A kind of organosilicon modified polyurethane solution and its preparation method and application

Abstract

The present invention discloses a kind of organosilicon modified polyurethane solution and its preparation method and application, and belongs to the technical field of conductive materials. The organosilicon modified polyurethane solution comprises the following raw materials in parts by weight: 5-20 parts of diisocyanate, 20-50 parts of polyol, 1-20 parts of chain extender, 0.1-2 parts of end capping agent, 0.001-2 parts of catalyst and 10-1000 parts of solvent. A suitable amount of auxiliary agent is added to the organosilicon modified polyurethane solution to obtain conductive silver paste. The organosilicon modified polyurethane solution prepared by the method of the present invention can further improve the adhesion and aging resistance of the conductive silver paste, and the cost is low.

Description

Technical Field

[0001] The invention belongs to the technical field of conductive materials, and in particular relates to an organosilicon-modified polyurethane solution and a preparation method and application thereof. Background Art

[0002] Conductive silver paste is a very important conductive material in the electronics industry. After printing and curing, it can form a specific circuit according to the design. It plays a very important role in the fields of electronics, optoelectronics, semiconductors, medical treatment, and automobiles. In recent years, with the popularity of various new electronic consumer products and wearable devices, the market has higher and higher requirements for the flexibility and elasticity of conductive silver paste. Therefore, conductive silver paste with polyurethane (PU) as the resin matrix has been continuously developed.

[0003] At present, the PU source of domestic PU conductive silver paste is mainly thermoplastic polyurethane (TPU). After the TPU is fully dissolved with a solvent, other additives and silver powder are added, and the PU conductive silver paste is obtained after full dispersion, grinding and filtration. However, the material of TPU is classified as a thermoplastic elastomer and belongs to the plastic rubber industry. Therefore, TPU products mainly focus on indicators such as hardness, resilience, yellowing resistance, and melt index. As the basic resin of conductive silver paste, the industry is concerned about adhesion, bending resistance, moisture and heat resistance, solution viscosity, etc. It can be seen that although they are both PU materials, TPU and conductive silver paste have no correlation with the requirements of resin materials. Secondly, TPU products often keep their ingredients confidential, and people in the conductive silver paste industry cannot judge whether they meet the requirements through their product introductions, and can only test them one by one through the elimination method. Finally, due to the large molecular weight of TPU itself, it usually takes a long time to dissolve it with a solvent, which brings inconvenience to the production of conductive silver paste. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the present invention provides an organosilicon-modified polyurethane solution and a preparation method and application thereof.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical purposes: to provide a silicone-modified polyurethane solution (PU solution), comprising the following raw materials in parts by weight: 5-20 parts of diisocyanate, 20-50 parts of polyol, 1-20 parts of chain extender, 0.1-2 parts of end-capping agent, 0.001-2 parts of catalyst and 10-1000 parts of solvent.

[0007] Furthermore, the diisocyanate includes one or more of methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), methylene dicyclohexyl diisocyanate (HMDI), isophorone diisocyanate (IPDI) and diphenylmethane diisocyanate (MDI-50).

[0008] Furthermore, the molecular weight of the polyol is 500-4000, and includes one or more of polyester polyol, polyether polyol, polycarbonate polyol, polycaprolactone polyol and polytetramethylene glycol polyol.

[0009] Furthermore, the chain extender includes one or more of dihydric / trihydric alcohols with a molecular weight less than 300 and dihydric / trihydric amines with a molecular weight less than 500 (“ / ” here means “or”).

[0010] Furthermore, the end-capping agent has a molecular weight of less than 1000 and is one or more silane coupling agents containing at least one primary amine or secondary amine group.

[0011] Furthermore, the catalyst includes one or more of organic tin, organic antimony, organic bismuth, tertiary amine and imidazole.

[0012] Furthermore, the boiling point of the solvent is between 80-250° C., and includes one or more of esters, ketones, alcohols, ethers, amides, alkanes and aromatic hydrocarbons.

[0013] Technical purpose 2: Provide a method for preparing a silicone-modified polyurethane solution, comprising the following steps:

[0014] (1) Weigh the raw materials according to the mass ratio, add the polyol into a reactor filled with nitrogen, and remove water under vacuum at 50-120°C for 0.1-3h; cool the material after dehydration to below 40°C, then add diisocyanate, catalyst and solvent, stir well, and keep heating at 50-120°C for reaction for 0.1-3h; titrate the obtained sample according to GB / T 12009.4-2016 standard to determine its NCO value. If the theoretical value is not reached, continue the reaction until the NCO value reaches the theoretical value;

[0015] (2) Continue to add chain extender to the reaction product and heat the reaction at 50-120°C for 0.1-6h;

[0016] (3) Continue to add the end-capping agent to the reaction product and heat the reaction at 50-120°C for 0.1-3h;

[0017] (4) Cool to below 40°C and discharge.

[0018] Technical purpose three: Provide a conductive silver paste, comprising the following raw materials in parts by weight: 20-50 parts of silicone modified polyurethane solution, 0.1-1.0 parts of defoaming agent, 0.1-1.0 parts of dispersant, 0.1-1.0 parts of leveling agent, 0.1-1.0 parts of curing agent and 50-80 parts of silver powder.

[0019] Technical purpose four: Provide a method for preparing a conductive silver paste, comprising the following steps: weighing raw materials according to mass ratio, mixing and stirring the organosilicon-modified polyurethane solution, defoaming agent, dispersant, leveling agent and curing agent, adding silver powder and stirring again, grinding, and obtaining a conductive silver paste.

[0020] Compared with the prior art, the present invention has the following advantages and technical effects:

[0021] (1) PU resin can be directly synthesized according to demand, avoiding the blindness of R&D personnel in selecting TPU;

[0022] (2) The synthesis time is short, usually only about half of the TPU dissolution time, saving manpower and material resources;

[0023] (3) Directly adjust the performance of PU resin through the type and proportion of raw materials to avoid the defects of TPU itself;

[0024] (4) The synthesis cost is only 30-50% of the TPU price, reducing product costs;

[0025] (5) By controlling the type and proportion of the capping agent, the PU resin can cross-link in the air, further improving the adhesion and aging resistance of the silver paste. DETAILED DESCRIPTION

[0026] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0027] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0028] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0029] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0030] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0031] The present invention uses a direct synthesis method, uses the basic raw materials of PU and a solvent, and directly obtains the organosilicon-modified PU solution required for the conductive silver paste through a chemical reaction. In addition, the various properties of the product can be adjusted by adjusting the type, proportion and synthesis process of the PU raw materials, thereby meeting a series of requirements of the conductive silver paste for the resin. The organosilicon-modified PU obtained by the reaction reacts with each other under the action of moisture in the air with the help of the alkoxy group of the organosilicon, further increasing the molecular weight of the PU, while increasing the adhesion of the resin molecules to the silver powder and the silver paste substrate, thereby significantly improving the properties of the silver paste in terms of adhesion, weather resistance, and resistance to wet and hot aging.

[0032] The invention provides an organosilicon-modified polyurethane solution (PU solution), comprising the following raw materials in parts by weight: 5-20 parts of diisocyanate, 20-50 parts of polyol, 1-20 parts of chain extender, 0.1-2 parts of end-capping agent, 0.001-2 parts of catalyst and 10-1000 parts of solvent.

[0033] As a preferred embodiment of the present invention, the diisocyanate includes one or more of methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), methylene dicyclohexyl diisocyanate (HMDI), isophorone diisocyanate (IPDI) and diphenylmethane diisocyanate (MDI-50). More preferably, it is diphenylmethane diisocyanate or isophorone diisocyanate (IPDI).

[0034] As preferred in the present invention, the polyol includes one or more of polyester polyol, polyether polyol, polycarbonate polyol, polycaprolactone polyol, polytetrahydrofuran polyol with a molecular weight of 500-4000, more preferably polyester polyol and polytetrahydrofuran polyol with a molecular weight of 650-4000.

[0035] As preferred in the present invention, the chain extender includes one or more of dihydric or trihydric alcohols with a molecular weight of less than 300, and dihydric or trihydric amines with a molecular weight of less than 500. More preferably, it is hexanediol, diethylenetriamine or polyetheramine.

[0036] As a preferred embodiment of the present invention, the end-capping agent includes one or more silane coupling agents having a molecular weight of less than 1000 and containing at least one primary amine or secondary amine group, including but not limited to γ-aminopropyl triethoxysilane, γ-aminopropyl trimethoxysilane, γ-aminopropyl methyl diethoxysilane, γ-aminopropyl methyl dimethoxysilane, N-phenyl-γ-aminopropyl trimethoxysilane, N-(n-butyl)-γ-aminopropyl trimethoxysilane, N-β-(aminoethyl)-γ-aminopropyl methyl dimethoxysilane, N-β-(aminoethyl)-aminopropyl trimethoxysilane, N-β-(aminoethyl)-aminopropyl triethoxysilane, γ-diethylene triaminopropyl trimethoxysilane, bis-(γ-trimethoxysilyl propyl) amine, bis-(γ-triethoxysilyl propyl) amine, γ-piperazinyl propyl methyl dimethoxysilane or anilinomethyl triethoxysilane. Preferred is γ-aminopropyltrimethoxysilane or γ-aminopropyltriethoxysilane.

[0037] As a preferred embodiment of the present invention, the catalyst includes one or more of organotin, organoantimony, organobismuth, tertiary amine and imidazole, more preferably organotin, and most preferably dibutyltin dilaurate.

[0038] As a preferred embodiment of the present invention, the solvent includes one or more of esters, ketones, alcohols, ethers, amides, alkanes, and aromatic hydrocarbons with a boiling point between 80-250° C. More preferably, it is at least one of xylene, dibasic acid ester (DBE) or propylene glycol methyl ether acetate (PMA).

[0039] The present invention also provides a method for preparing a silicone-modified polyurethane solution, comprising the following steps:

[0040] Ingredients: Weigh 20-50 parts of polyol according to mass ratio;

[0041] Reaction: Add the polyol into a reactor filled with nitrogen, remove water under vacuum at 50-120°C for 0.1-3h, preferably react at 120°C for 2h; cool the dehydrated material to below 40°C, then add 5-20 parts of diisocyanate, 20-200 parts of solvent and 0.001-2 parts of catalyst, heat to 50-120°C under stirring, and heat to react for 0.1-3 hours; preferably react at 60°C for 2h;

[0042] Titration: Take a sample of the product obtained in step (2) and titrate its NCO value according to GB / T12009.4-2016. If the theoretical value is not reached, continue the reaction until the NCO value is ≤1.2;

[0043] (4) Chain extension: Add 1-20 parts of a chain extender to the product of step (3), maintain the temperature at 50-120°C, and heat the reaction for 0.1-6 hours;

[0044] (5) Capping: Add 0.1-2 parts of a capping agent to the product of step (4), maintain the temperature at 50-120° C., and heat the reaction for 0.1-3 hours;

[0045] (6) Discharging: After cooling the material to a suitable temperature below 40°C, discharge, seal and store.

[0046] The present invention also provides a conductive silver paste, comprising the following raw materials in parts by mass: 20-50 parts of organosilicon-modified polyurethane solution, 0.1-1.0 parts of defoaming agent, 0.1-1.0 parts of dispersant, 0.1-1.0 parts of leveling agent, 0.1-1.0 parts of curing agent and 50-80 parts of silver powder.

[0047] As a preferred embodiment of the present invention, the silver powder comprises nano silver powder and micron silver powder compounded in a mass ratio of (6-18) : (1-10).

[0048] As preferred embodiment of the present invention, the defoaming agent includes tributyl phosphate.

[0049] As preferred in the present invention, the dispersant includes fatty acid amide.

[0050] As preferred embodiment of the present invention, the leveling agent comprises polyacrylate.

[0051] As preferred embodiment of the present invention, the curing agent includes dicyandiamide.

[0052] The present invention also provides a method for preparing a conductive silver paste, comprising the following steps: weighing raw materials according to a mass ratio, mixing and evenly stirring an organosilicon-modified polyurethane solution, a defoamer, a dispersant, a leveling agent and a curing agent, adding silver powder and stirring again, and grinding with a three-roll grinder to obtain a conductive silver paste.

[0053] Unless otherwise specified, the "parts" described in the present invention are all based on mass parts.

[0054] The raw materials used in the following examples of the present invention are all commercially available.

[0055] In the following examples, the defoaming agent is tributyl phosphate; the curing agent is dicyandiamide; the leveling agent is polyacrylate; and the fatty acid amide.

[0056] The following examples serve as further illustrations of the technical solutions of the present invention.

[0057] Example 1

[0058] 1. A silicone-modified polyurethane solution (PU solution) composed of the following raw materials: diisocyanate (methylene diphenyl diisocyanate MDI-50) 1000g, polyol (polyester polyol with a molecular weight of 2000 + polytetramethylene glycol with a molecular weight of 650) 3300g, chain extender (polyether amine) 172.5g, end-capping agent (γ-aminopropyltrimethoxysilane) 100g, catalyst (T12 organotin catalyst) 0.5g, solvent (DBE2000g+PMA1000g) 3000g.

[0059] A preparation method of a silicone-modified polyurethane solution is as follows:

[0060] (1) Pass nitrogen into a cleaned reactor equipped with a stirring paddle and a thermometer to replace the air in it;

[0061] (2) 2000 g of 2000 molecular weight polyester polyol with a water content of ≤0.1% and 1300 g of 650 molecular weight polytetrahydrofuran polyol were placed in a reaction kettle, heated to 120°C, and vacuum-dried for 2 hours;

[0062] (3) Cool the material in (2) to below 40°C, add 2000g of dibasic acid ester (DBE), 1000g of propylene glycol methyl ether acetate (PMA), and 1000g of diphenylmethane diisocyanate (MDI-50), stir evenly, gradually heat to 60°C, and keep warm for 2h;

[0063] (4) One hour after the reaction starts, check the NCO value every 20 minutes. When NCO ≤ 1.2%, reduce the temperature;

[0064] (5) When the temperature of the material in (4) drops below 40°C, slowly add 172.5 g of polyetheramine (D230) with a molecular weight of 200 to extend the chain, and control the temperature of the material in the kettle not to exceed 80°C, and react for 2 hours;

[0065] (6) Slowly add 100 g of γ-aminopropyltrimethoxysilane (KH551) for end-capping, and control the temperature of the material in the kettle not to exceed 60 °C, and react for 2 h;

[0066] (7) The material in (6) is cooled to below 40° C. and discharged to obtain a silicone-modified polyurethane solution (PU solution).

[0067] 2. A conductive silver paste composed of the following raw materials: 40 g of silicone modified polyurethane solution (PU solution), 0.5 g of defoaming agent, 0.5 g of dispersant, 0.5 g of leveling agent, 0.8 g of curing agent, and 60 g of silver powder (nano silver powder (particle size 20 nm) and micron silver powder (particle size 1-3 μm) are compounded in a mass ratio of 15:10).

[0068] Preparation of a conductive silver paste:

[0069] The raw materials were weighed according to the mass ratio, the organosilicon-modified polyurethane solution, defoamer, dispersant, leveling agent and curing agent prepared above were mixed and stirred evenly, silver powder was added and stirred again, and the mixture was ground by a three-roll grinder for 45 minutes to obtain a conductive silver paste.

[0070] The above conductive silver paste was screen printed and dried at 150°C for 10 minutes. After testing, its pencil hardness was >2H, paper tape friction was >50 times, adhesion was 5B level, square resistance was <15mΩ / □ / mil, and elongation was >300%.

[0071] After double 85 (85℃, RH85%) aging for 500h, its pencil hardness is>2H, paper tape friction is>50 times, adhesion is 4B level, square resistance is<15mΩ / □ / mil, and elongation is>200%.

[0072] Comparative Example 1

[0073] The method for preparing the conductive silver paste is the same as that in Example 1, except that the PU solution is obtained by dissolving TPU. The specific method is as follows:

[0074] The above conductive silver paste was screen printed and dried at 150°C for 10 minutes. After testing, its pencil hardness was >2H, paper tape friction was >50 times, adhesion was 5B level, square resistance was 17mΩ / □ / mil, and elongation was 280%.

[0075] After double 85 (85℃, RH85%) aging for 500h, its pencil hardness is>2H, paper tape friction is>50 times, adhesion is 4B level, square resistance is 15mΩ / □ / mil, and elongation is 200%.

[0076] The above data show that the performance of the conductive silver paste prepared by the organosilicon-modified PU resin obtained by the synthesis method of Example 1 of the present invention is much higher than that of similar products obtained by TPU dissolution.

[0077] Example 2

[0078] 1. A silicone-modified polyurethane solution (PU solution), composed of the following raw materials: diisocyanate (isophorone diisocyanate) 666g, polyol (polyester polyol with a molecular weight of 4000 + polytetramethylene glycol with a molecular weight of 1000) 5000g, chain extender (hexanediol + diethylenetriamine) 115.75g, end-capping agent (γ-aminopropyltriethoxysilane) 58g, catalyst (dibutyltin dilaurate) 0.1g, solvent (xylene 1000g + DBE 3000g) 4000g.

[0079] A preparation method of a silicone-modified polyurethane solution is as follows:

[0080] (1) Pass nitrogen into a cleaned reactor equipped with a stirring paddle and a thermometer to replace the air in it;

[0081] (2) 4000 g of 4000 molecular weight polyester polyol with a water content of ≤0.1% and 1000 g of 1000 molecular weight polytetrahydrofuran polyol were placed in a reaction kettle, heated to 120°C, and vacuum-dried for 2 hours;

[0082] (3) Cool the material in (2) to below 40°C, add 3000g DBE, 1000g xylene, 666g isophorone diisocyanate (IPDI), 0.1g dibutyltin dilaurate (T12) organic tin catalyst, stir evenly, gradually heat to 70°C, and keep warm for 3h;

[0083] (4) One hour after the reaction starts, check the NCO value every 20 minutes. When NCO ≤ 1.2, reduce the temperature;

[0084] (5) When the temperature of the material in (4) drops below 40°C, slowly add a mixed solution of 90 g of hexanediol and 25.75 g of diethylenetriamine with a molecular weight of 200 to extend the chain, and control the temperature of the material in the kettle not to exceed 80°C. React for 2 h.

[0085] (6) Slowly add 58 g of γ-aminopropyltriethoxysilane (KH550) for end-capping, and control the temperature of the material in the kettle not to exceed 60 °C, and react for 2 h;

[0086] (7) The material in (6) is cooled to below 40° C. and discharged to obtain a silicone-modified polyurethane solution (PU solution).

[0087] 2. A conductive silver paste composed of the following raw materials: 40 g of silicone modified polyurethane solution (PU solution), 0.5 g of defoaming agent, 0.5 g of dispersant, 0.5 g of leveling agent, 0.8 g of curing agent, and 60 g of silver powder (nano silver powder (particle size 20 nm) and micron silver powder (particle size 1-3 μm) are compounded in a mass ratio of 15:10).

[0088] Preparation of a conductive silver paste:

[0089] The raw materials were weighed according to the mass ratio, the organosilicon-modified polyurethane solution, defoamer, dispersant, leveling agent and curing agent prepared above were mixed and stirred evenly, silver powder was added and stirred again, and the mixture was ground by a three-roll grinder for 45 minutes to obtain a conductive silver paste.

[0090] The above conductive silver paste was screen printed and dried at 150°C for 10 minutes. After testing, its pencil hardness was >2H, paper tape friction was >50 times, adhesion was 5B level, square resistance was 11mΩ / □ / mil, and elongation was 315%.

[0091] After double 85 (85℃, RH85%) aging for 500h, its pencil hardness is>2H, paper tape friction is>50 times, adhesion is 4B level, square resistance is 14mΩ / □ / mil, and elongation is 254%.

[0092] Comparative Example 2

[0093] The method for preparing the conductive silver paste is the same as that in Example 2, except that the PU solution is obtained by dissolving TPU. The specific method is as follows:

[0094] The above conductive silver paste was screen printed and dried at 150°C for 10 minutes. After testing, its pencil hardness was >2H, paper tape friction was >50 times, adhesion was 5B level, square resistance was 18mΩ / □ / mil, and elongation was >295%.

[0095] After double 85 (85℃, RH85%) aging for 500h, its pencil hardness is>2H, paper tape friction is>50 times, adhesion is 4B level, square resistance is 15mΩ / □ / mil, and elongation is 195%.

[0096] The above data show that the performance of the conductive silver paste prepared by the organosilicon-modified PU resin obtained by the synthesis method of Example 1 of the present invention is much higher than that of similar products obtained by TPU dissolution.

[0097] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A conductive silver paste, characterized in that: The method comprises the following raw materials in parts by weight: 20-50 parts of organosilicon-modified polyurethane solution, 0.1-1.0 parts of defoaming agent, 0.1-1.0 parts of dispersant, 0.1-1.0 parts of leveling agent, 0.1-1.0 parts of curing agent and 50-80 parts of silver powder; The organosilicon-modified polyurethane solution comprises the following raw materials in parts by weight: 5-20 parts of diisocyanate, 20-50 parts of polyol, 1-20 parts of chain extender, 0.1-2 parts of end-capping agent, 0.001-2 parts of catalyst and 10-1000 parts of solvent; The end-capping agent has a molecular weight of less than 1000 and contains one or more silane coupling agents of at least one primary or secondary amine group; The chain extender includes one or more of dihydric / trihydric alcohols with a molecular weight less than 300 and dihydric / trihydric amines with a molecular weight less than 500; The catalyst includes one or more of organic tin, organic antimony, organic bismuth and tertiary amine; The method for preparing the organosilicon-modified polyurethane solution comprises the following steps: Weigh the raw materials according to the mass ratio, add the polyol into a reactor filled with nitrogen, and remove water in a vacuum at 50-120°C for 0.1-3h; Cool the dehydrated material to below 40°C, then add diisocyanate, catalyst and solvent, stir well, and heat at 50-120°C for 0.1-3h; Continue to add chain extender to the reaction product, keep heating at 50-120°C for 0.1-6h; Continue to add the end-capping agent to the reaction product, and heat the reaction at 50-120°C for 0.1-3h; Cool to below 40°C and discharge.

2. The conductive silver paste according to claim 1, characterized in that: The diisocyanate includes one or more of methylene diphenyl diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, methylene dicyclohexyl diisocyanate and isophorone diisocyanate.

3. The conductive silver paste according to claim 1, characterized in that: The molecular weight of the polyol is 500-4000, and includes one or both of polyester polyol and polyether polyol.

4. The conductive silver paste according to claim 1, characterized in that: The boiling point of the solvent is between 80-250° C. and includes one or more of esters, ketones, alcohols, ethers, amides, alkanes and aromatic hydrocarbons.

5. A method for preparing a conductive silver paste as claimed in any one of claims 1 to 4, characterized in that: The method comprises the following steps: weighing raw materials according to mass ratio, mixing and evenly stirring an organosilicon-modified polyurethane solution, a defoamer, a dispersant, a leveling agent and a curing agent, adding silver powder, stirring again, and grinding to obtain a conductive silver paste.