difference with the silver powder at high temperatures, and the less likely the silver paste will crack inside; (2) The epoxy groups are symmetrically distributed, the overall polarity of the resin is small, and the compatibility with the silver paste is good; (3) The benzene ring structure in the resin molecule has a π-electron conjugation effect, which can improve the electron transport capability.

[0043] Preferably, the first resin is selected from TH10 resin of Huizhou Tenghui Technology Co., Ltd., MC39 resin of Wuxi Honghui New Materials, and VAM and FVAM resins of Pangao Chemical. The second resin is selected from MF3102 of Hubei Zhenzhengfeng New Materials Co., Ltd., S500 (epoxy group 3) of Nantong Xinnaxi New Materials Co., Ltd., EPM420 and EPM426 of Shandong Lingdu New Materials Co., Ltd., S720 of Nantong Xinnaxi New Materials Co., Ltd., and MF4101 and MF4101H (epoxy group 4) of Hubei Zhenzhengfeng New Materials Co., Ltd. The product contains 5% curing agent, and the resin structure is as follows:

[0044]

[0045] Preferably, the second resin molecule contains 3-4 epoxy groups, and the number of crosslinking points increases exponentially with increasing functionality. During the curing process, it can undergo multi-dimensional crosslinking reactions with the curing agent to form a high-density three-dimensional network structure. The three-dimensional network locks the molecular chains through covalent bonds, making it difficult to depolymerize at high temperatures, thus providing extremely strong adhesion and high-temperature resistance, capable of withstanding reflow soldering processes at 300℃. In addition, the higher the degree of resin crosslinking, the smaller the coefficient of thermal expansion, and the smaller the CTE difference with the silver powder at high temperatures, making it less prone to cracking inside the silver paste.

[0046] In some preferred embodiments, the resin is selected from a combination of TH10 and MF4101, wherein the TH10 resin is used to provide dispersibility and conductivity, and the MF4101 tetrafunctional epoxy resin contains two benzene rings, has a strong conjugated structure, has better conductivity than resins without a conjugated structure, has a symmetrical functional group structure, low polarity, and good compatibility with silver paste.

[0047] In some specific embodiments, the pore-filling silver paste may also include 1 to 5 parts of curing agent, leveling agent and / or thixotropic agent, etc.

[0048] In some specific embodiments, the surface of the silver powder contains short-chain fatty acids with ≤18 carbon atoms. Commercially available physical-prepared nano-silver powder typically has a surface modified with short-chain fatty acids (such as Ag-S0800 from Ningbo Guangxin Nanomaterials Co., Ltd.), which helps improve the dispersibility of the silver powder and prevent agglomeration. The morphology of the silver powder is spherical or near-spherical, selected from any one or more of the following: silver powder with a particle size D50 = 200–500 nm, silver powder with a D50 = 500 nm–1 μm, and silver powder with a D50 = 1–3 μm. If the particle size is too large, it can easily lead to difficulties in ejecting material from 30 μm diameter printing needles; if the particle size is too small, it can easily lead to difficulties in dispersion and an inability to increase solids content.

[0049] In some specific embodiments, the silver powder dispersion aid is selected from at least one of polyhydroxycarboxylic acid esters, polyhydroxycarboxylic acid amides, and modified polyurea compounds containing acidic groups. AKN01 from Foshan Qianyou Chemical Co., Ltd., BYK106, BYKR606, and BYKR607 from BYK Chemical, KMT-8866 from Foshan Kening New Materials Co., Ltd., and UQ810S from Yoka Chemical, etc., are preferred. Their application in the pore-filling silver paste helps improve the dispersibility of silver powder in the organic phase, ensuring uniform distribution of silver particles, preventing sedimentation and flow within the organic phase, greatly improving the dispersibility of the silver paste, and significantly increasing the discharge capacity (smooth discharge from 30μm orifices, enabling pore filling with a diameter ≤50μm). It also imparts thixotropic and shape-retention properties to the silver paste, preventing flow due to gravity after pore filling, thus avoiding pore top collapse and defects.

[0050] In some specific embodiments, the solvent includes 0.1 to 2 parts of a first solvent and 0.5 to 5 parts of a second solvent, wherein the boiling point of the first solvent is below 160°C and the boiling point of the second solvent is above 190°C; more preferably, the boiling point of the first solvent is between 140 and 160°C and the boiling point of the second solvent is between 190 and 220°C.

[0051] In some specific embodiments, the solvent is selected from any one or more of aliphatic ketones or aliphatic esters with ≤12 carbon atoms; more preferably, the first solvent is selected from at least one of cyclohexanone, propylene glycol methyl ether acetate, methyl 2-methoxypropionate, 3,3-dimethoxy-2-butanone, and 2,2-dimethylcyclopentanone, and the second solvent is selected from at least one of isophorone, DBE, ethylene glycol diacetate, and diethylene glycol ethyl ether acetate.

[0052] In some specific embodiments, the solvent includes 0.1 to 1 part cyclohexanone, 0.1 to 1 part isophorone, 0.1 to 1 part DBE, 0.1 to 1 part ethylene glycol diacetate, and 0.1 to 1 part diethylene glycol ethyl ether acetate. Two or more solvents with different boiling points are selected and mixed. The resulting benzene ring structure exhibits an electron conjugation effect, improving electron transport capability. The solvent in the silver paste may include: solvents naturally contained in the purchased resin (evaporating at 100°C), cyclohexanone (boiling point 150°C), ethylene glycol diacetate (boiling point 190°C), DBE (boiling point 213°C), and isophorone (boiling point 215°C), forming an evaporation gradient of at least 150°C and 200°C, reducing the porosity caused by excessive solvent evaporation at the same temperature, and helping to form a dense and uniform morphological structure after pore filling and curing; in addition, the solvent may also include 0.1-1 parts of diethylene glycol ethyl ether acetate, which is used to improve dispersibility and surface drying, and improve output performance and printing pore filling operability.

[0053] In some specific embodiments, the printing continuous output time of the silver paste is >24h, the average conductivity is higher than 5.5kS / mm, and the conductivity after heat treatment at 300℃ for 1h is higher than 96%.

[0054] In some specific embodiments, the pore size of the silver powder filling is 30 to 200 μm, and it is particularly suitable for filling pores with a diameter of ≤50 μm.

[0055] A second aspect of the present invention provides a method for preparing the above-mentioned high-temperature resistant pore-filling silver paste, the method comprising the following steps:

[0056] Add the resin, silver powder dispersion additive, and silver powder to the solvent in parts by weight and disperse them evenly.

[0057] After the silver paste is dispersed and degassed, the pore-filling silver paste is obtained.

[0058] In some specific embodiments, the preparation method of the high-temperature resistant pore-filling silver paste specifically includes:

[0059] Homogenize the resin and solvent at 1000-1500 rpm for 5 minutes or more; then add the silver powder dispersion and alignment aid, and homogenize at 1000-1500 rpm for 3 minutes or more. Repeat the homogenization process two or more times to ensure that the silver powder dispersion and alignment aid is evenly dispersed; then add the silver powder in three or more batches, homogenizing at 800-1000 rpm for 3 minutes or more after each addition, until all the silver powder has been added.

[0060] Then homogenize the mixed material at 1000-1300 rpm for 3 minutes or more, repeating at least 3 times or more, to further disperse the silver paste.

[0061] The above silver paste was dispersed using a three-roll mill (pitch 80μm / 40μm-20μm / 10μm);

[0062] Continue homogenizing at 1000-1300 rpm for 3 minutes or more, repeating at least 3 times or more, to further disperse the silver paste;

[0063] Filtration process to remove impurities from silver paste;

[0064] The silver paste is placed in a homogenizer, and the air pressure is set to 3-6 kPa, the rotation speed is 1000-1500 rpm, and the time is 5 minutes or more to perform degassing treatment, so as to obtain the hole-filling silver paste for the direct-write 3D printing substrate.

[0065] The third aspect of the present invention provides the application of the above-mentioned high-temperature resistant hole-filling silver paste in direct-write 3D printing. Specifically, the direct-write 3D printing method can be used to fill holes in a substrate, wherein the substrate includes a glass substrate, a silicon substrate, or a PCB substrate.

[0066] Typical, but not limiting, the high-temperature resistant pore-filling silver paste of the present invention comprises, by weight, the following: 88 parts, 89 parts, 90 parts, 91 parts, 92 parts, 93 parts, or any two of these values ​​of silver powder; 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, or any two of these values ​​of resin; 1.0 part, 1.5 parts, 2.0 parts, 2.5 parts, 3.0 parts, 3.5 parts, 4.0 parts, 4.5 parts, 5.0 parts, 5.5 parts, 6.0 parts, or any two of these values ​​of solvent; and 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, or any two of these values ​​of silver powder dispersion and arrangement aid.

[0067] Typical, but not limiting, the high-temperature resistant pore-filling silver paste of the present invention further includes, by weight, 1 part, 2 parts, 3 parts, 4 parts, 5 parts or any two of these values ​​of curing agent, leveling agent and / or thixotropic agent.

[0068] Example 1

[0069] (1) Weigh 5 parts of TH10 resin, 2.5 parts of MF4101 resin, 0.5 parts of cyclohexanone, 0.25 parts of isophorone, 0.25 parts of DBE, 0.5 parts of ethylene glycol diacetate, and 0.5 parts of diethylene glycol ethyl ether acetate into a clean sample cup A, and homogenize at 1500 rpm for 5 min.

[0070] (2) Add 0.5 parts of AKN01 to sample cup A, put it into a homogenizer and homogenize at 1500 rpm for 3 min. Repeat the homogenization twice to make the silver powder dispersed and the additives evenly dispersed.

[0071] (3) Weigh 90 parts of nano silver powder (Ningbo Guangxin Nanomaterials Co., Ltd. Ag-S0800, D50=800nm) into sample cup B, add 1 / 3 of it into sample cup A, stir manually with a spatula until initially mixed, put it into a homogenizer at 800rpm for 3min to further disperse evenly, repeat this step 3 times until all the silver powder in sample cup B is added;

[0072] (4) Place sample cup A into a homogenizer and homogenize at 1300 rpm for 3 minutes. After one homogenization, remove it and let it stand until the silver paste in the sample cup cools to room temperature. Then perform the next homogenization. Repeat this cycle 3 times to further disperse the silver paste in sample cup A.

[0073] (5) Use a three-roll mill (pitch 80μm / 40μm-20μm / 10μm) to disperse the silver paste in sample cup A, and transfer the silver paste after three-roll milling into sample cup C;

[0074] (6) Place sample cup C into a homogenizer and homogenize at 1300 rpm for 3 minutes. After one homogenization, remove it and let it stand until the silver paste in the sample cup cools to room temperature. Then perform the next homogenization. Repeat this process 3 times to further disperse the silver paste in sample cup C.

[0075] (7) The silver paste in sample cup C was filtered through a 10μm filter to remove impurities from the silver paste;

[0076] (8) Place the silver paste into a homogenizer, set the air pressure to 5 kPa, the rotation speed to 1500 rpm, and the time to 5 min for degassing treatment to obtain the final product, silver paste. The morphology after filling and curing is as follows: Figure 1 As shown, the morphology after heat treatment at 300℃ for 1 hour is as follows. Figure 2 As shown.

[0077] Example 2

[0078] The multifunctional epoxy resin in step (1) was changed to EPM420: 2.5 parts of EPM420 were added to sample cup A, and the rest of the process was the same as in Example 1.

[0079] Example 3

[0080] Change the multifunctional epoxy resin in step (1) to S720: Add 2.5 parts of S720 to sample cup A, and the rest of the process is the same as in Example 1.

[0081] Example 4

[0082] The multifunctional epoxy resin in step (1) was changed to MF3102: 2.5 parts of MF3102 were added to sample cup A, and the rest of the process was the same as in Example 1. The morphology after pore filling and curing is as follows. Figure 3 As shown, the morphology after heat treatment at 300℃ for 1 hour is as follows. Figure 4 As shown.

[0083] Example 5

[0084] Change the multifunctional epoxy resin in step (1) to S500: Add 2.5 parts of S500 to sample cup A, and the rest of the process is the same as in Example 1.

[0085] Example 6

[0086] Change the size of the nano silver powder in step (3) to D50 = 500 nm: Weigh 90 parts of nano silver powder (D50 = 500 nm) in sample cup B, and the rest of the process is the same as in Example 1.

[0087] Example 7

[0088] Change the silver powder arrangement aid in step (2) to BYK106: Add 0.5 parts of BYK106 to sample cup A, and the rest of the process is the same as in Example 1.

[0089] Example 8

[0090] The mass fraction of silver powder in step (3) was changed to 88 parts, and the rest of the process was the same as in Example 1.

[0091] Example 9

[0092] The mass fraction of silver powder in step (3) was changed to 93 parts, and the rest of the process was the same as in Example 1.

[0093] Example 10

[0094] The mass fraction of the silver powder dispersion and arrangement aid in step (2) was changed to 0.1 parts, and the rest of the process was the same as in Example 1.

[0095] Example 11

[0096] The mass fraction of MF4101 resin in step (1) was changed to 6 parts, and the rest of the process was the same as in Example 1.

[0097] Comparative Example 1

[0098] The multifunctional epoxy resin MF4101 in step (1) was changed to MF3285 (without benzene rings in the molecular formula and asymmetrical distribution of epoxy groups in the molecular formula): 2.5 parts of MF3285 were added to sample cup A, and the rest of the process was the same as in Example 1.

[0099] Comparative Example 2

[0100] Change the multifunctional epoxy resin MF4101 in step (1) to S500m (the epoxy groups in the molecular formula are asymmetrically distributed): Add 2.5 parts of S500m to sample cup A, and the rest of the process is the same as in Example 1.

[0101] Comparative Example 3

[0102] The multifunctional epoxy resin MF4101 in step (1) was changed to the difunctional epoxy resin E51: 2.5 parts of E51 were added to sample cup A, and the rest of the process was the same as in Example 1. The morphology after filling and curing is as follows. Figure 5 As shown, the morphology after heat treatment at 300℃ for 1 hour is as follows. Figure 6 As shown.

[0103] Comparative Example 4

[0104] The multifunctional epoxy resin MF4101 in step (1) was changed to the monofunctional epoxy resin CY179: 2.5 parts of CY179 were added to sample cup A, and the rest of the process was the same as in Example 1. The morphology after pore filling and curing is as follows. Figure 7 As shown, the morphology after heat treatment at 300℃ for 1 hour is as follows. Figure 8 As shown.

[0105] Performance testing

[0106] Test method for continuous printing output time: The prepared silver paste is loaded into a 3cc feed tube. A glass needle with an inner diameter of 30μm is installed at the feed tube outlet. The air pressure is set to 35psi, the air outlet valve is opened to start output and timing is started until the needle is completely blocked and no more material can be output. Furthermore, after extensive verification, it can be considered that if the silver paste can be stably output for more than 24 hours without clogging the needle during printing, it meets the usage requirements. Therefore, the standard for judging whether the silver paste can output continuously for a long time is set at 24 hours, and a flow rate fluctuation of less than 10% is considered stable.

[0107] High-temperature resistance test method: The prepared silver paste was loaded into a 3cc tube. A glass needle with an inner diameter of 25μm was installed at the outlet of the tube. The tube was then fixed to a pressure pen, and the air pressure was set to 20psi. A high-precision direct-write 3D printing device was used to perform a TGV pore-filling test. The pore diameter was 50μm, the pore depth was 250μm, and the number of pores filled was 5000. After pore filling, the sample was cured in an oven at 200℃ for 60 minutes. The conductivity of the filled pores was tested with a multimeter. A conductivity ≥5kS / mm was considered as continuity. The cured sample was then heat-treated at 300℃ for 1 hour. The morphology of the silver paste inside the pores was observed by grinding the sample. If there were no cracks or pores in the silver paste inside the pores, it was considered to have good high-temperature resistance and could withstand a 300℃ reflow soldering process.

[0108] The results of the silver paste output test and its high temperature resistance are shown in Table 1.

[0109] Table 1

[0110]

[0111]

[0112] As shown in Table 1, the silver paste prepared using this invention possesses high dispersibility, high conductivity, and high temperature resistance. It can achieve continuous, stable, and uniform feeding from a 30μm diameter needle. After filling and curing, the internal structure is dense and uniform, without cracks, collapse, or leakage. The average conductivity is higher than 5.5 kS / mm, and the conductivity is higher than 96%. Furthermore, after heat treatment at 300℃ for 1 hour, the conductivity remains unchanged and still higher than 96%, demonstrating excellent high-temperature stability. It is suitable for filling substrate holes in direct-write 3D printing. Comparing Examples 1, 2, 3, 4, and 5 with Comparative Example 1, it can be seen that when using MF3205 epoxy resin, although the resin contains three epoxy groups, its structural formula lacks a benzene ring conjugated structure (structural formula shown below), resulting in poor electron transport capability of the silver paste, with an average conductivity far below 5 kS / mm. Moreover, the asymmetrical distribution of the groups and relatively high polarity lead to poor compatibility with the silver paste, short continuous feeding time, and large flow fluctuations.

[0113]

[0114] Comparing Examples 1, 2, 3, 4, 5 with Comparative Example 2, it can be seen from the data in Table 1 that although the resin S500m used in Comparative Example 2 contains three epoxy groups and a benzene ring in its molecule, the three epoxy groups are distributed in the meta position on the benzene ring (the structural formula is shown below), which is not completely symmetrical, has relatively high polarity, poor compatibility with silver paste, and poor continuous discharge performance.

[0115]

[0116] Comparing Examples 1, 2, 3, 4, 5 with Comparative Examples 3, 4, and 5, the data in Table 1 shows that E51 used in Comparative Examples 3 and 4 is a bifunctional epoxy resin (viscosity > 10000 cps), and CY179 is a monofunctional epoxy resin. The curing crosslinking degree is low, the high temperature resistance is poor, and the coefficient of thermal expansion is high. At high temperature, the movement of molecular chains causes gaps to be generated between the silver powder and the microscopic layer. Macroscopically, the silver paste is prone to large cracks. After heat treatment at 300°C for 1 hour, the conductivity drops sharply.

Claims

1. A high-temperature resistant, pore-filling silver paste, characterized in that, The raw materials, by weight, include: 88-93 parts silver powder, 4-11 parts resin, 1-6 parts solvent and 0.1-0.5 parts silver powder dispersion and arrangement aid. The resin includes a first resin and a second resin. The first resin is selected from polyolefin thermoplastic resins with maleic anhydride grafted as the main resin. The second resin is selected from glycidylamine epoxy resins with ≥3 epoxy groups and symmetrical distribution and containing benzene rings. The mass ratio of the first resin to the second resin is (1-5):

1.

2. The high-temperature resistant pore-filling silver paste according to claim 1, characterized in that, The surface of the silver powder contains short-chain fatty acids with ≤18 carbon atoms.

3. The high-temperature resistant pore-filling silver paste according to claim 1, characterized in that, The silver powder dispersion and arrangement aid is selected from at least one of the following: polyhydroxycarboxylic acid esters containing acidic groups, polyhydroxycarboxylic acid amides, and modified polyurea compounds.

4. The high-temperature resistant pore-filling silver paste according to claim 1, characterized in that, The solvent comprises 0.1 to 2 parts of a first solvent and 0.5 to 5 parts of a second solvent, wherein the boiling point of the first solvent is below 160 °C and the boiling point of the second solvent is above 190 °C.

5. The high-temperature resistant pore-filling silver paste according to claim 4, characterized in that, The solvent is selected from any one or more fatty ketones or fatty esters with ≤12 carbon atoms.

6. The high-temperature resistant pore-filling silver paste according to claim 1, characterized in that, The silver powder has a spherical or near-spherical shape.

7. The high-temperature resistant pore-filling silver paste according to claim 1, characterized in that, The silver powder is selected from any one or more of the following: silver powder with a particle size of D50 = 200~500 nm, silver powder with a particle size of D50 = 500 nm~1 µm, and silver powder with a particle size of D50 = 1~3 µm.

8. The high-temperature resistant pore-filling silver paste according to claim 1, characterized in that, The silver paste is continuously dispensed for >24 h under a printing needle with a 30 µm aperture, has an average conductivity ≥5.5 kS / mm, and a conductivity ≥96% after heat treatment at 300 ℃ for 1 h.

9. A method for preparing the high-temperature resistant pore-filling silver paste according to any one of claims 1-8, characterized in that, Includes the following steps: Add the resin, silver powder dispersion additive, and silver powder to the solvent in parts by weight and disperse them evenly. After the silver paste is dispersed and degassed, the pore-filling silver paste is obtained.

10. The application of the high-temperature resistant pore-filling silver paste according to claims 1-8 or the high-temperature resistant pore-filling silver paste prepared by the preparation method according to claim 9 in direct-write 3D printing.

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