Preparation of core-shell nickel-coated copper composite powder by electroless plating with the assistance of alternative ultrasonic vibration and mechanical stirring
[Introduction]The electroless plating bath and process parameters need to be optimized to enhance the dispersibility and coating quality of nickel-coated copper powder,thereby improving its antioxidation and conductivity when being used as conductive fillers in electronic paste.[Method]The copper powder was activated in a PdCl2-containing solution firstly,followed by electroless plating in an acidic bath with the assistance of alternative ultrasonic vibration and mechanical stirring to produce core-shell-structured nickel-coated copper powder.The micromorphology and crystal structure of the nickel coating were characterized by scanning electron microscopy(SEM)and X-ray diffraction(XRD).The effects of the compositions of activation solution and plating as well as different stirring methods on the electroless plating quality were studied.The nickel coating coverage and anti-oxidizability of the nickel-coated copper powder prepared under the optimized conditions were characterized through SEM observation,energy-dispersive spectroscopic(EDS)mapping,and thermogravimetric analysis.[Result]The composition of activation solution for copper powder was optimized as follows:PdCl2 0.50 mmol/L,HCl 2.40 mol/L,and polyoxyethylene(20)oleyl ether 2.0 g/L.The composition of electroless plating bath was optimized as follows:nickel sulfate 0.037 5 mol/L,sodium acetate 0.15 mol/L,acetic acid 0.27 mol/L,polyoxyethylene(20)oleyl ether 2.0 g/L,and polyvinylpyrrolidone 1.5 g/L.The dropping rate of reductant solution(i.e.3.367 mol/L sodium hypophosphite)was determined as 2.5 mL/h.[Conclusion]The nickel-coated copper powder prepared under the optimized conditions exhibited high coating coverage,good compactness,uniform dispersion,and excellent anti-oxidizability.
nickel-coated copper powderelectroless platingalternative ultrasonic vibration and mechanical stirringconductive fillerantioxidation
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