Silver-coated copper powder and preparation method thereof

Abstract

The invention discloses silver-coated copper powder and a preparation method thereof, and belongs to the technical field of metal powder preparation. The preparation method comprises the following steps that S1, a base solution containing a first reducing agent and a first complexing agent and a copper salt dispersion solution containing copper salt and a first dispersing agent are provided, the pH of the base solution is adjusted to be alkaline, then the copper salt dispersion solution is added for a reaction, and copper powder is obtained after separation and washing; s2, adding copper powder and a second dispersant into water to obtain a copper powder dispersion liquid, and providing a silver-amine complex solution containing a silver source and a second complexing agent and a second reducing agent solution; and S3, the silver-amine complex solution and the second reducing agent solution are dropwise added into the copper powder dispersion liquid for reaction, and the silver-coated copper powder is obtained after separation, washing and drying. The silver-coated copper powder prepared through the method is low in silver content, the silver layer structure is stable and compact, no scattered silver nanoparticles exist, and good conductivity and stability are achieved. Therefore, the method has a good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of metal powder preparation technology, specifically relating to a silver-coated copper powder and its preparation method. Background Technology

[0002] In recent years, the global photovoltaic industry has experienced explosive growth. However, as a core raw material for silver paste preparation, the cost pressure from its large-scale consumption is becoming increasingly prominent. Currently, the cost of silver has become one of the main bottlenecks restricting the large-scale development of the photovoltaic industry. Against this backdrop, improving the utilization rate of silver through technological innovation and effectively reducing the amount of silver consumed per unit of production capacity has become a key breakthrough for promoting cost reduction and efficiency improvement in the photovoltaic industry and enhancing its market competitiveness, which has profound strategic significance for the sustainable development of the industry.

[0003] At room temperature, copper's conductivity is second only to silver, and it offers a significant price advantage, theoretically meeting the application requirements of electronic pastes. However, copper powder suffers from significant thermal instability, readily undergoing oxidation at room temperature. Copper oxides exhibit high impedance, making it difficult to achieve the conductivity required for practical applications. By using silver-coated copper technology to deposit a nano-silver layer on the surface of copper powder, the thermal stability problem of copper powder can be solved while significantly reducing the amount of silver used, thereby substantially reducing costs while still meeting the technical requirements for paste performance.

[0004] Currently, the main method for preparing silver-coated copper powder is physical atomization of copper powder, followed by liquid-phase reduction silver plating. However, physical atomization of copper powder requires large-scale equipment, has high equipment and technical requirements, a long preparation cycle, low production efficiency, and relatively high costs. Furthermore, the very smooth surface of the copper powder, lacking active sites, affects the subsequent silver plating effect. In addition, the above process is cumbersome and requires pretreatment of the copper powder to remove the organic coating and oxide layers on the surface, as well as sensitization and activation treatment. Simultaneously, the cumbersome silver plating process leads to high production costs, and the poor coating effect of the silver layer results in a decline in the performance of the prepared silver-coated copper powder. Summary of the Invention

[0005] The purpose of this invention is to provide a silver-coated copper powder and its preparation method. This addresses the problems in existing silver-coated copper powder preparation processes, such as poor silver coating, which leads to a decrease in the performance of the prepared silver-coated copper powder.

[0006] In a first aspect, the present invention provides a method for preparing silver-coated copper powder, comprising the following steps: S1, providing a base liquid containing a first reducing agent and a first complexing agent, and a copper salt dispersion containing a copper salt and a first dispersant, adjusting the pH of the base liquid to alkaline, then adding the copper salt dispersion and reacting, and obtaining copper powder after separation and washing; S2, adding the copper powder and the second dispersant to water to obtain a copper powder dispersion, and providing a silver amine complex solution containing a silver source and a second complexing agent, and a second reducing agent solution; S3, adding the silver amine complex solution and the second reducing agent solution dropwise to the copper powder dispersion for reaction, and obtaining silver-coated copper powder after separation, washing, and drying.

[0007] In this invention, the inventors discovered that copper powder prepared by the liquid-phase reduction method exhibits uniform particle size distribution and good dispersibility. Furthermore, after being coated with a silver layer, the resulting silver-coated copper powder has a low silver content and a stable, dense silver layer structure, free of scattered silver nanoparticles and without particle agglomeration. The silver nanoparticle coating effectively inhibits copper powder oxidation, thus improving the conductivity and stability of the silver-coated copper powder. In addition, the preparation method provided by this invention is simple, uses inexpensive and readily available raw materials, and is suitable for large-scale industrial production of silver-coated copper powder.

[0008] In some embodiments, in step S1, the concentration of copper salt in the copper salt dispersion is 0.5-3.0 mol / L, and the mass ratio of copper salt to the first dispersant is 16.73:(0.5-1.5); the molar ratio of the first reducing agent to copper salt in the base liquid is (1.2-3):1, and the mass ratio of the first reducing agent to the first complexing agent is 2:(0.5-1.5); the volume ratio of the base liquid to the copper salt dispersion is (4-6):(0.5-1.5).

[0009] In some embodiments, in step S1, the first reducing agent includes at least one of ascorbic acid, sodium hypophosphite, sodium borohydride, hydrazine hydrate, and formaldehyde; and / or the first complexing agent includes sodium citrate; and / or the copper salt includes at least one of copper sulfate pentahydrate, copper nitrate, copper chloride, and copper acetate; and / or the first dispersant includes at least one of PEG, PVA, sodium pyrophosphate, sodium tripolyphosphate, sodium metaphosphate, and sodium dodecyl sulfate.

[0010] In some implementations, step S1 specifically includes reacting for 1-3 hours at a stirring rate of 200-400 rad / min and a temperature of 60-80°C.

[0011] In some embodiments, in step S2, the concentration of copper powder in the copper powder dispersion is 0.1-1.5 mol / L, and the mass ratio of copper powder to the second dispersant is 100:(2-30).

[0012] In some embodiments, in step S2, the concentration of the silver source in the silver amine complex solution is 0.1-1.5 mol / L, and the mass ratio of the silver source to the second complexing agent is 5:(4-5); the concentration of the second reducing agent solution is 0.1-1.0 mol / L.

[0013] In some embodiments, in step S2, the second dispersant includes at least one of PEG, PVA, PVP, gelatin, sodium dodecyl sulfate, and hexadecyltrimethylammonium bromide; and / or the silver source includes silver nitrate; and / or the second complexing agent includes at least one of tetraethylenepentamine, diethylenetriamine, polyethylenepolyamine, and ethylenediaminetetraacetic acid; and / or the second reducing agent includes at least one of ascorbic acid, glucose, hydrogen peroxide, hydrazine hydrate, sodium borohydride, and triethanolamine.

[0014] In some embodiments, in step S3, the volume ratio of the silver amine complex solution, the second reducing agent solution, and the copper powder dispersion is (0.8-1.2):(0.8-1.2):(1.5-2.5); the dropping rate of both the silver amine complex solution and the second reducing agent solution is 5-30 mL / min.

[0015] In some implementations, step S3 specifically includes reacting for 5-15 minutes at room temperature and a stirring rate of 300-600 rad / min.

[0016] In a second aspect, the present invention provides a silver-coated copper powder, which is prepared by any of the above-described preparation methods.

[0017] The beneficial effects of this invention are as follows: Unlike existing technologies, the copper powder prepared by this invention using a liquid-phase reduction method has a uniform particle size distribution and good dispersibility. Furthermore, after being coated with a silver layer, the resulting silver-coated copper powder has a low silver content and a stable, dense silver layer structure, with no scattered silver nanoparticles and no particle agglomeration. The silver nanoparticle coating effectively inhibits the oxidation of the copper powder, which is beneficial for improving the conductivity and stability of the silver-coated copper powder. In addition, the preparation method provided by this invention is simple, uses inexpensive and readily available raw materials, and is suitable for large-scale industrial production of silver-coated copper powder. Attached Figure Description

[0018] Figure 1 This is a flowchart of the preparation method of silver-coated copper powder in this invention; Figure 2 The above are the SEM results of the copper powder prepared in Example 1 of this invention; Figure 3 The above are the SEM results of the silver-coated copper powder prepared in Example 1 of this invention; Figure 4 The above are the SEM results of the silver-coated copper powder prepared in Comparative Example 1 of this invention. Figure 5 The image shows the SEM results of the silver-coated copper powder prepared in Comparative Example 2 of this invention. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Experimental methods not specified in the examples are generally performed under conventional conditions and as described in the manual, or as recommended by the manufacturer. Unless otherwise specified, the general equipment, materials, reagents, etc. used are commercially available.

[0021] Currently, existing silver-coated copper powder preparation processes suffer from problems such as poor silver coating effect, leading to a decline in the performance of the prepared silver-coated copper powder.

[0022] To address the problems in existing silver-coated copper powder preparation processes, such as poor silver coating effect leading to decreased performance of the prepared silver-coated copper powder, this invention provides a silver-coated copper powder and its preparation method.

[0023] In a first aspect, the present invention provides a method for preparing silver-coated copper powder, comprising the following steps: S1, providing a base liquid containing a first reducing agent and a first complexing agent, and a copper salt dispersion containing a copper salt and a first dispersant, adjusting the pH of the base liquid to alkaline, then adding the copper salt dispersion and reacting, and obtaining copper powder after separation and washing; S2, adding the copper powder and the second dispersant to water to obtain a copper powder dispersion, and providing a silver amine complex solution containing a silver source and a second complexing agent, and a second reducing agent solution; S3, adding the silver amine complex solution and the second reducing agent solution dropwise to the copper powder dispersion for reaction, and obtaining silver-coated copper powder after separation, washing, and drying.

[0024] The method for preparing silver-coated copper powder provided by this invention utilizes a liquid-phase reduction method to produce copper powder with uniform particle size distribution and good dispersibility. Furthermore, after being coated with a silver layer, the resulting silver-coated copper powder exhibits low silver content and a stable, dense silver layer structure, free of scattered silver nanoparticles and without particle agglomeration. The silver nanoparticle coating effectively inhibits copper powder oxidation, thereby improving the conductivity and stability of the silver-coated copper powder. In addition, the preparation method provided by this invention is simple, uses inexpensive and readily available raw materials, and is suitable for large-scale industrial production of silver-coated copper powder.

[0025] In some embodiments, in step S1, the concentration of copper salt in the copper salt dispersion is 0.5-3.0 mol / L, and the mass ratio of copper salt to the first dispersant is 16.73:(0.5-1.5); the molar ratio of the first reducing agent to copper salt in the base liquid is (1.2-3):1, and the mass ratio of the first reducing agent to the first complexing agent is 2:(0.5-1.5); the volume ratio of the base liquid to the copper salt dispersion is (4-6):(0.5-1.5).

[0026] In this invention, by controlling the contents of the first reducing agent, the first complexing agent, the copper salt, and the first dispersant within a specific range, the raw materials can be fully reacted to obtain copper powder with uniform particle size distribution and good dispersibility.

[0027] In some embodiments, in step S1, the first reducing agent includes at least one of ascorbic acid, sodium hypophosphite, sodium borohydride, hydrazine hydrate, and formaldehyde; and / or the first complexing agent includes sodium citrate; and / or the copper salt includes at least one of copper sulfate pentahydrate, copper nitrate, copper chloride, and copper acetate; and / or the first dispersant includes at least one of PEG, PVA, sodium pyrophosphate, sodium tripolyphosphate, sodium metaphosphate, and sodium dodecyl sulfate.

[0028] Understandably, the types of the first reducing agent, the first complexing agent, the copper salt, and the first dispersant can be selected from conventional reducing agents, complexing agents, copper salts, and dispersants in the existing technology according to actual needs, as long as they can perform reduction, complexation, dispersion, and provide a copper source.

[0029] In some implementations, step S1 specifically includes reacting for 1-3 hours at a stirring rate of 200-400 rad / min and a temperature of 60-80°C.

[0030] In this invention, by controlling the temperature, stirring rate, and time of the liquid-phase reduction reaction within a specific range, the reaction can be completed, resulting in copper powder with a more uniform particle size distribution and better dispersibility.

[0031] In some implementations, the pH of the base solution is 8-11 in step S1.

[0032] In this invention, controlling the pH of the base solution within a specific range facilitates the reaction of the raw materials.

[0033] In some implementations, step S1 includes washing until the conductivity is ≤20 μS / cm.

[0034] In this invention, washing removes impurities from the copper powder, facilitating the subsequent production of silver-coated copper powder with superior performance.

[0035] In some embodiments, in step S2, the concentration of copper powder in the copper powder dispersion is 0.1-1.5 mol / L, and the mass ratio of copper powder to the second dispersant is 100:(2-30).

[0036] In some embodiments, in step S2, the concentration of the silver source in the silver amine complex solution is 0.1-1.5 mol / L, and the mass ratio of the silver source to the second complexing agent is 5:(4-5); the concentration of the second reducing agent solution is 0.1-1.0 mol / L.

[0037] In this invention, by controlling the contents of copper powder, second dispersant, silver source, second complexing agent and second reducing agent within a specific range, the raw materials are allowed to react fully, resulting in silver-coated copper powder with low silver content and a stable and dense silver layer structure.

[0038] In some embodiments, in step S2, the second dispersant includes at least one of PEG, PVA, PVP, gelatin, sodium dodecyl sulfate, and hexadecyltrimethylammonium bromide; and / or the silver source includes silver nitrate; and / or the second complexing agent includes at least one of tetraethylenepentamine, diethylenetriamine, polyethylenepolyamine, and ethylenediaminetetraacetic acid; and / or the second reducing agent includes at least one of ascorbic acid, glucose, hydrogen peroxide, hydrazine hydrate, sodium borohydride, and triethanolamine.

[0039] Understandably, the types of the second dispersant, silver source, second complexing agent, and second reducing agent can be selected from conventional dispersants, silver sources, complexing agents, and reducing agents in the prior art according to actual usage needs, as long as they can perform dispersion, complexation, reduction, and provide a silver source.

[0040] In some embodiments, in step S3, the volume ratio of the silver amine complex solution, the second reducing agent solution, and the copper powder dispersion is (0.8-1.2):(0.8-1.2):(1.5-2.5); the dropping rate of both the silver amine complex solution and the second reducing agent solution is 5-30 mL / min.

[0041] In this invention, by controlling the dropping rate of the silver amine complex solution and the second reducing agent solution within a specific range, the raw materials can be fully reacted, thereby further improving the performance of the silver-coated copper powder.

[0042] In some implementations, step S3 specifically includes reacting for 5-15 minutes at room temperature and a stirring rate of 300-600 rad / min.

[0043] In this invention, by controlling the temperature, stirring rate, and time of the silver plating reaction within a specific range, the reaction can be completed, further yielding silver-coated copper powder with low silver content and a stable and dense silver layer structure.

[0044] In some embodiments, step S3 includes washing with deionized water and / or organic solvents until the conductivity is ≤20 μS / cm; drying includes drying at a temperature of 50-70°C for 5-7 hours.

[0045] In this invention, washing removes impurities from the silver-coated copper powder, thereby further improving its performance.

[0046] Understandably, the type of organic solvent can be selected from conventional organic solvents in the prior art according to actual usage needs, as long as it can efficiently remove impurities. For example, in this invention, ethanol is preferred as the organic solvent.

[0047] In a second aspect, the present invention provides a silver-coated copper powder, which is prepared by any of the above-described preparation methods.

[0048] The silver-coated copper powder provided by this invention has a low silver content and a stable and dense silver layer structure, with no scattered silver nanoparticles and no agglomeration between particles, and has good conductivity and stability.

[0049] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0050] Please see Figure 1 The flowchart below illustrates the preparation method of silver-coated copper powder according to the present invention. Specifically, the preparation method of silver-coated copper powder includes the following steps: S1, providing a base liquid containing a first reducing agent and a first complexing agent, and a copper salt dispersion containing a copper salt and a first dispersant, adjusting the pH of the base liquid to alkaline, then adding the copper salt dispersion and reacting, and obtaining copper powder after separation and washing; S2, adding the copper powder and the second dispersant to water to obtain a copper powder dispersion, and providing a silver amine complex solution containing a silver source and a second complexing agent, and a second reducing agent solution; S3, adding the silver amine complex solution and the second reducing agent solution dropwise to the copper powder dispersion for reaction, and obtaining silver-coated copper powder after separation, washing, and drying.

[0051] Example 1 A method for preparing silver-coated copper powder includes the following steps: S1. Weigh 400g of ascorbic acid and 200g of sodium citrate and add them to 5000mL of deionized water. Stir and dissolve to obtain the base solution. At the same time, weigh 334.6g of copper sulfate pentahydrate and 20g of PEG-600 and dissolve them in 1000mL of deionized water to obtain a copper salt dispersion. Continue to add ammonia water to the base solution to adjust the pH of the base solution to 9.0. Then slowly add the copper salt dispersion to the base solution and react at a stirring rate of 300rad / min and a temperature of 70℃ for 2h to obtain a copper powder suspension. After solid-liquid separation and washing until the conductivity is ≤20uS / cm, copper powder is obtained. S2. Add the copper powder obtained in step S1 and 2g of PEG-600 to 1000mL of deionized water to obtain a copper powder dispersion; weigh 25g of silver nitrate and dissolve it in 500mL of deionized water, then add 22g of tetraethylenepentamine until the solution becomes clear to obtain a silver amine complex solution; weigh 20g of ascorbic acid and dissolve it in 500mL of deionized water to obtain a second reducing agent solution; S3. The silver amine complex solution and the second reducing agent solution obtained in step S2 are added dropwise to the copper powder dispersion at a rate of 18 mL / min. After the addition is complete, the mixture is reacted for 10 min at room temperature and a stirring rate of 450 rad / min to obtain a silver-coated copper powder suspension. The suspension is then separated into solid and liquid components and washed with deionized water and ethanol until the conductivity is ≤20 uS / cm. Finally, the suspension is dried in a vacuum drying oven at 60℃ for 6 h to obtain silver-coated copper powder.

[0052] Example 2 A method for preparing silver-coated copper powder includes the following steps: S1. Weigh 480g of ascorbic acid and 240g of sodium citrate and add them to 5000mL of deionized water. Stir and dissolve to obtain the base solution. At the same time, weigh 334.6g of copper sulfate pentahydrate and 20g of PEG-600 and dissolve them in 1000mL of deionized water to obtain a copper salt dispersion. Continue to add ammonia water to the base solution to adjust the pH of the base solution to 9.0. Then slowly add the copper salt dispersion to the base solution and react at a stirring rate of 300rad / min and a temperature of 70℃ for 2h to obtain a copper powder suspension. After solid-liquid separation and washing until the conductivity is ≤20uS / cm, copper powder is obtained. S2. Add the copper powder obtained in step S1 and 2g of PEG-600 to 1000mL of deionized water to obtain a copper powder dispersion; weigh 32g of silver nitrate and dissolve it in 500mL of deionized water, then add 30g of tetraethylenepentamine until the solution becomes clear to obtain a silver amine complex solution; weigh 25.6g of ascorbic acid and dissolve it in 500mL of deionized water to obtain a second reducing agent solution. S3. The silver amine complex solution and the second reducing agent solution obtained in step S2 are added dropwise to the copper powder dispersion at a rate of 18 mL / min. After the addition is complete, the mixture is reacted for 10 min at room temperature and a stirring rate of 450 rad / min to obtain a silver-coated copper powder suspension. The suspension is then separated into solid and liquid components and washed with deionized water and ethanol until the conductivity is ≤20 uS / cm. Finally, the suspension is dried in a vacuum drying oven at 60℃ for 6 h to obtain silver-coated copper powder.

[0053] Comparative Example 1 The preparation method of the silver-coated copper powder in this comparative example is basically the same as that in Example 1. The difference is that in step S2, 25g of silver nitrate is directly dissolved in 500mL of deionized water without adding tetraethylenepentamine to obtain a silver nitrate solution.

[0054] Comparative Example 2 The preparation method of the silver-coated copper powder in this comparative example is basically the same as that in Example 1. The difference is that in step S2, 25g of silver nitrate is directly dissolved in 500mL of deionized water, and ammonia is added until the solution becomes clear to obtain a silver ammonia solution.

[0055] Performance testing SEM tests were performed on the copper powder and silver-coated copper powder prepared in Example 1, and the results are as follows: Figure 2-3 As shown.

[0056] from Figure 2-3 As can be seen, the prepared copper powder is spherical, well dispersed, and does not show obvious agglomeration. The particle size distribution is relatively uniform, with an average particle size of 3.5 μm. The silver-coated copper powder prepared has a relatively complete silver layer, with no obvious scattered silver particles or flakes, and the particle size distribution is similar to that of the copper powder.

[0057] Furthermore, SEM analysis was performed on the silver-coated copper powders prepared in Comparative Examples 1 and 2, and the results are as follows: Figure 4-5 As shown.

[0058] from Figure 4-5 As can be seen from the results, the silver coating effect of the silver-coated copper powder prepared in the comparative examples is not good. In comparative example 1, there are free silver nanoparticles and a lot of silver flocs growing on the surface of the copper powder. In comparative example 2, the surface of the silver layer is very rough and there are many protrusions formed by the proliferation of silver nanoparticles.

[0059] Furthermore, the performance of the silver-coated copper powders prepared in Examples 1-3 and Comparative Examples 1-2 was tested, and the results are shown in Table 1 below.

[0060] Table 1 Performance Test Results

[0061] As can be seen from Table 1, the silver-coated copper powder prepared in Examples 1-2 has a high silver content and a high tap density. In Comparative Examples 1-2, silver nitrate solution or silver ammonia solution was used for coating, and the results showed that the silver content and tap density were reduced to a certain extent. The results indicate that the silver coating effect of the silver-coated copper powder prepared in the comparative examples is not good.

[0062] In summary, the copper powder prepared by the liquid-phase reduction method has a uniform particle size distribution and good dispersibility. After being coated with a silver layer, the silver content in the prepared silver-coated copper powder is low and the silver layer structure is stable and dense, with no scattered silver nanoparticles and no agglomeration between particles. The coating of the nano-silver layer can effectively inhibit the oxidation of copper powder, which is beneficial to improving the conductivity and stability of the silver-coated copper powder.

[0063] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0064] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing silver-coated copper powder, characterized in that, Includes the following steps: S1. Provide a base solution containing a first reducing agent and a first complexing agent, and a copper salt dispersion containing a copper salt and a first dispersant. Adjust the pH of the base solution to alkaline, then add the copper salt dispersion and react. After separation and washing, copper powder is obtained. S2. Add the copper powder and the second dispersant to water to obtain a copper powder dispersion, and provide a silver amine complex solution containing a silver source and a second complexing agent, and a second reducing agent solution. S3. The silver amine complex solution and the second reducing agent solution are added dropwise to the copper powder dispersion to react. After separation, washing and drying, silver-coated copper powder is obtained.

2. The method for preparing silver-coated copper powder according to claim 1, characterized in that, In step S1, the concentration of copper salt in the copper salt dispersion is 0.5-3.0 mol / L, and the mass ratio of copper salt to the first dispersant is 16.73:(0.5-1.5); the molar ratio of the first reducing agent to the copper salt in the base liquid is (1.2-3):1, and the mass ratio of the first reducing agent to the first complexing agent is 2:(0.5-1.5); the volume ratio of the base liquid to the copper salt dispersion is (4-6):(0.5-1.5).

3. The method for preparing silver-coated copper powder according to claim 1, characterized in that, In step S1, the first reducing agent includes at least one of ascorbic acid, sodium hypophosphite, sodium borohydride, hydrazine hydrate, and formaldehyde; and / or the first complexing agent includes sodium citrate; and / or the copper salt includes at least one of copper sulfate pentahydrate, copper nitrate, copper chloride, and copper acetate; and / or the first dispersant includes at least one of PEG, PVA, sodium pyrophosphate, sodium tripolyphosphate, sodium metaphosphate, and sodium dodecyl sulfate.

4. The method for preparing silver-coated copper powder according to claim 1, characterized in that, In step S1, the reaction specifically includes: reacting for 1-3 hours at a stirring rate of 200-400 rad / min and a temperature of 60-80℃.

5. The method for preparing silver-coated copper powder according to claim 1, characterized in that, In step S2, the concentration of copper powder in the copper powder dispersion is 0.1-1.5 mol / L, and the mass ratio of copper powder to the second dispersant is 100:(2-30).

6. The method for preparing silver-coated copper powder according to claim 1, characterized in that, In step S2, the concentration of the silver source in the silver amine complex solution is 0.1-1.5 mol / L, and the mass ratio of the silver source to the second complexing agent is 5:(4-5). The concentration of the second reducing agent solution is 0.1-1.0 mol / L.

7. The method for preparing silver-coated copper powder according to claim 1, characterized in that, In step S2, the second dispersant includes at least one of PEG, PVA, PVP, gelatin, sodium dodecyl sulfate, and hexadecyltrimethylammonium bromide; and / or the silver source includes silver nitrate; and / or the second complexing agent includes at least one of tetraethylenepentamine, diethylenetriamine, polyethylenepolyamine, and ethylenediaminetetraacetic acid; and / or the second reducing agent includes at least one of ascorbic acid, glucose, hydrogen peroxide, hydrazine hydrate, sodium borohydride, and triethanolamine.

8. The method for preparing silver-coated copper powder according to claim 1, characterized in that, In step S3, the volume ratio of the silver amine complex solution, the second reducing agent solution, and the copper powder dispersion is (0.8-1.2):(0.8-1.2):(1.5-2.5). The dropping rates of both the silver amine complex solution and the second reducing agent solution are 5-30 mL / min.

9. The method for preparing silver-coated copper powder according to claim 1, characterized in that, In step S3, the reaction specifically includes: reacting for 5-15 minutes at room temperature and a stirring rate of 300-600 rad / min.

10. A silver-coated copper powder, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.

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