Silver-coated copper powder with uniform silver layer as well as preparation method and application of silver-coated copper powder

Abstract

The invention discloses silver-coated copper powder with a uniform silver layer and a preparation method and application of the silver-coated copper powder, and relates to the technical field of conductive materials and metal powder preparation.The silver-coated copper powder is characterized in that organic matter and an oxide layer on the surface of copper powder are removed through an acidic or alkaline solvent, and then a small amount of alcamines reagent is added and evenly stirred to serve as a copper powder interface reduction protective agent; then, one reagent of silver nitrate, silver ammonia and a silver nitrate-alkylol amine complexing solution is added to serve as a seed layer silver plating solution; according to the method, the silver layer coating stability of the silver-coated copper powder in the prior art can be improved, the coating surface of the silver layer is smoother, coating is more complete, the phenomenon that a copper core is exposed is reduced, and the silver-coated copper powder with the uniform silver layer coating is obtained. And the volume resistivity is relatively low.

Description

Technical Field

[0001] The invention relates to the technical field of conductive material and metal powder preparation, and in particular to silver-coated copper powder with uniform silver layer and a preparation method and application thereof. Background Art

[0002] With the rapid development of industries such as semiconductors, photovoltaics, and electronic information, various electronic components are increasingly demanding conductive powders, including silver powder, silver-coated copper powder, copper powder, and other conductive powders. As a core-shell conductive powder, silver-coated copper powder has a conductivity that is almost the same as that of pure silver powder in some application scenarios, but the cost of silver-coated copper powder is significantly lower than that of pure silver powder, and various industries have begun to partially replace the more expensive pure silver powder. For micro-nano-sized silver-coated copper powder, the surface interface layer of the silver-coated copper powder is a silver layer, which has certain oxidation resistance and storage stability; for pure copper powder, the highly active copper layer on the surface interface is usually prone to oxidation, and some special passivation processes are required to maintain the high conductivity and stability of the copper powder. It can be seen that silver-coated copper powder has a good application prospect, and in recent years, there have been more and more studies on the preparation and application of silver-coated copper powder.

[0003] Common preparation methods for silver-coated copper powder include physical and chemical methods, and the chemical method includes replacement and reduction methods. At present, a major difficulty in the research of micro-nano silver-coated copper powder is how to densely coat the silver layer on the copper core to keep the silver-copper interface tightly bonded, while at the same time reducing the copper layer exposure, maintaining uniform silver coating, and reducing surface silver layer defects under low silver content conditions to achieve high conductivity and stability of the powder. In the existing technology, researchers use a variety of methods to improve the integrity of the silver layer coating. For example: silver plating is carried out by a combination of replacement and reduction, such as the technical solutions disclosed in patent applications with publication numbers CN116037920A, CN106148926A, and CN118180395A; or stabilizing reactions such as adding complexing agents and stabilizers are used, such as the technical solution disclosed in the invention patent application with publication number CN117399617A. However, the above technical solutions all have problems in the surface treatment of copper powder and the intermediate process of silver plating. If the treatment is not appropriate, there will be a problem of slow oxidation at the interface of the copper powder before silver plating, resulting in uneven silver layer coating and the silver layer may not be tight to the copper core, affecting the electrical properties and stability of the powder application, and requiring very high operating personnel. Summary of the invention

[0004] The purpose of the present invention is to provide a new method for preparing silver-coated copper powder with uniform silver layer, which can improve the silver layer coating stability of the silver-coated copper powder in the prior art. By adopting a surface treatment reagent and reduction reagent-an amine reagent, the silver layer coating surface is made smoother and the coating is more complete, the copper core exposure phenomenon is reduced, and at the same time, the obtained silver-coated copper powder is kept to have excellent conductivity.

[0005] The present invention is achieved through the following technical solutions: A method for preparing silver-coated copper powder with uniform silver layer, comprising the steps of surface treatment of copper powder, silver plating of seed layer, reduction silver plating and powder post-treatment. Among them: the copper powder surface treatment is to first use acid and alkali reagents to remove organic matter and oxide layer on the copper powder surface, pour out the supernatant, and then add a small amount of alcohol amine reagent as a copper powder interface protective agent. The amount of alcohol amine reagent added is 4-30% of the copper powder mass, and the temperature is 15-80℃; Reduction silver plating is to add alcohol amine reagents and alkaline silver source oxidants in sequence after the silver plating reaction of the seed layer is completed; The alcoholamine reagents include one or more of ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, N-propyldiethanolamine, N-butyldiethanolamine, N-tert-butyldiethanolamine and their hydrochlorides and phosphates.

[0006] Furthermore, in the reduction silver plating step, the molar amount of the alcohol amine reagent added is 0.1 to 10 times the molar amount of the alkaline silver source.

[0007] Furthermore, the alkaline silver source oxidant includes one or more of silver ammonia and silver nitrate-alcoholamine complex solution; when the alkaline silver source oxidant is added, the added mass of silver is 3-30% of the mass of the copper powder.

[0008] Furthermore, in the reduction silver plating step, the reaction temperature is controlled to be 15-60°C.

[0009] Furthermore, in the seed layer silver plating step, after adding a copper complexing agent and / or a dispersant to the suspension, a reagent selected from silver nitrate, silver ammonia, and silver nitrate-alcoholamine complex solution is added, wherein the mass of silver added is 1-5% of the mass of the copper powder, and the reaction temperature is 15-60°C.

[0010] Furthermore, the copper complexing agent includes one or more of ethylenediaminetetraacetic acid, diethylenetriamine, triethylenetetramine, tetraethylenepentamine and sodium salts thereof; the dispersant includes one or more of polyvinyl pyrrolidone, polyethylene glycol, polyvinyl alcohol, methyl cellulose, sodium dodecyl sulfonate and sodium dodecylbenzene sulfonate.

[0011] Furthermore, the silver nitrate-alcoholamine complex solution includes one or more of silver nitrate-ethanolamine, silver nitrate-diethanolamine, silver nitrate-triethanolamine, silver nitrate-N-methyldiethanolamine, silver nitrate-N-ethyldiethanolamine, silver nitrate-N-propyldiethanolamine, silver nitrate-N-butyldiethanolamine, and silver nitrate-N-tert-butyldiethanolamine complex solutions.

[0012] Furthermore, the molar ratio of silver nitrate to alcoholamine in the silver nitrate-alcoholamine complex solution is 1:1-6.

[0013] The silver-coated copper powder prepared by the preparation method described in any one of the above items meets the following indicators: Appearance: The surface is smooth; Specific surface area: ≤ the specific surface area of ​​the initial copper powder; Acid-resistant solvent: Soak the powder in a 36% acetic acid aqueous solution for 6 hours, and the supernatant is transparent and colorless; The body resistance of low silver-containing paste made of micron-sized silver-coated copper powder is less than 9μΩ•cm.

[0014] Application of silver-coated copper powder in photovoltaic slurry, electronic slurry, electromagnetic shielding filler or conductive adhesive, wherein the silver-coated copper powder is obtained by the above-mentioned preparation method.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. In the present invention, considering that when preparing micro-nano-sized silver-coated copper powder, there is a situation that the copper powder is slowly oxidized for a period of time after the copper powder surface treatment step, resulting in uneven silver layer coating on the powder surface of the silver-copper powder finally prepared, insufficient tightness of the silver-copper interface, and increased silver layer defects on the powder surface, the present invention adds an alcohol amine reagent as a protective molecule for the copper powder in the copper powder surface activation step. At the same time, an alcohol amine reagent is added as a reducing agent and an alkaline silver source to participate in the reaction during the silver plating step reduction process to control the coated silver layer.

[0016] 2. In the present invention, while using an alcoholamine reagent as a protective agent for copper powder, it is also used as a reducing agent for subsequent reduction silver plating. After the seed layer silver plating step, the newly added alcoholamine reagent can be adsorbed to the newly added silver-copper interface layer as an interface protective agent, and at the same time, it can be combined with the alcoholamine reagent free in the suspension as a pH sustained-release agent to improve the compatibility of the reaction pH.

[0017] 3. In the present invention, the alcoholamine reagent is used as a reducing agent in the reduction silver plating step, and the reduction reaction speed is moderate, because the alcoholamine itself can be adsorbed to the copper core interface, and the new carboxyl group formed after reduction is more easily adsorbed to the copper core interface, inducing the reduced silver atoms to grow on the surface of the copper core, thereby obtaining a silver-coated copper powder with a smooth silver layer.

[0018] Fourth, in the present invention, there is another scheme that uses silver nitrate-alcoholamine complex solution as a silver source oxidant to chelate and slowly release silver ions to participate in the reaction and reduce the chemical components in the synthesis.

[0019] 5. In the present invention, the silver-coated copper powder is obtained by adopting this scheme, the surface of the electron microscope morphology is smooth, the specific surface area is less than or equal to the initial copper powder, it is resistant to acidic solvents, and the body resistance of the low silver-containing slurry is less than 9μΩ·cm. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a SEM image of the silver-coated copper powder prepared in Example 1.

[0021] Figure 2 This is the SEM image of the silver-coated copper powder prepared in Example 2.

[0022] Figure 3 This is the SEM image of the silver-coated copper powder prepared in Comparative Example 1.

[0023] Figure 4 This is the SEM image of the silver-coated copper powder prepared in Comparative Example 2. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present disclosure should be the usual meanings understood by people with ordinary skills in the field to which the present disclosure belongs.

[0025] In the present invention, the alcohol amine reagent includes one or more of ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, N-propyldiethanolamine, N-butyldiethanolamine, N-tert-butyldiethanolamine and their hydrochlorides and phosphates. In the following embodiments, ethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine and triethanolamine hydrochloride are used as examples to illustrate the present scheme, and the reagents involved are all reagents purchased on the market.

[0026] In the present invention, the copper complexing agent includes one or more of ethylenediaminetetraacetic acid, diethylenetriamine, triethylenetetramine, tetraethylenepentamine and sodium salt thereof. In the following embodiments, ethylenediaminetetraacetic acid is taken as an example to illustrate this scheme, and the reagents involved are all reagents purchased on the market.

[0027] In the present invention, the dispersant includes one or more of polyvinyl pyrrolidone, polyethylene glycol, polyvinyl alcohol, methyl cellulose, sodium dodecyl sulfonate, and sodium dodecylbenzene sulfonate. In the following embodiments, polyvinyl pyrrolidone is taken as an example to illustrate this scheme, and the reagents involved are all reagents purchased on the market.

[0028] In the present invention, the silver nitrate-alcoholamine complex solution includes one or more of silver nitrate-ethanolamine, silver nitrate-diethanolamine, silver nitrate-triethanolamine, silver nitrate-N-methyldiethanolamine, silver nitrate-N-ethyldiethanolamine, silver nitrate-N-propyldiethanolamine, silver nitrate-N-butyldiethanolamine, and silver nitrate-N-tert-butyldiethanolamine complex solutions. In the following embodiments, silver nitrate-ethanolamine is taken as an example to illustrate this scheme, and the reagents involved are all reagents purchased on the market.

[0029] In the present invention, the copper powder has various morphologies and sizes, including spherical, dendritic, flake, etc., and the particle size is preferably 0.5-10 μm. In the following examples, spherical copper powder of about 3.0 μm is used for illustration, and flake, dendritic copper powder and powders of other sizes are not repeated.

[0030] Example 1 A method for preparing silver-coated copper powder with uniform silver layer, which relates to the technical field of conductive materials and nanomaterials, comprises the following steps: S1. Surface treatment of copper powder: Disperse 100 g of spherical copper powder with an average particle size of 3.0 μm in 200 mL of 2% nitric acid solution, treat at 30°C for 20 min to remove organic matter and oxide layer on the surface of the copper powder, and pour out the supernatant; quickly add 20 g of ethanolamine and 800 g of deionized water and stir at 30°C for 5 min to form a copper powder suspension.

[0031] S2, seed layer silver plating: prepare 100g of 3% silver ammonia solution and keep it at 30℃. Pour 20g of ethylenediaminetetraacetic acid powder into the copper powder suspension and stir for 5min, then add the silver ammonia solution into the copper powder suspension at a rate of 100mL / min; S3. Reduction silver plating: add 56 g of ethanolamine and stir for 5 min; add 150 g of silver ammonia solution (containing 10 g of silver) at 80 mL / min.

[0032] S4, powder post-treatment: The material after reduction silver plating is filtered, the solid phase is dried in a vacuum oven at 80°C, and then pulverized and sieved with 200 mesh to obtain silver-coated copper powder. The electron microscope morphology, specific surface area, and acid resistance of the powder are tested. The electron microscope image of the silver-coated copper powder obtained in this embodiment is shown in Figure 1 .

[0033] Example 2 S1. Surface treatment of copper powder: 100 g of spherical copper powder with an average particle size of 3.0 μm was dispersed in 200 mL of 5% sulfuric acid solution, treated at 30°C for 20 min, and the supernatant was poured out; 5 g of triethanolamine and 800 g of deionized water were quickly added and stirred at 45°C for 5 min to form a copper powder suspension.

[0034] S2, seed layer silver plating: prepare 100g of 3% silver nitrate solution and keep it at 45°C. Pour 20g of ethylenediaminetetraacetic acid powder and 5g of polyvinyl pyrrolidone into the copper powder suspension and stir for 5min, then add silver nitrate into the copper powder suspension at a rate of 100mL / min; S3. Reduction silver plating: add 20.69 g of triethanolamine and stir for 5 min; add 150 g of silver ammonia solution (containing 10 g of silver) at 80 mL / min.

[0035] S4, powder post-treatment: The material after reduction silver plating is filtered, the solid phase is dried in a vacuum oven at 80°C, and then pulverized and sieved with 200 mesh to obtain silver-coated copper powder. The electron microscope morphology, specific surface area, and acid resistance of the powder are tested. The electron microscope image of the silver-coated copper powder obtained in this embodiment is shown in Figure 2 .

[0036] Example 3 S1. Surface treatment of copper powder: Disperse 100 g of spherical copper powder with an average particle size of 3.0 μm in 200 mL of 2% nitric acid solution at 30°C for 20 min, and pour off the supernatant; quickly add 6 g of triethanolamine and 800 g of deionized water and stir at 60°C for 5 min to form a copper powder suspension.

[0037] S2, seed layer silver plating: prepare 100g of 3% silver nitrate solution and keep it at 60℃. Pour 20g of ethylenediaminetetraacetic acid powder into the copper powder suspension and stir for 5min, then add silver nitrate into the copper powder suspension at a rate of 100mL / min; S3. Reduction silver plating: add 11.4 g of triethanolamine and stir for 5 min; add 150 g of silver ammonia solution (containing 10 g of silver) at 80 mL / min.

[0038] S4, powder post-treatment: the material after reduction silver plating is filtered, the solid phase is dried in a vacuum oven at 80°C, and then pulverized and sieved with 200 mesh to obtain silver-coated copper powder. The powder's electron microscope morphology, specific surface area, and acid resistance are tested.

[0039] Example 4 S1. Surface treatment of copper powder: 100 g of spherical copper powder with an average particle size of 3.0 μm was dispersed in 200 mL of 5% sulfuric acid solution, treated at 30°C for 20 min, and the supernatant was poured out; 20 g of ethanolamine and 800 g of deionized water were quickly added and stirred at 30°C for 5 min to form a copper powder suspension.

[0040] S2, seed layer silver plating: prepare silver nitrate-ethanolamine solution, take 300g of deionized water, add 20.4g of silver nitrate, add 22.1g of ethanolamine, and stir at 30°C for 10min. Pour 20g of ethylenediaminetetraacetic acid powder into the copper powder suspension and stir for 5min, then add 75g of silver nitrate-ethanolamine solution into the copper powder suspension at a speed of 80mL / min; S3, reduction silver plating: add 28 g of ethanolamine and stir for 5 min; add the remaining silver nitrate-ethanolamine solution in step S2 at 100 mL / min.

[0041] S4, powder post-treatment: the material after reduction silver plating is filtered, the solid phase is dried in a vacuum oven at 80°C, and then pulverized and sieved with 200 mesh to obtain silver-coated copper powder. The powder's electron microscope morphology, specific surface area, and acid resistance are tested.

[0042] Example 5 S1. Surface treatment of copper powder: 100 g of spherical copper powder with an average particle size of 3.0 μm was dispersed in 200 mL of a 2% nitric acid solution, and treated at 45°C for 20 min to remove organic matter and an oxide layer on the surface of the copper powder, and the supernatant was poured off; 20 g of N-methyldiethanolamine and 800 g of deionized water were quickly added and stirred at 45°C for 5 min to form a copper powder suspension.

[0043] S2, seed layer silver plating: prepare 100g of 3% silver ammonia solution and keep it at 45°C. Pour 20g of ethylenediaminetetraacetic acid powder and 18g of polyethylene glycol into the copper powder suspension and stir for 5min, then add the silver ammonia solution into the copper powder suspension at a rate of 100mL / min; S3. Reduction silver plating: add 43 g of N-methyldiethanolamine and stir for 5 min; add 150 g of silver ammonia solution (containing 10 g of silver) at 80 mL / min.

[0044] S4, powder post-treatment: the material after reduction silver plating is filtered, the solid phase is dried in a vacuum oven at 80°C, and then pulverized and sieved with 200 mesh to obtain silver-coated copper powder. The powder's electron microscope morphology, specific surface area, and acid resistance are tested.

[0045] Example 6 S1. Surface treatment of copper powder: 100 g of spherical copper powder with an average particle size of 3.0 μm was dispersed in 200 mL of a 2% nitric acid solution, and treated at 45°C for 20 min to remove organic matter and an oxide layer on the surface of the copper powder, and the supernatant was poured off; 20 g of N-ethyldiethanolamine and 800 g of deionized water were quickly added and stirred at 45°C for 5 min to form a copper powder suspension.

[0046] S2, seed layer silver plating: prepare 100g of 3% silver ammonia solution and keep it at 45°C. Pour 20g of ethylenediaminetetraacetic acid powder and 5g of polyvinyl alcohol into the copper powder suspension and stir for 10min, then add the silver ammonia solution into the copper powder suspension at a rate of 100mL / min; S3. Reduction silver plating: add 48 g of N-ethyldiethanolamine and stir for 5 min; add 150 g of silver ammonia solution (containing 10 g of silver) at 80 mL / min.

[0047] S4, powder post-treatment: the material after reduction silver plating is filtered, the solid phase is dried in a vacuum oven at 80°C, and then pulverized and sieved with 200 mesh to obtain silver-coated copper powder. The powder's electron microscope morphology, specific surface area, and acid resistance are tested.

[0048] Example 7 S1. Surface treatment of copper powder: disperse 100 g of spherical copper powder with an average particle size of 3.0 μm in 200 mL of 2% nitric acid solution, treat at 45°C for 20 min to remove organic matter and oxide layer on the surface of the copper powder, and pour out the supernatant; quickly add 10 g of triethanolamine hydrochloride and 800 g of deionized water and stir at 45°C for 5 min to form a copper powder suspension.

[0049] S2, seed layer silver plating: prepare 100g of 3% silver ammonia solution and keep it at 45°C. Pour 20g of ethylenediaminetetraacetic acid powder into the copper powder suspension and stir for 5min, then add the silver ammonia solution into the copper powder suspension at a rate of 100mL / min; S3. Reduction silver plating: add 26.8 g of triethanolamine hydrochloride and stir for 5 min; add 150 g of silver ammonia solution (containing 10 g of silver) at 80 mL / min.

[0050] S4, powder post-treatment: the material after reduction silver plating is filtered, the solid phase is dried in a vacuum oven at 80°C, and then pulverized and sieved with 200 mesh to obtain silver-coated copper powder. The powder's electron microscope morphology, specific surface area, and acid resistance are tested.

[0051] Comparative Example 1 S1. Surface treatment of copper powder: 100 g of spherical copper powder with an average particle size of 3.0 μm was dispersed in 200 mL of 2% nitric acid solution at 30°C for 20 min, the supernatant was poured off, and 800 g of pure water was added to form a copper powder suspension.

[0052] S2, seed layer silver plating: prepare 100g of 3% silver ammonia solution and keep it at 30℃. Pour 20g of ethylenediaminetetraacetic acid powder into the copper powder suspension and stir for 5min, then add the silver ammonia solution into the copper powder suspension at a rate of 100mL / min; S3. Reduction silver plating: add 43.4 g of glucose and stir for 10 min; add 150 g of silver ammonia solution (containing 10 g of silver) at 80 mL / min.

[0053] S4, powder post-treatment: the material after reduction silver plating treatment is filtered, the solid phase is dried in a vacuum oven at 80°C, and then pulverized and sieved with 200 mesh to obtain silver-coated copper powder. The electron microscope morphology, specific surface area, and acid resistance of the powder are tested. The electron microscope image of the silver-coated copper powder obtained in this example is shown in Figure 3 .

[0054] Comparative Example 2 S1. Surface treatment of copper powder: 100 g of spherical copper powder with an average particle size of 3.0 μm was dispersed in 200 mL of 2% nitric acid solution at 30°C for 20 min, the supernatant was poured off, and 800 g of pure water was added to form a copper powder suspension.

[0055] S2, seed layer silver plating: prepare 100g of 3% silver ammonia solution and keep it at 30°C. Pour 20g of ethylenediaminetetraacetic acid powder into the copper powder suspension and stir for 5min, then add silver nitrate into the copper powder suspension at a rate of 100mL / min; S3. Reduction silver plating: add 56 g of ethanolamine and stir for 5 min; add 150 g of silver ammonia solution (containing 10 g of silver) at 80 mL / min.

[0056] S4, powder post-treatment: the material after reduction silver plating treatment is filtered, the solid phase is dried in a vacuum oven at 80°C, and then pulverized and sieved with 200 mesh to obtain silver-coated copper powder. The electron microscope morphology, specific surface area, and acid resistance of the powder are tested. The electron microscope image of the silver-coated copper powder obtained in this example is shown in Figure 4 .

[0057] Product performance testing The present invention observes the roughness of the powder surface and the presence or absence of defects such as microscopic holes through scanning electron microscope (SEM) photos; observes whether the specific surface area of ​​the copper powder increases after being coated with a layer of silver through a specific surface area test, and macroscopically judges the roughness and holes; and observes the color of the upper acetic acid solution by soaking the powder in a 36% acetic acid aqueous solution for 6 hours. If it is colorless, the silver layer is well coated. If it is blue, it means that there is microscopic copper exposure. The test results of the above experimental part are as follows: Table 1 As shown in Table 1, the silver-coated copper powders obtained by the preparation method disclosed in the present invention (the silver-coated copper powders after treatment in Examples 1 to 7) show that the SEM surface is smoother, and the specific surface area is smaller than the specific surface area of ​​the initial copper powder and the silver-coated copper powders after treatment in Comparative Examples 1 and 2. It can be seen that the silver-coated copper powders after treatment are significantly smoother and have better silver layer coverage. At the same time, after each group of powders is soaked in acetic acid for 6 hours, the upper acetic acid solution still shows colorless, which also reflects that the silver layer coverage of the powders in Examples 1 to 7 is better.

[0058] If during the preparation process, no alcohol amine reagent is added as a "reducing protective agent" to activate the copper powder surface, the SEM surface of the powder may be relatively smooth overall (with local silver bumps), but the acid reagent resistance is poor, as shown in Comparative Example 2.

[0059] In order to further evaluate the electrical properties of silver-coated copper powder, the powders of the above groups were prepared with silver-copper slurry with a silver content of 20%. The silver-copper slurry included epoxy resin, phthalic anhydride, diethylene glycol butyl ether acetate, a small amount of pure silver fine powder, etc. The solid content was 90-93%. The body resistance of each group was tested after drying and curing at 200°C. The results are shown in Table 2.

[0060] Table 2 It can be seen from Table 2 that under the same particle size, after drying and curing at 200°C, the silver-coated copper powder obtained by the preparation method of the present invention has a lower body resistance, which is less than 7μΩ·cm, and has a lower resistivity (lower than 9μΩ·cm), which is also lower than the body resistivity of Comparative Examples 1 and 2.

[0061] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing silver-coated copper powder with uniform silver layer, characterized in that: It includes copper powder surface treatment, seed layer silver plating, reduction silver plating and powder post-treatment steps. Among them: the copper powder surface treatment is to first remove the organic matter and oxide layer on the copper powder surface, pour out the supernatant, and then add a small amount of alcohol amine reagent as a copper powder interface protective agent. The amount of alcohol amine reagent added is 4-30% of the copper powder mass, and the temperature is 15-80°C; Reduction silver plating is to add alcohol amine reagents and alkaline silver source oxidants in sequence after the silver plating reaction of the seed layer is completed; The alcoholamine reagents include one or more of ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, N-propyldiethanolamine, N-butyldiethanolamine, N-tert-butyldiethanolamine and their hydrochlorides and phosphates.

2. The method for preparing a silver-coated copper powder with a uniform silver layer according to claim 1, characterized in that: In the reduction silver plating step, the molar amount of the alcohol amine reagent added is 0.1 to 10 times the molar amount of the alkaline silver source.

3. The method for preparing a silver-coated copper powder with a uniform silver layer according to claim 1, characterized in that: The alkaline silver source oxidant includes one or more of silver ammonia and silver nitrate-alcoholamine complex solution; when the alkaline silver source oxidant is added, the added mass of silver is 3-30% of the mass of the copper powder.

4. The method for preparing a silver-coated copper powder with a uniform silver layer according to claim 1, characterized in that: In the reduction silver plating step, the reaction temperature is controlled at 15~60°C.

5. The method for preparing a silver-coated copper powder with a uniform silver layer according to claim 1, characterized in that: In the seed layer silver plating step, after adding a copper complexing agent and / or a dispersant to the suspension, a reagent selected from silver nitrate, silver ammonia, and silver nitrate-alcoholamine complex solution is added, wherein the mass of silver added is 1-5% of the mass of the copper powder, and the reaction temperature is 15-60°C.

6. The method for preparing a silver-coated copper powder with a uniform silver layer according to claim 5, characterized in that: The copper complexing agent includes one or more of ethylenediaminetetraacetic acid, diethylenetriamine, triethylenetetramine, tetraethylenepentamine and sodium salts thereof; the dispersant includes one or more of polyvinyl pyrrolidone, polyethylene glycol, polyvinyl alcohol, methyl cellulose, sodium dodecyl sulfonate and sodium dodecylbenzene sulfonate.

7. The method for preparing a silver-coated copper powder with a uniform silver layer according to claim 3 or 5, characterized in that: The silver nitrate-alcoholamine complex solution includes one or more of silver nitrate-ethanolamine, silver nitrate-diethanolamine, silver nitrate-triethanolamine, silver nitrate-N-methyldiethanolamine, silver nitrate-N-ethyldiethanolamine, silver nitrate-N-propyldiethanolamine, silver nitrate-N-butyldiethanolamine, and silver nitrate-N-tert-butyldiethanolamine complex solutions.

8. The method for preparing a silver-coated copper powder with a uniform silver layer according to claim 5, characterized in that: The molar ratio of silver nitrate to alcoholamine in the silver nitrate-alcoholamine complex solution is 1:1-6.

9. The silver-coated copper powder prepared by the preparation method according to any one of claims 1 to 8, characterized in that: Silver-coated copper powder meets the following indicators: Appearance: The surface is smooth; Specific surface area: ≤ the specific surface area of ​​the initial copper powder; Acid-resistant solvent: Soak the powder in a 36% acetic acid aqueous solution for 6 hours, and the supernatant is transparent and colorless; The body resistance of low silver-containing paste made of micron-sized silver-coated copper powder is less than 9μΩ•cm.

10. Application of silver-coated copper powder in photovoltaic slurry, electronic slurry, electromagnetic shielding filler or conductive adhesive, characterized in that: The silver-coated copper powder is obtained by the preparation method according to any one of claims 1 to 8.

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