High-strength bending-resistant conductive silver adhesive and preparation method thereof

Abstract

The invention discloses a high-strength bending-resistant conductive silver adhesive and a preparation method thereof.The preparation method comprises the following steps that an alkoxy end-capping reagent and a composite catalyst are added into 107 adhesive for a reaction, and alkoxy-terminated 107 adhesive is obtained; the preparation method comprises the following steps: adding fumed silica into alkoxy-terminated 107 glue, kneading, and grinding to obtain a base material; adding a plasticizer, a cross-linking agent, an accelerant, a coupling agent, a dispersing agent, a flatting agent and conductive powder into the base material, and uniformly mixing; by limiting the preparation process and the raw materials, the prepared high-strength bending-resistant conductive silver adhesive has the advantages of good toughness, high strength, large-angle bending resistance and suitability for multiple bending requirements, and the conductive silver adhesive has high conductivity and heat conductivity coefficients and can be used for producing halogen-free, tin-free and other products with high environmental protection requirements; in addition, the conductive adhesive provided by the invention uses an organic silicon system, has good biocompatibility, can be cured at room temperature as single and double components, and is convenient to operate and high in efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of conductive silver paste, and particularly relates to a high-strength and bend-resistant conductive silver paste and a preparation method thereof. Background Art

[0002] Conductive silver paste is a silver powder-containing glue with conductive function. Since the matrix resin of conductive silver paste is an adhesive, an appropriate curing temperature can be selected for bonding. For example, epoxy resin adhesive can be cured at room temperature to 150°C, which is much lower than the welding temperature of more than 200°C for tin-lead welding. This avoids the material deformation, thermal damage of electronic devices, and formation of internal stress that may be caused by welding at high temperature. At the same time, due to the rapid development of miniaturization and microminiaturization of electronic components and high density and high integration of printed circuit boards, the minimum pitch of 0.65 mm for lead-tin welding far cannot meet the actual requirements of conductive connection, while conductive silver paste can be made into a slurry to achieve a very high line resolution. Moreover, the process of conductive silver paste is simple, easy to operate, can improve production efficiency, and also avoids environmental pollution caused by heavy metal lead in tin-lead solder. Therefore, conductive silver paste is an ideal choice to replace tin-lead welding for conductive connection.

[0003] At present, conductive silver paste has been widely used in the encapsulation and bonding of electronic components and assemblies such as liquid crystal displays (LCDs), light-emitting diodes (LEDs), integrated circuit (IC) chips, printed circuit board assemblies (PCBAs), dot matrix blocks, ceramic capacitors, membrane switches, smart cards, radio frequency identification, etc., and there is a trend to gradually replace traditional tin soldering. However, the existing conductive silver paste has problems of low tensile strength and poor bend resistance, which affects its scope of use.

[0004] In view of this, the present invention is specifically proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-strength and bend-resistant conductive silver paste and a preparation method thereof. The conductive silver paste of the present invention has excellent conductive performance, and at the same time has high tensile strength, elongation at break, and high fold resistance.

[0006] In order to achieve the above object of the present invention, the following technical solutions are specifically adopted:

[0007] The first aspect of the present invention provides a preparation method of a high-strength and bend-resistant conductive silver paste, and the preparation method includes the following steps:

[0008] (a) Add an alkoxy-terminated agent and a composite catalyst to 107 glue for reaction to obtain alkoxy-terminated 107 glue;

[0009] (b) Add fumed silica to the alkoxy-terminated 107 glue for kneading, and then grind to obtain a base material;

[0010] (c) Add a plasticizer, a crosslinking agent, an accelerator, a coupling agent, a dispersant, a leveling agent, and a conductive powder to the base material and mix them evenly to obtain the high-strength bend-resistant conductive silver paste.

[0011] Preferably, in the step (a), the 107 glue is composed of a high-molecular-weight 107 and a low-molecular-weight 107 with a mass ratio of (1-4):(1-4). The viscosity of the high-molecular-weight 107 is 20,000-60,000 (25 °C, mPa·s), and the viscosity of the low-molecular-weight 107 is 1,000-8,000 (25 °C, mPa·s).

[0012] Preferably, in the step (a), the alkoxy-capped agent is methyltrimethoxysilane or methyltriethoxysilane; the composite catalyst is composed of an amine catalyst and an acid catalyst. The amine catalyst is selected from at least one of triethylamine, diethylenetriamine, triethylenetetramine, diethanolamine, and triethanolamine, and the acid catalyst is selected from at least one of acetic acid, formic acid, and trifluoromethanesulfonic acid.

[0013] Preferably, in the step (a), the molar ratio of the 107 glue to the alkoxy-capped agent is 1:(2-3), and the addition amount of the composite catalyst is 0.5%-5% of the mass of the 107 glue;

[0014] The reaction temperature is 50-120 °C, the time is 2-8 h, and the generated alcohol is distilled out during the reaction.

[0015] Preferably, in the step (b), the addition amount of the fumed silica is 8%-25% of the mass of the alkoxy-capped 107 glue;

[0016] The fumed silica is hydrophobic fumed silica or hydrophilic fumed silica; when the fumed silica is hydrophilic fumed silica, a treating agent is also added to the alkoxy-capped 107 glue. The addition amount of the treating agent is 10%-40% of the mass of the hydrophilic fumed silica, and the treating agent is silazane, silane, or silicone oil.

[0017] Preferably, in the step (b), the kneading includes kneading at 80 °C for 1-3 h, kneading at 100-160 °C for 1-4 h, and then kneading at a vacuum degree greater than -0.08 Mpa and 100-160 °C for 2-8 h; the grinding is carried out by grinding with a three-roll mill 1-3 times.

[0018] Preferably, in the step (c), the mass ratio of the base material, the plasticizer, the crosslinking agent, the accelerator, the coupling agent, the dispersant, the leveling agent, and the conductive powder is 100:(0-1):(0.5-8):(0.05-1):(0.5-5):(0.01-1):(0.01-1):(200-600).

[0019] Preferably, in the step (c), the conductive powder is silver powder or silver-coated copper powder; the silver powder is composed of flaky silver powder and other forms of silver powder with a mass ratio of (60-90):(10-40), and the other forms of silver powder are selected from at least one of spherical silver powder, rod-shaped silver powder, quasi-spherical silver powder or irregular-shaped silver powder. The particle size of the flaky silver powder is 2-20 μm, and the D50 of the other forms of silver powder is 1-50 μm;

[0020] The plasticizer is white oil, mineral oil or silicone oil; the cross-linking agent is methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane or vinyltriethoxysilane; the promoter is titanate, zirconate or organic selenium; the coupling agent is KH-550, KH-560 or KH-792; the dispersant is a silicone-based dispersant or a polyether-based dispersant, and the leveling agent is a silicone-based leveling agent or a polyether-based leveling agent.

[0021] Preferably, in the step (c), a solvent, a color paste and other fillers are further added to the base material;

[0022] The addition amount of the solvent is 1%-20% of the mass of the base material; the addition amount of the color paste is 0.001%-0.1% of the mass of the base material; the addition amount of the other fillers is 1%-15% of the mass of the base material;

[0023] The solvent is an ester solvent, an ether solvent, a benzene solvent or an alkane solvent, and the other fillers are selected from at least one of calcium carbonate, silica powder, talc powder, transparent powder, barium sulfate, alumina, aluminum nitride and graphene.

[0024] The second aspect of the present invention provides a high-strength and bend-resistant conductive silver glue prepared by the above preparation method.

[0025] Compared with the prior art, the beneficial effects of the present invention at least include:

[0026] By defining the preparation process and each raw material, the high-strength and bend-resistant conductive silver glue prepared by the present invention has good toughness, high strength, and is resistant to large-angle bending, meeting the requirements of multiple bends. Specifically, the tensile strength can reach more than 6 KN / m, the elongation at break can reach more than 400%, and it can be bent by more than 270 degrees. Moreover, this conductive silver glue has a high electrical and thermal conductivity coefficient, can be used for products with high environmental protection requirements such as halogen-free and tin-free, and the conductivity can reach 5×10 －5 mΩ / cm or less, and the thermal conductivity can reach more than 15 W / m·k; in addition, the conductive glue of the present invention uses an organosilicon system, has good biocompatibility, can be cured at room temperature in single or double components, is easy to operate and has high efficiency. Detailed implementation mode

[0027] The embodiments of the technical solution of the present invention will be described in detail below in conjunction with the embodiments. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, so they are only examples and cannot be used to limit the protection scope of the present invention.

[0028] It should be noted that unless otherwise specified, the technical terms or scientific terms used in this application should have the ordinary meanings understood by those skilled in the art to which the present invention belongs.

[0029] The embodiment of the present invention provides a preparation method of a high-strength and bend-resistant conductive silver paste, and the preparation method includes the following steps:

[0030] (a) Add an alkoxy-terminated agent and a composite catalyst to the 107 glue for reaction to obtain alkoxy-terminated 107 glue;

[0031] (b) Add fumed silica to the alkoxy-terminated 107 glue for kneading, and then grind it to obtain a base material;

[0032] (c) Add a plasticizer, a cross-linking agent, a promoter, a coupling agent, a dispersant, a leveling agent and conductive powder to the base material and mix them evenly to obtain the high-strength and bend-resistant conductive silver paste.

[0033] Through the limitation of the preparation process and each raw material, the high-strength and bend-resistant conductive silver paste prepared by the present invention has good toughness, high strength, and resistance to large-angle bending, and meets the requirements of multiple bends. Specifically, the tensile strength can reach more than 6 KN / m, the elongation at break can reach more than 400%, and it can be bent more than 270 degrees. Moreover, this conductive silver paste has a high conductivity and thermal conductivity coefficient, and can be used for products with high environmental protection requirements such as halogen-free and tin-free. The conductivity can reach below 5×10 －5 mΩ / cm, and the thermal conductivity can reach more than 15 W / m·k; in addition, the conductive paste of the present invention uses an organosilicon system, has good biocompatibility, can be cured at room temperature in single or double components, is convenient to operate, and has high efficiency.

[0034] In one embodiment, in the step (a), the 107 glue is composed of high-molecular-weight 107 and low-molecular-weight 107 with a mass ratio of (1-4):(1-4). The viscosity of the high-molecular-weight 107 is 20,000-60,000, and the viscosity of the low-molecular-weight 107 is 1,000-8,000.

[0035] In one embodiment, in the step (a), the alkoxy-terminated agent is methyltrimethoxysilane or methyltriethoxysilane; the composite catalyst is composed of an amine catalyst and an acid catalyst. The amine catalyst is selected from at least one of triethylamine, diethylenetriamine, triethylenetetramine, diethanolamine and triethanolamine, and the acid catalyst is selected from at least one of acetic acid, formic acid and trifluoromethanesulfonic acid.

[0036] In one embodiment, in the step (a), the molar ratio of the 107 glue and the alkoxy capping agent is 1∶(2 - 3), and the addition amount of the composite catalyst is 0.5% - 5% of the mass of the 107 glue;

[0037] The reaction temperature is 50 - 120 °C, the time is 2 - 8 h, and the generated alcohol is distilled out during the reaction process.

[0038] In one embodiment, in the step (b), the addition amount of the fumed silica is 8% - 25% of the mass of the alkoxy-capped 107 glue;

[0039] The fumed silica is hydrophobic fumed silica or hydrophilic fumed silica; when the fumed silica is hydrophilic fumed silica, a treating agent is further added to the alkoxy-capped 107 glue, and the addition amount of the treating agent is 10% - 40% of the mass of the hydrophilic fumed silica, and the treating agent is silazane, silane or silicone oil.

[0040] In one embodiment, in the step (b), the kneading includes kneading at 80 °C for 1 - 3 h, kneading at 100 - 160 °C for 1 - 4 h, and then kneading at a vacuum degree greater than -0.08 Mpa and 100 - 160 °C for 2 - 8 h; the grinding is carried out by grinding with a three-roll mill for 1 - 3 times.

[0041] In one embodiment, in the step (c), the mass ratio of the base material, plasticizer, cross-linking agent, accelerator, coupling agent, dispersant, leveling agent and conductive powder is 100∶(0 - 1)∶(0.5 - 8)∶(0.05 - 1)∶(0.5 - 5)∶(0.01 - 1)∶(0.01 - 1)∶(200 - 600).

[0042] In one embodiment, in the step (c), the conductive powder is silver powder or silver-coated copper powder; the silver powder is composed of flaky silver powder and other-shaped silver powder with a mass ratio of (60 - 90)∶(10 - 40), and the other-shaped silver powder is selected from at least one of spherical silver powder, rod-shaped silver powder, quasi-spherical silver powder or irregular-shaped silver powder, the particle size of the flaky silver powder is 2 - 20 μm, and the D50 of the other-shaped silver powder is 1 - 50 μm;

[0043] The plasticizer is white oil, mineral oil or silicone oil; the cross-linking agent is methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane or vinyltriethoxysilane; the accelerator is titanate, zirconate or organic selenium; the coupling agent is KH-550, KH-560 or KH-792; the dispersant is a silicone-based dispersant or a polyether-based dispersant, and the leveling agent is a silicone-based leveling agent or a polyether-based leveling agent.

[0044] In one embodiment, in the step (c), a solvent, a color paste and other fillers are further added to the base material;

[0045] The addition amount of the solvent is 1% - 20% of the mass of the base material; the addition amount of the color paste is 0.001% - 0.1% of the mass of the base material; the addition amount of other fillers is 1% - 15% of the mass of the base material;

[0046] The solvent is an ester solvent, an ether solvent, a benzene solvent or an alkane solvent; the other fillers are selected from at least one of calcium carbonate, silica powder, talc powder, transparent powder, barium sulfate, alumina, aluminum nitride and graphene.

[0047] Another embodiment of the present invention provides a high-strength bend-resistant conductive silver paste prepared by the above preparation method.

[0048] The technical solution of the present invention will be further described in detail through specific embodiments below.

[0049] Example 1

[0050] This example is a preparation method of a high-strength bend-resistant conductive silver paste, and the preparation method includes the following steps:

[0051] (a) Add an alkoxy capping agent and a composite catalyst to 107 glue and react at 50 °C for 8 h. During the reaction, the generated alcohol is distilled out to obtain alkoxy-capped 107 glue. Among them, 107 glue can be composed of high molecular weight 107 and low molecular weight 107 with a mass ratio of 1:4. The viscosity of high molecular weight 107 is 40000 (25 °C, mPa·s), and the viscosity of low molecular weight 107 is 5000 (25 °C, mPa·s); the alkoxy capping agent is methyltrimethoxysilane; the composite catalyst is composed of an equal mass of an amine catalyst and an acid catalyst. The amine catalyst is triethylamine, and the acid catalyst is acetic acid; the molar ratio of 107 glue to the alkoxy capping agent is 1:2, and the addition amount of the composite catalyst is 5% of the mass of 107 glue;

[0052] (b) Add fumed silica to the alkoxy-capped 107 glue and knead at 80 °C for 1 h, knead at 100 °C for 4 h, then knead at a vacuum degree greater than -0.08 Mpa and 100 °C for 8 h, and then grind 3 times with a three-roll mill to obtain the base material; the addition amount of fumed silica is 8% of the mass of the alkoxy-capped 107 glue; the fumed silica is hydrophobic fumed silica;

[0053] (c) Add a plasticizer, a cross-linking agent, a promoter, a coupling agent, a dispersant, a leveling agent and a conductive powder to the base material and mix them evenly to obtain the high-strength bend-resistant conductive silver paste. Among them, the mass ratio of the base material, the plasticizer, the cross-linking agent, the promoter, the coupling agent, the dispersant, the leveling agent and the conductive powder is 100:1:0.5:1:0.5:1:1:600;

[0054] The conductive powder is silver powder; the silver powder is composed of flaky silver powder and other-shaped silver powder with a mass ratio of 90:10. The other-shaped silver powder is spherical silver powder. The particle size of the flaky silver powder is 2-20 μm, and the D50 of the spherical silver powder is 2 μm;

[0055] The plasticizer is mineral oil; the crosslinking agent is methyltrimethoxysilane; the promoter is tetra-isopropyl titanate; the coupling agent is KH-550; the dispersant is BYK104s silicone dispersant, and the leveling agent is BYK-333 silicone leveling agent.

[0056] Example 2

[0057] This example is a preparation method of a high-strength bend-resistant conductive silver paste. The preparation method includes the following steps:

[0058] (a) Add an alkoxy-capping agent and a composite catalyst to the 107 glue and react at 120 °C for 2 h. During the reaction, the generated alcohol is evaporated to obtain alkoxy-capped 107 glue. Among them, the 107 glue can be composed of high-molecular-weight 107 and low-molecular-weight 107 with a mass ratio of 4:1. The viscosity of the high-molecular-weight 107 is 40000 (25 °C, mPa·s), and the viscosity of the low-molecular-weight 107 is 5000 (25 °C, mPa·s); the alkoxy-capping agent is methyltriethoxysilane; the composite catalyst is composed of an equal mass of an amine catalyst and an acid catalyst. The amine catalyst is diethylenetriamine, and the acid catalyst is formic acid; the molar ratio of the 107 glue to the alkoxy-capping agent is 1:3, and the addition amount of the composite catalyst is 0.5% of the mass of the 107 glue;

[0059] (b) Add fumed silica to the alkoxy-capped 107 glue and knead at 80 °C for 3 h, then knead at 160 °C for 1 h, and then knead at a vacuum degree greater than -0.08 Mpa and 160 °C for 2 h, and then grind once with a three-roll mill to obtain the base material; the addition amount of fumed silica is 25% of the mass of the alkoxy-capped 107 glue;

[0060] The fumed silica is hydrophilic fumed silica, and a treating agent is also added to the alkoxy-capped 107 glue. The addition amount of the treating agent is 10% of the mass of the hydrophilic fumed silica, and the treating agent is silicone oil;

[0061] (c) Add a plasticizer, a crosslinking agent, a promoter, a coupling agent, a dispersant, a leveling agent, and a conductive powder to the base material and mix them evenly to obtain the high-strength bend-resistant conductive silver paste. Among them, the mass ratio of the base material, the plasticizer, the crosslinking agent, the promoter, the coupling agent, the dispersant, the leveling agent, and the conductive powder is 100:0.1:8:0.05:5:0.01:0.01:200;

[0062] The conductive powder is silver powder; the silver powder is composed of flaky silver powder and silver powder in other forms with a mass ratio of 60:40. The silver powder in other forms is spherical silver powder. The particle size of the flaky silver powder is 2-20 μm, and the D50 of the spherical silver powder is 2 μm;

[0063] The plasticizer is mineral oil; the crosslinking agent is methyltriethoxysilane; the promoter is tetra-isopropyl titanate; the coupling agent is KH-550; the dispersant is BYK104s silicone dispersant, and the leveling agent is BYK-333 silicone leveling agent.

[0064] Example 3

[0065] This example is a preparation method of a high-strength and bend-resistant conductive silver glue. The preparation method includes the following steps:

[0066] (a) Add an alkoxy-terminated agent and a composite catalyst to the 107 glue and react at 100 °C for 6 h. During the reaction process, the generated alcohol is distilled out to obtain alkoxy-terminated 107 glue. Among them, the 107 glue can be composed of high-molecular-weight 107 and low-molecular-weight 107 with a mass ratio of 3:2. The viscosity of the high-molecular-weight 107 is 40000 (25 °C, mPa·s), and the viscosity of the low-molecular-weight 107 is 5000 (25 °C, mPa·s); the alkoxy-terminated agent is methyltrimethoxysilane; the composite catalyst is composed of an equal mass of an amine catalyst and an acid catalyst. The amine catalyst is triethylamine, and the acid catalyst is acetic acid; the molar ratio of the 107 glue to the alkoxy-terminated agent is 1:3, and the addition amount of the composite catalyst is 2% of the mass of the 107 glue;

[0067] (b) Add fumed silica to the alkoxy-terminated 107 glue and knead at 80 °C for 2 h, knead at 140 °C for 3 h, then knead at a vacuum degree greater than -0.08 Mpa and 140 °C for 5 h, and then grind twice with a three-roll mill to obtain the base material; the addition amount of fumed silica is 15% of the mass of the alkoxy-terminated 107 glue;

[0068] The fumed silica is hydrophilic fumed silica, and a treating agent is also added to the alkoxy-terminated 107 glue. The addition amount of the treating agent is 25% of the mass of the hydrophilic fumed silica, and the treating agent is hexamethyldisilazane;

[0069] (c) Add a plasticizer, a crosslinking agent, a promoter, a coupling agent, a dispersant, a leveling agent, and a conductive powder to the base material and mix them evenly to obtain the high-strength and bend-resistant conductive silver glue. Among them, the mass ratio of the base material, the plasticizer, the crosslinking agent, the promoter, the coupling agent, the dispersant, the leveling agent, and the conductive powder is 100:0.5:4:0.5:3:0.5:0.5:400;

[0070] The conductive powder is silver powder; the silver powder is composed of flaky silver powder and other-shaped silver powder with a mass ratio of 70:30. The other-shaped silver powder is spherical silver powder. The particle size of the flaky silver powder is 2-20 μm, and the D50 of the spherical silver powder is 2 μm;

[0071] The plasticizer is silicone oil; the cross-linking agent is methyltrimethoxysilane; the promoter is tetra-isopropyl titanate; the coupling agent is KH-550; the dispersant is BYK104s silicone dispersant, and the leveling agent is BYK-333 silicone leveling agent.

[0072] Comparative Example 1

[0073] This comparative example is a preparation method of a high-strength bend-resistant conductive silver glue. The preparation method includes the following steps:

[0074] (a) Add hydrophilic fumed silica to 107 glue and knead at 80 °C for 2 h, then knead at 140 °C for 3 h, and then knead at a vacuum degree greater than -0.08 Mpa and 140 °C for 5 h. Then grind twice with a three-roll mill to obtain the base material; the addition amount of hydrophilic fumed silica is 15% of the mass of 107 glue. Among them, 107 glue can be composed of high-molecular-weight 107 and low-molecular-weight 107 with a mass ratio of 3:2. The viscosity of high-molecular-weight 107 is 40000 (25 °C, mPa·s), and the viscosity of low-molecular-weight 107 is 5000 (25 °C, mPa·s);

[0075] The hydrophilic fumed silica is hydrophilic fumed silica. A treating agent is also added to the alkoxy-terminated 107 glue. The addition amount of the treating agent is 25% of the mass of the hydrophilic fumed silica. The treating agent is hexamethyldisilazane;

[0076] (b) Add a plasticizer, a cross-linking agent, a promoter, a coupling agent, a dispersant, a leveling agent and a conductive powder to the base material and mix evenly to obtain the high-strength bend-resistant conductive silver glue. Among them, the mass ratio of the base material, the plasticizer, the cross-linking agent, the promoter, the coupling agent, the dispersant, the leveling agent and the conductive powder is 100:0.5:4:0.5:3:0.5:0.5:400;

[0077] The conductive powder is silver powder; the silver powder is composed of flaky silver powder and other-shaped silver powder with a mass ratio of 70:30. The other-shaped silver powder is spherical silver powder. The particle size of the flaky silver powder is 2-20 μm, and the D50 of the spherical silver powder is 2 μm;

[0078] The plasticizer is silicone oil; the cross-linking agent is methyltrimethoxysilane; the promoter is tetra-isopropyl titanate; the coupling agent is KH-550; the dispersant is BYK104s silicone dispersant, and the leveling agent is BYK-333 silicone leveling agent.

[0079] Comparative Example 2

[0080] This comparative example is a preparation method of a high-strength bend-resistant conductive silver paste. The preparation method includes the following steps:

[0081] (a) Add an alkoxy-terminated agent and a composite catalyst to the 107 glue and react at 100 °C for 6 h. During the reaction process, the generated alcohol is distilled out to obtain alkoxy-terminated 107 glue. Among them, the 107 glue can be composed of high-molecular-weight 107 and low-molecular-weight 107 with a mass ratio of 3:2. The viscosity of the high-molecular-weight 107 is 40000 (25 °C, mPa·s), and the viscosity of the low-molecular-weight 107 is 5000 (25 °C, mPa·s); the alkoxy-terminated agent is methyltrimethoxysilane; the composite catalyst is composed of an equal mass of an amine catalyst and an acid catalyst. The amine catalyst is triethylamine, and the acid catalyst is acetic acid; the molar ratio of the 107 glue to the alkoxy-terminated agent is 1:3, and the addition amount of the composite catalyst is 2% of the mass of the 107 glue;

[0082] (b) Add a plasticizer, a cross-linking agent, a promoter, a coupling agent, a dispersant, a leveling agent, and a conductive powder to the alkoxy-terminated 107 glue and mix them evenly to obtain the high-strength bend-resistant conductive silver paste. Among them, the mass ratio of the alkoxy-terminated 107 glue, the plasticizer, the cross-linking agent, the promoter, the coupling agent, the dispersant, the leveling agent, and the conductive powder is 100:0.5:4:0.5:3:0.5:0.5:400;

[0083] The conductive powder is silver powder; the silver powder is composed of flaky silver powder and other-shaped silver powder with a mass ratio of 70:30. The other-shaped silver powder is spherical silver powder. The particle size of the flaky silver powder is 2-20 μm, and the D50 of the spherical silver powder is 2 μm;

[0084] The plasticizer is silicone oil; the cross-linking agent is methyltrimethoxysilane; the promoter is tetra-isopropyl titanate; the coupling agent is KH-550; the dispersant is BYK104s silicone dispersant, and the leveling agent is BYK-333 silicone leveling agent.

[0085] Experimental example

[0086] Respectively obtain the high-strength bend-resistant conductive silver pastes prepared in Example 3 and Comparative Examples 1-2;

[0087] Use a volume resistance tester method to detect the conductivity of the above different high-strength bend-resistant conductive silver pastes. The detection results are shown in Table 1;

[0088] Use a thermal conductivity tester to detect the thermal conductivity of the above different high-strength bend-resistant conductive silver pastes. The detection results are shown in Table 1;

[0089] Use a tensile machine to detect the tensile strength of the above different high-strength bend-resistant conductive silver pastes. The detection results are shown in Table 1;

[0090] The elongation at break of the above-mentioned different high-strength bend-resistant conductive silver pastes was detected using a tensile testing machine, and the test results are shown in Table 1;

[0091] The bend resistance of the above-mentioned different high-strength bend-resistant conductive silver pastes was detected using a bend fatigue tester, and the test results are shown in Table 1;

[0092] Table 1

[0093]

[0094] As can be seen from Table 1:

[0095] Compared with the comparative example, the high-strength bend-resistant conductive silver paste prepared in this application has more excellent electrical and thermal conductivity, as well as mechanical properties.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered by the scope of the claims and the description of the present invention.

Claims

1. A method for preparing high-strength and bending-resistant conductive silver paste, characterized in that: The preparation method comprises the following steps: (a) adding an alkoxy end-capping agent and a composite catalyst to 107 glue to carry out a reaction to obtain alkoxy end-capped 107 glue; (b) adding fumed silica to alkoxy-terminated 107 glue, kneading, and then grinding to obtain a base material; (c) adding a plasticizer, a cross-linking agent, a accelerator, a coupling agent, a dispersant, a leveling agent and a conductive powder to the base material and mixing them evenly to obtain the high-strength and bending-resistant conductive silver paste.

2. The preparation method according to claim 1, characterized in that: In the step (a), the 107 glue is composed of high molecular weight 107 and low molecular weight 107 in a mass ratio of (1-4): (1-4), the viscosity of the high molecular weight 107 is 20000-60000, and the viscosity of the low molecular weight 107 is 1000-8000.

3. The preparation method according to claim 1, characterized in that: In the step (a), the alkoxy end-capping agent is methyltrimethoxysilane or methyltriethoxysilane; the composite catalyst is composed of an amine catalyst and an acid catalyst, the amine catalyst is selected from at least one of triethylamine, diethylenetriamine, triethylenetetramine, diethanolamine and triethanolamine, and the acid catalyst is selected from at least one of acetic acid, formic acid and trifluoromethanesulfonic acid.

4. The preparation method according to claim 1, characterized in that: In the step (a), the molar ratio of 107 glue to the alkoxy end-capping agent is 1: (2-3), and the added amount of the composite catalyst is 0.5% to 5% of the mass of the 107 glue; The reaction temperature is 50-120°C and the reaction time is 2-8 hours. The generated alcohol is evaporated during the reaction.

5. The preparation method according to claim 1, characterized in that: In the step (b), the amount of fumed silica added is 8% to 25% of the mass of the alkoxy-terminated 107 glue; The fumed silica is hydrophobic fumed silica or hydrophilic fumed silica; when the fumed silica is hydrophilic silica, a treating agent is further added to the alkoxy-terminated 107 glue, and the added amount of the treating agent is 10% to 40% of the mass of the hydrophilic fumed silica, and the treating agent is silazane, silane or silicone oil.

6. The preparation method according to claim 1, characterized in that: In the step (b), kneading includes kneading at 80° C. for 1 to 3 hours, kneading at 100 to 160° C. for 1 to 4 hours, and then kneading at a vacuum degree greater than -0.08 MPa and 100 to 160° C. for 2 to 8 hours; and grinding is performed by grinding with a three-roll mill for 1 to 3 times.

7. The preparation method according to claim 1, characterized in that: In the step (c), the mass ratio of the base material, plasticizer, crosslinking agent, accelerator, coupling agent, dispersant, leveling agent and conductive powder is 100: (0-1): (0.5-8): (0.05-1): (0.5-5): (0.01-1): (0.01-1): (200-600).

8. The preparation method according to claim 1, characterized in that: In the step (c), the conductive powder is silver powder or silver-coated copper powder; the silver powder is composed of flaky silver powder and other forms of silver powder in a mass ratio of (60-90): (10-40), the other forms of silver powder is selected from at least one of spherical silver powder, rod-shaped silver powder, quasi-spherical silver powder or irregular silver powder, the particle size of the flaky silver powder is 2-20 μm, and the D50 of the other forms of silver powder is 1-50 μm; The plasticizer is white oil, mineral oil or silicone oil; the crosslinking agent is methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane or vinyltriethoxysilane; the accelerator is titanate, zirconate or organic selenium; the coupling agent is KH-550, KH-560 or KH-792; the dispersant is an organic silicon dispersant or a polyether dispersant, and the leveling agent is an organic silicon leveling agent or a polyether leveling agent.

9. The preparation method according to claim 1, characterized in that: In the step (c), solvent, color paste and other fillers are added to the base material; The amount of solvent added is 1% to 20% of the base material mass; the amount of color paste added is 0.001% to 0.1% of the base material mass; the amount of other fillers added is 1% to 15% of the base material mass; The solvent is an ester solvent, an ether solvent, a benzene solvent or an alkane solvent, and other fillers are selected from at least one of calcium carbonate, silicon powder, talcum powder, transparent powder, barium sulfate, aluminum oxide, aluminum nitride and graphene.

10. High-strength, bending-resistant conductive silver paste prepared by the preparation method according to any one of claims 1 to 9.

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