High tap density spherical silver-coated copper powder and method for preparing the same
By controlling the reaction conditions and solution heating temperature through open-container chemical silver plating, a high-density silver-coated copper powder with a solid silver layer was prepared. This solved the problems of low tap density and complex process of silver-coated copper powder in the prior art, improved the flowability and conductivity of the powder, simplified the process, and reduced the difficulty of wastewater treatment.
Patent Information
- Application Number
- CN202610400070.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-30
- Publication Date
- 2026-06-12
AI Technical Summary
Existing methods for preparing silver-coated copper powder have problems such as low tap density, easy agglomeration of powder particles, and insufficient surface coating, which affect the printing accuracy and conductivity of electronic components. Furthermore, existing processes are complex, have poor safety, and are difficult to treat wastewater.
By employing an open-container chemical silver plating method, controlling reaction conditions and solution heating temperature, and using metal sulfides and industrial concentrated sulfuric acid as catalysts, the method avoids premature complexation of silver ions and the addition of high-viscosity dispersants, thus preparing silver-coated copper powder with a thin and compact silver layer and achieving high tap density.
A high-tap-density spherical silver-coated copper powder with a silver layer firmly attached to the surface of copper powder was prepared, which improved the powder's flowability and conductivity, simplified the process, reduced the difficulty of wastewater treatment, and improved safety.
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Figure CN122184351A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of silver-coated copper powder preparation technology, and particularly relates to a high tap density spherical silver-coated copper powder and its preparation method. Background Technology
[0002] In fields such as electronic pastes and solar cell electrode coatings, spherical silver powder is widely used due to its excellent electrical and thermal conductivity. However, the scarcity and high price of silver resources severely restrict the cost control and large-scale development of downstream industries. To reduce the amount of silver used, silver-coated copper powder, with its core-shell structure of copper core and silver shell, has become an ideal substitute for silver powder, combining low cost and high conductivity.
[0003] Currently, the main methods for preparing silver-coated copper powder include chemical silver plating and electroplating. Among these, chemical silver plating has become the mainstream technology due to its simple process and good coating uniformity. However, silver-coated copper powder prepared by existing processes generally suffers from low tap density, and the powder particles are prone to agglomeration and incomplete surface coating. This results in poor fluidity and low solid content during slurry preparation, which in turn affects the printing accuracy and conductivity stability of electronic components. At the same time, existing silver plating processes relying on silver complexes generally suffer from a loose silver layer, resulting in a lower tap density of silver-plated copper powder than copper powder. This is highly unfavorable for fields with high requirements for slurry wet weight, such as heterojunction battery slurries.
[0004] In the prior art, the paper "A Method for Preparing Micron-Sized Spherical Silver-Coated Copper Powder for Electronic Industry" discloses a method for preparing silver-coated copper powder using a two-stage vacuum kneading method. This method is complex, and solid oxalate is prone to explosion when heated, resulting in poor process safety. Furthermore, the washing solution in this process has a complex composition, making wastewater treatment difficult.
[0005] In the prior art, the method for preparing ultrafine spherical silver-coated copper powder discloses a process where a dense film is formed on the surface of copper powder using a specific activator. This film can rapidly form a complex with silver ions in solution. Simultaneously, under the action of a specific reducing agent, silver ions are reduced to fine silver nanoparticles that are adsorbed onto the copper powder surface. Silver ions in solution form a dense silver layer that coats the copper powder surface through two-dimensional nucleation, resulting in silver-coated copper powder with high density, high conductivity, and high oxidation resistance. However, this method uses an inert gas protective atmosphere for surface silver plating, which places high demands on equipment. Furthermore, the process uses OP series emulsifiers as dispersants, resulting in high-viscosity wastewater that is difficult to clean. Pre-coating the copper powder surface with an activator before silver plating increases the thickness of the silver layer and reduces the particle tap density.
[0006] In the prior art, the invention "Spherical Silver-Coated Copper Powder for Silver Paste of N-type HJT Solar Cell Electrodes and its Preparation Method" discloses a method using a copper powder solution as the base liquid and reacting a mixed reducing agent with two different reducing abilities with a silver ammonia solution for silver plating. This method produces a dense silver layer with good conductivity. However, this method uses a mixed reducing agent for silver plating. The weaker reducing agent has a weaker reducing ability; adding too little will not have any reducing effect. Adding too much weaker reducing agent will cause it to adsorb onto the copper powder surface, reducing the surface cleanliness of the copper particles and decreasing the silver plating effect. Simultaneously, the weaker reducing agent contributes to a loose silver layer, reducing the bulk density of the low-silver-coated copper powder.
[0007] In summary, developing a mild, cost-controllable method for preparing silver-coated copper powder with high tap density is of great significance for promoting cost reduction and efficiency improvement in the field of electronic materials. Summary of the Invention
[0008] In view of the current technical status of silver plating processes, which are complex, have certain safety risks, produce complex wastewater, are highly dependent on equipment, produce thick silver layers, and have high particle packing density, this invention proposes a high tap density spherical silver-coated copper powder and its preparation method. This invention does not require inert gas protection, can achieve chemical silver plating in an open container, and produces a thin silver layer that adheres firmly to the surface of the copper powder. The tap density of the silver-coated copper powder is close to that of pure copper powder.
[0009] The first aspect of this invention discloses a method for preparing high-tap-density spherical silver-coated copper powder, the method comprising: S1. Place spherical copper powder in a reaction vessel, add 4-10 times the weight of pure water, and obtain a copper powder solution by mechanical stirring. S2. Prepare a silver nitrate aqueous solution with a concentration of 0.5 mol / L; prepare a ferrous sulfate aqueous solution with a concentration of 1.2 mol / L; heat both solutions to a temperature range of 35-70℃. S3. Add 0.5%-15% of copper powder by weight of metal sulfide and 0.7%-12% of copper powder by weight of industrial concentrated sulfuric acid to the copper powder solution reaction base liquid. After stirring for 2-5 minutes, add the oxidant and reducing agent dropwise into the copper powder solution reaction base liquid in a bidirectional manner through a peristaltic pump. S4. After the addition is complete, the precipitated silver-coated copper powder is washed with pure water and anhydrous ethanol respectively, and then dried under vacuum to obtain spherical silver-coated copper powder.
[0010] According to the method of the first aspect of the present invention, in S1, the average particle size of the spherical copper powder is between 1 and 6 μm.
[0011] According to the method of the first aspect of the present invention, in S1, a copper powder solution is obtained by mechanical stirring, wherein the temperature of the copper powder solution reaction substrate is in the range of 35-70°C, and the rotation speed is controlled in the range of 160-260 r / min.
[0012] According to the method of the first aspect of the present invention, in S3, the oxidant and the reducing agent are added dropwise into the copper powder solution reaction substrate by a peristaltic pump in both directions, wherein the flow rate is controlled within the range of 5-40 ml / min, and the dropwise addition process of the two solutions starts and ends simultaneously.
[0013] According to the method of the first aspect of the present invention, in S4, the precipitated silver-coated copper powder is washed with pure water until the conductivity is less than 10 μm / cm.
[0014] According to the method of the first aspect of the present invention, in S2, the two solutions are heated to a range of 45-55°C.
[0015] According to the method of the first aspect of the present invention, in S3, the metal sulfide is selected from alkali metal elements, and the industrial concentrated sulfuric acid is diluted with pure water to a mass concentration of 10-20%.
[0016] According to the method of the first aspect of the present invention, in S4, the vacuum drying temperature is controlled within the range of 40-55°C.
[0017] The second aspect of this invention discloses a high tap density spherical silver-coated copper powder, which is prepared using the method of the first aspect of this invention.
[0018] In summary, this invention reduces the reaction rate of silver nitrate by avoiding premature complexation of silver ions. Without adding stannous chloride as a silver site reagent on the copper surface, without pre-activating the copper powder surface, and without adding emulsifiers, gum arabic, or other highly viscous reagents as dispersing and complexing agents, a high-tap-density spherical silver-coated copper powder with a thin silver layer, a firm adhesion of the silver layer to the copper powder surface, and a tap density close to that of pure copper powder is prepared. Attached Figure Description
[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0020] Figure 1 Electron micrograph of copper powder according to the first embodiment of the present invention; Figure 2 This is a schematic diagram of silver-coated copper powder according to the first embodiment of the present invention; Figure 3 Electron micrograph of copper powder according to the second embodiment of the present invention; Figure 4 This is a schematic diagram of silver-coated copper powder according to the second embodiment of the present invention; Figure 5 Electron micrograph of copper powder according to the third embodiment of the present invention; Figure 6 This is a schematic diagram of silver-coated copper powder according to a third embodiment of the present invention; Figure 7 This is a slurry diagram before rolling, as shown in the comparative example according to the present invention. Figure 8 This is a comparative example of the rolled slurry according to the present invention. Detailed Implementation
[0021] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of 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 skilled in the art without creative effort are within the scope of protection of the present invention.
[0022] Liquid-phase chemical methods are inexpensive, controllable, reproducible, and suitable for industrial production. This invention reduces the reaction rate of silver nitrate by avoiding pre-complexation of silver ions. Without adding stannous chloride as a silver site reagent on the copper surface, without pre-activating the copper powder surface, and without adding emulsifiers, gum arabic, or other high-viscosity reagents as dispersing or complexing agents, a high-tap-density spherical silver-coated copper powder with a thin silver layer, firm adhesion to the copper powder surface, and a tap density close to that of pure copper powder is prepared.
[0023] The first aspect of this invention discloses a method for preparing high-tap-density spherical silver-coated copper powder, the method comprising: S1. Take a certain amount of commercially available spherical copper powder with an average particle size between 1-6μm and place it in a reaction vessel. Add 4-10 times the mass of pure water to the copper powder. Mechanically stir the copper powder solution, control the reaction liquid temperature at 35-70℃, and control the rotation speed at 160-260 r / min. S2. Prepare a silver nitrate aqueous solution with a concentration of 0.5 mol / L and a ferrous sulfate aqueous solution with a concentration of 1.2 mol / L, and heat both solutions to 35-70℃; S3. Add 0.5%-15% (by weight of copper powder) of metal sulfide and 0.7%-12% (by weight of copper powder) of concentrated industrial sulfuric acid to the reaction base solution. After stirring for 2-5 minutes, add the oxidant and reducing agent dropwise into the copper powder base solution using a peristaltic pump, maintaining a flow rate of 5-40 ml / min. The flow rate must be set to ensure that both solutions start and stop simultaneously. S4. After the addition is complete, wash the precipitated silver-coated copper powder with pure water until the conductivity is less than 10 μm / cm, and then wash it once with anhydrous ethanol. Then, vacuum dry to obtain the spherical silver-coated copper powder.
[0024] As a further improvement of the present invention, in S1, the spherical copper powder is preferably prepared by chemical reduction.
[0025] As a further improvement of the present invention, in S2, the temperature is controlled at 45-55°C.
[0026] As a further improvement of the present invention, in S3, the metal sulfide is selected from alkali metal elements, and industrial concentrated sulfuric acid can be diluted with pure water to a mass concentration of 10-20%.
[0027] As a further improvement of the present invention, in S4, the drying temperature is controlled at 40-55°C.
[0028] The second aspect of this invention discloses a high tap density spherical silver-coated copper powder, which is prepared using the method of the first aspect of this invention.
[0029] The first embodiment of the present invention will be described below.
[0030] 1 kg of spherical copper powder with an average particle size of 1.9 μm and a tap density of 3.6 g / cm³ was poured into a reaction vessel, and 7 kg of pure water was added. Mechanical stirring was started, and the temperature of the reaction solution was controlled at 55°C. 10 g of sodium sulfide and 13 g of concentrated industrial sulfuric acid were added to the reaction solution, and stirring was continued for 5 minutes. Pre-prepared silver nitrate solution (0.5 mol / L) and ferrous sulfate solution (1.2 mol / L), heated to 45°C, were added dropwise to the copper powder solution using a peristaltic pump at a flow rate of 27 ml / min for 2 hours. The solution was then washed and dried to obtain spherical silver-coated copper powder. The silver content of the obtained silver-coated copper powder was (15.0 ± 0.5%), the average particle size was 2.0 μm, and the tap density was 3.6 g / cm³. The electron micrograph of the copper powder in this example is attached. Figure 1 Silver-plated copper powder (see attached) Figure 2 .
[0031] The second embodiment of the present invention will be described below.
[0032] 1 kg of spherical copper powder with an average particle size of 4.3 μm and a tap density of 5.3 g / cm³ was poured into a reaction vessel, and 5.7 kg of pure water was added. Mechanical stirring was started, and the temperature of the reaction solution was controlled at 57°C. 13 g of sodium sulfide and 9 g of concentrated industrial sulfuric acid were added to the reaction solution, and stirring was continued for 5 minutes. Pre-prepared silver nitrate solution (0.5 mol / L) and ferrous sulfate solution (1.2 mol / L), heated to 49°C, were added dropwise to the copper powder solution using a peristaltic pump at a flow rate controlled at 18 ml / min for 4 hours. The solution was then washed and dried to obtain spherical silver-coated copper powder. The silver content of the obtained silver-coated copper powder was (20.0 ± 0.5%), the average particle size was 4.5 μm, and the tap density was 5.0 g / cm³. The electron micrograph of the copper powder in this example is attached. Figure 3 Silver-plated copper powder (see attached) Figure 4 .
[0033] The third embodiment of the present invention will be described below.
[0034] 1 kg of spherical copper powder with an average particle size of 5.4 μm and a tap density of 5.5 g / cm³ was poured into a reaction vessel, and 5 kg of pure water was added. Mechanical stirring was started, and the temperature of the reaction solution was controlled at 53°C. 7 g of sodium sulfide and 15 g of concentrated industrial sulfuric acid were added to the reaction solution, and stirring was continued for 5 minutes. Pre-prepared silver nitrate solution (0.5 mol / L) and ferrous sulfate solution (1.2 mol / L), heated to 49°C, were added dropwise to the copper powder solution using a peristaltic pump at a flow rate controlled at 23 ml / min for 1.5 hours. The solution was then washed and dried to obtain spherical silver-coated copper powder. The silver content of the obtained silver-coated copper powder was (10.0 ± 0.5%), the average particle size was 5.6 μm, and the tap density was 5.5 g / cm³. The electron micrograph of the copper powder in this example is attached. Figure 5 Silver-plated copper powder (see attached) Figure 6 .
[0035] The following describes a comparative example of the present invention.
[0036] The silver-coated copper powder of the second embodiment was prepared into a slurry with 80% solid content, rolled 10 times with a three-roll mill, and the color change of the silver paste before and after rolling was observed.
[0037] Prepare the slurry according to the following formula.
[0038] Organic carrier preparation: Weigh 55g of bisphenol A epoxy resin, 15g of imidazole curing agent, 28g of diglycidyl ether diluent, and 2g of 3-mercaptopropyltrimethoxysilane, place them in a beaker, and mechanically stir at 500 rpm for 30 minutes until they are evenly mixed.
[0039] Slurry preparation: Weigh 20g of silver-coated copper powder and 5g of the above organic carrier, and stir evenly with a glass rod.
[0040] The spacing settings for the ceramic three-roll mill are as follows: 10μm for pre-rolling and 7.5μm for finishing.
[0041] Observe the photos of the slurry before and after rolling. See the photos before rolling. Figure 7 See after rolling Figure 8 .
[0042] Observations showed that the silver-plated copper paste did not turn red, further demonstrating that the silver layer of this process is thick and durable.
[0043] In summary, this invention reduces the reaction rate of silver nitrate by avoiding premature complexation of silver ions. Without adding stannous chloride as a silver site reagent on the copper surface, without pre-activating the copper powder surface, and without adding emulsifiers, gum arabic, or other highly viscous reagents as dispersing and complexing agents, a high-tap-density spherical silver-coated copper powder with a thin silver layer, a firm adhesion of the silver layer to the copper powder surface, and a tap density close to that of pure copper powder is prepared.
[0044] Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementations of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, several modifications and improvements can be made 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 the present invention should be determined by the appended claims.
Claims
1. A method for preparing high-tap-density spherical silver-coated copper powder, characterized in that, The method includes: S1. Place spherical copper powder in a reaction vessel, add 4-10 times the weight of pure water, and obtain a copper powder solution by mechanical stirring. S2. Prepare a silver nitrate aqueous solution with a concentration of 0.5 mol / L; prepare a ferrous sulfate aqueous solution with a concentration of 1.2 mol / L; heat both solutions to a temperature range of 35-70℃. S3. Add 0.5%-15% of copper powder by weight of metal sulfide and 0.7%-12% of copper powder by weight of industrial concentrated sulfuric acid to the copper powder solution reaction base liquid. After stirring for 2-5 minutes, add the oxidant and reducing agent dropwise into the copper powder solution reaction base liquid in a bidirectional manner through a peristaltic pump. S4. After the addition is complete, the precipitated silver-coated copper powder is washed with pure water and anhydrous ethanol respectively, and then dried under vacuum to obtain spherical silver-coated copper powder.
2. The method for preparing high-tap-density spherical silver-coated copper powder according to claim 1, characterized in that, In S1, the average particle size of the near-spherical copper powder is between 1 and 6 μm.
3. The method for preparing high-tap-density spherical silver-coated copper powder according to claim 2, characterized in that, In S1, a copper powder solution is obtained by mechanical stirring, wherein the temperature of the copper powder solution reaction substrate is in the range of 35-70℃, and the rotation speed is controlled in the range of 160-260 r / min.
4. The method for preparing high-tap-density spherical silver-coated copper powder according to claim 3, characterized in that, In S3, the oxidant and reducing agent are added dropwise into the copper powder solution reaction substrate by a peristaltic pump in both directions, wherein the flow rate is controlled within the range of 5-40 ml / min, and the dropwise addition of the two solutions starts and ends simultaneously.
5. The method for preparing high tap density spherical silver-coated copper powder according to claim 4, characterized in that, In S4, the precipitated silver-coated copper powder is washed with pure water until the conductivity is less than 10 μm / cm.
6. The method for preparing high-tap-density spherical silver-coated copper powder according to claim 5, characterized in that, In S2, both solutions are heated to a temperature range of 45-55°C.
7. The method for preparing high-tap-density spherical silver-coated copper powder according to claim 6, characterized in that, In S3, alkali metal elements are selected for metal sulfides, and industrial concentrated sulfuric acid is diluted with pure water to a mass concentration of 10-20%.
8. The method for preparing high tap density spherical silver-coated copper powder according to claim 7, characterized in that, In S4, the vacuum drying temperature is controlled within the range of 40-55℃.
9. A high tap density spherical silver-coated copper powder, characterized in that, The high tap density spherical silver-coated copper powder is prepared using the method described in any one of claims 1-8.