Preparation and surface modification method of silver-coated copper powder

Abstract

The invention belongs to the technical field of metal powder materials, and particularly relates to a preparation and surface modification method of silver-coated copper powder. Comprising the following steps that copper powder activated through a mixed acid solution and a dispersing agent are dissolved in ethyl alcohol, and copper powder turbid liquid is obtained; dropwise adding the silver complexing solution into the copper powder turbid liquid under the condition of water bath heating for reaction to obtain silver-coated copper powder turbid liquid; then, a reducing agent solution is dropwise added into the silver-coated copper powder turbid liquid, silver ions in the solution are further reduced, solid-liquid separation, washing and drying are conducted, and primary silver-coated copper powder is obtained; and finally, the silver-coated copper powder is subjected to surface modification, and the dispersity of the silver-coated copper powder is improved. The preparation method of the silver-coated copper powder provided by the invention is simple in process, and in the chemical oxidation reduction process, the prepared silver-coated copper powder is compact in silver coating, complete in coating, low in resistivity and good in oxidation resistance by regulating and controlling the concentration of silver ions and the complexing agent, the reaction temperature, the type of the dispersing agent, the dripping rate and the type of the surface modifier.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal powder materials, and particularly relates to a preparation and surface modification method of silver-coated copper powder. Background Art

[0002] With the accelerating transformation of the global energy structure towards cleaner energy, photovoltaic power generation, as the core technology of renewable energy, its industrialization process is severely restricted by the scarcity and price volatility of precious metal silver (Ag). The silver price has continued to operate at a high level in 2025 (the peak exceeded 32 US dollars per ounce), resulting in the fact that conductive silver paste accounts for as high as 35%-50% of the non-silicon cost of photovoltaic cells, becoming the core bottleneck restricting the large-scale development of the industry. In this context, silver-coated copper conductive paste, with the advantages of replacing the silver core with a copper core and high conductivity, has become a breakthrough technical path.

[0003] Silver-coated copper powder has both the high conductivity and oxidation resistance of silver and the low cost advantage of copper by coating a silver layer on the surface of copper powder. However, the existing technologies have the following problems: First, coating layer defects: The traditional chemical replacement method easily leads to a loose silver layer, high porosity, and easy oxidation of the copper core; Second, weak interfacial bonding: The bonding strength of the silver-copper interface is low, and the silver layer is prone to peeling off after multiple processing (such as rolling slurry); Third, poor dispersibility: The powder is prone to agglomeration, affecting the printing uniformity of the slurry; Fourth, complex process: Multiple silver plating, high-temperature treatment or expensive equipment are required, making it difficult to produce on a large scale.

[0004] In response to the industry pain points of current low-temperature conductive silver-coated copper slurry, the existing technologies have tried to improve the performance by step-by-step silver plating, adding dispersants or surface modification, but there are still bottlenecks such as high cost and cumbersome process. Providing a preparation method for silver-coated copper powder with low cost and high performance has become one of the problems that urgently need to be solved in this field. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technologies, the present invention provides a preparation method of silver-coated copper powder through an innovative surface modification process and step-by-step reaction design. The silver-coated copper powder after surface treatment has a dense silver coating, good dispersibility, low resistivity, and excellent oxidation resistance, which can significantly improve the comprehensive performance of the silver-coated copper powder.

[0006] To achieve the purpose of this invention, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a preparation method of silver-coated copper powder with good coating rate. The preparation method includes the following steps:

[0008] (1) Pretreatment of copper powder

[0009] Mix the copper powder with the mixed acid solution, then perform ultrasonic stirring treatment and centrifugal separation to remove surface oxides and organic pollutants. Repeat the above steps three times, and wash with deionized water three times until the filtrate is neutral (pH = 7), and perform centrifugal separation after each treatment.

[0010] Dissolve the copper powder surface-activated by the mixed acid solution and the dispersant solution in water to obtain a copper powder suspension.

[0011] (2) Prepare silver-coated copper powder by liquid-phase chemical deposition reaction

[0012] Under the condition of water bath heating, dropwise add the silver complex solution to the copper powder suspension for reaction to obtain a silver-coated copper powder suspension. After continuously reacting for 20 min, dropwise add the reducing agent solution to the silver-coated copper powder suspension to further reduce the unreacted silver ions in the solution, and continuously react for 30 min to obtain a completely reacted silver-coated copper powder suspension. After the completely reacted silver-coated copper powder suspension undergoes sedimentation and solid-liquid separation, wash the separated solid with ethanol and dry it to obtain silver-coated copper powder.

[0013] (3) Surface modification treatment of silver-coated copper powder

[0014] Mix the dried silver-coated copper powder with the surface modifier, perform ultrasonic treatment for 40 min, then perform solid-liquid separation, washing, and drying to obtain surface-modified silver-coated copper powder, which increases the dispersibility of the silver-coated copper powder.

[0015] Preferably, in step (1), the mixed acid solution includes multiple of HCl solution, HNO3 solution, H2SO4 solution, and H2O2 solution, the pH of the mixed acid solution is 1.5 - 2.5, and the solid-liquid ratio of the copper powder to the mixed acid solution is 1:30 - 1:50.

[0016] Preferably, the ultrasonic stirring treatment in step (1) is carried out for 20 - 40 minutes under an ultrasonic field intensity of 30 kHz - 40 kHz.

[0017] Preferably, the concentration of the dispersant solution in step (1) is 0.1 mol / L - 0.5 mol / L, and the mass of the dispersant is 0.1 - 0.3 times the mass of the copper powder. The dispersant includes one or more of polyvinylpyrrolidone, ethanol, Triton, sodium dodecyl sulfate, and OP-10, and the solid-liquid ratio of the copper powder dispersion suspension is 1:80 - 1:120.

[0018] Preferably, the temperature of the water bath heating in step (2) is 40 - 60 °C.

[0019] Preferably, the dropping rate in step (2) is 10 - 15 mL / min.

[0020] Preferably, the silver complex solution in step (2) includes a mixed solution of a silver source solution and a complexing agent. The silver source solution is an AgNO3 solution with a concentration of 0.01 mol / L to 0.06 mol / L; the complexing agent is one or more of ethylenediaminetetraacetic acid, tartaric acid, and citric acid; the mass ratio of the complexing agent to the silver powder is (0.5 to 1.5):1, and the solid-liquid ratio of the silver-coated copper powder suspension is 1:200 to 1:500.

[0021] Preferably, the reducing agent in step (2) is one or more of ascorbic acid, glucose, ferrous sulfate, and hydrazine hydrate. The concentration of the reducing agent solution is 0.1 mol / L to 0.5 mol / L, and the solid-liquid ratio of the fully reacted silver-coated copper powder suspension is 1:200 to 1:500.

[0022] Preferably, the surface modifier in step (3) is at least one of oleic acid, sodium oleate, oleic acid amide, polyethylene glycol, oxalic acid, and stearic acid. The mass of the surfactant is 1% to 20% of the theoretical mass of the generated silver-coated copper powder.

[0023] In a second aspect, the present invention provides a surface-modified silver-coated copper powder prepared by using the preparation method provided in the first aspect.

[0024] The numerical ranges described in the present invention not only include the specific point values listed above, but also any point values between the above numerical ranges not listed. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the ranges.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) Through the synergistic effect of the optimized mixed acid activation system and the chemical deposition process, the present invention significantly improves the denseness and uniformity of the silver coating. The multi-stage surface treatment process effectively removes impurities on the surface of the copper powder and forms an active substrate. Combined with the complexation deposition reaction with temperature control, the layered growth of silver atoms on the surface of the copper substrate is realized. The obtained silver-coated copper powder has a complete and continuous silver layer coating structure, significantly enhancing the antioxidant stability while maintaining a low resistivity.

[0027] (2) The present invention innovatively combines a composite surface modifier with an ultrasonic dispersion process, successfully solving the agglomeration problem of silver-coated copper powder. Through the self-assembled coating of the surface modifier on the powder surface, not only the dispersion stability of the powder in different media is enhanced, but also an effective antioxidant barrier is constructed. The modified silver-coated copper powder exhibits excellent processing adaptability and long-term storage stability in the application of conductive pastes, expanding its application potential in the field of photovoltaic cells. Description of the Drawings

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments.

[0029] Figure 1 SEM diagram of the activated spherical copper powder of Example 1;

[0030] Figure 2 XRD diagram of the silver-coated copper powder of Example 1;

[0031] Figure 3 SEM diagram of the silver-coated copper powder of Example 1;

[0032] Figure 4 SEM diagram of the silver-coated copper powder of Example 2;

[0033] Figure 5 SEM diagram of the silver-coated copper powder of Comparative Example 2;

[0034] Figure 6 SEM diagram of the silver-coated copper powder of Comparative Example 3. Specific Embodiments

[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, the following further illustrates the present application with reference to embodiments. The embodiments are only for illustrative purposes, and equivalent adjustments or substitutions made by those skilled in the art based on the core idea of the present invention are within the scope of protection.

[0036] Those skilled in the art should understand that the sequence numbers of the steps described in the embodiments do not limit the execution order, and each step can be adjusted according to actual needs;

[0037] The terms (such as "comprising" and "including") used in the embodiments of the present invention should be interpreted in a broad sense, and the singular form includes the plural meaning;

[0038] Those skilled in the art should understand that the numerical ranges in the embodiments of the present invention should be regarded as disclosing all intermediate values and sub-intervals between their upper and lower limits, and the intervals can independently include or exclude the endpoints;

[0039] Unless otherwise specified, the technical terms used herein are interpreted according to the conventional interpretation in the art. When the cited literature conflicts with the present application, the content of the present application takes precedence;

[0040] It should be noted that the raw materials and reagents used in the embodiments are all commercially available products or prepared by conventional methods in the art.

[0041] The following will further elaborate on the technical methods of the present invention with reference to specific embodiments.

[0042] This embodiment provides a method for preparing silver-coated copper powder, including the following steps:

[0043] Example 1

[0044] A preparation and surface modification method of silver-coated copper powder, comprising the following steps:

[0045] (1) Pretreatment of copper powder

[0046] Take 0.5 g of spherical copper powder with a particle size of 1 - 3 μm, and mix it with a mixed acid solution (H2SO4:H2O2 = 4:1 vol%) with pH = 1.0 at a solid-liquid ratio of 1:40; treat it in a 35 kHz ultrasonic field for 30 min, wash it with deionized water to neutral after centrifugal separation, repeat pickling three times, and then dry it at 75 °C to obtain activated copper powder. Mix the activated copper powder with 60 ml of 0.4 mol / L Triton dispersant solution (the dosage is 0.25 times the mass of the copper powder) to form a copper suspension with a solid-liquid ratio of 1:120.

[0047] (2) Preparation of silver-coated copper powder by liquid-phase chemical deposition reaction

[0048] Place the copper suspension prepared in step (1) in a 55 °C water bath, and dropwise add an AgNO3-ethylenediaminetetraacetic acid complex solution (AgNO3 concentration 0.05 mol / L, the mass ratio of complexing agent to silver is 0.75:1) at a rate of 10 mL / min; after reacting for 20 min, dropwise add 60 ml of 0.4 mol / L ascorbic acid solution, and continue to react for 30 min; after sedimentation, take the precipitate, wash it three times with ethanol, and then dry it in a 60 °C vacuum to obtain silver-coated copper powder.

[0049] (3) Surface modification treatment of silver-coated copper powder

[0050] Mix the dried silver-coated copper powder with an oleic acid-polyethylene glycol composite modifier (the dosage is 8% of the powder mass); after ultrasonic treatment for 40 min, centrifuge it, wash it twice with ethanol, and dry it at 70 °C to obtain the finished product of surface-modified silver-coated copper powder.

[0051] Example 2

[0052] A preparation and surface modification method of silver-coated copper powder, comprising the following steps:

[0053] (1) Pretreatment of copper powder

[0054] Take 1 g of spherical copper powder with a particle size of 1 - 3 μm, and mix it with a mixed acid solution (HCl:HNO3:H2O2 = 3:1:0.5 vol%) with pH = 1.8 at a solid-liquid ratio of 1:30; treat it in a 40 kHz ultrasonic field for 25 min, repeat pickling three times after centrifugal separation; wash it with deionized water to neutral, and mix it with 80 ml of 0.2 mol / L polyvinylpyrrolidone solution (the dosage is 0.15 times the mass of the copper powder) to form a copper suspension with a solid-liquid ratio of 1:80.

[0055] (2) Preparation of silver-coated copper powder by liquid-phase chemical deposition reaction

[0056] Place the copper suspension in a 55 °C water bath and add 120 ml of AgNO3-EDTA-2Na complex solution (AgNO3 concentration 0.04 mol / L, mass ratio of complexing agent to silver 0.8:1) at a rate of 10 mL / min; after reacting for 20 min, add 50 ml of 0.4 mol / L glucose solution and continue reacting for 30 min; after sedimentation, take the precipitate, wash it three times with ethanol, and then place it in a 60 °C vacuum dryer to obtain silver-coated copper powder.

[0057] (3) Surface modification of silver-coated copper powder

[0058] Mix the dried silver-coated copper powder with a stearic acid modifier (dosage 8% of the powder mass); after ultrasonic treatment for 40 min, centrifuge, wash it twice with ethanol, and dry it at 70 °C to obtain the surface-modified silver-coated copper powder product.

[0059] Example 3

[0060] A method for preparing and surface-modifying silver-coated copper powder, comprising the following steps:

[0061] (1) Pretreatment of copper powder

[0062] Take 0.8 g of spherical copper powder with a particle size of 1-3 μm and mix it with a mixed acid solution (HNO3:H2O2 = 2:1 vol%) with a pH of 2.2 at a solid-liquid ratio of 1:50; treat it in a 30 kHz ultrasonic field for 40 min, centrifuge and separate, and repeat pickling three times; wash it with deionized water until neutral, and mix it with 96 ml of 0.2 mol / L Triton dispersant solution (dosage 0.15 times the mass of the copper powder) to form a copper suspension with a solid-liquid ratio of 1:120.

[0063] (2) Preparation of silver-coated copper powder by liquid-phase chemical deposition reaction

[0064] Place the copper suspension in a 60 °C water bath and add 192 ml of AgNO3-tartaric acid complex solution (AgNO3 concentration 0.06 mol / L, mass ratio of complexing agent to silver 1.2:1) at a rate of 12 mL / min; after reacting for 20 min, add 96 ml of 0.5 mol / L hydrazine hydrate solution and continue reacting for 30 min; after sedimentation, take the precipitate, wash it three times with ethanol, and then place it in a 60 °C vacuum dryer to obtain silver-coated copper powder.

[0065] (3) Surface modification of silver-coated copper powder

[0066] Mix the dried silver-coated copper powder with an oxalic acid-succinic acid composite modifier (mass ratio 1:1, dosage 12% of the powder mass); after ultrasonic treatment for 40 min, centrifuge, wash it twice with ethanol, and dry it at 70 °C to obtain the surface-modified silver-coated copper powder product.

[0067] Comparative Example 1

[0068] Comparative Example 1 provides a method for preparing and surface modifying a silver-coated copper powder. The difference from Example 1 is that Comparative Example 1 does not include the pretreatment of the copper powder as follows:

[0069] A method for preparing silver-coated copper powder comprises the following steps:

[0070] (1) No pretreatment of copper powder

[0071] Take 0.5g of spherical copper powder with a particle size of 1-3μm, and do not mix it with the mixed acid solution. Mix the copper powder with 60ml of 0.4mol / L Triton dispersant solution (the amount used is 0.25 times the mass of the copper powder) to form a copper suspension with a solid-liquid ratio of 1:120.

[0072] (2) Preparation of silver-coated copper powder by liquid phase chemical deposition reaction

[0073] The copper suspension prepared in step (1) is placed in a 55°C water bath, and a AgNO3-ethylenediaminetetraacetic acid complex solution (AgNO3 concentration 0.05 mol / L, complexing agent to silver mass ratio 0.75:1) is added dropwise at a rate of 10 mL / min; after reacting for 20 min, 60 ml of 0.4 mol / L ascorbic acid solution is added dropwise, and the reaction is continued for 30 min; after settling, the precipitate is taken, washed three times with ethanol, and then dried in a vacuum at 60°C to obtain silver-coated copper powder.

[0074] (3) Surface modification of silver-coated copper powder

[0075] The dried silver-coated copper powder was mixed with an oleic acid-polyethylene glycol composite modifier (the dosage was 8% of the powder mass); the mixture was ultrasonically treated for 40 minutes and then centrifuged, washed twice with ethanol, and dried at 70° C. to obtain a surface-modified silver-coated copper powder product.

[0076] The product prepared in this comparative example 1 was detected by SEM, and it was found that the silver-coated copper powder was in block form, with a coverage rate of less than 50%. The average particle size measured by a laser particle size distribution instrument was 1.2 to 3.6 μm.

[0077] Comparative Example 2

[0078] Comparative Example 2 provides a method for preparing and surface modifying a silver-coated copper powder. The difference from Example 1 is that in Comparative Example 2, a silver complex solution is added without gradient, as follows:

[0079] A method for preparing silver-coated copper powder comprises the following steps:

[0080] (1) Pretreatment of copper powder

[0081] Take 0.5 g of spherical copper powder with a particle size of 1 - 3 μm and mix it with a mixed acid solution (H2SO4:H2O2 = 4:1 vol%) with pH = 1.0 at a solid-liquid ratio of 1:40; treat it in a 35 kHz ultrasonic field for 30 min, wash it with deionized water to neutrality after centrifugal separation, repeat acid washing three times and then dry it at 75 °C to obtain activated copper powder. Mix the activated copper powder with 60 ml of 0.4 mol / L Triton dispersant solution (the dosage is 0.25 times the mass of the copper powder) to form a copper suspension with a solid-liquid ratio of 1:120.

[0082] (2) Preparation of silver-coated copper powder by liquid-phase chemical deposition reaction

[0083] Place the copper suspension prepared in step (1) in a 55 °C water bath and directly add an AgNO3-ethylenediaminetetraacetic acid complex solution (AgNO3 concentration 0.05 mol / L, the mass ratio of the complexing agent to silver is 0.75:1); after reacting for 20 min, add 60 ml of 0.4 mol / L ascorbic acid solution dropwise and continue to react for 30 min; take the precipitate after sedimentation, wash it three times with ethanol and then place it in a 60 °C vacuum drying to obtain silver-coated copper powder.

[0084] (3) Surface modification treatment of silver-coated copper powder

[0085] Mix the dried silver-coated copper powder with an oleic acid-polyethylene glycol composite modifier (the dosage is 8% of the powder mass); after ultrasonic treatment for 40 min, centrifuge it, wash it twice with ethanol, and dry it at 70 °C to obtain the finished product of surface-modified silver-coated copper powder.

[0086] It can be known from SEM detection of the product prepared in Comparative Example 2 that silver particles agglomerate into micron-sized clusters on the surface of the copper core and are distributed in a dot-like manner, and are prone to falling off during subsequent processing.

[0087] Comparative Example 3

[0088] Comparative Example 3 provides a method for the preparation and surface modification of silver-coated copper powder. The difference from Example 2 is that in Comparative Example 3, an AgNO3 solution is directly added dropwise without the participation of a complexing agent, and the specific steps are as follows:

[0089] A method for preparing silver-coated copper powder, comprising the following steps:

[0090] (1) Pretreatment of copper powder

[0091] Take 1 g of spherical copper powder with a particle size of 1 - 3 μm and mix it with a mixed acid solution (HCl:HNO3:H2O2 = 3:1:0.5 vol%) at pH = 1.8 in a solid-liquid ratio of 1:30; treat it in a 40 kHz ultrasonic field for 25 min, repeat pickling three times after centrifugal separation; wash it with deionized water until neutral, and mix it with 80 ml of 0.2 mol / L polyvinylpyrrolidone solution (the dosage is 0.15 times the mass of the copper powder) to form a copper suspension with a solid-liquid ratio of 1:80.

[0092] (2) Preparation of silver-coated copper powder by liquid-phase chemical deposition reaction

[0093] Place the copper suspension in a 55 °C water bath and drip 120 ml of AgNO3 solution (AgNO3 concentration 0.04 mol / L, complexing agent to silver mass ratio 0.8:1) at a rate of 10 mL / min; after reacting for 20 min, drip 50 ml of 0.4 mol / L glucose solution and continue reacting for 30 min; take the precipitate after sedimentation, wash it three times with ethanol and then place it in a 60 °C vacuum dryer to obtain silver-coated copper powder.

[0094] (3) Surface modification treatment of silver-coated copper powder

[0095] Mix the dried silver-coated copper powder with a stearic acid modifier (the dosage is 8% of the powder mass); after ultrasonic treatment for 40 min, centrifuge, wash it twice with ethanol, and dry it at 70 °C to obtain the finished product of surface-modified silver-coated copper powder.

[0096] It can be seen from the SEM detection of the product prepared in this Comparative Example 3 that the silver-coated copper powder is unevenly coated. After EDS analysis, it can be known that many silver particles are generated during the reaction and agglomerate seriously, and are unevenly dispersed in the silver-coated copper powder.

[0097] Comparative Example 4

[0098] The preparation method of silver-coated copper powder provided in Comparative Example 4 is different from that of Example 3 in that Comparative Example 4 does not add a surface modifier and directly dries the powder, specifically as follows:

[0099] A preparation method of silver-coated copper powder includes the following steps:

[0100] (1) Pretreatment of copper powder

[0101] Take 0.8 g of spherical copper powder with a particle size of 1 - 3 μm and mix it with a mixed acid solution (HNO3:H2O2 = 2:1 vol%) at pH = 2.2 in a solid-liquid ratio of 1:50; treat it in a 30 kHz ultrasonic field for 40 min, repeat pickling three times after centrifugal separation; wash it with deionized water until neutral, and mix it with 96 ml of 0.2 mol / L Triton dispersant solution (the dosage is 0.15 times the mass of the copper powder) to form a copper suspension with a solid-liquid ratio of 1:120.

[0102] (2) Preparation of silver-coated copper powder by liquid-phase chemical deposition reaction

[0103] Place the copper suspension in a 60°C water bath and dropwise add 192 ml of AgNO3-tartaric acid complex solution at a rate of 12 mL / min (AgNO3 concentration 0.06 mol / L, mass ratio of complexing agent to silver 1.2:1); after reacting for 20 min, dropwise add 96 ml of 0.5 mol / L hydrazine hydrate solution and continue reacting for 30 min; after sedimentation, take the precipitate, wash it three times with ethanol and then place it in a 60°C vacuum dryer to obtain silver-coated copper powder.

[0104] It can be seen from the SEM detection of the product prepared in Comparative Example 4 that the silver particles of the silver-coated copper powder agglomerate seriously.

[0105] The resistivity test results of the above-mentioned comparative examples and Example 20MP tablets annealed in an air atmosphere are summarized in Table 1.

[0106] Table 1

[0107] Analysis: The resistivity of the silver-coated copper powder of the Example 20MP tablets annealed in an air atmosphere is better than that of the silver-coated copper powder of the comparative example 20MP tablets annealed in an air atmosphere, proving that the silver-coated copper powder prepared in the Example has better antioxidant properties and electrical properties.

[0108] The above is only the preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art, several improvements and refinements made without departing from the principle of the present invention should be regarded as within the protection scope of the present invention.

Claims

1. A preparation and surface modification method of silver-coated copper powder, characterized in that, It includes the following steps: (1) Pretreatment of copper powder Mix the copper powder with a mixed acid solution, perform ultrasonic stirring treatment, and then carry out centrifugal separation to remove surface oxides and organic pollutants. Repeat the above steps three times, and wash with deionized water three times until the filtrate is neutral (pH = 7). Centrifugal separation is carried out after each treatment. Dissolve the copper powder surface-activated by the mixed acid solution and the dispersant solution in water to obtain a copper powder suspension. (2) Preparation of silver-coated copper powder by liquid-phase chemical deposition reaction Under the condition of water bath heating, dropwise add a silver complex solution to the copper powder suspension for reaction to obtain a silver-coated copper powder suspension. After reacting for 20 min, dropwise add a reducing agent solution to the silver-coated copper powder suspension to further reduce the unreacted silver ions in the solution, and continue to react for 30 min to obtain a completely reacted silver-coated copper powder suspension. After the completely reacted silver-coated copper powder suspension undergoes sedimentation and solid-liquid separation, the separated solid is washed with ethanol, dried, and silver-coated copper powder is obtained. (3) Surface modification treatment of silver-coated copper powder Mix the dried silver-coated copper powder with a surface modifier, perform ultrasonic treatment for 40 min, then carry out solid-liquid separation, washing, and drying to obtain surface-modified silver-coated copper powder, which increases the dispersibility of the silver-coated copper powder.

2. The preparation and surface modification method of silver-coated copper powder according to claim 1, characterized in that, In the step (1), the mixed acid solution includes multiple of HCl solution, HNO3 solution, H2SO4 solution, and H2O2 solution. The pH of the mixed acid solution is 1.5 - 2.5, and the solid-liquid ratio of the copper powder to the mixed acid solution is 1:30 - 1:

50.

3. The preparation and surface modification method of a silver-coated copper powder according to claim 1, characterized in that, In the step (1), the ultrasonic stirring treatment is carried out for 30 - 45 minutes under an ultrasonic field intensity of 30 kHz - 40 kHz.

4. The preparation and surface modification method of a silver-coated copper powder according to claim 1, characterized in that In the step (1), the concentration of the dispersant solution is 0.1 mol / L - 0.5 mol / L, and the mass of the dispersant is 0.1 - 0.3 times the mass of the copper powder. The dispersant includes one or more of polyvinylpyrrolidone, ethanol, Triton, sodium dodecyl sulfate, and OP-10. The solid-liquid ratio of the copper powder dispersed suspension is 1:80 - 1:

120.

5. The preparation and surface modification method of a silver-coated copper powder according to claim 1, characterized in that, In the step (2), the temperature of the water bath heating is 40 - 60 °C.

6. The preparation and surface modification method of a silver-coated copper powder according to claim 1, characterized in that, In the step (2), the dropping rate is 10 - 15 mL / min.

7. The preparation and surface modification method of a silver-coated copper powder according to claim 1, characterized in that In the step (2), the silver complex solution includes a mixed solution of a silver source solution and a complexing agent. The silver source solution is AgNO3 solution with a concentration of 0.01 mol / L - 0.06 mol / L; the complexing agent is one or more of ethylenediaminetetraacetic acid, tartaric acid, and citric acid; the mass ratio of the complexing agent to the silver powder is (0.5 - 1.5):1, and the solid-liquid ratio of the silver-coated copper powder suspension is 1:200 - 1:

500.

8. The preparation and surface modification method of silver-coated copper powder according to claim 1, characterized in that In the step (2), the reducing agent is one or more of ascorbic acid, glucose, ferrous sulfate, and hydrazine hydrate. The concentration of the reducing agent solution is 0.1 mol / L - 0.5 mol / L, and the solid-liquid ratio of the completely reacted silver-coated copper powder suspension is 1:200 - 1:

500.

9. The preparation and surface modification method of silver-coated copper powder according to claim 1, characterized in that, In the step (3), the surface modifier is at least one of oleic acid, polyethylene glycol, succinic acid, oxalic acid, and stearic acid, and the mass of the surfactant is 1% to 20% of the theoretical mass of the produced silver-coated copper powder.

10. The preparation and surface modification method of a silver-coated copper powder according to claim 1, characterized in that, The micron-sized silver-coated copper powder is obtained by the preparation method according to any one of claims 1-8.

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