A silver-coated copper powder and its preparation method

Abstract

This invention discloses a silver-coated copper powder and its preparation method, comprising: etching copper powder with a composite alkaline reagent to obtain pretreated copper powder; the composite alkaline reagent is a mixture containing a surfactant and an aliphatic polyamine; preparing a copper solution with the pretreated copper powder; adding silver plating solution dropwise to the copper solution to carry out a chemical silver plating reaction to obtain silver-coated copper powder. This invention has the following characteristics: 1) the chemical silver plating reaction is a one-step process and can be achieved in a single container; 2) the chemical silver plating reaction time is short, not exceeding 60 minutes; 3) the prepared silver layer is dense at 5 nm resolution; 4) the silver content in the silver-coated copper powder is adjustable within the range of 15wt% to 60wt%; 5) the silver ion utilization rate is close to 100%; 6) the temperature process window is wide.

Description

Technical Field

[0001] This invention relates to the field of conductive materials, specifically to a silver-coated copper powder and its preparation method. Background Technology

[0002] The core component of photovoltaic technology is the solar photovoltaic panel. With the continuous iteration of photovoltaic cell technology, the demand for grid lines on these panels is increasing. Silver powder, due to its excellent conductivity and high reflectivity, has always been a key material for manufacturing these grid lines. However, the ever-increasing demand for silver makes economic factors a crucial consideration. The industry has been searching for alternatives to silver powder.

[0003] Silver-coated copper powder is a promising and viable alternative. Copper's abundant resources, cost-effectiveness, and excellent electrical conductivity make it a suitable candidate. Good conductivity and oxidation resistance can be achieved by coating copper powder with a layer of silver. However, the performance of the powder is often limited in most cases due to insufficient density of the silver layer.

[0004] Silver-coated copper powder has been developed for a considerable period, with related research beginning at the beginning of this century. For example, patent specification CN119159074A discloses a method for preparing silver-coated copper powder, including: reacting a copper-containing complexing mother liquor, a silver source, and a reducing agent; the raw materials for preparing the copper-containing complexing mother liquor include: copper powder, a chelating agent, a dispersant, and a modifying additive; the modifying additive includes at least one of: ethylenediamine, ammonium carbonate, ammonia, tetraethylenepentamine, polyethylenepolyamine, imidazole, pyridazine, pyrimidine, and pyrazine. As another example, patent specification CN118218588A discloses a method for preparing silver-coated copper powder, which first improves the antioxidant properties of copper powder through displacement silver plating; then, a reduction silver plating process is used to reduce a dense silver layer on the surface of the crude silver-coated copper powder.

[0005] A review of relevant data reveals that the methods for achieving dense silver layers have significant shortcomings in recent years. These problems include: (1) the silver layers are stacked in a discrete island-like manner, resulting in a large number of voids; (2) the reaction is carried out in multiple steps, which is cumbersome and time-consuming, affecting large-scale production; (3) the reaction is carried out in organic solvents, which poses a risk of waste liquid treatment; and (4) the utilization rate of silver ions is low.

[0006] The main reason for the problem is the unavoidable side reaction of copper nucleus replacement during silver ion reduction deposition. The regulation of both reactions' rates has a significant impact on the initial nucleation stage, directly affecting the uniformity of silver ion nucleation on the copper surface. Uniform silver ion nucleation is a necessary condition for dense silver layer growth. Previous methods typically employed a strategy of slowing down the overall silver ion deposition rate in the initial stage to achieve slow, uniform nucleation. This included two-step coating using either a silver ion concentration gradient or a reducing agent concentration gradient. However, this method suffers from low efficiency and is unsuitable for large-scale production.

[0007] Therefore, finding a low-cost and efficient method for preparing silver-coated copper powder that can be mass-produced with uniform silver coating has very high economic and industrial value. Summary of the Invention

[0008] To address the aforementioned technical problems and shortcomings in this field, the present invention provides a silver-coated copper powder and its preparation method. The present invention has the following characteristics: 1) the chemical silver plating reaction is a one-step process that can be achieved in a single container; 2) the chemical silver plating reaction time is short, completed in no more than 60 minutes; 3) the prepared silver layer is dense at 5 nm resolution; 4) the silver content in the silver-coated copper powder is adjustable within the range of 15wt% to 60wt%; 5) the silver ion utilization rate is close to 100%; and 6) the temperature process window is wide.

[0009] The specific technical solution is as follows:

[0010] In a first aspect, the present invention provides a method for preparing silver-coated copper powder, comprising:

[0011] Copper powder is etched using a composite alkaline reagent to obtain pretreated copper powder; the composite alkaline reagent is a mixture containing surfactant and aliphatic polyamine.

[0012] Prepare copper solution using pretreated copper powder;

[0013] Silver plating solution is added dropwise to a copper solution to carry out a chemical silver plating reaction, resulting in silver-coated copper powder.

[0014] This invention addresses the problem of poor uniformity in the early stages of silver nucleation by proposing an etching method to eliminate high-energy sites on the surface of the copper nucleus, thereby increasing the activation energy of the substitution reaction between silver ions and the copper nucleus. This weakens the competition between the substitution and reduction reactions in the early stages of coating, and the direct addition of a reducing agent can maintain the uniformity of coating while promoting rapid nucleation.

[0015] In the method for preparing silver-coated copper powder, the preferred particle size of the copper powder is 0.3 to 1 micrometer.

[0016] Preferably, in the method for preparing the silver-coated copper powder, the copper powder is first subjected to surface impurities and oxides before etching with a composite alkaline reagent. Specifically, this may include: placing the copper powder in a mixed solution of ammonium sulfate and ammonia, ultrasonically peeling off surface impurities and oxides, and then washing.

[0017] Preferably, the solvent in the mixed solution for removing surface impurities and oxides is water.

[0018] In the process of removing surface impurities and oxides, the preferred ratio of the mass of the copper powder to the volume of the mixed solution is 5-15 g:1 L, for example, 10 g:1 L.

[0019] The removal of surface impurities and oxides is carried out, and the concentration of ammonium sulfate in the mixed solution is preferably 0.08~0.12 M, for example 0.1 M.

[0020] The removal of surface impurities and oxides is carried out, and the mass concentration of NH3 in the mixed solution is preferably 0.6% to 0.7%.

[0021] The removal of surface impurities and oxides is carried out, and the ultrasonic frequency of the ultrasonic stripping is preferably 30~50kHz, such as 40kHz.

[0022] The removal of surface impurities and oxides is carried out, and the ultrasonic peeling time is preferably 5 to 15 minutes, such as 10 minutes.

[0023] Preferably, in the method for preparing the silver-coated copper powder, the solvent in the composite alkaline reagent is water.

[0024] In the method for preparing silver-coated copper powder, the mass ratio of the composite alkaline reagent to the copper powder is preferably 25-30:1, such as 26:1, 26.5:1, 27:1, 28:1, 29:1, etc.

[0025] In the method for preparing silver-coated copper powder, the surfactant preferably includes at least one of polyvinylpyrrolidone (PVP) and alkylphenol polyoxyethylene ether (e.g., OP-10), and more preferably includes OP-10.

[0026] As the concentration of surfactant increases, on the one hand, the surfactant will combine with the copper surface, affecting the etching effect; on the other hand, the cleaning time cost increases. In the method for preparing the silver-coated copper powder, the surfactant in the mixture is preferably 0.1% to 2% by mass, for example, 0.5%, 1%, 1.5%, etc.

[0027] This invention employs aliphatic polyamines, which have a significant effect on copper etching. In the preparation method of the silver-coated copper powder, the aliphatic polyamine preferably includes at least one of ethylenediamine (EDA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA), more preferably including ethylenediamine and tetraethylenepentamine, and even more preferably including ethylenediamine and tetraethylenepentamine in a volume ratio of 1:10~20 (e.g., 1:15). Long-chain aliphatic polyamines have a higher etching effect on copper than short-chain aliphatic polyamines, but there is a possibility of over-etching. Since the binding sites of long-chain and short-chain aliphatic polyamines on copper are consistent, introducing an appropriate proportion of EDA can avoid excessive loss of the copper core.

[0028] In the method for preparing silver-coated copper powder, the mass percentage of the aliphatic polyamine in the mixture is preferably 1% to 5%, such as 2%, 2.5%, 3%, 3.5%, 4%, etc.

[0029] The preferred specific operation of etching the copper powder with a composite alkaline reagent in the preparation method of the silver-coated copper powder includes: stirring the mixture of copper powder and composite alkaline reagent, ultrasonically etching, cleaning, and drying.

[0030] In the specific operation of etching copper powder with a composite alkaline reagent, the stirring speed is preferably 100~2000 rpm, more preferably 250~350 rpm, such as 300 rpm.

[0031] In the specific operation of etching copper powder with a composite alkaline reagent, the frequency of the ultrasound is preferably 30~50 kHz, such as 40 kHz.

[0032] In the specific operation of etching copper powder with a composite alkaline reagent, the etching time is preferably not less than 10 minutes and not more than 24 hours, and more preferably 10 to 15 minutes.

[0033] Preferably, in the method for preparing silver-coated copper powder, the solvent in the copper solution is water.

[0034] In the method for preparing silver-coated copper powder, the mass concentration of the pretreated copper powder in the copper solution is preferably 1% to 5%, such as 2%, 3%, 3.5%, 4%, etc.

[0035] In the method for preparing silver-coated copper powder, the copper solution preferably also contains a reducing agent, a complexing agent, and a dispersant.

[0036] The reducing agent preferably includes one or more of D-glucose, L-glucose, ascorbic acid, sodium ascorbate, citric acid, and ammonium citrate, and more preferably includes D-glucose.

[0037] The complexing agent in the copper solution preferably includes one or more of potassium sodium tartrate, triethylenetetramine, ethylenediamine, and ammonium hydroxide, and more preferably includes triethylenetetramine and combinations thereof.

[0038] The dispersant preferably includes one or more of gum arabic, hexadecylamine (HAD), PVP, and alkylphenol polyoxyethylene ether (e.g., OP-10), and more preferably includes OP-10.

[0039] The mass concentration of the reducing agent in the copper solution is preferably 1% to 5%, such as 2%, 3%, 3.5%, 4%, etc.

[0040] The preferred mass concentration of the complexing agent in the copper solution is 1% to 5%, such as 1.5%, 2%, 3%, 3.5%, 4%, etc.

[0041] The concentration of the dispersant should not be too high. As the concentration of the dispersant increases, on the one hand, the dispersant will combine with the copper surface, affecting the silver coating effect; on the other hand, the cleaning time cost increases. The preferred mass concentration of the dispersant in the copper solution is 0.1% to 2%, such as 0.5%, 0.8%, 0.9%, 1%, 1.5%, etc.

[0042] If the pH of the copper solution is too low, the reaction will be slow and the silver utilization rate will be low; if it is too high, the silver coating will be uneven. The preferred pH of the copper solution is 8.5-11, more preferably 9-10, and even more preferably 9.5±0.2.

[0043] Preferably, in the method for preparing the silver-coated copper powder, the solvent in the silver plating solution is water.

[0044] Preferably, in the method for preparing silver-coated copper powder, the silver plating solution contains silver ions and a complexing agent, and the silver ions and the complexing agent form a stable complex.

[0045] The source of the silver ions preferably includes one or more of silver nitrate and silver acetate, and more preferably includes silver nitrate.

[0046] The complexing agent in the silver plating solution preferably includes one or more of triethylenetetramine, tetraethylenepentamine, ethylenediamine, disodium ethylenediaminetetraacetate (EDTA-2Na), and ammonia.

[0047] The preferred mass concentration of silver ions in the silver plating solution is 0.1% to 2%, such as 0.5%, 0.8%, 0.9%, 1%, 1.5%, etc.

[0048] The mass concentration of the complexing agent in the silver plating solution is preferably 0.1% to 2%, such as 0.5%, 0.7%, 1%, 1.5%, etc.

[0049] To achieve a dense silver layer, in the method for preparing the silver-coated copper powder, the dropping rate of the silver plating solution added to the copper solution, based on a copper solution volume of 100%, is preferably no more than 20% / min, and more preferably 1%-20% / min, such as 5% / min, 8% / min, 9% / min, 10% / min, 11% / min, 12% / min, 15% / min, etc.

[0050] The method for preparing silver-coated copper powder involves reducing silver atoms onto the surface of pretreated copper powder during the chemical silver plating reaction to obtain silver-coated copper powder.

[0051] The method for preparing silver-coated copper powder preferably involves conducting the chemical silver plating reaction while the pretreated copper powder is in a uniform suspension state. The uniform suspension state of the pretreated copper powder can be maintained by methods such as stirring and ultrasonic dispersion to ensure its dispersibility and uniformity. The stirring speed can be adjusted according to the container volume, preferably 100-2000 rpm, more preferably 300-600 rpm, such as 500 rpm. The ultrasonic frequency for ultrasonic dispersion is preferably 30-50 kHz, such as 40 kHz.

[0052] The method for preparing silver-coated copper powder has a wide temperature window for the chemical silver plating reaction, but it is not suitable for preparation at low or high temperatures, as this severely affects the morphology and efficiency. The preferred temperature for the chemical silver plating reaction in the method for preparing silver-coated copper powder is 20-60℃, more preferably 25-45℃.

[0053] In the method for preparing the silver-coated copper powder, the chemical silver plating reaction time is preferably no more than 60 min, and more preferably 10-30 min.

[0054] Preferably, in the method for preparing silver-coated copper powder, after the chemical silver plating reaction is completed, solid-liquid separation, solid washing, and drying are performed to obtain silver-coated copper powder.

[0055] The silver content significantly affects antioxidant properties at lower levels. When the silver layer is denser, the intrinsic dewetting temperature of the silver layer is the core factor affecting antioxidant properties. Therefore, the silver content needs to be adjustable during preparation. In the preparation method of this invention, the silver layer growth does not meet the conditions for a self-limiting reaction, and theoretically, silver-coated copper powder with a silver content exceeding 60 wt% can be prepared. A dense silver layer can also be formed at lower silver contents. At a silver content of 16 wt%, the silver-coated copper powder prepared by the method of this invention exhibits a dense silver layer under SEM 5 nm resolution observation. Preferably, the silver content in the silver-coated copper powder of this invention is 15%~60%, for example, 16%.

[0056] Secondly, the present invention provides silver-coated copper powder prepared by the method for preparing silver-coated copper powder described in the first aspect.

[0057] The silver-coated copper powder of this invention can be used to make conductive pastes, etc.

[0058] Compared with the prior art, the beneficial effects of this invention are as follows:

[0059] 1. A silver-coated copper powder with a dense silver layer of 0.3~1 micrometer was prepared. By etching the copper surface, the surface morphology and energy barrier were flattened, laying the foundation for the uniform nucleation of silver particles, so that the chemical silver plating reaction can be carried out in one step in a single container.

[0060] 2. The chemical silver plating reaction time is short, and it can be completed in no more than 60 minutes.

[0061] 3. The prepared silver layer is dense at a resolution of 5 nm.

[0062] 4. The silver content in copper-coated silver powder can be adjusted within the range of 15wt% to 60wt%, and a dense silver layer can be achieved at 16wt%.

[0063] 5. The utilization rate of silver ions is close to 100%.

[0064] 6. The temperature process window is relatively wide. Attached Figure Description

[0065] Figure 1 These are scanning electron microscope (SEM) images of the copper powder raw materials used in the various embodiments and comparative examples in the specific implementation details.

[0066] Figure 2 This is an SEM image of the pretreated copper powder from Example 1.

[0067] Figure 3 This is a SEM image of the silver-coated copper core-shell powder from Example 1.

[0068] Figure 4 This is a SEM image of the silver-coated copper core-shell powder from Example 2.

[0069] Figure 5 This is a SEM image of the silver-coated copper core-shell powder from Example 3.

[0070] Figure 6 This is a SEM image of the silver-coated copper core-shell powder in the early stage of nucleation in Example 4.

[0071] Figure 7 SEM images of silver-copper core-shell powder in the early nucleation stage for comparison. Detailed Implementation

[0072] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Operating methods not specifically specified in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer.

[0073] Example 1:

[0074] Copper powder pretreatment:

[0075] (1) Oxide layer removal:

[0076] Weigh 20 g of copper powder raw material with a particle size of approximately 0.3~1 μm (morphology as shown in the image). Figure 1 As shown in the figure, add 2L of 0.1M ammonium sulfate solution and 50 mL of concentrated ammonia (25wt%~28wt%), and place in a 40 kHz ultrasonic cleaner for 10 minutes to remove surface oxides and impurities.

[0077] (2) Etching of copper surface:

[0078] Transfer the mixture to a centrifuge tube and centrifuge at 8000 rpm for 5 minutes. Discard the supernatant. Wash the mixture three times with deionized water. Finally, disperse the copper powder in 500 mL of deionized water, add 5 mL of OP-10, 15 mL of TETA and 1 mL of EDA, stir at 300 rpm and place in a 40 kHz ultrasonic cleaner for 10 minutes.

[0079] (3) Cleaning and drying:

[0080] The mixture was transferred to a centrifuge tube and centrifuged at 8000 rpm for 5 minutes, then the supernatant was discarded. The mixture was washed three times with deionized water, and finally, the copper powder was dispersed in 50 mL of anhydrous ethanol and dried in a vacuum oven at 60℃ for 12 hours to obtain pretreated copper powder (morphology as shown). Figure 2 (As shown), seal and store for later use.

[0081] Preparation of copper solution:

[0082] (1) Solution preparation:

[0083] 2 g of pretreated copper powder was dispersed in 50 mL of aqueous solution containing 2 g of D-glucose, 0.7 g of potassium sodium tartrate and 0.5 mL of OP-10.

[0084] (2) Mixing and pH adjustment:

[0085] Add 0.15 mL of TETA as a surface complexing agent, adjust the pH of the system to 9.5 ± 0.2 with 0.1 M dilute ammonia solution (calibrated with a pH meter or pH test paper), and sonicate for 5 minutes until uniformly mixed; the solution turns blue-brown. A stable copper solution is obtained.

[0086] Silver plating solution preparation:

[0087] (1) Silver ion complexation:

[0088] Weigh 1.4 g silver nitrate (AgNO3) and 0.5 g EDTA-2Na, dissolve them in 100 mL deionized water, and stir magnetically until completely dissolved (operate in the dark).

[0089] (2) TETA titration:

[0090] While stirring continuously, add TETA dropwise (approximately 0.3–0.5 mL) until the solution changes from turbid to colorless and transparent, indicating that silver ions have formed a stable complex with TETA ([Ag(TETA)]). + A clear silver plating solution was obtained.

[0091] Chemical silver plating reaction:

[0092] (1) Reaction initiation:

[0093] Transfer all the prepared copper solution to a 500 mL glass reactor and place it in a 40 kHz ultrasonic cleaner. Turn on the magnetic stirring (500 rpm) to ensure that the copper powder is uniformly suspended (with no sediment at the bottom).

[0094] (2) Plating solution droplet addition:

[0095] The silver plating solution was slowly added dropwise at a rate of 10 mL / min using a constant flow pump, while controlling the reaction temperature at 35±10℃. After the addition was complete, the reaction continued for 10-20 minutes until the solution turned light gray and the silver-coated copper powder completely settled.

[0096] (3) Product processing:

[0097] The precipitate was collected by centrifugation, washed three times successively with deionized water and ethanol, and dried under vacuum at 60°C to obtain silver-coated copper core-shell powder, with the morphology as shown in the image. Figure 3 As shown.

[0098] Example 2: The etching time in Example 1 was extended, specifically, the copper surface was stirred at 300 rpm and treated in a 40 kHz ultrasonic cleaner for 30 minutes during the etching process. All other steps remained the same as in Example 1. The morphology of the resulting silver-coated copper core-shell powder is as follows: Figure 4 As shown.

[0099] Example 3: While maintaining the same silver ion concentration, the amount of silver used was increased. Specifically, during the silver ion complexation process, 2.8 g of silver nitrate (AgNO3) and 1 g of EDTA-2Na were weighed and dissolved in 200 mL of deionized water. The mixture was magnetically stirred until completely dissolved (operation in the dark). All other steps were the same as in Example 1. The morphology of the resulting silver-coated copper core-shell powder is as follows: Figure 5 As shown.

[0100] Example 4: The only difference from Example 1 is that the silver plating solution is not completely added during the droplet addition process; it is only added for 30 seconds, and then subsequent product processing is carried out. All other aspects are the same, resulting in silver-coated copper core-shell powder in the early stage of nucleation, with the morphology as shown below. Figure 6 As shown, a fine and dense silver layer can be seen.

[0101] Comparative Example: The only difference from Example 4 is the etching process on the copper-free surface; all other aspects are the same. Silver-coated copper core-shell powder in the early nucleation stage was obtained, with the morphology as shown below. Figure 7 As shown.

[0102] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for preparing silver-coated copper powder, characterized in that, include: Copper powder was etched using a composite alkaline reagent to obtain pretreated copper powder. The composite alkaline reagent is a mixture containing a surfactant and an aliphatic polyamine, wherein the aliphatic polyamine includes at least one of ethylenediamine, triethylenetetramine, and tetraethylenepentamine; the specific operation of etching copper powder with the composite alkaline reagent includes: stirring the mixture of copper powder and composite alkaline reagent, ultrasonically etching, cleaning, and drying. A copper solution is prepared using pretreated copper powder; the copper solution also contains a reducing agent, a complexing agent, and a dispersant. Silver plating solution is added dropwise to a copper solution to carry out a chemical silver plating reaction, resulting in silver-coated copper powder.

2. The method for preparing silver-coated copper powder according to claim 1, characterized in that, The copper powder has a particle size of 0.3 to 1 micrometer.

3. The method for preparing silver-coated copper powder according to claim 1, characterized in that, Before etching with a composite alkaline reagent, the copper powder is first subjected to surface impurities and oxides removal, specifically including: placing the copper powder in a mixed solution of ammonium sulfate and ammonia, ultrasonically peeling off surface impurities and oxides, and then washing. The solvent in the mixed solution is water; The ratio of the mass of the copper powder to the volume of the mixed solution is 5~15 g:1 L; The concentration of ammonium sulfate in the mixed solution is 0.08~0.12 M; The mass concentration of NH3 in the mixed solution is 0.6%~0.7%; The ultrasonic frequency of the ultrasonic ablation is 30~50 kHz; The ultrasonic ablation time is 5 to 15 minutes.

4. The method for preparing silver-coated copper powder according to claim 1, characterized in that, The solvent in the composite alkaline reagent is water; The mass ratio of the composite alkaline reagent to the copper powder is 25~30:1; The surfactant includes at least one of PVP and alkylphenol polyoxyethylene ether; The surfactant in the mixture has a mass percentage of 0.1% to 2%; The aliphatic polyamines include ethylenediamine and tetraethylenepentamine; The aliphatic polyamine has a mass percentage content of 1% to 5% in the mixture; In the specific operation of etching copper powder with a composite alkaline reagent, the stirring speed is 100~2000 rpm; In the specific operation of etching copper powder with a composite alkaline reagent, the frequency of the ultrasound is 30~50 kHz; In the specific operation of etching copper powder with a composite alkaline reagent, the etching time shall be no less than 10 minutes and no more than 24 hours.

5. The method for preparing silver-coated copper powder according to claim 4, characterized in that, The aliphatic polyamine includes ethylenediamine and tetraethylenepentamine in a volume ratio of 1:10~20; In the specific operation of etching copper powder with a composite alkaline reagent, the stirring speed is 250~350 rpm; In the specific operation of etching copper powder with a composite alkaline reagent, the etching time is 10-15 minutes.

6. The method for preparing silver-coated copper powder according to claim 1, characterized in that, The solvent in the copper solution is water; The mass concentration of pretreated copper powder in the copper solution is 1%~5%; The reducing agent includes one or more of D-glucose, L-glucose, ascorbic acid, sodium ascorbate, citric acid, and ammonium citrate; The complexing agent in the copper solution includes one or more of potassium sodium tartrate, triethylenetetramine, ethylenediamine, and ammonium hydroxide. The dispersant includes one or more of gum arabic, hexadecylamine, PVP, and alkylphenol polyoxyethylene ether; The mass concentration of the reducing agent in the copper solution is 1% to 5%; The mass concentration of the complexing agent in the copper solution is 1%~5%; The mass concentration of the dispersant in the copper solution is 0.1%~2%; The pH of the copper solution is 8.5~11.

7. The method for preparing silver-coated copper powder according to claim 6, characterized in that, The pH of the copper solution is 9-10.

8. The method for preparing silver-coated copper powder according to claim 7, characterized in that, The pH of the copper solution is 9.5 ± 0.

2.

9. The method for preparing silver-coated copper powder according to claim 1, characterized in that, The solvent in the silver plating solution is water; The silver plating solution contains silver ions and a complexing agent, and the silver ions and the complexing agent form a stable complex. The sources of the silver ions include one or more of silver nitrate and silver acetate; The complexing agent in the silver plating solution includes one or more of triethylenetetramine, tetraethylenepentamine, ethylenediamine, disodium ethylenediaminetetraacetate, and ammonia. The mass concentration of silver ions in the silver plating solution is 0.1%~2%; The mass concentration of the complexing agent in the silver plating solution is 0.1% to 2%.

10. The method for preparing silver-coated copper powder according to claim 1, characterized in that, With the copper solution volume as 100%, the dropping rate of silver plating solution added to the copper solution should not exceed 20% / min.

11. The method for preparing silver-coated copper powder according to claim 10, characterized in that, With the copper solution volume as 100%, the dropping rate of silver plating solution added to the copper solution is 1%-20% / min.

12. The method for preparing silver-coated copper powder according to claim 1, characterized in that, The chemical silver plating reaction is carried out in a state where the pretreated copper powder is uniformly suspended; The temperature of the chemical silver plating reaction is 20~60℃; The chemical silver plating reaction time shall not exceed 60 min.

13. The method for preparing silver-coated copper powder according to claim 12, characterized in that, The temperature of the chemical silver plating reaction is 25~45℃; The chemical silver plating reaction takes 10-30 minutes.

14. The method for preparing silver-coated copper powder according to claim 1, characterized in that, The silver content in the silver-coated copper powder is 15% to 60% by mass.

15. The silver-coated copper powder prepared by the method according to any one of claims 1 to 14.

Images