Complexation Chemistry in Nickel and Copper-Nickel Alloy Plating from Citrate Baths

Abstract

Following a previous study of the influence of solution chemistry on the electrodeposition kinetics for copper deposition from complexing citrate baths, the present work examines the corresponding influence for nickel and copper-nickel alloys. The distributions of various metal-citrate chelates, computed as a function of bath composition and pH, are combined with model mechanisms for electrodeposition kinetics involving adsorbed blocking intermediates. The methodology permits not only interpretation of the partial-current curves measured in nickel-citrate baths, but also of the partial-current curves determined for copper and for nickel in composition citrate baths. For the case of codeposition, the copper behavior is similar to that observed without nickel, whereas the nickel deposition is catalyzed by the copper. When correctly accounting for solution chemistry, a simple model is sufficient to describe the essential features of the single nickel and the codeposition kinetics. © 2005 The Electrochemical Society. All rights reserved.