Conductive silver adhesive, preparation method and application thereof

Abstract

The application relates to a conductive silver glue and a preparation method and application thereof, and belongs to the technical field of bonding materials.The conductive silver glue comprises an epoxy resin, an active diluent, a curing agent, an accelerator and silver powder; the epoxy resin comprises a main body resin and an auxiliary resin; the main body resin comprises a glycidyl amine type epoxy resin; and the auxiliary resin comprises a combination of a phenolic epoxy resin, a triphenylmethane type epoxy resin and an alicyclic epoxy resin.The conductive silver glue provided by the application is a high-reliability conductive silver glue of an epoxy resin system, has the characteristics of high moisture and heat resistance, high high-temperature bonding force, high residual glue rate and low resin overflow, effectively solves the problem that the existing conductive silver glue has low reliability under high-temperature and high-humidity conditions, is suitable for complex scenes, and has a simple preparation method and controllable cost.

Description

Technical Field

[0001] This invention relates to the field of adhesive materials technology, and in particular to a conductive silver paste, its preparation method, and its application. Background Technology

[0002] Conductive silver paste is an adhesive that uses silver powder as a conductive medium, combining bonding and conductivity. Due to its mature technology and characteristics such as good thermal conductivity and low resistance, it is widely used in electronic manufacturing fields such as LED packaging, automotive electronics, and outdoor electronics, and is a core bonding material in the modern electronics industry. In recent years, with the continuous improvement of electronic component performance and the corresponding increase in integrated circuit packaging density, electronic components are gradually developing towards miniaturization and high integration. This places more stringent requirements on the reliability of semiconductor packaging materials, and traditional conductive silver paste can no longer meet these reliability demands. High resistance to damp heat is a core indicator of reliability; it must resist water molecule corrosion in long-term damp heat environments to avoid problems such as conductivity degradation and adhesive failure, otherwise it will lead to device failure and shortened lifespan.

[0003] To improve the reliability of conductive silver paste, existing technologies typically employ the addition of highly heat-resistant, low-hygroscopic resins, such as bismaleimide (BMI) resin and naphthalene-based epoxy resin. However, these resins are mostly solid powders or high-viscosity fluids, often requiring the addition of large amounts of reactive diluents to ensure workability. However, the addition of low-heat-resistant reactive diluents reduces the high-temperature resistance and adhesion of the conductive paste, while also causing resin precipitation, affecting subsequent wire bonding and chip mounting processes. Furthermore, it is difficult to achieve a balance between good workability and high-temperature adhesion.

[0004] CN115873532A discloses a low-modulus, high-bonding-strength conductive adhesive, its preparation method, and its application. The conductive adhesive is a conductive silver paste based on modified (meth)acrylate resin, which still exhibits excellent bonding strength after high-temperature and high-humidity aging. However, it overlooks the fact that acrylic-based silver pastes have lower conductivity than epoxy-based pastes at the same silver content, often requiring the addition of a higher proportion of silver powder, leading to increased costs. Furthermore, the resin overflow problem in acrylic-based conductive silver pastes is typically more severe and harder to control than in epoxy resin systems.

[0005] Therefore, designing and developing a highly reliable conductive silver paste based on an epoxy system has become an urgent problem to be solved. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a conductive silver paste, its preparation method, and its applications. The conductive silver paste is a high-reliability conductive silver paste based on an epoxy resin system. It exhibits good thermal and electrical conductivity, high resistance to damp heat, high high-temperature adhesion, high residual adhesive rate, and low resin overflow. This effectively solves the problem of low reliability of existing conductive silver pastes under high temperature and humidity conditions, making it suitable for complex scenarios, and its preparation method is simple and cost-controllable.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a conductive silver paste, comprising epoxy resin, reactive diluent, curing agent, accelerator and silver powder;

[0009] The epoxy resin includes a main resin and auxiliary resins;

[0010] The main resin includes glycidyl amine type epoxy resin;

[0011] The auxiliary resin includes a combination of phenolic epoxy resin, triphenylmethane epoxy resin and alicyclic epoxy resin.

[0012] This invention optimizes the composition of conductive silver paste by using glycidylamine epoxy resin as the main resin and adding specific auxiliary resins (triphenylmethane epoxy resin, phenolic resin, and alicyclic epoxy resin) to form a well-constructed interwoven cross-linked network. This results in better stress dispersion on the polymer, leading to excellent adhesion strength even under harsh conditions such as high temperature and high humidity. This effectively solves the problem of low reliability of existing conductive silver pastes under high temperature and high humidity conditions. Furthermore, the conductive silver paste of this invention also has advantages such as high residual rate and low resin overflow, making it well-suited for various complex scenarios and highly practical.

[0013] Furthermore, the auxiliary resins used in this invention are a combination of triphenylmethane epoxy resin, phenolic resin, and alicyclic epoxy resin. The three resins, when compounded, form a dense cross-linked interpenetrating network structure, which not only improves the overall matrix's resistance to hydrolysis and damp heat aging, but also optimizes the interfacial bonding stability between the resin and conductive silver powder. This effectively curbs failure phenomena such as conductive path deterioration, interfacial delamination, increased voids, and resistance shift under high temperature and high humidity conditions. Thus, it can exert a good synergistic effect, enabling the obtained conductive silver paste to have low resin precipitation and suitable viscosity, further improving the bonding strength of the conductive silver paste and its reliability under high temperature and high humidity conditions. At the same time, it can also reduce resin precipitation and increase the residual adhesive rate.

[0014] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0015] As a preferred embodiment of the present invention, the mass ratio of the main resin to the auxiliary resin in the epoxy resin is (5-8):(3-5), wherein (5-8) can be, for example, 5, 5.5, 6, 6.5, 7, 7.5 or 8, and (3-5) can be, for example, 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4, 4.6, 4.8 or 5, and the specific values ​​between the above values ​​are not exhaustively listed in the present invention due to space limitations and for the sake of brevity.

[0016] Preferably, the mass ratio of phenolic epoxy resin, triphenylmethane epoxy resin, and alicyclic epoxy resin in the auxiliary resin is (1.5-2):(1-1.5):(1-1.5), where (1.5-2) can be, for example, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, or 2, and (1-1.5) can be, for example, 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, or 1.5. Specific values ​​between the above values ​​are not exhaustively listed here for space limitations and for the sake of brevity.

[0017] In this invention, by optimizing the mass ratio of phenolic epoxy resin, triphenylmethane epoxy resin, and alicyclic epoxy resin in the auxiliary resin, a dense interpenetrating cross-linked network with complementary advantages and balanced performance can be formed among the three resin components with different structures and properties. This avoids the performance defects of a single resin and the performance offsetting problem of multiple resins, maximizing the synergistic effect of the three components. This reduces the risk of failure of the conductive silver paste under high temperature and high humidity environments, such as water absorption degradation, interfacial debonding, resistance drift, and colloid cracking, thereby improving the bonding reliability and electrical stability of the conductive silver paste. When the mass ratio of the three components exceeds this preferred range, the cross-linking structure, interfacial bonding state, and overall damp heat resistance of the resin system will become unbalanced. Some performance shortcomings will be continuously amplified, leading to a decrease in the overall damp heat resistance reliability of the conductive silver paste, making it unable to better meet the requirements of harsh high temperature and high humidity conditions. Simultaneously, it will also increase resin precipitation and reduce the residual adhesive rate of the resulting conductive silver paste.

[0018] Preferably, the silver powder includes spherical silver powder and / or flake silver powder.

[0019] Preferably, the silver powder is a combination of spherical silver powder and flake silver powder.

[0020] Preferably, the mass ratio of the spherical silver powder to the flake silver powder is 1:(2-3), wherein (2-3) can be, for example, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 or 3, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0021] In this invention, flake silver powder can form large-area surface contact overlaps to construct a continuous and efficient conductive and thermally conductive main network; spherical silver powder has good fluidity and can fill the gaps between flake silver powder, reducing accumulation porosity and increasing contact points. By using spherical and flake silver powder together and optimizing their weight ratio, a multi-level stacking structure of "layer overlap and spherical dense filling" can be better formed, effectively reducing the system porosity and interfacial contact thermal resistance. Under the premise of ensuring the fluidity of the slurry during construction, the dense thermal conductive pathway is maximized, thereby significantly improving the thermal conductivity of the obtained conductive silver paste. At the same time, it can also better balance the viscosity and conductivity of the system. When the mass of both is relatively low, meaning the mass ratio of flake silver powder is relatively high, the powder aggregates and clumps together, increasing the viscosity of the system, increasing the porosity of the adhesive layer, and resulting in less dense contact, thus increasing thermal resistance and reducing thermal conductivity. When the mass of both is relatively high, meaning the mass ratio of flake silver powder is relatively low, it is difficult to form a continuous surface contact thermal conductive network, ultimately resulting in a significant reduction in the thermal conductivity and thermal conductivity coefficient of the silver paste. At the same time, it also leads to excessively low thixotropy of the resulting silver paste, resulting in poor application performance.

[0022] Preferably, the conductive silver paste comprises the following components in parts by weight:

[0023] 40-120 parts epoxy resin;

[0024] 4-40 parts of reactive diluent;

[0025] 4-40 parts of curing agent;

[0026] Accelerator 1.5-5 parts;

[0027] 280-440 parts silver powder.

[0028] This invention achieves better overall interaction by limiting the content of each component of the conductive silver paste. As a result, the conductive silver paste not only has suitable viscosity and conductivity, but also has the characteristics of high resistance to damp heat, high high temperature adhesion, high residual rate and low resin overflow.

[0029] The epoxy resin in the conductive silver paste provided by this invention can be 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, 100 parts, 110 parts or 120 parts by weight, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range.

[0030] The active diluent in the conductive silver paste provided by this invention can be 4 parts, 8 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts or 40 parts by weight, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range.

[0031] The weight percentage of the curing agent in the conductive silver paste provided by this invention can be 4 parts, 8 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts or 40 parts, as well as specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range.

[0032] The weight percentage of the accelerator in the conductive silver paste provided by this invention can be 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, or 5 parts, as well as specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range.

[0033] The weight percentage of silver powder in the conductive silver paste provided by this invention can be 280 parts, 300 parts, 320 parts, 340 parts, 360 parts, 380 parts, 400 parts, 420 parts, or 440 parts, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0034] Preferably, the active diluent comprises any one or a combination of at least two of p-tert-butyl monoglycidyl ether, hexanediol diglycidyl ether, butylene glycol diglycidyl ether, or phenyl glycidyl ether.

[0035] Preferably, the curing agent comprises any one or a combination of at least two of imidazole, phenolic resin, dicyandiamide (DICY or DCD), or diaminodiphenyl sulfone (DDS).

[0036] Preferably, the accelerator includes imidazole accelerators and / or tertiary amine accelerators.

[0037] This invention does not impose any special requirements on the specific types of imidazole and tertiary amine accelerators selected; conventional imidazole and tertiary amine accelerators in the art are applicable. Examples of imidazole accelerators include, but are not limited to, Ajinomoto's PN-23 and PN-23J, and Shikoku Chemical's 2E4MZ, 2E4MZ-CN, 2MA-OK, or 4-methyl-2-phenylimidazole, etc.; examples of tertiary amine accelerators include, but are not limited to, Ajinomoto's MY-24 and MY-25, etc.

[0038] Preferably, the conductive silver paste further includes a coupling agent.

[0039] Preferably, the coupling agent includes any one or a combination of at least two of the following: epoxy silane coupling agents (such as KH-560), amino silane coupling agents (such as KH-550), methacryloxy silane coupling agents (such as KH-570), vinyl silane coupling agents (such as KH-151, KH-152), or mercaptosilane coupling agents (such as KH-580, KH-590).

[0040] Preferably, the coupling agent is in the form of 0.4-1 parts by weight, for example, 0.4 parts, 0.45 parts, 0.5 parts, 0.55 parts, 0.6 parts, 0.65 parts, 0.7 parts, 0.75 parts, 0.8 parts, 0.85 parts, 0.9 parts, 0.95 parts, or 1 part, as well as specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0041] Preferably, the conductive silver paste further includes a conductivity promoter.

[0042] Preferably, the conductivity promoter comprises a monocarboxylic acid and / or a dicarboxylic acid.

[0043] Preferably, the monocarboxylic acid includes any one or a combination of at least two of 5-aminosalicylic acid, tyrosine, 3,5-dihydroxybenzoic acid, or 3-hydroxybenzoic acid.

[0044] Preferably, the dicarboxylic acid includes any one or a combination of at least two of adipic acid, glutaric acid, or succinic acid.

[0045] Preferably, the conductivity promoter is 0.4-1 part by weight, for example, 0.4 parts, 0.45 parts, 0.5 parts, 0.55 parts, 0.6 parts, 0.65 parts, 0.7 parts, 0.75 parts, 0.8 parts, 0.85 parts, 0.9 parts, 0.95 parts, or 1 part, as well as specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0046] In a second aspect, the present invention provides a method for preparing conductive silver paste as described in the first aspect, the method comprising the following steps:

[0047] The conductive silver paste is obtained by mixing epoxy resin, reactive diluent, curing agent, accelerator, optional coupling agent, optional conductivity accelerator and silver powder.

[0048] Preferably, the mixing process includes first mixing the epoxy resin with the reactive diluent, then sequentially adding an optional coupling agent, an optional conductivity accelerator, a curing agent, and an accelerator for a second mixing, followed by adding silver powder for a third mixing.

[0049] It should be noted that, in order to improve the mixing efficiency during the first mixing of epoxy resin and reactive diluent in this invention, the liquid epoxy resin and reactive diluent can be mixed first, and then the solid epoxy resin can be added for thorough dissolution and mixing.

[0050] Preferably, the temperature of the first mixing is 70-80℃, for example, it can be 70℃, 71℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 80℃, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0051] Preferably, the first mixing is carried out under stirring, and the stirring speed is 10-30 rpm, for example, 10 rpm, 12 rpm, 14 rpm, 16 rpm, 18 rpm, 20 rpm, 22 rpm, 24 rpm, 26 rpm, 28 rpm or 30 rpm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0052] Preferably, the first mixing time is 10-20 min, for example, it can be 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min or 20 min, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific point values ​​included in the range.

[0053] Preferably, the first mixing process further includes a cooling step, wherein the cooling temperature is 20-30°C. For example, it can be 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, or 30°C, as well as specific values ​​between these values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0054] Preferably, the second mixing is carried out under stirring, and the stirring speed is 10-30 rpm, for example, 10 rpm, 12 rpm, 14 rpm, 16 rpm, 18 rpm, 20 rpm, 22 rpm, 24 rpm, 26 rpm, 28 rpm or 30 rpm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0055] Preferably, the second mixing time is 10-20 min, for example, it can be 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min or 20 min, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific point values ​​included in the range.

[0056] Preferably, the third mixing is carried out under stirring, and the stirring speed is 20-40 rpm, for example, 20 rpm, 22 rpm, 24 rpm, 26 rpm, 28 rpm, 30 rpm, 32 rpm, 34 rpm, 36 rpm, 38 rpm or 40 rpm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0057] Preferably, the time for the third mixing is 20-30 min, for example, it can be 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific point values ​​included in the range.

[0058] Preferably, the third mixing process further includes grinding and post-processing steps.

[0059] Preferably, after grinding, the particle size of the mixture is ≤15 μm, more preferably 8-15 μm, for example, it can be 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm, as well as specific particle values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific particle values ​​included in the range.

[0060] In this invention, grinding removes large particles and silver powder agglomerates from the silver paste and ensures thorough mixing of the mother liquor and silver powder. In actual production, the particle size can be determined by sieving.

[0061] Preferably, the post-processing includes vacuum degassing, wherein the vacuum degassing time is 30-40 min and the vacuum degree is ≤-0.095 MPa. The 30-40 min can be, for example, 30 min, 31 min, 32 min, 33 min, 34 min, 35 min, 36 min, 37 min, 38 min, 39 min, or 40 min, and the vacuum degree can be, for example, -0.095 MPa, -0.096 MPa, -0.097 MPa, or -0.098 MPa, as well as specific values ​​between these ranges. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0062] Preferably, the vacuum degassing is carried out under stirring, and the stirring speed is 20-40 rpm, for example, 20 rpm, 22 rpm, 24 rpm, 26 rpm, 28 rpm, 30 rpm, 32 rpm, 34 rpm, 36 rpm, 38 rpm or 40 rpm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0063] Preferably, the preparation method of the conductive silver paste specifically includes the following steps:

[0064] (1) Mix the epoxy resin and reactive diluent at 70-80℃ and 10-30 rpm for 10-20 min according to the formula;

[0065] (2) After the mixture in step (1) has cooled to 20-30°C, add coupling agent, conductivity promoter, curing agent and accelerator in sequence, and mix for a second time at 10-30 rpm for 10-20 min;

[0066] (3) After adding silver powder to the mixing system of step (2), mix for a third time at 20-40 rpm for 20-30 min to obtain a mixture;

[0067] (4) Grind the mixture from step (3) to a particle size ≤15 μm;

[0068] (5) Degas the mixture after grinding in step (4) under vacuum at 20-40 rpm for 30-40 min, with a vacuum degree ≤-0.095 MPa, to obtain the conductive silver paste.

[0069] Thirdly, the present invention provides an application of conductive silver paste as described in the first aspect in adhesive materials.

[0070] Compared with the prior art, the present invention has at least the following beneficial effects:

[0071] (1) The present invention optimizes the composition of conductive silver paste. By using glycidylamine epoxy resin as the main resin and adding specific auxiliary resins (triphenylmethane epoxy resin, phenolic resin and alicyclic epoxy resin) for compounding, a cross-linked network with interpenetration can be well constructed, thereby dispersing the stress on the polymer and maintaining excellent bonding strength under harsh conditions such as high temperature and high humidity. This effectively solves the problem of low reliability of existing conductive silver paste under high temperature and high humidity conditions. At the same time, the conductive silver paste of the present invention also has the advantages of high residual rate and low resin overflow, which can be well adapted to a variety of complex scenarios and has strong practicality.

[0072] (2) The conductive silver paste provided by this invention is a high-reliability conductive silver paste with suitable and stable viscosity (viscosity of 7500-16000 mPa·s, viscosity change rate after 24 h ≤6%), and excellent conductivity (volume resistivity ≤1.5×10). -3 It has excellent properties including Ω·cm, thermal conductivity (≥2 W / (m·K)), bonding performance (chip thrust ≥13 kgF at 25℃, chip thrust ≥3 kgF at 260℃), and resistance to damp heat (after PCT aging, chip thrust ≥6 kgF at 25℃, chip thrust ≥2 kgF at 260℃); at the same time, it has high residual glue rate (≥75% before aging, ≥60% after aging) and low resin overflow (resin precipitation <10 μm). Attached Figure Description

[0073] Figure 1 This is a resin precipitation diagram of the conductive silver paste obtained in Example 1;

[0074] Figure 2 The image shows the residual adhesive on the chip obtained in Example 1, where (1) represents before aging and (2) represents after aging.

[0075] Figure 3 The image shows the resin precipitation of the conductive silver paste obtained in Comparative Example 1.

[0076] Figure 4 The image shows the residual adhesive on the chip obtained from Comparative Example 3, where (1) represents before aging and (2) represents after aging. Detailed Implementation

[0077] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0078] Unless otherwise specified, the materials and equipment involved in the following specific embodiments are all conventional materials and equipment in the art and will not affect the technical effect of the present invention. Among them, the planetary mill is the Japanese PRIMIX HIVIS MIX Model2P-1, and the three-roll mill is Zhongyi ZYTR-50T.

[0079] Unless otherwise specified, all reagents and raw materials used in the following examples and comparative examples are commercially available products. Some raw material information is shown in Table 1:

[0080] Table 1

[0081]

[0082] Example 1

[0083] This embodiment provides a conductive silver paste and its preparation method, wherein the conductive silver paste comprises the following components in parts by weight:

[0084] 42 parts of glycidyl amine type epoxy resin;

[0085] 14 parts of phenolic epoxy resin;

[0086] 8 parts of triphenylmethane type epoxy resin;

[0087] 8 parts of alicyclic epoxy resin;

[0088] 17 parts of p-tert-butyl monoglycidyl ether;

[0089] Hardener 1 (DDS) 8 parts;

[0090] Accelerator 1 (2MA-OK) 2 parts;

[0091] Coupling agent 1 (KH560) 0.5 parts;

[0092] Conductivity promoter 1 (adipic acid) 0.5 parts;

[0093] 85 parts of spherical silver powder;

[0094] 215 parts of flake silver powder.

[0095] The preparation method of the conductive silver paste specifically includes the following steps:

[0096] (1) Heat glycidylamine epoxy resin, triphenylmethane epoxy resin, alicyclic epoxy resin and p-tert-butyl monoglycidyl ether to 75°C in the planetary reactor, add phenolic epoxy resin, keep the temperature constant, stir manually until the solid resin is completely dissolved, then start the planetary reactor and stir at 20 rpm for 15 min.

[0097] (2) After the mixture from step (1) has cooled to 25°C, add KH560, adipic acid, DDS and 2MA-OK in sequence, then start the planetary mixer and stir at 20 rpm for 15 min.

[0098] (3) After adding the spherical silver powder and flake silver powder to the mixing system of step (2), start the planetary machine and stir at 30 rpm for 25 min to obtain the mixture;

[0099] (4) Grind the mixture from step (3) to 10 μm using a three-roll mill;

[0100] (5) The mixture after grinding in step (4) was degassed under vacuum at 30 rpm for 35 min with a vacuum degree of 0.095 MPa to obtain conductive silver paste.

[0101] The resin precipitation pattern of the conductive silver paste is shown in the figure. Figure 1 As shown, its residual adhesive pattern on the chip is as follows: Figure 2 As shown.

[0102] Example 2

[0103] This embodiment provides a conductive silver paste and its preparation method, wherein the conductive silver paste comprises the following components in parts by weight:

[0104] 25 parts of glycidyl amine type epoxy resin;

[0105] 10 parts of phenolic epoxy resin;

[0106] 5 parts of triphenylmethane type epoxy resin;

[0107] 5 parts of alicyclic epoxy resin;

[0108] 10 parts of 1,4-butanediol diglycidyl ether;

[0109] Curing agent 2 (imidazole) 5 parts;

[0110] Accelerator 2 (4-methyl-2-phenylimidazole) 2 parts;

[0111] Coupling agent 2 (KH550) 0.6 parts;

[0112] Conductivity promoter 1 (adipic acid) 0.6 parts;

[0113] 120 parts of spherical silver powder;

[0114] 240 parts of flake silver powder.

[0115] The preparation method of the conductive silver paste specifically includes the following steps:

[0116] (1) In the planetary reactor, glycidylamine epoxy resin, triphenylmethane epoxy resin, alicyclic epoxy resin and 1,4-butanediol diglycidyl ether are heated to 70°C, phenolic epoxy resin is added, the temperature is kept constant, and the solid resin is manually stirred until it is completely dissolved. Then the planetary reactor is started and stirred at 30 rpm for 20 min.

[0117] (2) After the mixture from step (1) has cooled to 20°C, KH550, adipic acid, imidazole and 4-methyl-2-phenylimidazolium are added in sequence, and then the planetary mixer is started and stirred at 10 rpm for 20 min.

[0118] (3) After adding the spherical silver powder and flake silver powder to the mixing system of step (2), start the planetary machine and stir at 20 rpm for 30 min to obtain the mixture;

[0119] (4) Grind the mixture from step (3) to 8 μm using a three-roll mill;

[0120] (5) The mixture after grinding in step (4) was degassed under vacuum at 20 rpm for 40 min with a vacuum degree of 0.09 MPa to obtain conductive silver paste.

[0121] Example 3

[0122] This embodiment provides a conductive silver paste and its preparation method, wherein the conductive silver paste comprises the following components in parts by weight:

[0123] 83 parts of glycidylamine type epoxy resin;

[0124] 15.6 parts of phenolic epoxy resin;

[0125] 10.7 parts of triphenylmethane-type epoxy resin;

[0126] 10.7 parts of alicyclic epoxy resin;

[0127] 35 parts of phenyl glycidyl ether;

[0128] Hardener 3 (DCD) 35 parts;

[0129] Accelerator 3 (PN-23) 5 parts;

[0130] Coupling agent 1 (KH560) 0.8 parts;

[0131] Conductivity promoter 2 (5-aminosalicylic acid) 0.4 parts;

[0132] 110 parts of spherical silver powder;

[0133] 330 parts of flake silver powder.

[0134] The preparation method of the conductive silver paste specifically includes the following steps:

[0135] (1) Heat glycidylamine epoxy resin, triphenylmethane epoxy resin, alicyclic epoxy resin and phenyl glycidyl ether to 80°C in the planetary reactor, add phenolic epoxy resin, keep the temperature constant, stir manually until the solid resin is completely dissolved, then start the planetary reactor and stir at 10 rpm for 10 min.

[0136] (2) After the mixture from step (1) has cooled to 25°C, KH560, 5-aminosalicylic acid, DCD and PN-23 are added in sequence, and then the planetary mixer is started and stirred at 30 rpm for 10 min.

[0137] (3) After adding the spherical silver powder and flake silver powder to the mixing system of step (2), start the planetary machine and stir at 40 rpm for 20 min to obtain the mixture;

[0138] (4) Grind the mixture from step (3) to 15 μm using a three-roll mill;

[0139] (5) The mixture after grinding in step (4) was degassed under vacuum at 40 rpm for 30 min with a vacuum degree of 0.08 MPa to obtain conductive silver paste.

[0140] Example 4

[0141] This embodiment provides a conductive silver paste and its preparation method. The only difference between this embodiment and Example 1 is that the weight parts of phenolic epoxy resin, triphenylmethane epoxy resin and alicyclic epoxy resin are adjusted to 11.3 parts, 9 parts and 9.7 parts respectively, that is, the mass ratio of the three is 1.5:1.2:1.3. The other raw materials, contents and preparation methods are the same as in Example 1.

[0142] Example 5

[0143] This embodiment provides a conductive silver paste and its preparation method. The only difference between this embodiment and Example 1 is that the weight parts of phenolic epoxy resin, triphenylmethane epoxy resin and alicyclic epoxy resin are adjusted to 12 parts, 9 parts and 9 parts respectively, that is, the mass ratio of the three is 2:1.5:1.5. All other raw materials, contents and preparation methods are the same as in Example 1.

[0144] Example 6

[0145] This embodiment provides a conductive silver paste and its preparation method. The only difference between this embodiment and Example 1 is that the weight parts of phenolic epoxy resin, triphenylmethane epoxy resin and alicyclic epoxy resin are adjusted to 9 parts, 10.5 parts and 10.5 parts respectively, that is, the mass ratio of the three is 1.4:1.6:1.6. All other raw materials, contents and preparation methods are the same as in Example 1.

[0146] Example 7

[0147] This embodiment provides a conductive silver paste and its preparation method. The only difference between this embodiment and Example 1 is that the weight parts of phenolic epoxy resin, triphenylmethane epoxy resin and alicyclic epoxy resin are adjusted to 16.6 parts, 6.7 parts and 6.7 parts respectively, that is, the mass ratio of the three is 2.2:0.9:0.9. All other raw materials, contents and preparation methods are the same as in Example 1.

[0148] Example 8

[0149] This embodiment provides a conductive silver paste and its preparation method. The only difference between this embodiment and Embodiment 1 is that the weight parts of spherical silver powder and flake silver powder are adjusted to 100 parts and 200 parts, respectively. All other raw materials, contents and preparation methods are the same as in Embodiment 1.

[0150] Example 9

[0151] This embodiment provides a conductive silver paste and its preparation method. The only difference between this embodiment and Embodiment 1 is that the weight parts of spherical silver powder and flake silver powder are adjusted to 75 parts and 225 parts, respectively. All other raw materials, contents and preparation methods are the same as in Embodiment 1.

[0152] Example 10

[0153] This embodiment provides a conductive silver paste and its preparation method. The only difference between this embodiment and Embodiment 1 is that the weight parts of spherical silver powder and flake silver powder are adjusted to 120 parts and 180 parts, respectively. All other raw materials, contents and preparation methods are the same as in Embodiment 1.

[0154] Example 11

[0155] This embodiment provides a conductive silver paste and its preparation method. The only difference between this embodiment and Embodiment 1 is that the weight parts of spherical silver powder and flake silver powder are adjusted to 60 parts and 240 parts, respectively. All other raw materials, contents and preparation methods are the same as in Embodiment 1.

[0156] Comparative Example 1

[0157] This comparative example provides a conductive silver paste and its preparation method. The only difference from Example 1 is that phenolic epoxy resin is not added; instead, the reduced weight proportions are proportionally allocated to triphenylmethane-type epoxy resin and alicyclic epoxy resin (the mass ratio of the two in Example 1). All other raw materials, contents, and preparation methods are the same as in Example 1. The resin precipitation pattern of the conductive silver paste is shown below. Figure 3 As shown.

[0158] Comparative Example 2

[0159] This comparative example provides a conductive silver paste and its preparation method. The only difference between this example and Example 1 is that triphenylmethane epoxy resin is not added, and its reduced weight is proportionally allocated to phenolic epoxy resin and alicyclic epoxy resin (the mass ratio of the two in Example 1). All other raw materials, contents, and preparation methods are the same as in Example 1.

[0160] Comparative Example 3

[0161] This comparative example provides a conductive silver paste and its preparation method. The only difference from Example 1 is that it omits the alicyclic epoxy resin, and the reduced weight percentage is proportionally allocated to the phenolic epoxy resin and triphenylmethane epoxy resin (the same mass ratio as in Example 1). All other raw materials, contents, and preparation methods are the same as in Example 1. The residual adhesive image of the conductive silver paste on the chip is shown below. Figure 4 As shown.

[0162] Comparative Example 4

[0163] This comparative example provides a conductive silver paste, which is a one-component epoxy conductive silver paste purchased from Henkel Ablestik 84-1LMISR4.

[0164] The conductive silver pastes provided in Examples 1-11 and Comparative Examples 1-4 were subjected to performance tests. The specific test methods / standards are as follows:

[0165] (1) Viscosity change rate: The initial viscosity and the viscosity after 24 hours of storage were tested respectively (ambient temperature was 25℃). The equipment model was BROOKFIELD DV3T, CP51Z rotor, and the viscosity was tested at 5 rpm.

[0166] (2) Die-Shear Strength: The die-shear strength test method refers to "HG / T 5912-2021 Conductive Adhesives". The silicon wafer size is 2mm×2mm; the substrate is silver-plated copper sheet; the curing conditions are 175℃×1.0h in a forced-air oven; the test equipment is a DAGE-4000P multi-functional push-pull tester, Nordson DAGE Precision Industries LTD, USA. The shear strength is the magnitude of the push force (unit is kgF); 10 samples of each adhesive are used, and the average value is taken. When measuring the push force at 260℃, the temperature control heating platform is set to the desired temperature and stabilized for 5 minutes after reaching the target temperature before the push force is measured.

[0167] (3) Chip residual adhesive rate: The residual adhesive on the substrate after the thrust damage was observed by optical microscope, and the area ratio of the part with residual adhesive (the percentage relative to the chip area) was evaluated. The arithmetic mean of 10 samples was taken.

[0168] (4) Moisture and heat resistance: The chip thrust silicon wafer was steamed in a PCT aging chamber. The equipment model was HV-50Ⅱ, and the conditions were 16 h @ 121℃, 2 bar water vapor. Then the chip thrust test and residual glue rate evaluation were carried out.

[0169] (5) Evaluation of resin precipitation: After the conductive adhesive applied to the silver-plated copper sheet has cured, it is observed by optical microscope and the size of the resin precipitation (i.e., RBO) around the conductive adhesive is measured.

[0170] (6) Volume resistivity: The test method refers to "HG / T 5912-2021 Conductive Adhesives". The resistance is measured by the four-probe method, and then the volume resistivity of the silver paste is calculated.

[0171] (7) Thermal conductivity: The test method refers to "HG / T 5912-2021 Conductive Adhesives" and is measured by laser flash method.

[0172] The test results are shown in Tables 2 and 3.

[0173] Table 2

[0174]

[0175] Table 3

[0176]

[0177] According to the test results in Tables 2 and 3:

[0178] (1) As can be seen from Examples 1 to 11, the present invention, by using glycidylamine type epoxy resin as the main resin and adding specific auxiliary resins (triphenylmethane type epoxy resin, phenolic resin and alicyclic epoxy resin) for compounding, enables the obtained conductive silver paste to have a suitable and stable viscosity (viscosity of 7500-16000 mPa·s, viscosity change rate after 24h ≤6%), and also has excellent conductivity (volume resistivity ≤1.5×10). -3 It exhibits excellent thermal conductivity (≥2 W / (m·K)) and bonding performance (chip thrust ≥13 kgF at 25℃ and ≥3 kgF at 260℃); at the same time, it has excellent high-temperature and high-humidity reliability (after PCT damp heat aging, chip thrust ≥6 kgF at 25℃ and ≥2 kgF at 260℃), high residual glue rate (≥75% before aging and ≥60% after aging), and low resin overflow (resin precipitation <10 μm).

[0179] (2) By comparing Examples 6 and 7 with Examples 1, 4 and 5, it can be seen that in Examples 6 and 7, the mass ratio of phenolic epoxy resin, triphenylmethane epoxy resin and alicyclic epoxy resin in the auxiliary resin used exceeds (1.5-2):(1-1.5):(1-1.5). The resulting conductive silver paste has a lower chip thrust and a lower chip residue rate at both room temperature and high temperature. After PCT damp heat aging, the chip thrust (especially at high temperature of 260°C) decreases, and the chip residue rate is less than 70%. This shows that by optimizing the mass ratio of specific resin combinations in the auxiliary resin, the present invention can further improve the damp heat resistance reliability of the obtained conductive silver paste, reduce resin precipitation, and increase the residue rate.

[0180] (3) According to the comparison between Examples 10 and 11 and Examples 1, 8 and 9, it can be seen that in Example 10, the mass of spherical silver powder and flake silver powder is relatively high, that is, the mass ratio of flake silver powder is relatively low, the silver paste lacks a continuous surface contact heat conduction path, and the thermal conductivity is significantly reduced; in Example 11, the mass of spherical silver powder and flake silver powder is relatively low, that is, the mass ratio of flake silver powder is relatively high, at this time the powder is stacked and agglomerated, the viscosity of the system increases, the porosity increases, and the thermal conductivity is also reduced; indicating that by controlling the mass ratio of spherical silver powder and flake silver powder, the present invention can further improve the thermal conductivity of the obtained conductive silver paste while balancing the viscosity and conductivity of the system.

[0181] (4) By comparing Comparative Examples 1-3 with Example 1, it can be seen that by selecting a combination of triphenylmethane epoxy resin, phenolic resin and alicyclic epoxy resin as auxiliary resins, the present invention can enable the three to better exert synergistic effects, so that the resulting conductive silver paste has low resin precipitation and suitable viscosity, further improving the bonding strength of the conductive silver paste and its reliability under high temperature and high humidity conditions, while also reducing resin precipitation and increasing the residual adhesive rate. When phenolic epoxy resin is missing (Comparative Example 1), the resin precipitation surges to 118 μm, the interface cross-linking is insufficient and the resin overflow is serious; when triphenylmethane epoxy resin is missing (Comparative Example 2), there is a lack of rigid heat-resistant skeleton, and the high-temperature thrust drops significantly after humid heat aging (the change rate of chip thrust at 260°C can reach 35.7%); when alicyclic epoxy resin is missing (Comparative Example 3), the system fluidity and interface wettability are poor, the residual adhesive rate is only 50%, and the residual adhesive rate further drops to 36% after PCT aging, and the interface is very easy to delaminate.

[0182] (5) By comparing Comparative Example 4 with Examples 1-11, it can be seen that although the commercially available silver paste (Comparative Example 4) has good initial viscosity stability and lower resistivity, its heat resistance and damp heat resistance reliability are significantly different. The thrust at 260°C is only 1.5 kgF, and after PCT damp heat aging, the thrust drops to 0.6 kgF and the residual adhesive rate is only 20%. It is very easy to fail to bond under high temperature and high humidity conditions, which cannot meet the requirements of high reliability electronic packaging. This shows that the high temperature thrust, bonding strength after aging and residual adhesive rate of the conductive silver paste provided by the present invention are far superior to commercially available products, and it also has multiple advantages such as low resin overflow, long-term damp heat resistance, high thermal conductivity and high bonding strength.

[0183] In summary, by further optimizing the specific types and contents of the components in the formulation of the conductive silver paste, this invention enables the obtained conductive silver paste to possess superior viscosity and stability (viscosity of 8000-10000 mPa·s, viscosity change rate ≤5% after 24 h) and better conductivity (volume resistivity ≤8×10⁻⁶). -4 Ω·cm, further optimized to 1.9-2.1×10 -4The product exhibits excellent performance in terms of heat resistance, thermal conductivity (≥3.5 W / (m·K), up to 4.5 W / (m·K)), bonding performance (chip thrust ≥15 kgF at 25℃, chip thrust ≥3.5 kgF at 260℃; further optimized to 17-23 kgF at 25℃, chip thrust 4-5 kgF at 260℃), and resistance to damp heat (after PCT damp heat aging, chip thrust ≥9.5 kgF at 25℃, chip thrust ≥3 kgF at 260℃; further optimized to 10.5-13.5 kgF at 25℃, chip thrust 3.5-4.5 kgF at 260℃), with higher residual glue rate (≥80% before aging, ≥65% after aging; further optimized to ≥85% before aging, ≥80% after aging), and lower resin overflow (resin exudation ≤7 μm, further optimized to 2-4 μm).

[0184] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A conductive silver paste, characterized in that, Includes epoxy resin, reactive diluent, curing agent, accelerator, and silver powder; The epoxy resin includes a main resin and auxiliary resins; The main resin includes glycidyl amine type epoxy resin; The auxiliary resin includes a combination of phenolic epoxy resin, triphenylmethane epoxy resin and alicyclic epoxy resin.

2. The conductive silver paste according to claim 1, characterized in that, The mass ratio of the main resin to the auxiliary resin in the epoxy resin is (5-8):(3-5).

3. The conductive silver paste according to claim 1, characterized in that, The mass ratio of phenolic epoxy resin, triphenylmethane epoxy resin and alicyclic epoxy resin in the auxiliary resin is (1.5-2):(1-1.5):(1-1.5).

4. The conductive silver paste according to claim 1, characterized in that, The silver powder includes spherical silver powder and / or flake silver powder.

5. The conductive silver paste according to claim 4, characterized in that, The silver powder is a combination of spherical silver powder and flake silver powder; The mass ratio of the spherical silver powder to the flake silver powder is 1:(2-3).

6. The conductive silver paste according to any one of claims 1-5, characterized in that, The conductive silver paste comprises the following components in parts by weight: 40-120 parts epoxy resin; 4-40 parts of reactive diluent; 4-40 parts of curing agent; Accelerator 1.5-5 parts; 280-440 parts silver powder.

7. The conductive silver paste according to claim 1, characterized in that, The active diluent includes any one or a combination of at least two of p-tert-butyl monoglycidyl ether, hexanediol diglycidyl ether, butanediol diglycidyl ether or phenyl glycidyl ether. The curing agent includes any one or a combination of at least two of imidazole, phenolic resin, dicyandiamide or diaminodiphenyl sulfone; The accelerators include imidazole accelerators and / or tertiary amine accelerators; The conductive silver paste also includes a coupling agent; The coupling agent includes any one or a combination of at least two of the following: epoxy silane coupling agent, amino silane coupling agent, methacryloxy silane coupling agent, vinyl silane coupling agent, or mercapto silane coupling agent. The coupling agent is present in parts by weight of 0.4-1 parts; The conductive silver paste also includes a conductivity promoter; The conductivity promoter includes monocarboxylic acids and / or dicarboxylic acids; The monocarboxylic acid includes any one or a combination of at least two of 5-aminosalicylic acid, tyrosine, 3,5-dihydroxybenzoic acid, or 3-hydroxybenzoic acid. The dicarboxylic acid includes any one or a combination of at least two of adipic acid, glutaric acid, or succinic acid. The conductivity promoter is present in parts by weight of 0.4-1 parts.

8. A method for preparing conductive silver paste according to any one of claims 1-7, characterized in that, The preparation method includes the following steps: The conductive silver paste is obtained by mixing epoxy resin, reactive diluent, curing agent, accelerator, optional coupling agent, optional conductivity accelerator and silver powder.

9. The method for preparing conductive silver paste according to claim 8, characterized in that, The mixing process includes first mixing epoxy resin with reactive diluent, then sequentially adding optional coupling agent, optional conductivity promoter, curing agent and accelerator for a second mixing, and finally adding silver powder for a third mixing. The temperature for the first mixing is 70-80℃ and the time is 10-20 min; The first mixing is carried out under stirring at a speed of 10-30 rpm; The first mixing process also includes a cooling step, wherein the cooling temperature is 20-30°C. The second mixing time is 10-20 minutes; The second mixing is carried out under stirring at a speed of 10-30 rpm; The third mixing time is 20-30 minutes; The third mixing is carried out under stirring at a speed of 20-40 rpm; The third mixing process also includes grinding and post-processing steps; After the grinding process, the particle size of the mixture is ≤15 μm; The post-processing includes vacuum degassing, wherein the vacuum degassing time is 30-40 min and the vacuum degree is ≤-0.095 MPa; The vacuum degassing is carried out under stirring at a speed of 20-40 rpm.

10. The application of the conductive silver paste as described in any one of claims 1-7 in an adhesive material.

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