Conductive slurry and preparation method of antioxidant copper powder in conductive slurry

Abstract

The invention discloses conductive paste which comprises the following raw materials in percentage by mass: 60-90% of antioxidant copper powder, 1-30% of thermosetting resin, 0.1-5% of a curing agent, 0.5-5% of an additive and 0.1-10% of a diluent, the antioxidant copper powder is one or a combination of more of micro-nano sheet-shaped or sphere-like copper powder organically coated by a hydrothermal method, and the average particle size is 0.1-5 [mu] m. The copper powder is coated with the organic matter through the hydrothermal method, so that the surface of the copper powder and the organic matter can be well combined to form a compact organic matter film layer, and meanwhile, the organic matter can evenly form a protection layer on the surface of the copper powder and a surface wrinkle area through a high-temperature and high-pressure liquid phase environment. The selected organic matters contain carboxylic acid or hydroxyl groups, and the organic matters and the surface of the copper powder are not only physically combined but also chemically bonded, so that the formed protective film layer can effectively prevent the action of oxygen and the copper powder, a relatively good anti-oxidation effect is realized, meanwhile, the protective film layer in the slurry is not easily damaged by components in the slurry, and the service life of the slurry is prolonged. And the excellent oxidation resistance is still kept after the slurry is cured.

Description

Technical Field

[0001] The invention relates to the field of anti-oxidation copper powder conductive paste, and in particular to a conductive paste and a method for preparing the anti-oxidation copper powder in the conductive paste. Background Art

[0002] Conductive paste is one of the most basic key materials in the modern electronics industry and is the core functional material that makes up electronic devices. Conductive paste is widely used in various electronic components, including chip resistors, chip capacitors, chip inductors, thick film integrated circuits, semiconductor packaging, etc. It is widely used in mobile communications, the Internet of Things, aerospace, solar photovoltaics, automotive electrical appliances, LED lighting, flexible electronics and other fields.

[0003] Conductive paste is usually composed of a conductive phase, a bonding phase and an organic carrier, which are fully mixed and dispersed to form a uniform paste. A specific application process (such as screen printing, spraying or 3D printing) is used to form a specific circuit, and the conductive functional characteristics are achieved through high-temperature sintering or low-temperature curing. The conductive phase is usually a micro-nano powder of gold, silver, palladium, platinum, copper, aluminum, nickel, tungsten, molybdenum, graphite, etc. The bonding phase is divided into a glass bonding phase (high-temperature sintering type) and a resin bonding phase (low-temperature curing type) due to different metallization processes. Low-temperature curing conductive paste is also called resin conductive paste, which is usually used in scenarios where the substrate cannot tolerate high temperature and conductive bonding. Low-temperature curing antioxidant conductive paste is usually a paste composed of metal powder, thermoplastic or thermosetting resin, active or inactive organic solvent, surfactant, thixotropic agent, etc., which is formed by screen printing technology to form a conductive film layer and cured at 150-250°C.

[0004] With the rapid development of flexible electronic technology, low-temperature curing silver electronic paste has been widely used and developed. However, the high price of silver has led to high costs of components. Copper and silver have similar resistivities, and the price is about one percent of silver. However, copper is more easily oxidized in the air than silver to form copper oxide and cuprous oxide, resulting in a significant decrease in conductivity. In electronic pastes, copper micro-nano powders are usually used as conductive phases. Copper powders with smaller particle sizes and larger specific surface areas are more susceptible to oxidation. Therefore, how to better solve the oxidation resistance of copper powder is one of the key technologies of electronic pastes. The current more mature technology is to coat silver on the surface of copper, which can not only ensure good conductivity but also delay the oxidation of copper powder, but its cost is still high. Organic polymer-coated copper powder can also delay the oxidation of copper to a certain extent, but the organic matter in the electronic paste often dissolves, causing the copper powder to be exposed and then oxidized. Therefore, the antioxidant treatment of copper powder and the electronic paste formulation technology have an important influence on the conductivity and antioxidant properties of copper electronic paste. Summary of the invention

[0005] The object of the present invention is to provide a conductive paste.

[0006] The invention also provides a method for preparing oxidation-resistant copper powder in a conductive paste.

[0007] The innovation of the present invention is that the antioxidant copper powder in the present invention has excellent conductive properties and antioxidant properties when used in conductive paste. The conductive paste in this patent can be better suitable for flexible circuits, RFID devices, MLCC soft terminals and HJT photovoltaic cells, etc.

[0008] To achieve the above-mentioned invention object, the technical solution of the present invention is: a conductive paste, characterized in that it comprises the following raw materials in percentage by mass: 60-90% of antioxidant copper powder, 1-30% of thermosetting resin, 0.1-5% of curing agent, 0.5-5% of additive, and 0.1-10% of diluent; The antioxidant copper powder is one or more combinations of micro-nano flake or quasi-spherical copper powder organically coated by hydrothermal method, and has an average particle size of 0.1-5 μm.

[0009] Furthermore, the thermosetting resin is one or a mixture of a blocked polyurethane prepolymer and an epoxy resin mixture.

[0010] Furthermore, the thermosetting resin is a mixture of a blocked polyurethane prepolymer and an epoxy resin mixture, and the mass ratio of the blocked polyurethane prepolymer to the epoxy resin mixture is 4:1 to 1:4.

[0011] Furthermore, the blocked polyurethane prepolymer is methyl ethyl ketone oxime (C 3 H 7 The invention discloses a novel epoxy resin composition comprising: a diisocyanate (MDI) chain-extended by a polyester diol and blocked by N-butylene glycol (NO), wherein the average molecular weight of the polyester diol is 300-3000, and the molar ratio of the polyester diol to the diisocyanate (MDI) is 3:1-1:3; and the epoxy resin mixture is a mixture of bisphenol A epoxy resin and bisphenol F epoxy resin, wherein the mixing mass ratio is 1:2-2:1, the viscosity is 1000-1500 Pa·s, and the epoxy equivalent is 160-170.

[0012] Furthermore, the curing agent is a mixture of a latent curing agent and a curing accelerator in a mass ratio of 100:1 to 100:10, wherein the latent curing agent is any one or more mixtures of 2-phenyl-4-methylimidazole (2P4MZ), 1-cyanoethyl-2-ethyl-4-methylimidazole trimellitate (2E4MZ-CNS), 2,4-diamino-6[2'-methylimidazole-(1')]ethyl-S-triazine triisocyanate adduct (2MA-OK), 2-phenyl-4,5-dihydroxymethylimidazole (2PHZ), 2-phenyl-4-methyl-5-hydroxymethylimidazole (2P4MHZ), 1-cyanoethyl-2-phenyl-4,5-di(cyanoethylmethyl)imidazole (2PHZ-CN), etc.; the curing accelerator is any one or more mixtures of dibutyltin dilaurate, stannous octoate, bismuth laurate, bismuth isooctanoate, ethylamine boron trifluoride, etc.

[0013] Furthermore, the additive is any one or more mixtures of polyamide wax, oleic acid, n-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and polyether-modified polysiloxane.

[0014] Furthermore, the diluent is any one or more mixtures of diethylene glycol butyl ether acetate, propylene glycol phenyl ether, alcohol ester dodecahydrate, polyethylene glycol diglycidyl ether, and hexahydrophthalic acid diglycidyl ester.

[0015] A method for preparing anti-oxidation copper powder in a conductive paste, characterized in that it comprises the following steps: (1) soaking one or more combinations of micro-nano flake or quasi-spherical copper powder in a 5-18 mol / L formic acid solution at a speed of 400-500 rpm for 30 min, and filtering the solution to obtain treated copper powder; (2) adding the organic coating agent solution to the treated copper powder, and using an emulsifier at 10000-20000 rpm to emulsify and coat for 3-5 minutes to obtain an emulsified coated copper powder liquid; (3) transferring the emulsified coated copper powder liquid to a high-pressure reactor, placing the high-pressure reactor in an oven at 150-200° C. for 4-24 hours, and performing hydrothermal coating to obtain a hydrothermal coated copper powder liquid; (4) The hydrothermal coated copper powder solution is filtered to remove the supernatant, and the washed copper powder is washed with deionized water until the resistivity of the washing solution is ≥18 MΩ to obtain a washed copper powder, and the washed copper powder is placed in a freeze dryer for freeze drying to obtain an antioxidant copper powder.

[0016] Furthermore, in the step (1), the mass ratio of the copper powder to the formic acid solution is 1:2, and in the step (2), the mass ratio of the organic coating agent to the copper powder is 0.1:1 to 20:1.

[0017] Furthermore, the organic coating agent is ascorbic acid (C6 H 8 O 6 ), malic acid (C 4 H 6 O 5 ), succinic acid (C 4 H 6 O 4 ), lactic acid (CH 3 CH(OH)COOH), tartaric acid (C 4 H 6 O 6 ), benzoic acid (C 6 H 5 COOH), adipic acid (C 6 H 10 O 4 ), glucose (C 6 H 12 O 6 ), salicylic acid (C 7 H 6 O 3 ), acrylic acid (CH 2 =CHCOOH), decanoic acid (C 10 H 20 O 2 ) , citric acid (C 6 H 8 O 7 ), lauric acid (C 12 H 24 O 2 ), Caprylic acid (C 8 H 16 O 2 ), nonanoic acid (C 9 H 18 O 2 ), oleic acid (C 18 H 34 O 2 ), linoleic acid (C 18 H 32 O 2 ), phytic acid (C 6 H 18 O 24 P 6 ), coumaric acid (C 9 H 8 O 3 ), p-hydroxybenzoic acid (C 7 H 6 O 3 ), vanillic acid (C 8 H 8 O 4 ), Salvia miltiorrhiza acid (C 26 H 22 O10 ) etc.

[0018] The beneficial effects of the present invention are: 1. The present invention adopts a hydrothermal method to coat copper powder with organic matter, so that the surface of the copper powder and the organic matter can be well combined to form a dense organic film layer. At the same time, the high temperature and high pressure liquid phase environment can make the organic matter evenly form a protective layer on the surface of the copper powder and the surface wrinkle area. The selected organic matter contains carboxylic acid or hydroxyl groups. The organic matter and the surface of the copper powder are not only physically combined but also chemically bonded. The protective film layer formed in this way can effectively prevent the action of oxygen and copper powder, and achieve a good antioxidant effect. At the same time, the protective film layer in the slurry is not easily destroyed by the components in the slurry, ensuring that the slurry still maintains excellent antioxidant properties after curing. The selected organic coating agent has a small molecular weight, and the organic film layer formed after dehydration and drying is thin, which ensures the conductive properties of the copper powder.

[0019] 2. The present invention uses thermosetting resin, curing agent and additive as organic phase, which can achieve good printing screen performance, and the cured film layer is dense and flat, has strong adhesion to the substrate and good flexibility. The epoxy resin mixture with a viscosity of 1000-1500mPa·s is beneficial to the slurry forming properties and adhesion properties of the slurry, the blocked polyurethane prepolymer can achieve good flexibility of the film layer, the curing accelerator can appropriately reduce the curing temperature of the blocked polyurethane prepolymer, and the curing agent has good latency, which is beneficial to the storage of the slurry.

[0020] 3. The antioxidant copper powder and conductive paste of the present invention are suitable for curing in the range of 120-200°C, and can meet the application of different substrates. After being fully mixed with the conductive powder, the organic matter can fully coat the conductive powder to achieve good rheological properties, improve printing accuracy, and have excellent filling effect. During the curing process, the blocked polyurethane prepolymer self-polymerizes, and the blocked polyurethane prepolymer-epoxy copolymerizes to form a polymer, achieving excellent flexibility of the film layer. The polymer is coated on the surface of the conductive powder to form a dense cured film layer, and at the same time, the polymer forms a good bond with the substrate. The cured organic matter is cross-linked to form a polymer-copper-polymer composite conductive chain, and the conductive performance of the slurry is guaranteed. The retention of the polymer further enhances the oxidation resistance of the slurry. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of resistivity and anti-oxidation performance evaluation.

[0022] Figure 2 It is the resistivity and oxidation resistance electrode screen printing diagram.

[0023] Figure 3 It is a printed screen image for adhesion strength. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings.

[0025] Example 1: A conductive paste comprising the following raw materials in percentage by mass: 60% of the antioxidant copper powder of Example 6, 30% of a thermosetting resin, 2% of a curing agent, 5% of an additive, and 3% of a diluent; The antioxidant copper powder is a micro-nano flaky copper powder organically coated by a hydrothermal method, with an average particle size of 0.1~5μm.

[0026] The thermosetting resin is a blocked polyurethane prepolymer.

[0027] The end-capped polyurethane prepolymer is methyl ethyl ketone oxime (C 3 H 7 NO)-blocked diisocyanate (MDI) chain-extended by polyester diol, the average molecular weight of the polyester diol is 300-3000, and the molar ratio of polyester diol to diisocyanate (MDI) is 3:1; The curing agent is a mixture of a latent curing agent and a curing accelerator in a mass ratio of 100:1, the latent curing agent is 2-phenyl-4-methylimidazole (2P4MZ), and the curing accelerator is dibutyltin dilaurate.

[0028] The additive is polyamide wax.

[0029] The diluent is diethylene glycol butyl ether acetate.

[0030] Example 2: A conductive paste comprising the following raw materials in percentage by mass: 90% of the antioxidant copper powder of Example 7, 1% of a thermosetting resin, 0.1% of a curing agent, 0.5% of an additive, and 8.4% of a diluent; The antioxidant copper powder is a micro-nano spherical copper powder organically coated by a hydrothermal method, with an average particle size of 0.1~5μm.

[0031] Thermosetting resins are epoxy resin mixtures.

[0032] The epoxy resin mixture is a mixture of bisphenol A epoxy resin and bisphenol F epoxy resin, with a mixing mass ratio of 1:2, a viscosity of 1000-1500 Pa·s, and an epoxy equivalent of 160-170.

[0033] The curing agent is a mixture of a latent curing agent and a curing accelerator in a mass ratio of 100:5, the latent curing agent is 1-cyanoethyl-2-ethyl-4-methylimidazolium trimellitate (2E4MZ-CNS), and the curing accelerator is stannous octoate.

[0034] The additive is oleic acid.

[0035] The diluent is propylene glycol phenyl ether.

[0036] Embodiment 3: A conductive paste comprises the following raw materials in percentage by mass: 68% of the antioxidant copper powder of Embodiment 6, 15% of a thermosetting resin, 5% of a curing agent, 2% of an additive, and 10% of a diluent; The antioxidant copper powder is a micro-nano flaky copper powder organically coated by a hydrothermal method, with an average particle size of 0.1~5μm.

[0037] The thermosetting resin is a mixture of a blocked polyurethane prepolymer and an epoxy resin mixture, and the mass ratio of the blocked polyurethane prepolymer to the epoxy resin mixture is 4:1.

[0038] The end-capped polyurethane prepolymer is methyl ethyl ketone oxime (C 3 H 7 The invention discloses a novel epoxy resin composition comprising: a diisocyanate (MDI) chain-extended by a polyester diol and blocked by NO, wherein the average molecular weight of the polyester diol is 300-3000, and the molar ratio of the polyester diol to the diisocyanate (MDI) is 1:2; and the epoxy resin mixture is a mixture of bisphenol A epoxy resin and bisphenol F epoxy resin, wherein the mixing mass ratio is 1:1, the viscosity is 1000-1500 Pa·s, and the epoxy equivalent is 160-170.

[0039] The curing agent is a mixture of a latent curing agent and a curing accelerator in a mass ratio of 100:10, the latent curing agent is 2,4-diamino-6[2'-methylimidazole-(1')]ethyl-S-triazine triisocyanate adduct (2MA-OK), and the curing accelerator is bismuth laurate.

[0040] The additive is n-β-(aminoethyl)-γ-aminopropyltrimethoxysilane.

[0041] The diluent is alcohol ester twelve.

[0042] Example 4: A conductive paste comprising the following raw materials in percentage by mass: 75% of the antioxidant copper powder of Example 8, 18.9% of a thermosetting resin, 3% of a curing agent, 3% of an additive, and 0.1% of a diluent; The antioxidant copper powder is a combination of micro-nano flake or spherical copper powder organically coated by a hydrothermal method, and the average particle size is 0.1-5 μm.

[0043] The thermosetting resin is a mixture of a blocked polyurethane prepolymer and an epoxy resin mixture, and the mass ratio of the blocked polyurethane prepolymer to the epoxy resin mixture is 1:2.

[0044] The end-capped polyurethane prepolymer is methyl ethyl ketone oxime (C 3 H 7The invention discloses a novel epoxy resin composition comprising: a diisocyanate (MDI) chain-extended by a polyester diol and blocked by NO, wherein the average molecular weight of the polyester diol is 300-3000, and the molar ratio of the polyester diol to the diisocyanate (MDI) is 1:3; and the epoxy resin mixture is a mixture of bisphenol A epoxy resin and bisphenol F epoxy resin, wherein the mixing mass ratio is 2:1, the viscosity is 1000-1500 Pa·s, and the epoxy equivalent is 160-170.

[0045] The curing agent is a mixture of a latent curing agent and a curing accelerator in a mass ratio of 100:8, the latent curing agent is 2-phenyl-4,5-dihydroxymethylimidazole (2PHZ); the curing accelerator is any one or more mixtures of bismuth isooctanoate, boron trifluoride ethylamine, etc.

[0046] The additive is polyether-modified polysiloxane.

[0047] The diluent is polyethylene glycol diglycidyl ether.

[0048] Embodiment 5: A conductive paste comprises the following raw materials in percentage by mass: 65% of the antioxidant copper powder of Embodiment 8, 23% of a thermosetting resin, 4% of a curing agent, 4% of an additive, and 4% of a diluent; The antioxidant copper powder is a combination of micro-nano flake or spherical copper powder organically coated by a hydrothermal method, and the average particle size is 0.1-5 μm.

[0049] The thermosetting resin is a mixture of a blocked polyurethane prepolymer and an epoxy resin mixture.

[0050] The thermosetting resin is a mixture of a blocked polyurethane prepolymer and an epoxy resin mixture, and the mass ratio of the blocked polyurethane prepolymer to the epoxy resin mixture is 1:4.

[0051] The end-capped polyurethane prepolymer is methyl ethyl ketone oxime (C 3 H 7 The invention discloses a novel epoxy resin composition comprising: a diisocyanate (MDI) chain-extended by a polyester diol and blocked by N-butylene glycol (NO), wherein the average molecular weight of the polyester diol is 300-3000, and the molar ratio of the polyester diol to the diisocyanate (MDI) is 1:1; and the epoxy resin mixture is a mixture of bisphenol A epoxy resin and bisphenol F epoxy resin, wherein the mixing mass ratio is 3:2-2:1, the viscosity is 1000-1500 Pa·s, and the epoxy equivalent is 160-170.

[0052] The curing agent is a mixture of a latent curing agent and a curing accelerator in a mass ratio of 100:3, wherein the latent curing agent is any one or more mixtures of 2-phenyl-4-methylimidazole (2P4MZ), 1-cyanoethyl-2-ethyl-4-methylimidazole trimellitate (2E4MZ-CNS), 2,4-diamino-6[2'-methylimidazole-(1')]ethyl-S-triazine triisocyanate adduct (2MA-OK), 2-phenyl-4,5-dihydroxymethylimidazole (2PHZ), 2-phenyl-4-methyl-5-hydroxymethylimidazole (2P4MHZ), 1-cyanoethyl-2-phenyl-4,5-di(cyanoethylmethyl)imidazole (2PHZ-CN), etc.; the curing accelerator is any one or more mixtures of dibutyltin dilaurate, stannous octoate, bismuth laurate, bismuth isooctanoate, ethylamine boron trifluoride, etc.

[0053] The additive is any one or more mixtures of polyamide wax, oleic acid, n-β-(aminoethyl)-γ-aminopropyltrimethoxysilane and polyether-modified polysiloxane.

[0054] The diluent is any one or more mixtures of diethylene glycol butyl ether acetate, propylene glycol phenyl ether, alcohol ester dodecahydrate, polyethylene glycol diglycidyl ether, and hexahydrophthalic acid diglycidyl ester.

[0055] Embodiment 6: A method for preparing an oxidation-resistant copper powder in a conductive paste, comprising the following steps: (1) The micro-nano flaky copper powder was immersed in a 5 mol / L formic acid solution at 400 rpm for 30 min, and the solution was filtered to obtain the treated copper powder, wherein the mass ratio of the copper powder to the formic acid solution was 1:2; (2) Adding the organic coating agent solution to the treated copper powder, using an emulsifier at 10000 rpm for 3 min to obtain an emulsified coated copper powder solution, the mass ratio of the organic coating agent to the copper powder is 0.1:1, and the organic coating agent is ascorbic acid (C 6 H 8 O 6 ); (3) transferring the emulsified coated copper powder liquid to a high-pressure reactor, placing the high-pressure reactor in an oven at 150° C. for 4 hours, and performing hydrothermal coating to obtain a hydrothermal coated copper powder liquid; (4) The hydrothermal coated copper powder solution is filtered to remove the supernatant, and the washed copper powder is washed with deionized water until the resistivity of the washing solution is ≥18 MΩ to obtain a washed copper powder, and the washed copper powder is placed in a freeze dryer for freeze drying to obtain an antioxidant copper powder.

[0056] Embodiment 7: A method for preparing an oxidation-resistant copper powder in a conductive paste, comprising the following steps: (1) The micro-nano spherical copper powder is immersed in a 10 mol / L formic acid solution at 450 rpm for 30 min, and the solution is filtered to obtain the treated copper powder; (2) Add the organic coating agent solution to the treated copper powder, and use an emulsifier at 15000 rpm for 4 minutes to obtain an emulsified coated copper powder solution. The mass ratio of the organic coating agent to the copper powder is 10:1. The organic coating agent is malic acid (C 4 H 6 O 5 ); (3) transferring the emulsified coated copper powder liquid to a high-pressure reactor, placing the high-pressure reactor in an oven at 180° C. for 10 hours, and performing hydrothermal coating to obtain a hydrothermal coated copper powder liquid; (4) The hydrothermal coated copper powder solution is filtered to remove the supernatant, and the washed copper powder is washed with deionized water until the resistivity of the washing solution is ≥18 MΩ to obtain a washed copper powder, and the washed copper powder is placed in a freeze dryer for freeze drying to obtain an antioxidant copper powder.

[0057] Embodiment 8: A method for preparing an antioxidant copper powder in a conductive paste, comprising the following steps: (1) The copper powder of micro-nano flake or spherical combination is immersed in 18 mol / L formic acid solution at a speed of 500 rpm for 30 min, and the solution is filtered to obtain the treated copper powder; (2) Add the organic coating agent solution to the treated copper powder, and use an emulsifier at 20000 rpm for 5 min to obtain an emulsified coated copper powder solution. The mass ratio of the organic coating agent to the copper powder is 20:1. The organic coating agent is succinic acid (C 4 H 6 O 4 ); (3) transferring the emulsified coated copper powder liquid to a high-pressure reactor, placing the high-pressure reactor in an oven at 200° C. for 24 hours, and performing hydrothermal coating to obtain a hydrothermal coated copper powder liquid; (4) The hydrothermal coated copper powder solution is filtered to remove the supernatant, and the washed copper powder is washed with deionized water until the resistivity of the washing solution is ≥18 MΩ to obtain a washed copper powder, and the washed copper powder is placed in a freeze dryer for freeze drying to obtain an antioxidant copper powder.

[0058] Example 9: Referring to Example 8, the organic coating agent is ascorbic acid (C 6 H 8 O 6 ), malic acid (C 4 H 6 O 5 ), succinic acid (C 4 H 6 O 4 ), lactic acid (CH 3CH(OH)COOH), tartaric acid (C 4 H 6 O 6 ), benzoic acid (C 6 H 5 COOH), adipic acid (C 6 H 10 O 4 ), glucose (C 6 H 12 O 6 ), salicylic acid (C 7 H 6 O 3 ), acrylic acid (CH 2 =CHCOOH), decanoic acid (C 10 H 20 O 2 ) , citric acid (C 6 H 8 O 7 ), lauric acid (C 12 H 24 O 2 ), Caprylic acid (C 8 H 16 O 2 ), nonanoic acid (C 9 H 18 O 2 ), oleic acid (C 18 H 34 O 2 ), linoleic acid (C 18 H 32 O 2 ), phytic acid (C 6 H 18 O 24 P 6 ), coumaric acid (C 9 H 8 O 3 ), p-hydroxybenzoic acid (C 7 H 6 O 3 ), vanillic acid (C 8 H 8 O 4 ), Salvia miltiorrhiza acid (C 26 H 22 O 10 ) etc.

[0059] Comparative Example 1: Referring to Example 1, the anti-oxidation copper powder was replaced with micro-nano flaky copper powder without surface coating.

[0060] Comparative Example 2: Referring to Example 2, the anti-oxidation copper powder was replaced with micro-nano spherical copper powder without surface coating.

[0061] Comparative Example 3: Referring to Example 1, 50% of the antioxidant copper powder was replaced with micro-nano flaky copper powder without surface coating.

[0062] Comparative Example 4: Referring to Example 2, 50% of the antioxidant copper powder was replaced with micro-nano spherical copper powder without surface coating.

[0063] The resistivity and TGA weight gain of the antioxidant copper powders of Examples 6 to 8, the micro-nano flaky copper powders without surface coating, and the micro-nano quasi-spherical copper powders without surface coating were tested according to the following method. The results are shown in Table 1.

[0064] Resistivity: Weigh 1±0.1g of copper powder and place it in a cylindrical mold with a diameter of 6mm and a height of 10mm under a pressure of 5Mpa. Use a four-wire needle resistance meter to measure its resistance and calculate the resistivity according to formula (1).

[0065] Formula (1) In the formula, is the resistivity, in Ω·cm; R is the resistance, in Ω; h is the sample height, in cm; d is the bottom diameter of the sample, in cm, and π is the circumference of a circle. Usually, the smaller the resistivity of the sample, the better.

[0066] (2) TGA weight gain: Weigh 0.1±0.01g of copper powder and place it in a 0.4ml alumina crucible. Heat the temperature from room temperature to 200℃ at a rate of 5℃ / min in an air atmosphere, then keep the temperature for 60min, and calculate the weight gain ratio of the sample. Generally, the lower the sample weight gain ratio, the better the antioxidant property of the sample.

[0067] Table 1 Performance test results of hydrothermal coated copper powder in Examples 1 to 12 　 <![CDATA[Resistivity (×10 -4 Ω·cm )]]> TGA weight gain (%) Example 6 65.33 2.32 Example 7 1.63 0.38 Example 8 21.39 0.76 Comparative Example 1 1783.54 12.2 Comparative Example 2 1552.81 16.4 The conductive pastes prepared in the above Examples 1 to 4 and Comparative Examples 1 to 4 were tested for viscosity, resistivity, anti-oxidation resistivity, and adhesion strength according to the following methods. The results are shown in Table 2.

[0068] (1) Viscosity: Stir the sample evenly with a mixing knife, take a small amount of the sample and put it into a small sample adapter, place it in a 25℃ water bath for 10 minutes, use a Brookfield HBT rotary viscometer 14# rotor, rotate at 10rpm for 1 minute, and read the viscosity data. Viscosity affects the printing characteristics of the conductive paste. Too low viscosity can easily cause edge diffusion and leakage, while too high viscosity can cause edge burrs and printing stickiness. The viscosity of the conductive paste is usually required to be 30~100Pa·s to meet the requirements of screen printing.

[0069] (2) Resistivity: Stir the sample evenly with a slurry knife, take a small amount of the sample, and Figure 2 The wire mesh shown in (a) is used to make Ag electrodes on an alumina substrate ( Figure 1 As shown in (b)), using Figure 2 (b) Screen printed copper conductive paste ( Figure 1 After printing, allow to level naturally for 3 to 5 minutes, pre-cure at 120°C for 10 minutes, and cure at 200°C for 30 minutes to ensure that the thickness of the cured film is 10 to 25 μm. Use a resistance tester to overlap Figure 1 The average resistivity is calculated by formula (2) on the silver electrode in (b): (2) In the formula, is the average resistivity, in units of Ω·cm ; Is a single resistor, unit is Ω ; w is the electrode width, in units of cm; l is the electrode length, in units of cm, h i is the electrode thickness, in units of cm; i = 1, 2…n; n For the measurement quantity, take n = 4. It is usually expected that the resistivity of the film layer is as small as possible.

[0070] (3) Stir the sample evenly with a mixing knife, take a small amount of the sample, and Figure 2 The wire mesh shown in (a) is used to make Ag electrodes on an alumina substrate ( Figure 1 As shown in (b)), using Figure 2 (b) Screen printed copper conductive paste ( Figure 1 After printing, allow to level naturally for 3 to 5 minutes, pre-cure at 120°C for 10 minutes, and cure at 200°C for 30 minutes to ensure that the thickness of the cured film is 10 to 25 μm. Use a resistance tester to overlap Figure 1 The resistance value of the silver electrode in (b) is tested, and the average resistivity is calculated by formula (2): The electrode sheet was placed in a 60°C blast oven and taken out after 1000 hours. The resistance value was tested and the resistivity after vulcanization was calculated according to formula (2): Formula (3) calculates the change rate of sulfurized resistance.

[0071] (3) In the formula, is the rate of change of antioxidant resistance; is the initial resistivity of the electrode, in units of Ω·cm ; is the resistivity after oxidation, in units of Ω·cm It is usually desired that the resistivity change of the film layer be as small as possible.

[0072] (4) Adhesion: Use a mixing knife to stir the sample evenly, take a small amount of the sample, and use Figure 3 The screen pattern shown is a 2.5mm×2.5mm pattern printed on an alumina substrate; after printing, it is naturally leveled for 3 to 5 minutes, and a 2mm×2mm alumina square is glued to the electrode, pre-cured at 120℃ for 10 minutes, and cured at 200℃ for 30 minutes, ensuring that the thickness of the cured film layer is 10 to 15μm. The adhesion strength of the slurry is tested using a thrust tester. Adhesion strength is a characteristic of the product in combination with the substrate, and the greater the adhesion strength, the better.

[0073] Table 2 Performance of conductive pastes of Examples 1 to 4 and Comparative Examples 1 to 4 Viscosity (Pa·s) <![CDATA[Resistivity (×10 -4 Ω·cm )]]> Oxidation resistance change rate (%) <![CDATA[Adhesion strength (N / mm 2 )]]> Example 1 58.3 12.74 10.95 11.3 Example 2 82.9 0.91 1.47 10.5 Example 3 98.1 1.15 1.53 8.6 Example 4 106.4 1.02 3.12 7.4 Comparative Example 1 79.2 785.51 19.29 9.1 Comparative Example 2 79.2 1088.43 13.72 6.3 Comparative Example 3 77.6 348.19 16.86 8.7 Comparative Example 4 75.4 213.62 11.37 8.2 As shown in Tables 1 and 2, the electrode layer made of the antioxidant copper powder and the conductive paste thereof of the present invention has excellent resistivity, low oxidation resistance change rate, and good adhesion strength. The copper powder coated by the hydrothermal method in Examples 6 to 8 has good oxidation resistance compared to the micro-nano flaky copper powder without surface coating and the micro-nano spherical copper powder without surface coating. The conductive paste produced in Examples 1 to 4 has a suitable viscosity compared to Comparative Examples 1 to 4 to meet the requirements of screen printing. The paste exhibits good resistivity, oxidation resistance and adhesion strength, and can meet the requirements of electronic circuits for different applications.

[0074] The described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A conductive paste, characterized in that: The raw materials include the following mass percentages: 60-90% of anti-oxidation copper powder, 1-30% of thermosetting resin, 0.1-5% of curing agent, 0.5-5% of additive, and 0.1-10% of diluent; The antioxidant copper powder is one or more combinations of micro-nano flake or quasi-spherical copper powder organically coated by hydrothermal method, and has an average particle size of 0.1-5 μm.

2. The conductive paste according to claim 1, characterized in that: The thermosetting resin is one of a blocked polyurethane prepolymer and an epoxy resin mixture or a mixture of the two.

3. The conductive paste according to claim 2, characterized in that: The thermosetting resin is a mixture of a blocked polyurethane prepolymer and an epoxy resin mixture, and the mass ratio of the blocked polyurethane prepolymer to the epoxy resin mixture is 4:1 to 1:

4.

4. The conductive paste according to claim 3, characterized in that: The blocked polyurethane prepolymer is a polyester diol-chain-extended diisocyanate (MDI) blocked by methyl ethyl ketone oxime (C3H7NO) dissolved in a high boiling point solvent, wherein the polyester diol has an average molecular weight of 300-3000, and a molar ratio of the polyester diol to the diisocyanate (MDI) of 3:1-1:3; the epoxy resin mixture is a mixture of bisphenol A epoxy resin and bisphenol F epoxy resin, wherein the mixing mass ratio is 1:2-2:1, the viscosity is 1000-1500 Pa·s, and the epoxy equivalent is 160-170.

5. The conductive paste according to claim 1, characterized in that: The curing agent is a mixture of a latent curing agent and a curing accelerator in a mass ratio of 100:1 to 100:10, wherein the latent curing agent is any one or more mixtures of 2-phenyl-4-methylimidazole (2P4MZ), 1-cyanoethyl-2-ethyl-4-methylimidazole trimellitate (2E4MZ-CNS), 2,4-diamino-6[2'-methylimidazole-(1')]ethyl-S-triazine isocyanuric acid adduct (2MA-OK), 2-phenyl-4,5-dihydroxymethylimidazole (2PHZ), 2-phenyl-4-methyl-5-hydroxymethylimidazole (2P4MHZ), 1-cyanoethyl-2-phenyl-4,5-di(cyanoethylmethyl)imidazole (2PHZ-CN), etc.; the curing accelerator is any one or more mixtures of dibutyltin dilaurate, stannous octoate, bismuth laurate, bismuth isooctanoate, ethylamine boron trifluoride, etc.

6. The conductive paste according to claim 1, characterized in that: The additive is any one or more mixtures of polyamide wax, oleic acid, n-β-(aminoethyl)-γ-aminopropyltrimethoxysilane and polyether-modified polysiloxane.

7. The conductive paste according to claim 1, characterized in that: The diluent is any one or more mixtures of diethylene glycol butyl ether acetate, propylene glycol phenyl ether, alcohol ester dodecahydrate, polyethylene glycol diglycidyl ether, and hexahydrophthalic acid diglycidyl ester.

8. A method for preparing an antioxidant copper powder in a conductive paste as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: (1) soaking one or more combinations of micro-nano flake or quasi-spherical copper powder in a 5-18 mol / L formic acid solution at a speed of 400-500 rpm for 30 min, and filtering the solution to obtain treated copper powder; (2) adding the organic coating agent solution to the treated copper powder, and using an emulsifier at 10000-20000 rpm to emulsify and coat for 3-5 minutes to obtain an emulsified coated copper powder liquid; (3) transferring the emulsified coated copper powder liquid to a high-pressure reactor, placing the high-pressure reactor in an oven at 150-200° C. for 4-24 hours, and performing hydrothermal coating to obtain a hydrothermal coated copper powder liquid; (4) The hydrothermal coated copper powder solution is filtered to remove the supernatant, and the washed copper powder is washed with deionized water until the resistivity of the washing solution is ≥18 MΩ to obtain a washed copper powder, and the washed copper powder is placed in a freeze dryer for freeze drying to obtain an antioxidant copper powder.

9. The method for preparing the antioxidant copper powder in the conductive paste according to claim 8, characterized in that: In the step (1), the mass ratio of the copper powder to the formic acid solution is 1:2, and in the step (2), the mass ratio of the organic coating agent to the copper powder is 0.1:1 to 20:

1.

10. The method for preparing the antioxidant copper powder in the conductive paste according to claim 8, characterized in that: The organic coating agent is ascorbic acid (C6H8O6), malic acid (C4H6O5), succinic acid (C4H6O4), lactic acid (CH3CH(OH)COOH), tartaric acid (C4H6O6), benzoic acid (C6H5COOH), adipic acid (C6H 10 O4), glucose (C6H 12 O6), salicylic acid (C7H6O3), acrylic acid (CH2=CHCOOH), decanoic acid (C 10 H 20 O2), citric acid (C6H8O7), lauric acid (C 12 H 24 O2), octanoic acid (C8H 16 O2), nonanoic acid (C9H 18 O2), oleic acid (C 18 H 34 O2), linoleic acid (C 18 H 32 O2), phytic acid (C6H 18 O 24 P6), coumaric acid (C9H8O3), p-hydroxybenzoic acid (C7H6O3), vanillic acid (C8H8O4), salvia miltiorrhiza acid (C 26 H 22 O 10 ) etc.

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