Silver-coated copper powder preparation method based on coordination of double-complexing slow release and ultrasonic cavitation

Abstract

The invention discloses a silver-coated copper powder preparation method based on double-complexing slow release and ultrasonic cavitation cooperation, and relates to the technical field of electronic material functional powder. The preparation method specifically comprises the following steps that electrolytic copper powder is placed in acid liquor to be stirred and subjected to acid pickling, then filtering, washing and drying are conducted, and acid-pickled electrolytic copper powder is obtained; preparing a mixed aqueous solution of EDTA (Ethylene Diamine Tetraacetic Acid) and ammonium carbonate to form a solution A, and adding the acid-washed electrolytic copper powder into the solution A for ultrasonic dispersion to obtain a suspension; taking the solution A, and then adding silver nitrate into the solution A to obtain a solution B; adding the solution B into the suspension, and reacting under ultrasonic and stirring conditions to obtain a solid-liquid mixture after the reaction is finished; and the solid-liquid mixture is washed, filtered and dried, and the silver-coated copper powder based on double-complexing slow release and ultrasonic cavitation cooperation is obtained. According to the invention, through a dual-complexing slow release and ultrasonic cavitation synergistic mechanism, homogenization and silver-copper compact combination of a silver layer of the silver-coated copper powder are realized, and the silver-coated copper powder is suitable for high-end conductive paste.

Description

Technical Field

[0001] This invention relates to a method for preparing silver-coated copper powder based on the synergistic effect of dual complexation sustained release and ultrasonic cavitation, belonging to the field of functional powder technology for electronic materials. Background Technology

[0002] Silver-coated copper powder plays an important role in electronic conductive pastes, but the traditional chemical displacement method has inherent defects, with severe interference from copper ions: Cu dissolved in acidic environments... 2+ With Ag + Competitive deposition leads to a rough and uneven silver layer; uncontrolled silver ion release: the reaction rate of conventional silver salt solutions is too fast, easily causing localized accumulation of silver layers; low mass transfer efficiency: oxides on the copper powder surface hinder silver ion contact, and mechanical stirring makes it difficult to achieve uniform mass transfer. These defects restrict the application of silver-coated copper powder in precision electronic devices. Therefore, it is necessary to develop a silver-coated copper powder preparation process that combines dual-complexation slow release and ultrasonic cavitation to achieve a uniform distribution of the silver layer on the copper powder surface and improve the bonding ability between the silver layer and the copper powder. Summary of the Invention

[0003] To address the shortcomings of related technologies, this invention provides a method for preparing silver-coated copper powder based on the synergistic effect of dual-complexation sustained release and ultrasonic cavitation, which enables the slow release of Ag. + Reduce the reduction reaction rate and block Cu 2+ The advantages of this method are that it enables the preparation of uniform silver-coated copper powder with high bonding strength, solving the problems of poor uniformity and low adhesion of the silver layer in silver-coated copper powder for precision electronic devices.

[0004] One objective of this invention is to provide a method for preparing silver-coated copper powder based on the synergistic effect of dual-complex sustained release and ultrasonic cavitation, specifically including the following steps: (1) Pickling of copper powder: Electrolytic copper powder is placed in acid solution and stirred for pickling, then filtered, washed and dried to obtain pickled electrolytic copper powder.

[0005] (2) Constructing a dual complexation system: Prepare a mixed aqueous solution of EDTA and ammonium carbonate to form solution A, and add the acid-washed electrolytic copper powder to solution A and disperse it by ultrasonication to obtain a suspension.

[0006] (3) Preparation of silver complex solution: Take solution A, then add silver nitrate to solution A to obtain solution B.

[0007] (4) Synergistic reaction: Solution B is added to the suspension and reacted under ultrasonic and stirring conditions. After the reaction is completed, a solid-liquid mixture is obtained.

[0008] (5) Post-processing: The solid-liquid mixture is washed, filtered (preferably vacuum filtered) and dried to obtain silver-coated copper powder based on the synergistic effect of dual complexation slow release and ultrasonic cavitation.

[0009] Preferably, in step (1), the acid solution is a nitric acid aqueous solution with a mass percentage concentration of 3-6%; the amount of electrolytic copper powder added to the acid solution is 40-60 g / L; the conditions for stirring and acid washing are: stirring and acid washing at 100-300 rpm for 20-30 min at 20-30℃.

[0010] Preferably, in step (2), the concentration of EDTA in solution A is 0.05-0.2 mol / L, the concentration of ammonium carbonate is 0.025-0.1 mol / L, and the pH of solution A is 9.5±0.5; the amount of electrolytic copper powder added to the suspension after acid washing is 5-20 g / L; and the conditions for ultrasonic dispersion are: dispersion for 10-30 min at a frequency of 30-50 kHz and a power of 100-300 W.

[0011] Preferably, the concentration of silver nitrate in solution B in step (3) is 0.05-0.2 mol / L.

[0012] Preferably, in step (4), solution B is added to the suspension at a rate of 1-3 mL / min; solution B is added to the suspension at a mass ratio of copper in the suspension to silver in solution B of (3-6):1; the reaction conditions are: at a frequency of 35-45 kHz, a power density of 180-220 W / L, a rotation speed of 200-400 rpm, and a reaction temperature of 28-32℃ for 30-50 min.

[0013] Another objective of this invention is to provide a silver-coated copper powder based on the synergistic effect of dual complexation sustained release and ultrasonic cavitation, prepared using the method of this invention.

[0014] Mechanism of the invention: This invention utilizes the synergistic effect of dual-complexation sustained release and ultrasonic cavitation to enable EDTA to preferentially complex Cu. 2+ Inhibit Cu 2+ Competitive deposition effectively blocks Cu 2+ To minimize interference with the reduction process, the dual complexation system constructed in this invention operates in an alkaline environment with a pH of 9.5 ± 0.5, forming [Ag(CO3)2]. 3- Control Ag + The release rate is improved, and due to the synergistic effect of dual complexation and sustained release and ultrasonic cavitation, local high pressure is generated, which realizes the micro-jet to promote the directional transport of silver complexes, improves the mass transfer coefficient, and prepares silver-coated copper powder for high-end conductive paste. The silver-coated copper powder has a uniform silver layer and improved adhesion.

[0015] The beneficial effects of this invention are: This invention achieves the following effects through the synergistic effect of dual-complex sustained release and ultrasonic cavitation: (1) Significantly optimized uniformity of the silver layer: Cu was achieved through the synergistic effect of EDTA and ammonium carbonate complexation. 2+ It blocks interference and forms a slow-release silver complex [Ag(CO3)2]. 3- The synergistic effect of dual complexation and sustained release and ultrasonic cavitation removes oxides and enhances mass transfer with microjets, resulting in a higher mass transfer coefficient and a more uniform silver layer compared to traditional replacement processes.

[0016] (2) Significantly enhanced interfacial adhesion: The synergistic effect of dual complexation and sustained release and ultrasonic cavitation reduces the reaction activation energy, promotes dense bonding of silver and copper, improves adhesion, and meets the reliability requirements of high-end slurries. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0018] To better illustrate the purpose, technical solution, and advantages of this invention, the following detailed description will be provided in conjunction with specific embodiments. Unless otherwise specified, all chemical reagents used in the embodiments and comparative examples of this invention are of commercially available analytical grade. The ultrapure water used in the embodiments and comparative examples has a conductivity ≤0.5µS / cm, and the electrolytic copper powder used in the embodiments and comparative examples has a purity ≥99.99%.

[0019] Example 1 A method for preparing silver-coated copper powder based on the synergistic effect of dual-complexation sustained release and ultrasonic cavitation is shown in the process flow diagram below. Figure 1 As shown, the specific steps include: (1) Copper powder pickling: 100μm electrolytic copper powder was placed in a 5% (w / L) nitric acid aqueous solution (the amount of electrolytic copper powder added to the nitric acid aqueous solution was 50g / L). The mixture was pickled at 200rpm for 20min at 25℃, then filtered and washed with ultrapure water until no Cu was found. 2+ (The sample did not change color when tested with sodium diethyldithiocarbamate). After drying to remove moisture, the acid-washed electrolytic copper powder was obtained.

[0020] (2) Construction of a dual complexation system: A mixed aqueous solution of EDTA and ammonium carbonate was prepared using disodium ethylenediaminetetraacetate (EDTA-2Na) and ammonium carbonate to form solution A (the concentration of EDTA in solution A is 0.1 mol / L, the concentration of ammonium carbonate is 0.05 mol / L, and the pH value of solution A is 9.5). The acid-washed electrolytic copper powder was added to solution A and ultrasonically dispersed at a frequency of 40 kHz and a power of 200 W for 20 min to obtain a suspension (the amount of acid-washed electrolytic copper powder added to the suspension is 10 g / L).

[0021] (3) Preparation of silver complex solution: Take solution A, then add silver nitrate to solution A and stir until clear to obtain solution B (the concentration of silver nitrate in solution B is 0.1 mol / L).

[0022] (4) Synergistic reaction: Solution B was added to the suspension at a ratio of 5:1 (copper in suspension to silver in solution B) at a rate of 2 mL / min. The mixture was sonicated at a frequency of 40 kHz and a power density of 200 W / L, and mechanically stirred at a speed of 300 rpm. The reaction was carried out at 30 °C for 30 min. After the reaction was completed, a solid-liquid mixture was obtained.

[0023] (5) Post-processing: The solid-liquid mixture was washed 5 times with ultrapure water, filtered, and vacuum dried at 60°C for 2 hours to obtain silver-coated copper powder based on the synergistic effect of dual complexation sustained release and ultrasonic cavitation.

[0024] The uniformity and adhesion of the silver layer in the silver-coated copper powder prepared in this embodiment were tested, and the test methods are as follows: Silver layer uniformity test: A small amount of the silver-coated copper powder prepared in this embodiment was uniformly dispersed on conductive adhesive and then fixed on the sample stage of a scanning electron microscope. To improve the conductivity of the sample, gold sputtering was performed. The sample was placed in a scanning electron microscope, and an appropriate accelerating voltage (10-20kV) and magnification (5000-20000x) were selected to observe the surface morphology of the silver-coated copper powder. Multiple SEM images of different areas were taken, and elemental analysis was performed on multiple points on the surface of the silver-coated copper powder using an energy dispersive spectroscopy (EDS) analyzer. The silver (Ag) and copper (Cu) content at each point was recorded. The relative standard deviation (RSD) of the silver content at different points was calculated to evaluate the uniformity of the silver layer of the silver-coated copper powder in this embodiment. The lower the RSD, the better the uniformity of the silver layer.

[0025] Adhesion test: Accurately weigh a certain mass (m1) of the silver-coated copper powder prepared in this embodiment and place it in a beaker containing an appropriate amount of deionized water. Place the beaker in an ultrasonic cleaner and set the ultrasonic power and time (power 100W, time min). During the ultrasonic process, maintain the water temperature at 25-30°C. After ultrasonic treatment, centrifuge the solution and collect the precipitate. Wash the precipitate several times with deionized water, and then dry it at 60°C to constant weight. Weigh the dried sample mass (m2). Determine the silver content (w1 and w2) in the sample before and after ultrasonication using inductively coupled plasma mass spectrometry (ICP-MS).

[0026] Adhesion index calculation: The adhesion of the silver layer of copper-coated silver powder prepared in this embodiment is evaluated using the silver layer peeling rate (η). The formula is as follows: η=(w1m1-w2m2) / w1m1×100%, the lower the peeling rate, the stronger the adhesion of the silver layer.

[0027] Tests showed that the silver layer uniformity of the silver-coated copper powder prepared in this embodiment was ±3.5%, and the adhesion was 35.3 N / mm. 2 This indicates that this embodiment achieves Cu through the synergistic complexation of EDTA and ammonium carbonate. 2+ The process effectively blocks interference and enables the slow release of silver ions, which is beneficial for forming a uniform and high-purity silver layer. Furthermore, the synergistic effect of dual complexation and slow release with ultrasonic cavitation removes oxides from the surface of copper powder. The microjets promote the directional transport of silver complexes, improve the mass transfer coefficient, optimize the interfacial bonding ability between silver and copper, and achieve a dense silver-copper bond.

[0028] Example 2 A method for preparing silver-coated copper powder based on the synergistic effect of dual complexation sustained release and ultrasonic cavitation specifically includes the following steps: (1) Copper powder pickling: 100μm electrolytic copper powder was placed in a 3% (w / L) nitric acid aqueous solution (the amount of electrolytic copper powder added to the nitric acid aqueous solution was 40g / L). The mixture was pickled at 30℃ and stirred at 100rpm for 25min. Then it was filtered and washed with ultrapure water until no Cu was found. 2+ (The sample did not change color when tested with sodium diethyldithiocarbamate). After drying to remove moisture, the acid-washed electrolytic copper powder was obtained.

[0029] (2) Construction of a dual complexation system: A mixed aqueous solution of EDTA and ammonium carbonate was prepared using disodium EDTA-2Na and ammonium carbonate to form solution A (the concentration of EDTA in solution A is 0.05 mol / L, the concentration of ammonium carbonate is 0.025 mol / L, and the pH value of solution A is 9). The acid-washed electrolytic copper powder was added to solution A and ultrasonically dispersed at a frequency of 30 kHz and a power of 300 W for 10 min to obtain a suspension (the amount of acid-washed electrolytic copper powder added to the suspension is 5 g / L).

[0030] (3) Preparation of silver complex solution: Take solution A, then add silver nitrate to solution A and stir until clear to obtain solution B (the concentration of silver nitrate in solution B is 0.2 mol / L).

[0031] (4) Synergistic reaction: Solution B was added to the suspension at a mass ratio of 3:1 for copper in the suspension and silver in solution B at a rate of 1 mL / min. The mixture was sonicated at a frequency of 45 kHz and a power density of 180 W / L, and mechanically stirred at a speed of 200 rpm. The reaction was carried out at 28 °C for 50 min. After the reaction was completed, a solid-liquid mixture was obtained.

[0032] (5) Post-processing: The solid-liquid mixture was washed 5 times with ultrapure water, filtered, and vacuum dried at 60°C for 2 hours to obtain silver-coated copper powder based on the synergistic effect of dual complexation sustained release and ultrasonic cavitation.

[0033] The silver-coated copper powder prepared in this example was tested for silver layer uniformity and adhesion using the same method as in Example 1. The results showed that the silver layer uniformity of the silver-coated copper powder prepared in this example was ±10.3%, and the adhesion was 30.25 N / mm². 2 This indicates that this embodiment achieves Cu through the synergistic complexation of EDTA and ammonium carbonate. 2+ The process effectively blocks interference and enables the slow release of silver ions, which is beneficial for forming a uniform and high-purity silver layer. Furthermore, the synergistic effect of dual complexation and slow release with ultrasonic cavitation removes oxides from the surface of copper powder. The microjets promote the directional transport of silver complexes, improve the mass transfer coefficient, optimize the interfacial bonding ability between silver and copper, and achieve a dense silver-copper bond.

[0034] Example 3 A method for preparing silver-coated copper powder based on the synergistic effect of dual complexation sustained release and ultrasonic cavitation specifically includes the following steps: (1) Copper powder pickling: 100μm electrolytic copper powder was placed in a 6% (w / L) nitric acid aqueous solution (the amount of electrolytic copper powder added to the nitric acid aqueous solution was 60g / L). The mixture was pickled at 300rpm for 30min at 20℃, then filtered and washed with ultrapure water until no Cu was found. 2+ (The sample did not change color when tested with sodium diethyldithiocarbamate). After drying to remove moisture, the acid-washed electrolytic copper powder was obtained.

[0035] (2) Construction of a dual complexation system: A mixed aqueous solution of EDTA and ammonium carbonate was prepared using disodium EDTA-2Na and ammonium carbonate to form solution A (the concentration of EDTA in solution A is 0.2 mol / L, the concentration of ammonium carbonate is 0.1 mol / L, and the pH value of solution A is 10). The acid-washed electrolytic copper powder was added to solution A and ultrasonically dispersed at a frequency of 50 kHz and a power of 100 W for 30 min to obtain a suspension (the amount of acid-washed electrolytic copper powder added to the suspension is 20 g / L).

[0036] (3) Preparation of silver complex solution: Take solution A, then add silver nitrate to solution A and stir until clear to obtain solution B (the concentration of silver nitrate in solution B is 0.05 mol / L).

[0037] (4) Synergistic reaction: Solution B was added to the suspension at a ratio of 6:1 (copper in suspension to silver in solution B) at a rate of 3 mL / min. The mixture was sonicated at a frequency of 35 kHz and a power density of 220 W / L, and mechanically stirred at a speed of 400 rpm. The reaction was carried out at 32 °C for 40 min. After the reaction was completed, a solid-liquid mixture was obtained.

[0038] (5) Post-processing: The solid-liquid mixture was washed 5 times with ultrapure water, filtered, and vacuum dried at 60°C for 2 hours to obtain silver-coated copper powder based on the synergistic effect of dual complexation sustained release and ultrasonic cavitation.

[0039] The silver-coated copper powder prepared in this example was tested for silver layer uniformity and adhesion using the same method as in Example 1. The results showed that the silver layer uniformity of the silver-coated copper powder prepared in this example was ±7.1%, and the adhesion was 25.1 N / mm. 2 This indicates that this embodiment achieves Cu through the synergistic complexation of EDTA and ammonium carbonate. 2+ The process effectively blocks interference and enables the slow release of silver ions, which is beneficial for forming a uniform and high-purity silver layer. Furthermore, the synergistic effect of dual complexation and slow release with ultrasonic cavitation removes oxides from the surface of copper powder. The microjets promote the directional transport of silver complexes, improve the mass transfer coefficient, optimize the interfacial bonding ability between silver and copper, and achieve a dense silver-copper bond.

[0040] Comparative Example 1 A method for preparing silver-coated copper powder specifically includes the following steps: (1) Copper powder pickling: 100μm electrolytic copper powder was placed in a 5% (w / L) nitric acid aqueous solution (the amount of electrolytic copper powder added to the nitric acid aqueous solution was 50g / L). The mixture was pickled at 200rpm for 20min at 25℃, then filtered and washed with ultrapure water until no Cu was found. 2+ (The sample did not change color when tested with sodium diethyldithiocarbamate). After drying to remove moisture, the acid-washed electrolytic copper powder was obtained.

[0041] (2) Construction of complexation system: EDTA aqueous solution was prepared using disodium ethylenediaminetetraacetate (EDTA-2Na) to form solution A (the concentration of EDTA in solution A is 0.1 mol / L, and the pH value of solution A is 9.5). The acid-washed electrolytic copper powder was added to solution A and ultrasonically dispersed at a frequency of 40 kHz and a power of 200 W for 20 min to obtain a suspension (the amount of acid-washed electrolytic copper powder added to the suspension is 10 g / L).

[0042] (3) Preparation of silver complex solution: Take solution A, then add silver nitrate to solution A and stir until clear to obtain solution B (the concentration of silver nitrate in solution B is 0.1 mol / L).

[0043] (4) Synergistic reaction: Solution B was added to the suspension at a ratio of 5:1 (copper in suspension to silver in solution B) at a rate of 2 mL / min. The mixture was sonicated at a frequency of 40 kHz and a power density of 200 W / L, and mechanically stirred at a speed of 300 rpm. The reaction was carried out at 30 °C for 30 min. After the reaction was completed, a solid-liquid mixture was obtained.

[0044] (5) Post-processing: The solid-liquid mixture was washed 5 times with ultrapure water, filtered, and vacuum dried at 60°C for 2 hours to obtain silver-coated copper powder.

[0045] The silver-coated copper powder prepared in this comparative example was tested for silver layer uniformity and adhesion using the same testing method as in Example 1. The results showed that the silver layer uniformity of the silver-coated copper powder prepared in this comparative example was ±9.6%, and the adhesion was 19.5 N / mm. 2 This is because this comparative example only used EDTA as a complexing agent, and Cu was present during the concerted reaction process. 2+ Interference, causing Cu 2+ Competitive deposition leads to Ag + The reduction reaction is uneven and insufficient, which prevents the uniform precipitation of the silver layer and results in poor adhesion.

[0046] Comparative Example 2 A method for preparing silver-coated copper powder specifically includes the following steps: (1) Copper powder pickling: 100μm electrolytic copper powder was placed in a 5% (w / L) nitric acid aqueous solution (the amount of electrolytic copper powder added to the nitric acid aqueous solution was 50g / L). The mixture was pickled at 200rpm for 20min at 25℃, then filtered and washed with ultrapure water until no Cu was found. 2+ (The sample did not change color when tested with sodium diethyldithiocarbamate). After drying to remove moisture, the acid-washed electrolytic copper powder was obtained.

[0047] (2) Construction of complexation system: Prepare an aqueous solution of ammonium carbonate to form solution A (the concentration of ammonium carbonate in solution A is 0.05 mol / L, and the pH value of solution A is 9.5). Add the acid-washed electrolytic copper powder to solution A and ultrasonically disperse it for 20 min at a frequency of 40 kHz and a power of 200 W to obtain a suspension (the amount of acid-washed electrolytic copper powder added to the suspension is 10 g / L).

[0048] (3) Preparation of silver complex solution: Take solution A, then add silver nitrate to solution A and stir until clear to obtain solution B (the concentration of silver nitrate in solution B is 0.1 mol / L).

[0049] (4) Synergistic reaction: Solution B was added to the suspension at a ratio of 5:1 (copper in suspension to silver in solution B) at a rate of 2 mL / min. The mixture was sonicated at a frequency of 40 kHz and a power density of 200 W / L, and mechanically stirred at a speed of 300 rpm. The reaction was carried out at 30 °C for 30 min. After the reaction was completed, a solid-liquid mixture was obtained.

[0050] (5) Post-processing: The solid-liquid mixture was washed 5 times with ultrapure water, filtered, and vacuum dried at 60°C for 2 hours to obtain silver-coated copper powder.

[0051] The silver-coated copper powder prepared in this comparative example was tested for silver layer uniformity and adhesion using the same testing method as in Example 1. The results showed that the silver layer uniformity of the silver-coated copper powder prepared in this comparative example was ±14.8%, and the adhesion was 15.1 N / mm. 2 This is because this comparative example only uses ammonium carbonate as a complexing agent, which causes silver to rapidly deposit on the surface of copper powder during the preparation of the silver layer. The reaction is violent, the deposition kinetics of metallic silver are out of control, the silver layer is too thick in some areas and too thin in other areas, and the uniform precipitation of the silver layer cannot be achieved, resulting in poor adhesion.

[0052] Comparative Example 3 A method for preparing silver-coated copper powder specifically includes the following steps: (1) Copper powder pickling: 100μm electrolytic copper powder was placed in a 5% (w / L) nitric acid aqueous solution (the amount of electrolytic copper powder added to the nitric acid aqueous solution was 50g / L, and the pH value of solution A was 9.5). The solution was pickled at 200rpm for 20min at 25℃, then filtered and washed with ultrapure water until no Cu was found. 2+ (The sample did not change color when tested with sodium diethyldithiocarbamate). After drying to remove moisture, the acid-washed electrolytic copper powder was obtained.

[0053] (2) Construction of a dual complexation system: A mixed aqueous solution of EDTA and ammonium carbonate was prepared using disodium ethylenediaminetetraacetate (EDTA-2Na) and ammonium carbonate to form solution A (the concentration of EDTA in solution A is 0.1 mol / L, the concentration of ammonium carbonate is 0.05 mol / L, and the pH value of solution A is 9.5). The acid-washed electrolytic copper powder was added to solution A and ultrasonically dispersed at a frequency of 40 kHz and a power of 200 W for 20 min to obtain a suspension (the amount of acid-washed electrolytic copper powder added to the suspension is 10 g / L).

[0054] (3) Preparation of silver complex solution: Take solution A, then add silver nitrate to solution A and stir until clear to obtain solution B (the concentration of silver nitrate in solution B is 0.1 mol / L).

[0055] (4) Reaction: Add solution B to the suspension at a mass ratio of 5:1 for copper in the suspension and silver in solution B at a rate of 2 mL / min. Stir mechanically at 300 rpm and react at 30°C for 30 min. After the reaction is complete, a solid-liquid mixture is obtained.

[0056] (5) Post-processing: The solid-liquid mixture was washed 5 times with ultrapure water, filtered, and vacuum dried at 60°C for 2 hours to obtain silver-coated copper powder.

[0057] The silver-coated copper powder prepared in this comparative example was tested for silver layer uniformity and adhesion using the same testing method as in Example 1. The results showed that the silver layer uniformity of the silver-coated copper powder prepared in this comparative example was ±7.9%, and the adhesion was 17.4 N / mm. 2 This is because the comparative ratio synergistic reaction process only involves mechanical stirring and does not involve ultrasonic synergistic reaction. Although a uniform distribution of the silver layer is achieved, the lack of local high pressure and the failure to achieve micro-jet to promote the directional transport of the silver complex result in poor mass transfer of the silver complex and poor adhesion between the silver layer and copper powder.

[0058] Comparative Example 4 A method for preparing silver-coated copper powder specifically includes the following steps: (1) Copper powder pickling: 100μm electrolytic copper powder was placed in a 5% (w / L) nitric acid aqueous solution (the amount of electrolytic copper powder added to the nitric acid aqueous solution was 50g / L). The mixture was pickled at 200rpm for 20min at 25℃, then filtered and washed with ultrapure water until no Cu was found. 2+ (The sample did not change color when tested with sodium diethyldithiocarbamate). After drying to remove moisture, the acid-washed electrolytic copper powder was obtained.

[0059] (2) Preparation of suspension: Disperse the acid-washed electrolytic copper powder into ultrapure water and ultrasonically disperse it for 20 minutes at a frequency of 40kHz and a power of 200W to obtain a suspension. The amount of acid-washed electrolytic copper powder added to ultrapure water is 10g / L.

[0060] (3) Displacement reaction: 0.1 mol / L silver nitrate aqueous solution was added dropwise to the suspension at a mass ratio of 5:1 between copper in the suspension and silver in the silver nitrate aqueous solution. The mixture was mechanically stirred at 300 rpm and reacted at 30°C for 30 min. After the reaction was completed, a solid-liquid mixture was obtained.

[0061] (4) Post-processing: The solid-liquid mixture was washed 5 times with ultrapure water, filtered, and vacuum dried at 60°C for 2 hours to obtain silver-coated copper powder.

[0062] The silver-coated copper powder prepared in this comparative example was tested for silver layer uniformity and adhesion using the same testing method as in Example 1. The results showed that the silver layer uniformity of the silver-coated copper powder prepared in this comparative example was ±22.3%, and the adhesion was 14.7 N / mm. 2 This is because the comparative example uses a traditional displacement process to prepare silver-coated copper powder, which relies solely on the chemical potential difference between copper and silver ions to drive the process. The resulting interface bonding is not strong enough, and the silver layer is prone to peeling off during subsequent processing or use.

[0063] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing silver-coated copper powder based on the synergistic effect of dual-complexation sustained release and ultrasonic cavitation, characterized in that, Specifically, the following steps are included: (1) Pickling of copper powder: Electrolytic copper powder is placed in acid solution and stirred for pickling, then filtered, washed and dried to obtain pickled electrolytic copper powder; (2) Construction of a dual complexation system: Prepare a mixed aqueous solution of EDTA and ammonium carbonate to form solution A, and add the acid-washed electrolytic copper powder to solution A and disperse it by ultrasonication to obtain a suspension; (3) Preparation of silver complex solution: Take solution A, then add silver nitrate to solution A to obtain solution B; (4) Synergistic reaction: Solution B is added to the suspension and reacted under ultrasonic and stirring conditions. After the reaction is completed, a solid-liquid mixture is obtained. (5) Post-processing: The solid-liquid mixture is washed, filtered and dried to obtain silver-coated copper powder based on the synergy of dual complexation slow release and ultrasonic cavitation.

2. The method for preparing silver-coated copper powder based on the synergistic effect of dual-complex sustained release and ultrasonic cavitation according to claim 1, characterized in that, In step (1), the acid solution is a nitric acid aqueous solution with a mass percentage concentration of 3-6%; the amount of electrolytic copper powder added to the acid solution is 40-60 g / L; the conditions for stirring and acid washing are: stirring and acid washing at 100-300 rpm for 20-30 minutes at 20-30℃.

3. The method for preparing silver-coated copper powder based on the synergistic effect of dual-complex sustained release and ultrasonic cavitation according to claim 1, characterized in that, In step (2), the concentration of EDTA in solution A is 0.05-0.2 mol / L, the concentration of ammonium carbonate is 0.025-0.1 mol / L, and the pH of solution A is 9.5±0.5; the amount of electrolytic copper powder added to the suspension after acid washing is 5-20 g / L; the conditions for ultrasonic dispersion are: dispersion for 10-30 min at a frequency of 30-50 kHz and a power of 100-300 W.

4. The method for preparing silver-coated copper powder based on the synergistic effect of dual-complex sustained release and ultrasonic cavitation according to claim 1, characterized in that, In step (3), the concentration of silver nitrate in solution B is 0.05-0.2 mol / L.

5. The method for preparing silver-coated copper powder based on the synergistic effect of dual-complex sustained release and ultrasonic cavitation according to claim 1, characterized in that, In step (4), solution B is added to the suspension at a rate of 1-3 mL / min; solution B is added to the suspension at a mass ratio of copper in the suspension to silver in solution B of (3-6):1; the reaction conditions are: at a frequency of 35-45 kHz, a power density of 180-220 W / L, a rotation speed of 200-400 rpm, and a reaction temperature of 28-32℃ for 30-50 min.

6. The silver-coated copper powder based on the synergistic effect of dual complexation sustained release and ultrasonic cavitation prepared by the method according to any one of claims 1 to 5.

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