Electrochemical Study on Electroless Copper Plating Using Sodium Hypophosphite as Reductant

The process of electroless copper plating, using sodium hypophosphite as the reductant and sodium citrate as the chelating agent, was studied using liner sweep voltammetry. The effects of temperature, pH, and concentration of nickel ion on the anodic oxidation of hypophosphite and the cathodic reduction of copper ion were tested. The results indicated that the higher bath temperature accelerated both the anodic and the cathodic processes. The increasing pH value promoted hypophosphite oxidation, whereas it blocked the reduction of the copper ion. The nickel ion not only intensively catalyzed the hypophosphite oxidation but also codeposited with the copper ion to form the Cu-Ni alloy. With regard to its catalytic activity, this alloy enabled the continuation of the electroless copper plating reaction.