Silver-coated copper powder with uniform silver layer, preparation method and application thereof

Abstract

The invention discloses silver-coated copper powder with a uniform silver layer, a preparation method thereof, and an application thereof, and relates to the technical field of conductive materials and metal powder preparation. The invention comprises the following steps: using an acidic or alkaline solvent to remove organic matter and an oxide layer on the surface of the copper powder; then adding a small amount of an alcoholamine reagent and stirring evenly to serve as a copper powder interface reduction protective agent; then adding a reagent selected from silver nitrate, silver ammonia, and a silver nitrate-alcoholamine complex solution as a seed layer silver plating solution; finally, adding the alcoholamine reagent and an alkaline silver source oxidant in sequence to continue the silver plating reaction; drying and screening to obtain silver-coated copper powder with a uniform silver layer. The method can improve the silver layer coating stability of the silver-coated copper powder in the prior art, make the silver layer coating surface smoother and the coating more complete, reduce the phenomenon of copper core exposure, and have a lower bulk resistivity.

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 a uniform silver layer, 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, especially silver powder, silver-coated copper powder, and copper powder. As a conductive powder with a core-shell structure, silver-coated copper powder has a conductivity that is almost the same as that of pure silver powder in some application scenarios. However, 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; while 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 has been an increasing amount of research on the preparation and application of silver-coated copper powder.

[0003] Common preparation methods for silver-coated copper powder include physical and chemical methods, with chemical methods encompassing both replacement and reduction methods. Currently, a major challenge in the research of micro-nano silver-coated copper powders lies in how to densely coat the silver layer onto the copper core, maintaining a tight bond at the silver-copper interface while simultaneously minimizing copper exposure, ensuring uniform silver coating, and reducing surface silver defects at low silver concentrations to achieve high conductivity and stability. Currently, researchers employ various methods to improve the integrity of the silver 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 employed, such as the technical solution disclosed in the invention patent application with publication number CN117399617A. However, all of the above technical solutions involve the problem of slow oxidation of the copper powder interface during the surface treatment and silver plating process. If the treatment is not done properly, this can result in uneven silver coating and a loose connection between the silver layer and the copper core, affecting the electrical properties and stability of the powder, and placing very high demands on operator operation. Summary of the Invention

[0004] The present invention aims to provide a novel method for preparing silver-coated copper powder with a uniform silver layer, which can improve the silver coating stability of the silver-coated copper powder in the prior art. By using an alcoholamine reagent, which is a surface treatment reagent and a reducing agent, the silver coating surface is made smoother and the coating is more complete, the phenomenon of copper core exposure is reduced, and at the same time, the obtained silver-coated copper powder has excellent electrical conductivity.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for preparing silver-coated copper powder with a uniform silver layer, comprising the steps of copper powder surface treatment, seed layer silver plating, reduction silver plating and powder post-treatment.

[0007] 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℃.

[0008] 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;

[0009] 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.

[0010] Furthermore, in the reduction silver plating step, the molar amount of the alcoholamine reagent added is 0.1 to 10 times the molar amount of the alkaline silver source.

[0011] 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.

[0012] Furthermore, in the reduction silver plating step, the reaction temperature is controlled to be 15~60°C.

[0013] 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 the added silver is 1-5% of the mass of the copper powder, and the reaction temperature is 15-60°C.

[0014] 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 dodecylsulfonate and sodium dodecylbenzenesulfonate.

[0015] 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.

[0016] Furthermore, the molar ratio of silver nitrate to alcoholamine in the silver nitrate-alcoholamine complex solution is 1:1-6.

[0017] The silver-coated copper powder prepared by the preparation method described in any one of the above items meets the following indicators:

[0018] Appearance: smooth surface;

[0019] Specific surface area: ≤ the specific surface area of ​​the initial copper powder;

[0020] Acid-resistant solvent: Soak the powder in a 36% acetic acid aqueous solution for 6 hours. The supernatant is transparent and colorless.

[0021] The low silver content paste made of micron-sized silver-coated copper powder has a body resistance of less than 9μΩ•cm.

[0022] The silver-coated copper powder is used in photovoltaic slurry, electronic slurry, electromagnetic shielding filler or conductive adhesive. The silver-coated copper powder is obtained by the above-mentioned preparation method.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] First, in the present invention, considering that when preparing micro-nano-scale silver-coated copper powder, the copper powder may slowly oxidize after the surface treatment step, resulting in uneven silver coating on the powder surface, insufficient silver-copper interface bonding, and increased silver layer defects on the powder surface, the present invention adds an alcoholamine reagent as a protective molecule for the copper powder during the copper powder surface activation step. Furthermore, an alcoholamine reagent is added during the silver plating reduction process as a reducing agent to participate in the reaction with an alkaline silver source to control the silver coating.

[0025] 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 used as an interface protective agent to be adsorbed to the newly added silver-copper interface layer, 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.

[0026] 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. This is because the alcoholamine itself can be adsorbed to the copper core interface, and the new carboxyl groups formed after reduction are 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.

[0027] Fourth, in the present invention, there is another scheme using silver nitrate-alcoholamine complex solution as the silver source oxidant to chelate and slowly release silver ions to participate in the reaction, thereby reducing the chemical components in the synthesis.

[0028] 5. In the present invention, the silver-coated copper powder obtained by this scheme has a smooth surface under electron microscope, a specific surface area less than or equal to that of the initial copper powder, is resistant to acidic solvents, and has a low silver content slurry body resistance of less than 9μΩ·cm. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a SEM image of the silver-coated copper powder prepared in Example 1.

[0030] Figure 2 This is the SEM image of the silver-coated copper powder prepared in Example 2.

[0031] Figure 3 This is the SEM image of the silver-coated copper powder prepared in Comparative Example 1.

[0032] Figure 4 This is the SEM image of the silver-coated copper powder prepared in Comparative Example 2. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below with reference to the 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 examples of the present disclosure should be understood by those with ordinary skills in the field to which the present disclosure belongs.

[0034] In the present invention, the alcoholamine 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 examples, ethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, and triethanolamine hydrochloride are used as examples to illustrate this solution. The reagents involved are all commercially available reagents.

[0035] In the present invention, the copper complexing agent includes one or more of ethylenediaminetetraacetic acid, diethylenetriamine, triethylenetetramine, tetraethylenepentamine and sodium salts thereof. In the following embodiments, ethylenediaminetetraacetic acid is used as an example to illustrate this scheme, and the reagents involved are all commercially available reagents.

[0036] 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 used as an example to illustrate this solution, and the reagents involved are all commercially available reagents.

[0037] 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 used as an example to illustrate this solution, and the reagents involved are all commercially available reagents.

[0038] In the present invention, the copper powder has various morphologies and sizes, including spherical, dendritic, and flake-like shapes, with a preferred particle size of 0.5 to 10 μm. In the following examples, spherical copper powder of approximately 3.0 μm is used for illustration, and flake, dendritic, and other sized copper powders are not further discussed.

[0039] Example 1

[0040] A method for preparing silver-coated copper powder with a uniform silver layer, relating to the technical field of conductive materials and nanomaterials, comprises the following steps:

[0041] 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 to remove organic matter and oxide layer on the surface of the copper powder, and pour off 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.

[0042] S2. Silver plating of seed layer: Prepare 100g of 3% silver ammonia solution and keep it at 30°C. Pour 20g of EDTA powder into the copper powder suspension and stir for 5 minutes. Then, add the silver ammonia solution to the copper powder suspension at a rate of 100mL / min.

[0043] 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.

[0044] 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 powder electron microscopy morphology, specific surface area, and acid resistance are tested. The electron microscopy image of the silver-coated copper powder obtained in this example is shown in FIG. Figure 1 .

[0045] Example 2

[0046] 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 off; 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.

[0047] S2. Silver plating of seed layer: Prepare 100g of 3% silver nitrate solution and keep it at 45°C. Pour 20g of ethylenediaminetetraacetic acid powder and 5g of polyvinylpyrrolidone into the copper powder suspension and stir for 5 minutes. Then, add silver nitrate to the copper powder suspension at a rate of 100mL / min.

[0048] 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.

[0049] 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 powder electron microscopy morphology, specific surface area, and acid resistance are tested. The electron microscopy image of the silver-coated copper powder obtained in this example is shown in FIG. Figure 2 .

[0050] Example 3

[0051] 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.

[0052] S2. Silver plating of seed layer: Prepare 100g of 3% silver nitrate solution and keep it at 60°C. Pour 20g of EDTA powder into the copper powder suspension and stir for 5 minutes. Then, add silver nitrate to the copper powder suspension at a rate of 100mL / min.

[0053] 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.

[0054] S4. Powder Post-Processing: Filter the reduced silver-plated material, dry the solid phase in a vacuum oven at 80°C, pulverize, and sieve through 200 mesh to obtain silver-coated copper powder. Test the powder's electron microscopy morphology, specific surface area, and acid resistance.

[0055] Example 4

[0056] 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 at 30°C for 20 min, and the supernatant was poured off. 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.

[0057] S2. Silver plating of seed layer: 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 to the copper powder suspension at a rate of 80mL / min.

[0058] S3. Reduction silver plating: add 28 g of ethanolamine and stir for 5 min; then add the remaining silver nitrate-ethanolamine solution from step S2 at 100 mL / min.

[0059] S4. Powder Post-Processing: Filter the reduced silver-plated material, dry the solid phase in a vacuum oven at 80°C, pulverize, and sieve through 200 mesh to obtain silver-coated copper powder. Test the powder's electron microscopy morphology, specific surface area, and acid resistance.

[0060] Example 5

[0061] 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. 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.

[0062] S2. Silver plating of seed layer: 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 5 minutes. Then, add the silver ammonia solution to the copper powder suspension at a rate of 100mL / min.

[0063] 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.

[0064] S4. Powder Post-Processing: Filter the reduced silver-plated material, dry the solid phase in a vacuum oven at 80°C, pulverize, and sieve through 200 mesh to obtain silver-coated copper powder. Test the powder's electron microscopy morphology, specific surface area, and acid resistance.

[0065] Example 6

[0066] 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. 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.

[0067] S2. Silver plating of seed layer: 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 10 minutes. Then, add the silver ammonia solution to the copper powder suspension at a rate of 100mL / min.

[0068] 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.

[0069] S4. Powder Post-Processing: Filter the reduced silver-plated material, dry the solid phase in a vacuum oven at 80°C, pulverize, and sieve through 200 mesh to obtain silver-coated copper powder. Test the powder's electron microscopy morphology, specific surface area, and acid resistance.

[0070] Example 7

[0071] 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 and treat at 45°C for 20 min to remove organic matter and oxide layer on the surface of the copper powder. Pour off 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.

[0072] S2. Silver plating of seed layer: Prepare 100g of 3% silver ammonia solution and keep it at 45°C. Pour 20g of EDTA powder into the copper powder suspension and stir for 5 minutes. Then, add the silver ammonia solution to the copper powder suspension at a rate of 100mL / min.

[0073] 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.

[0074] S4. Powder Post-Processing: Filter the reduced silver-plated material, dry the solid phase in a vacuum oven at 80°C, pulverize, and sieve through 200 mesh to obtain silver-coated copper powder. Test the powder's electron microscopy morphology, specific surface area, and acid resistance.

[0075] Comparative Example 1

[0076] 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.

[0077] S2. Silver plating of seed layer: Prepare 100g of 3% silver ammonia solution and keep it at 30°C. Pour 20g of EDTA powder into the copper powder suspension and stir for 5 minutes. Then, add the silver ammonia solution to the copper powder suspension at a rate of 100mL / min.

[0078] 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.

[0079] S4, powder post-processing: 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 .

[0080] Comparative Example 2

[0081] 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.

[0082] S2. Silver plating of seed layer: Prepare 100g of 3% silver ammonia solution and keep it at 30°C. Pour 20g of EDTA powder into the copper powder suspension and stir for 5 minutes. Then, add silver nitrate to the copper powder suspension at a rate of 100mL / min.

[0083] 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.

[0084] S4, powder post-processing: 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 .

[0085] Product performance testing

[0086] The present invention uses scanning electron microscopy (SEM) images to observe the surface roughness of the powder and the presence of defects such as microscopic holes. A specific surface area test is used to observe whether the copper powder increases in specific surface area after being coated with a layer of silver, and to macroscopically assess the roughness and holes. The powder is immersed in a 36% acetic acid aqueous solution for 6 hours, and the color of the upper acetic acid solution is examined. If it is colorless, the silver coating is good; if it is blue, it indicates the presence of microscopic copper exposure. The test results of these experiments are as follows:

[0087] Table 1

[0088]

[0089] As shown in Table 1, the silver-coated copper powders obtained by the preparation method disclosed herein (treated silver-coated copper powders from Examples 1-7) exhibit smoother SEM surfaces and smaller specific surface areas than the initial copper powder and the treated silver-coated copper powders from Comparative Examples 1 and 2. This indicates that the treated silver-coated copper powders are significantly smoother and exhibit better silver coating. Furthermore, after soaking each powder group in acetic acid for 6 hours, the upper acetic acid solution remained colorless, further demonstrating that the powders from Examples 1-7 exhibit better silver coating.

[0090] If, during the preparation process, no alcohol amine reagent is added as a "reduction protective agent" to activate the copper powder surface, the powder SEM surface may also be relatively smooth overall (with local silver bumps), but the acid reagent resistance is poor, as shown in Comparative Example 2.

[0091] To further evaluate the electrical properties of silver-coated copper powder, the powders in each of the above groups were mixed with a silver-copper slurry containing 20% ​​silver. The slurry included epoxy resin, phthalic anhydride, diethylene glycol butyl ether acetate, a small amount of fine pure silver powder, and a solid content of 90-93%. The slurry was then dried and cured at 200°C and the bulk resistance of each group was tested. The results are shown in Table 2.

[0092] Table 2

[0093]

[0094] As can be seen from Table 2, under the condition of 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 volume resistance, which is less than 7 μΩ·cm, and has a lower resistivity (less than 9 μΩ·cm), which is also lower than the volume resistivity of Comparative Examples 1 and 2.

[0095] 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 scope of protection of the present invention.

Claims

1. A method for preparing silver-coated copper powder with a uniform silver layer, characterized in that: Including copper powder surface treatment, seed layer silver plating, reduction silver plating and powder post-processing steps, 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℃. In the seed layer silver plating step, the mass of silver added is 1-5% of the mass of the copper powder, and the reaction temperature is 15-60°C; Reduction silver plating is to control the reaction temperature to 15~60℃ after the silver plating reaction of the seed layer is completed, and then add alcohol amine reagents and alkaline silver source oxidants in sequence. The added mass of silver is 3~30% of the mass of the copper powder. 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 having a uniform silver layer according to claim 1, wherein: 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 having a uniform silver layer according to claim 1, wherein: The alkaline silver source oxidant includes one or more of silver ammonia and silver nitrate-alcoholamine complex solution.

4. The method for preparing a silver-coated copper powder having a uniform silver layer according to claim 1, wherein: 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.

5. The method for preparing a silver-coated copper powder having a uniform silver layer according to claim 4, wherein: 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 dodecylsulfonate and sodium dodecylbenzenesulfonate.

6. The method for preparing a silver-coated copper powder having a uniform silver layer according to claim 3 or 4, wherein: 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.

7. The method for preparing a silver-coated copper powder having a uniform silver layer according to claim 4, wherein: The molar ratio of silver nitrate to alcoholamine in the silver nitrate-alcoholamine complex solution is 1:1-6.

8. The silver-coated copper powder prepared by the preparation method according to any one of claims 1 to 7, characterized in that: Silver-coated copper powder meets the following indicators: Appearance: smooth surface; 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. The supernatant is transparent and colorless. The low silver content paste made of micron-sized silver-coated copper powder has a body resistance of less than 9μΩ•cm.

9. Application of silver-coated copper powder in photovoltaic slurry, electronic slurry, electromagnetic shielding filler or conductive adhesive, characterized by: The silver-coated copper powder is obtained by the preparation method according to any one of claims 1 to 7.

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