Electroless Pd–Ni–P alloy plating from ammonium–ethylenediamine solution

Abstract

The peculiarities of Pd–Ni–P alloy electroless plating from hypophosphite ammonium–ethylenediamine solutions have been investigated. A simple and effective method to control the alloy composition based on varying pH in the solution has been found. It has been detected that the lowering of pH from 12.0 to 7.6 stimulates a decrease in the partial rate of Pd(II) reduction and provides enrichment of the alloy with nickel from 0.3 to 82at.%. Simultaneous reduction of palladium and nickel with hypophosphite enables the formation of alloy containing amorphous palladium, solid solution of palladium in nickel, palladium and nickel phosphides. Alloying proceeds with an effect of depolarization inherent to both metals. The experimental results show that effectiveness of Pd and Ni alloying process arises from palladium cementation with nickel and acceleration of catalytic hypophosphite oxidation on freshly reduced palladium or nickel.