Water-based copper composite conductive paste and preparation method thereof

Abstract

The application relates to the technical field of electronic paste, and discloses a water-based copper composite conductive paste and a preparation method thereof. The water-based copper composite conductive paste contains the following components in mass fraction: a composite conductive phase 55-70%, a bonding phase 1-10%, potassium-based montmorillonite 1-10%, carboxymethyl cellulose 0.2-2.5%, a siliconizing agent 0.5-6%, a mineralizing agent 0.1-1%, polydimethylsiloxane 0.5-6%, a surfactant 0.3-3% and water 15-30%. The siliconizing agent is an organic silicon monomer and / or an organic silicon compound; and the composite conductive phase contains copper powder and a conductive reinforcing phase. The conductive paste uses water as a solvent, is green, environment-friendly and low in cost, only produces water vapor after solidification and sintering, and is discharged into the air through a pipeline without generating other toxic and harmful gases, thus not causing harm to the environment and not having negative effects on human health. Meanwhile, through the joint action of the raw material components, the obtained conductive paste has good oxidation resistance, suspension stability, rheological property, high-temperature stability and conductive performance, can be solidified at a low temperature, and can be used at a high temperature.

Description

Technical Field

[0001] This invention relates to the field of electronic paste technology, specifically to a water-based copper composite conductive paste and its preparation method. Background Technology

[0002] Conductive paste (electronic paste) is a new type of electronic material with the characteristics of high efficiency, environmental protection, energy saving and low cost. It has been widely used in the fields of solar cells, aerospace, sensitive components, resistor networks, displays, and electrode materials for lithium-ion batteries.

[0003] Currently, the most researched conductive pastes include gold (Au) paste, silver (Ag) paste, and copper (Cu) paste. Among them, Au has good stability, but its high price hinders industrial production; Ag has good conductivity and is slightly cheaper than Au, but it is still relatively expensive. Furthermore, Ag undergoes Ag+ migration during use, leading to a decrease in product performance and limiting its application range; Cu, as a cheap metal, is widely available, its conductivity is only slightly lower than Ag, and its price is only about 1% of Ag, making it widely favored in recent years.

[0004] Conductive pastes generally consist of three parts: a conductive phase, a binder phase, and an organic carrier. The organic carrier is usually composed of organic solvents, thickeners, and additives. Its function is to mix and disperse metal powders, binders, and other solid powders into a paste-like slurry. It controls the rheology, viscosity, and printability of the electronic paste and has a significant impact on the conductivity, surface morphology, and adhesion of the cured film.

[0005] Organic carriers primarily use organic solvents. The organic solvent content typically accounts for 70%-95% of the total mass of the organic carrier. It can dissolve thickeners and other auxiliary solvents, and has low volatility at room temperature. Commonly used organic solvents include diethylene glycol ether acetate, tributyl phthalate, tributyl citrate, leucate, and terpineol. A commonly used thickener is ethyl cellulose, a thermoplastic polymer soluble in many organic solvents. It is a white powder at room temperature and exhibits a wide range of solubility and viscosity characteristics. Other additives include silane coupling agents and surfactants.

[0006] The main disadvantages of organic carriers include their high price and the fact that their volatilization into the environment causes pollution and harms the health of workers. Furthermore, the choice and proportion of organic carriers directly affect the performance of electronic paste products. When organic carriers are used in conductive pastes, certain defects limit their application range.

[0007] Meanwhile, the existing conductive pastes have high curing temperatures, typically around 600-800℃, resulting in high energy consumption and a tendency to deform conductive film substrates and silicon wafers, which is detrimental to improving the lifespan of conductive films. Summary of the Invention

[0008] The purpose of this invention is to overcome the problems of adverse effects of organic carriers on the performance of electronic pastes and environmental pollution caused by them in the preparation process of existing electronic pastes. This invention provides a water-based copper composite conductive paste and its preparation method. The conductive paste is green and environmentally friendly, low in cost, has good anti-oxidation properties, and can be cured at low temperatures and used at high temperatures.

[0009] To achieve the above objectives, the present invention provides a water-based copper composite conductive paste, wherein the water-based copper composite conductive paste comprises the following components in the indicated mass fractions: 55%–70% composite conductive phase, 1%–10% binder phase, 1%–10% potassium montmorillonite, 0.2%–2.5% carboxymethyl cellulose, 0.5%–6% silicide, 0.1%–1% mineralizer, 0.5%–6% polydimethylsiloxane, 0.3%–3% surfactant, and 15%–30% water;

[0010] The silicide is an organosilicon monomer and / or an organosilicon compound;

[0011] The mineralizing agent is selected from at least one of ZnO, CaO, MgO and Fe2O3;

[0012] The composite conductive phase contains copper powder and a conductive reinforcing phase, wherein the mass ratio of the conductive reinforcing phase to the copper powder is 0.5 to 5:100.

[0013] Preferably, the silicide is selected from at least one of trimethylchlorosilane, hexamethyldisilazane, tert-butyldimethylchlorosilane, triisopropyloxysilane, dimethyldiacetoxysilane, di-tert-butyldichlorosilane, trimethylhydroxyethylsilane, and methyldiphenylhydroxyethylsilane.

[0014] Preferably, the binder phase is B503 ceramic resin and / or B9102 silicon-zirconium composite inorganic resin.

[0015] Preferably, the surfactant is Tween-80.

[0016] Preferably, the particle size D of the copper powder is... 50 The size is 1–10 μm;

[0017] Preferably, the copper powder is composed of copper powder a, copper powder b, and copper powder c, wherein the particle size D of copper powder a is... 50 The particle size D of the copper powder b is 0.5–2 μm. 50 The particle size D of the copper powder c is 4–6 μm.50 It is 9–10 μm;

[0018] Preferably, the mass ratio of copper powder a, copper powder b, and copper powder c is 1:0.8-1.2:0.8-1.2.

[0019] Preferably, the conductive reinforcing phase is nanoscale graphene sheets and / or carbon nanotubes.

[0020] A second aspect of the present invention provides a method for preparing the water-based copper composite conductive paste as described above, the method comprising the following steps:

[0021] (1) Mix some water with potassium montmorillonite to obtain potassium montmorillonite gel, then seal and cure;

[0022] (2) The matured potassium-based montmorillonite gel is mixed with polydimethylsiloxane, carboxymethyl cellulose, binder, silicide, mineralizer, surfactant, residual water and copper composite conductive phase to obtain a mixture. The mixture is then kneaded and ground.

[0023] Preferably, in step (1), the maturation time is 20 to 30 hours.

[0024] Preferably, in step (2), the process of kneading and grinding the mixture includes: putting the mixture into a high-speed double planetary continuous kneader for 1 to 5 uniform kneadings, and then putting it into a colloid mill for 1 to 5 grindings.

[0025] The technical solution provided by this invention is a different technical route from organic carriers. In this invention, water is used as a solvent, potassium-based montmorillonite is used as a suspending agent, carboxymethyl cellulose is used as a water-based thickener, and additives (silicifying agent, mineralizing agent and polydimethylsiloxane, etc.) are added to prepare a water-based carrier. A composite conductive phase and a binder phase are added to obtain a water-based copper composite conductive slurry.

[0026] Compared with the prior art, the beneficial effects of the water-based copper composite conductive paste of the present invention include:

[0027] (1) The water-based copper composite conductive paste of the present invention uses water as a solvent, which is green, environmentally friendly and low in cost. After curing and sintering, it only produces water vapor and is discharged into the air through the pipeline. It does not produce other toxic and harmful gases, does not harm the environment, and has no negative impact on human health.

[0028] (2) In this invention, potassium-based montmorillonite, water, carboxymethyl cellulose and other additives are mixed as a water-based carrier instead of the commonly used organic carrier, thus avoiding the adverse effects of using organic carriers on the performance of electronic pastes. At the same time, through the combined action of each raw material component, the resulting water-based copper composite conductive paste has good anti-oxidation properties, suspension stability, rheological properties and high temperature stability.

[0029] (3) In this invention, potassium-based montmorillonite, carboxymethyl cellulose, other additives and water are mixed as a water-based carrier. The raw materials used are widely available, energy-saving, environmentally friendly and low-cost. The preparation process is relatively simple and easy to promote.

[0030] (4) The water-based copper composite conductive paste of the present invention has excellent conductivity through the combined effect of each raw material component;

[0031] (5) The water-based copper composite conductive paste of the present invention has a low curing temperature. It can be cured to form a conductive film layer by holding at 150-350℃ for 15-100 minutes. During the curing process, a protective film is generated by the reaction of the siliconizing agent, which can prevent the copper conductive film from oxidizing during use. The water-based copper composite conductive paste can be used at temperatures in the range of 500-900℃ and below, and has high stability. Therefore, the water-based copper composite conductive paste can achieve low-temperature curing and high-temperature use. Detailed Implementation

[0032] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0033] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0034] This invention provides a water-based copper composite conductive paste, which comprises the following components by mass fraction: 55%–70% composite conductive phase, 1%–10% binder phase, 1%–10% potassium montmorillonite, 0.2%–2.5% carboxymethyl cellulose, 0.5%–6% silicide, 0.1%–1% mineralizer, 0.5%–6% polydimethylsiloxane, 0.3%–3% surfactant, and 15%–30% water;

[0035] The silicide is an organosilicon monomer and / or an organosilicon compound;

[0036] The mineralizing agent is selected from at least one of ZnO, CaO, MgO and Fe2O3;

[0037] The composite conductive phase contains copper powder and a conductive reinforcing phase, wherein the mass ratio of the conductive reinforcing phase to the copper powder is 0.5 to 5:100.

[0038] In this invention, polydimethylsiloxane is used as an antioxidant; simultaneously, the reaction products of the silicide can form a dense silicide film (also known as a glass film) on the surface of the conductive film layer of the slurry, thereby protecting the conductive film and preventing oxidation. Therefore, in this invention, the combined use of the silicide and the antioxidant polydimethylsiloxane can improve the antioxidant properties of the conductive film.

[0039] In a preferred embodiment, the silicide is selected from at least one of trimethylchlorosilane, hexamethyldisilazane, tert-butyldimethylchlorosilane, triisopropyloxysilane, dimethyldiacetoxysilane, ditert-butyldichlorosilane, trimethylhydroxyethylsilane, and methyldiphenylhydroxyethylsilane.

[0040] In this invention, potassium-based montmorillonite is used as a suspending agent to uniformly suspend the conductive components in deionized water, thereby improving the printing performance of the conductive paste. The thickener, carboxymethyl cellulose, assists the suspending agent in further improving the printability of the paste. This invention does not impose any particular restrictions on the specific source of the potassium-based montmorillonite; it can be prepared in-house or directly from commercially available products.

[0041] In this invention, by adding a small amount of mineralizer, sintering can be promoted and certain properties of the product can be improved, the sintering temperature can be reduced, and a certain reducing effect can be achieved, which can reduce the copper oxide produced by the occasional oxidation of a small amount of copper powder back into copper powder.

[0042] In a preferred embodiment, the water-based copper composite conductive paste comprises the following components by mass fraction: 57%–65% composite conductive phase, 4%–8% binder phase, 3%–7% potassium montmorillonite, 1%–2.5% carboxymethyl cellulose, 2%–5% silicide, 0.1%–1% mineralizer, 1%–4% polydimethylsiloxane, 0.5%–2% surfactant, and 15%–30% water.

[0043] In this invention, the binder phase bonds the composite conductive phase and other components to the substrate, improving the room temperature and high temperature adhesion performance of the conductive film. In a preferred embodiment, the binder phase is B503 ceramic resin and / or B9102 silicon-zirconium composite inorganic resin. By selecting the above resins as binder phases, the curing temperature of the prepared slurry is lower, and it can be used at higher temperatures. Specifically, B503 ceramic resin is a single-component ceramic resin that can be stored for a long time without losing its gloss, has excellent high temperature resistance, and good film-forming properties; its curing process is 180–280°C / 30 min. B9102 silicon-zirconium composite inorganic resin is a silicon-zirconium composite inorganic resin that can be used alone or mixed with organosilicon resins, etc. It has good temperature resistance, good compatibility, good ultra-high temperature resistance, and good film-forming properties; its curing process is 200–280°C / 30 min.

[0044] In this invention, the rheological properties of the slurry can be improved by adding a surfactant. In a preferred embodiment, the surfactant is Tween-80.

[0045] In this invention, the particle size D of the copper powder 50 The size ranges from 1 to 10 μm.

[0046] In a preferred embodiment, the copper powder is composed of copper powder a, copper powder b, and copper powder c, wherein the particle size D of copper powder a is... 50 The particle size D of the copper powder b is 0.5–2 μm. 50 The particle size D of the copper powder c is 4–6 μm. 50 The particle size is 9–10 μm. By mixing copper powders of different particle sizes, the density of the conductive film layer formed by the slurry can be improved.

[0047] More preferably, the mass ratio of copper powder a, copper powder b, and copper powder c is 1:0.8-1.2:0.8-1.2.

[0048] In the most preferred embodiment, the copper powder is composed of copper powder a, copper powder b, and copper powder c, wherein the particle size D of copper powder a is... 50 The particle size D of the copper powder b is 1 μm. 50 The particle size D of the copper powder c is 5 μm. 50 The size is 10 μm, and the mass ratio is 1:1:1.

[0049] In a preferred embodiment, the conductive reinforcing phase is nanoscale graphene sheets and / or carbon nanotubes. Nanoscale graphene sheets or carbon nanotubes have extremely high conductivity, and by selecting them as conductive reinforcing phases and adding them to copper powder, the conductivity of the conductive film can be improved.

[0050] This invention does not limit the specific preparation steps of the composite conductive phase, as long as the copper powder and the conductive reinforcing phase can be mixed as uniformly as possible. In a preferred embodiment, the composite conductive phase is prepared according to the following steps: mixing copper powder and the conductive reinforcing phase, and then ball milling, so as to make the copper powder and the conductive reinforcing phase mixed uniformly by ball milling.

[0051] More preferably, the composite conductive phase is prepared according to the following steps:

[0052] The copper powder is acid-washed, water-washed, and then dried to obtain the treated copper powder.

[0053] The conductive reinforcing phase was mixed with anhydrous ethanol, then ultrasonically vibrated, and then dried to obtain the treated conductive reinforcing phase.

[0054] The treated copper powder and the conductive reinforcing phase were mixed and then ball-milled to obtain a composite conductive phase.

[0055] This invention also proposes a method for preparing the water-based copper composite conductive paste as described above, the method comprising the following steps:

[0056] (1) Mix some water with potassium montmorillonite to obtain potassium montmorillonite gel, then seal and cure;

[0057] (2) The matured potassium-based montmorillonite gel is mixed with polydimethylsiloxane, carboxymethyl cellulose, binder, silicide, mineralizer, surfactant, residual water and copper composite conductive phase, and the resulting mixture is kneaded and ground.

[0058] In step (1) of this invention, the amount of water and the ratio of water to potassium-based montmorillonite are not particularly limited and can be designed according to actual conditions. In one specific embodiment, the mass ratio of water to potassium-based montmorillonite is 0.8 to 2:1.

[0059] In a preferred embodiment, the maturation time in step (1) is 20 to 30 hours.

[0060] In specific implementation, step (2) includes: mixing the remaining water with the potassium-based montmorillonite gel obtained in step (1) until uniform; then adding the binder phase, carboxymethyl cellulose, polydimethylsiloxane, silicide, mineralizer, surfactant, and composite conductive phase, and mixing them until uniform.

[0061] In a preferred embodiment, step (2) involves kneading and grinding the obtained mixture, which includes: feeding the mixture into a high-speed double planetary continuous kneader for 1 to 5 uniform kneadings, and then feeding it into a colloid mill for 1 to 5 grindings.

[0062] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited thereto. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available products.

[0063] Example 1

[0064] Weigh the following raw material components according to the following mass percentages: 60% composite conductive phase, 5% B503 ceramic resin, 5% potassium montmorillonite, 1.8% carboxymethyl cellulose, 3% silicide (trimethylchlorosilane), 3% polydimethylsiloxane, 0.2% mineralizer (ZnO), 1% surfactant (Tween-80), and 21% deionized water.

[0065] The composite conductive phase is prepared according to the following steps:

[0066] Copper powder with particle size D 50 Copper powder with a diameter of 1 μm (a) and a particle size (D) 50Copper powder b with a particle size D of 5 μm 50 Copper powder c with a thickness of 10μm was mixed in a mass ratio of 1:1:1. The copper powder was acid-washed with 5% dilute sulfuric acid to remove the oxide film on the surface. The acid-washed copper powder was repeatedly washed with distilled water until no white precipitate was obtained when the distilled water used to wash the copper powder was tested by barium chloride. After acid washing and water washing, the powder was placed in a vacuum drying oven and kept at 80℃ for 3 hours. After drying, clean copper powder was obtained.

[0067] Add an appropriate amount of anhydrous ethanol to a conductive reinforcing phase (nanographene sheet) accounting for 1% of copper powder, and then ultrasonically vibrate at room temperature for 50 minutes. Place the resulting dispersion in a vacuum drying oven and keep it at 55°C for 3 hours. After drying, a conductive reinforcing phase with high dispersibility is obtained.

[0068] The treated copper powder was mixed with the conductive reinforcing phase and then placed in a planetary ball mill for 20 minutes to ensure that the main conductive phase and the conductive reinforcing phase were mixed evenly, thus obtaining a composite conductive phase.

[0069] The preparation method of water-based copper composite conductive paste includes the following steps:

[0070] (1) Preparation of potassium-based montmorillonite gel

[0071] Add deionized water of equal mass to potassium montmorillonite to potassium montmorillonite, mix well, and then stir in a high-speed mixer for 9 minutes to prepare potassium montmorillonite gel. Seal and mature for 25 hours before use.

[0072] (2) Preparation of water-based copper composite conductive paste

[0073] The remaining deionized water was mixed evenly with the potassium-based montmorillonite gel prepared in step (1); then ceramic resin, polydimethylsiloxane, silicide, mineralizer, carboxymethyl cellulose, surfactant and composite conductive phase were added and mixed evenly to obtain a mixture; then all the mixture was put into a high-speed double planetary continuous kneader for 3 mixing; then put into a colloid mill for 3 colloid milling to continuously produce electronic paste, and finally efficiently produce water-based copper composite conductive paste.

[0074] Example 2

[0075] Weigh the following raw material components according to the following mass percentages: 62% composite conductive phase, 5% B503 ceramic resin, 5% potassium montmorillonite, 1.7% carboxymethyl cellulose, 3% silicide (trimethylchlorosilane), 3% polydimethylsiloxane, 0.3% mineralizer (CaO), 1% surfactant (Tween-80), and 19% deionized water.

[0076] The composite conductive phase is prepared according to the following steps:

[0077] Copper powder with particle size D 50 Copper powder with a diameter of 1 μm (a) and a particle size (D) 50 Copper powder b with a particle size D of 5 μm 50 Copper powder c with a thickness of 10μm was mixed in a mass ratio of 1:1:1. The copper powder was acid-washed with 6% dilute sulfuric acid to remove the oxide film on the surface. The acid-washed copper powder was repeatedly washed with distilled water until no white precipitate was obtained when the distilled water used to wash the copper powder was tested with barium chloride. The copper powder after acid washing and water washing was placed in a vacuum drying oven and kept at 80℃ for 3 hours. After drying, clean copper powder was obtained.

[0078] An appropriate amount of anhydrous ethanol was added to a conductive reinforcing phase (nanographene sheet) accounting for 1% of copper powder. After ultrasonic oscillation at room temperature for 50 minutes, the dispersion was placed in a vacuum drying oven and kept at 60℃ for 3 hours. After drying, a nano-carbon conductive reinforcing phase with high dispersibility was obtained.

[0079] The treated copper powder was mixed with the conductive reinforcing phase and then placed in a planetary ball mill for 20 minutes to ensure that the main conductive phase and the conductive reinforcing phase were mixed evenly to obtain a composite conductive phase.

[0080] The preparation method of water-based copper composite conductive paste includes the following steps:

[0081] (1) Preparation of potassium-based montmorillonite gel

[0082] Add deionized water of equal mass to potassium montmorillonite to potassium montmorillonite, mix well, and then stir in a high-speed mixer for 10 minutes to prepare potassium montmorillonite gel. Seal and mature for 24 hours before use.

[0083] (2) Preparation of water-based copper composite conductive paste

[0084] The remaining deionized water was mixed evenly with the nano-potassium-based montmorillonite gel prepared in step (1); then ceramic resin, polydimethylsiloxane, silicide, mineralizer, carboxymethyl cellulose, surfactant and composite conductive phase were added and mixed evenly; then all the mixture was put into a high-speed double planetary continuous kneader for 3 mixing; then put into a colloid mill for 4 colloid milling to continuously produce electronic paste, and finally efficiently obtain water-based copper composite conductive paste.

[0085] Example 3

[0086] Weigh the following raw material components according to the following mass percentages: 60% composite conductive phase, 7% B503 ceramic resin, 6% potassium montmorillonite, 2% polydimethylsiloxane, 1.6% carboxymethyl cellulose, 3.5% silicide (triisopropyloxysilane), 0.4% mineralizer (MgO), 1.5% surfactant (Tween-80), and 18% deionized water.

[0087] The composite conductive phase is prepared according to the following steps:

[0088] Copper powder with particle size D 50 Copper powder with a diameter of 1 μm (a) and a particle size (D) 50 Copper powder b with a particle size D of 5 μm 50 Copper powder c with a thickness of 10μm was mixed in a mass ratio of 1:1:1. The copper powder was acid-washed with 6% dilute sulfuric acid to remove the oxide film on the surface. The acid-washed copper powder was repeatedly washed with distilled water until no white precipitate was obtained when the distilled water used to wash the copper powder was tested with barium chloride. The copper powder after acid washing and water washing was placed in a vacuum drying oven and kept at 80℃ for 3 hours. After drying, clean copper powder was obtained.

[0089] An appropriate amount of anhydrous ethanol was added to the conductive reinforcing phase carbon nanotubes accounting for 1% of copper powder. After ultrasonic oscillation at room temperature for 50 minutes, the dispersion was placed in a vacuum drying oven and kept at 60℃ for 3 hours. After drying, a nano-carbon conductive reinforcing phase with high dispersibility was obtained.

[0090] The treated copper powder was mixed with the conductive reinforcing phase and then placed in a planetary ball mill for 20 minutes to ensure that the main conductive phase and the conductive reinforcing phase were mixed evenly to obtain a composite conductive phase.

[0091] The preparation method of water-based copper composite conductive paste includes the following steps:

[0092] (1) Preparation of potassium-based montmorillonite gel

[0093] Add deionized water of equal mass to potassium montmorillonite to potassium montmorillonite, mix well, and then stir in a high-speed mixer for 20 minutes to prepare potassium montmorillonite gel. Seal and mature for 24 hours before use.

[0094] (2) Preparation of water-based copper composite conductive paste

[0095] The remaining deionized water was mixed evenly with the potassium-based montmorillonite gel prepared in step (1); then ceramic resin, polydimethylsiloxane, carboxymethyl cellulose, silicide, mineralizer, surfactant Tween-80 and composite conductive phase were added and mixed evenly; then all the mixture was put into a high-speed double planetary continuous kneader for 3 mixing; then put into a colloid mill for 5 grinding to continuously produce electronic paste, and finally efficiently obtain water-based copper composite conductive paste.

[0096] Example 4

[0097] Weigh the following raw material components according to the mass percentage: 60% composite conductive phase, 4% potassium montmorillonite, 6% B9102 silicon-zirconium composite inorganic resin, 2.5% polydimethylsiloxane, 2% carboxymethyl cellulose, 4% silicide (triisopropyloxysilane), 0.5% mineralizer (ZnO), 1% surfactant (Tween-80), and 20% deionized water.

[0098] The composite conductive phase is prepared according to the following steps:

[0099] Copper powder with particle size D 50 Copper powder with a diameter of 1 μm (a) and a particle size (D) 50 Copper powder b with a particle size D of 5 μm 50 Copper powder c with a thickness of 10μm was mixed in a mass ratio of 1:1:1. The copper powder was acid-washed with 6% dilute sulfuric acid to remove the oxide film on the surface. The acid-washed copper powder was repeatedly washed with distilled water until no white precipitate was obtained when the distilled water used to wash the copper powder was tested with barium chloride. The copper powder after acid washing and water washing was placed in a vacuum drying oven and kept at 80℃ for 3 hours. After drying, clean copper powder was obtained.

[0100] An appropriate amount of anhydrous ethanol was added to the conductive reinforcing phase carbon nanotubes accounting for 1% of copper powder. After ultrasonic oscillation at room temperature for 50 minutes, the dispersion was placed in a vacuum drying oven and kept at 60℃ for 3 hours. After drying, a nano-carbon conductive reinforcing phase with high dispersibility was obtained.

[0101] The treated copper powder was mixed with the conductive reinforcing phase and then placed in a planetary ball mill for 20 minutes to ensure that the main conductive phase and the conductive reinforcing phase were mixed evenly to obtain a composite conductive phase.

[0102] The preparation method of water-based copper composite conductive paste includes the following steps:

[0103] (1) Preparation of potassium-based montmorillonite gel

[0104] Add deionized water of equal mass to potassium montmorillonite to potassium montmorillonite, mix well, and then stir in a high-speed mixer for 30 minutes to prepare potassium montmorillonite gel. Seal and mature for 24 hours before use.

[0105] (2) Preparation of water-based copper composite conductive paste

[0106] The remaining deionized water was mixed evenly with the potassium-based montmorillonite gel prepared in step (1); then B9102 silicon-zirconium composite inorganic resin, polydimethylsiloxane, carboxymethyl cellulose, silicide, mineralizer, surfactant Tween-80 and composite conductive phase were added and mixed evenly; then all the mixture was put into a high-speed double planetary continuous kneader for 4 mixings; then put into a colloid mill for 3 grindings to continuously produce electronic paste, and finally efficiently obtain water-based copper composite conductive paste.

[0107] Example 5

[0108] Weigh the following raw material components according to the mass percentage: 5% potassium-based montmorillonite, 60% composite conductive phase, 6% B9102 silicon-zirconium composite inorganic resin, 4% silicide (trimethylchlorosilane), 2% polydimethylsiloxane, 2.4% carboxymethyl cellulose, 0.6% mineralizer (ZnO), 1% surfactant (Tween-80), and 19% deionized water.

[0109] The composite conductive phase is prepared according to the following steps:

[0110] Copper powder with particle size D 50 Copper powder with a diameter of 1 μm (a) and a particle size (D) 50 Copper powder b with a particle size D of 5 μm 50 Copper powder c with a thickness of 10μm was mixed in a mass ratio of 1:1:1. The copper powder was acid-washed with 6% dilute sulfuric acid to remove the oxide film on the surface. The acid-washed copper powder was repeatedly washed with distilled water until no white precipitate was obtained when the distilled water used to wash the copper powder was tested with barium chloride. The copper powder after acid washing and water washing was placed in a vacuum drying oven and kept at 80℃ for 3 hours. After drying, clean copper powder was obtained.

[0111] An appropriate amount of anhydrous ethanol was added to the conductive reinforcing phase carbon nanotubes accounting for 1% of copper powder. After ultrasonic oscillation at room temperature for 50 minutes, the dispersion was placed in a vacuum drying oven and kept at 60℃ for 3 hours. After drying, a nano-carbon conductive reinforcing phase with high dispersibility was obtained.

[0112] The treated copper powder was mixed with the conductive reinforcing phase and then placed in a planetary ball mill for 20 minutes to ensure that the main conductive phase and the conductive reinforcing phase were mixed evenly to obtain a composite conductive phase.

[0113] The preparation method of water-based copper composite conductive paste includes the following steps:

[0114] (1) Preparation of potassium-based montmorillonite gel

[0115] Add deionized water of equal mass to potassium montmorillonite to potassium montmorillonite, mix well, and then stir in a high-speed mixer for 30 minutes to prepare potassium montmorillonite gel. Seal and mature for 24 hours before use.

[0116] (2) Preparation of water-based copper composite conductive paste

[0117] The remaining deionized water was mixed evenly with the potassium-based montmorillonite gel prepared in step (1); then B9102 silicon-zirconium composite inorganic resin, polydimethylsiloxane, silicide, mineralizer, carboxymethyl cellulose, surfactant Tween-80 and composite conductive phase were added and mixed evenly; then all the mixture was put into a high-speed double planetary continuous kneader for 5 mixing; then put into a colloid mill for 3 colloid milling for continuous production of electronic paste, and finally obtained water-based copper composite conductive paste efficiently.

[0118] Example 6

[0119] Weigh the following raw material components according to the mass percentage: 4% potassium-based montmorillonite, 60% composite conductive phase, 6% B9102 silicon-zirconium composite inorganic resin, 4% silicide (hexamethyldisilazane), 1.5% polydimethylsiloxane, 1.8% carboxymethyl cellulose, 0.7% mineralizer (CaO), 1% surfactant (Tween-80), and 21% deionized water.

[0120] The composite conductive phase is prepared according to the following steps:

[0121] Copper powder with particle size D 50 Copper powder with a diameter of 1 μm (a) and a particle size (D) 50 Copper powder b with a particle size D of 5 μm 50 Copper powder c with a thickness of 10μm was mixed in a mass ratio of 1:1:1. The copper powder was acid-washed with 6% dilute sulfuric acid to remove the oxide film on the surface. The acid-washed copper powder was repeatedly washed with distilled water until no white precipitate was obtained when the distilled water used to wash the copper powder was tested with barium chloride. After acid washing and water washing, the powder was placed in a vacuum drying oven and kept at 80℃ for 3 hours. After drying, clean copper powder was obtained.

[0122] An appropriate amount of anhydrous ethanol was added to a conductive reinforcing phase nano-graphene sheet containing 1% copper powder. After ultrasonic oscillation at room temperature for 50 minutes, the dispersion was placed in a vacuum drying oven and kept at 60°C for 3 hours. After drying, a nano-carbon conductive reinforcing phase with high dispersibility was obtained.

[0123] The treated copper powder was mixed with the conductive reinforcing phase and then placed in a planetary ball mill for 20 minutes to ensure that the main conductive phase and the conductive reinforcing phase were mixed evenly to obtain a composite conductive phase.

[0124] The preparation method of water-based copper composite conductive paste includes the following steps:

[0125] (1) Preparation of potassium-based montmorillonite gel

[0126] Add deionized water of equal mass to potassium montmorillonite to potassium montmorillonite, mix well, and then stir in a high-speed mixer for 30 minutes to prepare potassium montmorillonite gel. Seal and mature for 24 hours before use.

[0127] (2) Preparation of water-based copper composite conductive paste

[0128] The remaining deionized water was mixed evenly with the potassium-based montmorillonite gel prepared in step (1); then B9102 silicon-zirconium composite inorganic resin, polydimethylsiloxane, silicide, mineralizer, carboxymethyl cellulose, surfactant and composite conductive phase were added and mixed evenly; then all the mixture was put into a high-speed double planetary continuous kneader for two mixings; then put into a colloid mill for four grindings to continuously produce electronic paste, and finally efficiently obtain water-based copper composite conductive paste.

[0129] Example 7

[0130] The method described in Example 1 was implemented, except that the particle size D of the copper powder was different. 50 The value is 5μm (meaning copper powder a and c are replaced with an equal amount of copper powder b).

[0131] Comparative Example 1

[0132] The method described in Example 1 was implemented, except that the conductivity-enhancing phase was replaced with an equal amount of copper powder.

[0133] Comparative Example 2

[0134] The method described in Example 1 was carried out, except that the silicide was replaced with an equal amount of polydimethylsiloxane.

[0135] Comparative Example 3

[0136] The method described in Example 1 was carried out, except that polydimethylsiloxane was replaced with an equal amount of silicide.

[0137] Test Example 1

[0138] The water-based copper composite conductive pastes prepared in Examples 1-7 and Comparative Example 1 were subjected to conductivity tests. The conductivity of the conductive film formed by the curing of the water-based copper composite conductive paste was determined using the standard four-probe method. The resistivity of the conductive film was tested using an FT-340 digital four-probe resistivity meter manufactured by Ningbo Ruike Instruments. This instrument has a sheet resistance range of 1×10⁻⁶. -5 ~2×10 6 Ω / ρ, resistivity range of 1×10 -6 ~2×10 6 Ω·cm. The test results are shown in Table 1 below.

[0139] Table 1

[0140] Example 1 6.75 200 Example 2 7.86 200 Example 3 7.94 200 Example 4 7.55 200 Example 5 6.72 200 Example 6 7.53 200 Example 7 8.35 200 Comparative Example 1 8.98 200

[0141] As can be seen from the experimental results in Table 1, the water-based copper composite conductive paste prepared by the present invention has excellent conductivity and a low curing temperature.

[0142] Test Example 2

[0143] The water-based copper composite conductive pastes prepared in Example 1 and Comparative Examples 2-3 were cured at 200°C and then subjected to oxidation resistance tests at 60% humidity and 20°C. The test results are shown in Table 2 below.

[0144] Table 2

[0145] Example 1 No significant change after 500 days Comparative Example 2 No significant change after 400 days Comparative Example 3 No significant changes after 419 days

[0146] As shown in Table 2, the water-based copper composite conductive paste provided by this invention exhibits excellent oxidation resistance. Furthermore, a comparison of Example 1 and Comparative Examples 2-3 reveals that the combined use of polydimethylsiloxane and the silicide plays a crucial role in improving oxidation resistance; even the absence of either one significantly weakens the oxidation resistance, indicating that polydimethylsiloxane and the silicide have a synergistic effect in improving the oxidation resistance of the water-based copper composite conductive paste.

[0147] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A water-based copper composite conductive paste, characterized in that, The water-based copper composite conductive paste comprises the following components by mass fraction: 55%~70% composite conductive phase, 1%~10% binder phase, 1%~10% potassium montmorillonite, 0.2%~2.5% carboxymethyl cellulose, 0.5%~6% silicide, 0.1%~1% mineralizer, 0.5%~6% polydimethylsiloxane, 0.3%~3% surfactant, and 15%~30% water; The silicide is an organosilicon compound; The mineralizing agent is selected from at least one of ZnO, CaO, MgO and Fe2O3; The composite conductive phase contains copper powder and a conductive reinforcing phase, wherein the mass ratio of the conductive reinforcing phase to the copper powder is 0.5~5:100; The binder phase is B503 ceramic resin and / or B9102 silicon-zirconium composite inorganic resin.

2. The water-based copper composite conductive paste according to claim 1, characterized in that, The silicide is selected from at least one of trimethylchlorosilane, hexamethyldisilazane, tert-butyldimethylchlorosilane, triisopropyloxysilane, dimethyldiacetoxysilane, ditert-butyldichlorosilane, trimethylhydroxyethylsilane, and methyldiphenylhydroxyethylsilane.

3. The water-based copper composite conductive paste according to claim 1, characterized in that, The surfactant is Tween-80.

4. The water-based copper composite conductive paste according to claim 1, characterized in that, The particle size D of the copper powder 50 The range is 1~10μm.

5. The water-based copper composite conductive paste according to claim 1 or 4, characterized in that, The copper powder is composed of copper powder a, copper powder b, and copper powder c, wherein the particle size D of copper powder a is... 50 The particle size D of the copper powder b is 0.5~2μm. 50 The particle size D of the copper powder c is 4~6μm. 50 It is 9~10μm.

6. The water-based copper composite conductive paste according to claim 5, characterized in that, The mass ratio of copper powder a, copper powder b, and copper powder c is 1:0.8~1.2:0.8~1.

2.

7. The water-based copper composite conductive paste according to claim 1, characterized in that, The conductive reinforcement phase is nanoscale graphene sheets and / or carbon nanotubes.

8. A method for preparing the water-based copper composite conductive paste according to any one of claims 1-7, characterized in that, The method includes the following steps: (1) Mix some water with potassium montmorillonite to obtain potassium montmorillonite gel, then seal and cure; (2) The matured potassium-based montmorillonite gel is mixed with polydimethylsiloxane, carboxymethyl cellulose, binder, silicide, mineralizer, surfactant, residual water and composite conductive phase, and the resulting mixture is kneaded and ground.

9. The method according to claim 8, characterized in that, In step (1), the maturation time is 20~30h.

10. The method according to claim 8, characterized in that, In step (2), the process of kneading and grinding the mixture includes: putting the mixture into a high-speed double planetary continuous kneader for 1 to 5 uniform kneadings, and then putting it into a colloid mill for 1 to 5 grindings.