Preparation method of ultralow-porosity silver-coated copper powder

Abstract

The invention discloses a preparation method of ultralow-porosity silver-coated copper powder, and belongs to the technical field of metal powder surface modification. The preparation method comprises the following steps: adding copper powder into a mixed solution containing NaOH, SDS, Tween 80 and sodium citrate, and carrying out ultrasonic treatment; immersing the filtered solid into a H2SO4 solution for ultrasonic treatment, and secondarily dispersing the filtered solid into a NaOH solution for ultrasonic treatment to obtain an activated copper powder suspension; and the activated copper powder suspension is added into a mixed solution of sodium potassium tartrate tetrahydrate and erythrosine B, then the mixture is placed under ultrasonic and ultraviolet irradiation, finally, a silver ammonia solution is added for a reaction, and after the reaction is finished, washing, centrifugal separation and drying are conducted to obtain the ultralow-porosity silver-coated copper powder. The obtained ultralow-porosity silver-coated copper powder coating is low in porosity, high in bonding strength, high in oxidation resistance, high in coating uniformity and good in conductivity.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal powder surface modification, and particularly relates to a preparation method of ultra-low porosity silver-coated copper powder. BACKGROUND

[0002] In the field of electronic materials and conductive materials, silver-coated copper powder is widely used in electronic paste, electrode material and conductive adhesive due to its excellent conductivity and low cost. Silver-coated copper powder is mainly prepared by plating silver on the surface of copper powder, and has significant advantages in conductivity, oxidation resistance and cost. However, there are some defects in the preparation process of silver-coated copper powder in the prior art, such as high porosity, poor particle uniformity, and poor adhesion of the silver plating layer, which limits the application performance of silver-coated copper powder. At present, common silver-coated copper powder preparation methods include chemical silver plating, electroplating and reduction method. Although these methods can realize the silver plating on the surface of copper powder, it is usually difficult to control the porosity and uniformity of the particles. Specifically, the problems of high porosity, poor uniformity and poor adhesion of the silver plating layer will lead to the decrease of the conductivity and oxidation resistance of silver-coated copper powder.

[0003] Therefore, there is an urgent need for a new preparation method which can significantly reduce the porosity of silver-coated copper powder, improve the uniformity and adhesion of the silver plating layer, and thus improve the conductivity and stability of silver-coated copper powder. SUMMARY

[0004] To solve or partially solve the problems in the related art, the application provides a preparation method of ultra-low porosity silver-coated copper powder, which significantly reduces the porosity of silver-coated copper powder, improves the uniformity and adhesion of the silver plating layer by multi-step ultrasonic treatment, chemical activation, ultraviolet light irradiation, ultrasonic assisted reaction and optimized chemical reagent ratio. The ultra-low porosity silver-coated copper powder prepared by the application has significant advantages in conductivity, oxidation resistance and cost-effectiveness, and can meet the application requirements of high-performance electronic materials.

[0005] The application provides a preparation method of ultra-low porosity silver-coated copper powder, which comprises the following steps: (1) ultrasonic treatment of copper powder in a mixed solution containing NaOH, SDS, Tween 80 and sodium citrate; after filtration, the solid is immersed in an H2SO4 solution for ultrasonic treatment, and the filtered solid is dispersed in a NaOH solution for ultrasonic treatment to obtain an activated copper powder suspension; (2) adding the activated copper powder suspension into a mixed solution of potassium sodium tartrate and erythrosin B, and then placing it under ultrasonic wave and ultraviolet light irradiation; finally, adding silver ammonia solution for reaction, and then washing, centrifugal separation and drying to obtain ultra-low porosity silver-coated copper powder.

[0006] Preferably, the mass-volume ratio of the copper powder to the mixed solution containing NaOH, SDS, Tween 80 and sodium citrate is 5g:250ml; the mass concentration ratio of NaOH, SDS, Tween 80 and sodium citrate in the mixed solution containing NaOH, SDS, Tween 80 and sodium citrate is: 10:0.12:0.08:1-3, wherein the concentration of sodium citrate is 1-2 g / L, more preferably, the concentration of sodium citrate is 1.5-2.5 g / L. In the present application, SDS and Tween 80 need to be used in combination to achieve complete surface treatment of the copper powder. If one of them is missing, the porosity of the silver-coated copper powder obtained is significantly increased, the bonding strength of the silver layer to the copper powder is reduced, the conductivity is increased, and the uniformity of the silver layer is decreased.

[0007] Preferably, the concentration of the H2SO4 solution is 0.2 mol / L, and the concentration of the NaOH solution is 8 g / L.

[0008] Preferably, the mass concentration ratio of potassium sodium tartrate and erythrosin B in the mixed solution of potassium sodium tartrate and erythrosin B is 50:0.0005-0.002.

[0009] Preferably, the mass concentration of erythrosin B in the mixed solution of potassium sodium tartrate and erythrosin B is 0.5-2.0 mg / L; more preferably, the mass concentration of erythrosin B in the mixed solution of potassium sodium tartrate and erythrosin B is 0.8-1.5 mg / L. Preferably, the power of the ultrasonic wave is 100 W, and the frequency is 40 kHz; the wavelength of the ultraviolet light is 365±10 nm, and the power density is 50 mW / cm 2 .

[0010] Preferably, the ultraviolet light uses a pulse mode, and the light irradiation time is 10s and the intermittent time is 5s. If the pulse mode is not used, but continuous ultraviolet light irradiation is used, heat accumulation and photodegradation effects may occur, thereby affecting the uniformity and adhesion of the silver-coated copper powder coating.

[0011] Preferably, the silver-ammonia solution is prepared from AgNO3 and 28% ammonia water, wherein the concentration of AgNO3 is 0.15 mol / L.

[0012] The technical scheme provided by the present application has the following beneficial effects: (1) This invention first adopts a synergistic formula of "SDS + Tween 80 + sodium citrate" to deeply clean copper powder and complex and remove trace metal impurities, providing an ultra-high activity surface. Then, in the silver plating stage, erythrosine B is introduced in synergy with ultraviolet light and ultrasound to significantly enhance the photocatalytic reduction efficiency and uniformity. The invention also features a unique integrated continuous process of "alkali (containing chelating agent) - acid - alkali activation" and photochemical deposition to avoid intermediate oxidation. At the same time, the ultraviolet light irradiation adopts a pulse mode to optimize energy input, increasing the silver utilization rate by more than 40%. The coating has excellent comprehensive performance and is suitable for high-end electromagnetic shielding and conductive materials.

[0013] (2) The ultra-low porosity silver-coated copper powder coating obtained by the preparation method of the ultra-low porosity silver-coated copper powder described in this invention has low porosity, high bonding strength, strong oxidation resistance, high coating uniformity and good conductivity. Detailed Implementation

[0014] Example 1 A method for preparing ultra-low porosity silver-coated copper powder includes the following steps: (1) Add 5g of copper powder to 250mL of a mixed solution containing 10g / L NaOH, 0.12g / L SDS, 0.08g / L L-80 and 1.5g / L sodium citrate and sonicate at 40kHz for 8min. After filtration, immerse the solid in 200mL of 0.2mol / L H2SO4 solution and sonicate at 45kHz for 10min. After filtration, disperse the solid again in 200mL of 8g / L NaOH solution and sonicate for 8min to obtain an activated copper powder suspension.

[0015] (2) Add the activated copper powder suspension to 165 mL of a mixed solution containing 50 g / L potassium sodium tartrate and 0.5 mg / L erythrosine B, and then start the dual-mode energy field (ultrasound + ultraviolet light): ultrasound: power 100 W, frequency 40 kHz; pulsed ultraviolet light irradiation: wavelength 365 nm, power density 50 mW / cm², irradiation 10 s, interval 5 s; then add 150 mL of silver ammonia solution prepared with 0.15 mol / L AgNO3 and 28% ammonia water dropwise to the above mixture at a rate of 1.2 mL / min for 30 min reaction. After the reaction, wash with deionized water / ethanol alternately, centrifuge, and dry with infrared at 60°C for 4 h to obtain ultra-low porosity silver-coated copper powder.

[0016] Example 2 A method for preparing ultra-low porosity silver-coated copper powder includes the following steps: (1) Add 5g of copper powder to 250mL of a mixed solution containing 10g / L NaOH, 0.12g / L SDS, 0.08g / L L-80 and 2.5g / L sodium citrate and sonicate at 40kHz for 8min. After filtration, immerse the solid in 200mL of 0.2mol / L H2SO4 solution and sonicate at 45kHz for 10min. After filtration, disperse the solid again in 200mL of 8g / L NaOH solution and sonicate for 8min to obtain an activated copper powder suspension.

[0017] (2) Add the activated copper powder suspension to 165 mL of a mixed solution containing 50 g / L potassium sodium tartrate and 2.0 mg / L erythrosine B, and then start the dual-mode energy field (ultrasound + ultraviolet light): ultrasound: power 100 W, frequency 40 kHz; pulsed ultraviolet light irradiation: wavelength 365 nm, power density 50 mW / cm², irradiation 10 s, interval 5 s; then add 150 mL of silver ammonia solution prepared with 0.15 mol / L AgNO3 and 28% ammonia water dropwise to the above mixture at a rate of 1.2 mL / min for 30 min reaction. After the reaction, wash with deionized water / ethanol alternately, centrifuge, and dry with infrared at 60°C for 4 h to obtain ultra-low porosity silver-coated copper powder.

[0018] Comparative Example 1 A method for preparing silver-coated copper powder includes the following steps: (1) Add 5g of copper powder to 250mL of a mixed solution containing 10g / L NaOH, 0.12g / L SDS and 0.08g / L Tween 80 and sonicate at 40kHz for 8min. After filtration, immerse the solid in 200mL of 0.2mol / L H2SO4 solution and sonicate at 45kHz for 10min. After filtration, disperse the solid again in 200mL of 8g / L NaOH solution and sonicate for 8min to obtain an activated copper powder suspension.

[0019] (2) Add the activated copper powder suspension to 165 mL of a mixed solution containing 50 g / L potassium sodium tartrate and 0.5-2.0 mg / L erythrosine B, and then start the dual-mode energy field (ultrasound + ultraviolet light): ultrasound: power 100 W, frequency 40 kHz; pulsed ultraviolet light irradiation: wavelength 365 nm, power density 50 mW / cm², irradiation 10 s, interval 5 s; then add 150 mL of silver ammonia solution prepared with 0.15 mol / L AgNO3 and 28% ammonia water dropwise to the above mixture at a rate of 1.2 mL / min and react for 30 min. After the reaction, wash with deionized water / ethanol alternately, centrifuge, and dry with infrared at 60°C for 4 h to obtain silver-coated copper powder.

[0020] Comparative Example 2 A method for preparing silver-coated copper powder includes the following steps: (1) Add 5g of copper powder to 250mL of a mixed solution containing 10g / L NaOH, 0.12g / L SDS, 0.08g / L Tween 80 and 1.0-3.0g / L sodium citrate and sonicate at 40kHz for 8min. After filtration, immerse the solid in 200mL of 0.2mol / L H2SO4 solution and sonicate at 45kHz for 10min. After filtration, disperse the solid again in 200mL of 8g / L NaOH solution and sonicate for 8min to obtain an activated copper powder suspension.

[0021] (2) Add the activated copper powder suspension to 165 mL of 50 g / L potassium sodium tartrate solution, and then start the dual-mode energy field (ultrasound + ultraviolet light): ultrasound: power 100 W, frequency 40 kHz; pulsed ultraviolet light irradiation: wavelength 365 nm, power density 50 mW / cm², irradiation 10 s, interval 5 s; then add 150 mL of silver ammonia solution prepared with 0.15 mol / L AgNO3 and 28% ammonia water dropwise to the above mixture at a rate of 1.2 mL / min for 30 min reaction. After the reaction, wash with deionized water / ethanol alternately, centrifuge, and dry with infrared at 60°C for 4 h to obtain silver-coated copper powder.

[0022] Comparative Example 3 A method for preparing silver-coated copper powder includes the following steps: (1) Add 5g of copper powder to 250mL of a mixed solution containing 10g / L NaOH, 0.12g / L SDS, 0.08g / L L-80 and 1.0-3.0g / L sodium citrate and sonicate at 40kHz for 8min. After filtration, immerse the solid in 200mL of 0.2mol / L H2SO4 solution and sonicate at 45kHz for 10min. After filtration, disperse the solid again in 200mL of 8g / L NaOH solution and sonicate for 8min to obtain an activated copper powder suspension.

[0023] (2) Add the activated copper powder suspension to 165 mL of a mixed solution containing 50 g / L potassium sodium tartrate and 0.5-2.0 mg / L erythrosine B, and then start pulsed ultraviolet light irradiation: wavelength 365 nm, power density 50 mW / cm², irradiation for 10 s, and interval for 5 s; then add 150 mL of silver ammonia solution prepared with 0.15 mol / L AgNO3 and 28% ammonia water dropwise to the above mixture at a rate of 1.2 mL / min and react for 30 min. After the reaction, wash with deionized water / ethanol alternately, centrifuge, and dry with infrared at 60°C for 4 h to obtain silver-coated copper powder.

[0024] Comparative Example 4 A method for preparing silver-coated copper powder includes the following steps: (1) Add 5g of copper powder to 250mL of a mixed solution containing 10g / L NaOH, 0.12g / L SDS, 0.08g / L L-80 and 1.0-3.0g / L sodium citrate and sonicate at 40kHz for 8min. After filtration, immerse the solid in 200mL of 0.2mol / L H2SO4 solution and sonicate at 45kHz for 10min. After filtration, disperse the solid again in 200mL of 8g / L NaOH solution and sonicate for 8min to obtain an activated copper powder suspension.

[0025] (2) Add the activated copper powder suspension to 165 mL of a mixed solution containing 50 g / L potassium sodium tartrate and 0.5-2.0 mg / L erythrosine B, and then start the ultrasound: ultrasound power 100 W, frequency 40 kHz; then add 150 mL of silver ammonia solution prepared with 0.15 mol / L AgNO3 and 28% ammonia water dropwise to the above mixture at a rate of 1.2 mL / min for 30 min. After the reaction is completed, wash with deionized water / ethanol alternately, centrifuge, and dry with infrared at 60°C for 4 h to obtain silver-coated copper powder.

[0026] Example of effect This study tested the plating porosity, conductivity, bonding strength between the plating and copper powder, oxidation resistance, and silver layer thickness uniformity of the silver-coated copper powder prepared in Example 1 and Comparative Examples 1-4. The results are shown in Table 1.

[0027] Table 1 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 ultra-low porosity silver-coated copper powder, characterized in that: Includes the following steps: (1) Copper powder was added to a mixed solution containing NaOH, SDS, Tween 80 and sodium citrate and ultrasonically treated; the filtered solid was immersed in H2SO4 solution and ultrasonically treated; the filtered solid was then dispersed in NaOH solution and ultrasonically treated to obtain an activated copper powder suspension. (2) The activated copper powder suspension was added to a mixed solution of potassium sodium tartrate and erythrosine B, and then placed under ultrasonic and ultraviolet light. Finally, silver ammonia solution was added to carry out the reaction. After the reaction was completed, the mixture was washed, centrifuged and dried to obtain ultra-low porosity silver-coated copper powder.

2. The preparation method of ultra-low porosity silver-coated copper powder as described in claim 1, characterized in that: The mass-to-volume ratio of the copper powder to the mixed solution containing NaOH, SDS, Tween 80, and sodium citrate is 5 g: 250 ml; the mass concentration ratio of NaOH, SDS, Tween 80, and sodium citrate in the mixed solution is: 10:0.12:0.08:1-3, wherein the concentration of sodium citrate is 1-2 g / L.

3. The preparation method of ultra-low porosity silver-coated copper powder as described in claim 1, characterized in that: The concentration of the H2SO4 solution is 0.2 mol / L, and the concentration of the NaOH solution is 8 g / L.

4. The preparation method of ultra-low porosity silver-coated copper powder as described in claim 1, characterized in that: The mass concentration ratio of potassium sodium tartrate and erythrosine B in the mixed solution is 50:0.0005-0.

002.

5. The preparation method of ultra-low porosity silver-coated copper powder as described in claim 1, characterized in that: The ultrasonic wave has a power of 100W and a frequency of 40kHz; the ultraviolet light has a wavelength of 365±10nm and a power density of 50mW / cm². 2 .

6. The method for preparing ultra-low porosity silver-coated copper powder as described in claim 1, characterized in that: The ultraviolet light irradiation adopts a pulse mode, with 10 seconds of illumination followed by a 5-second interval.

7. The method for preparing ultra-low porosity silver-coated copper powder as described in claim 1, characterized in that: The silver ammonia solution is prepared by mixing AgNO3 and 28% ammonia solution, wherein the concentration of AgNO3 is 0.15 mol / L.

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