On the kinetics of copper electroless plating with hypophosphite reductant

Abstract

The electroless copper plating using sodium hypophosphite as the reductant and sodium citrate as the chelating agent was studied by gravimetric and electrochemical measurements. The effects of temperature, pH, boric acid, citrate, hypophosphite, nickel catalyst and copper concentration were tested. A chemical model was defined to determine the composition of all ionic species in the bath solution. The kinetics of the electroless copper deposition was interpreted on the basis of the dehydrogenation of the reductant, mixed potential theory and in the ionic speciation of the bath. Scanning electron microscopy, X-ray microanalysis by energy spectroscopy dispersion and X-ray diffraction applied on surfaces show that the deposits are composed by binary (Ni–Cu) and ternary alloys (Cu–Ni–P) and that their crystallinity depends on phosphorus content.