Development of electroless NiSnP plating with excellent bath stability using nickel hydroxide

ABSTRACT In general, NiSn alloys are known as plating films with elegant lustre and excellent corrosion resistance. Electroplating methods have already reached a practical application level because high Sn-containing films can be obtained. On the other hand, electroless plating methods have not yet reached the level of practical application because the Sn content in the deposited film is not only low but also the corrosion resistance is not sufficient. The authors have studied in detail the composition of electroless plating baths to obtain NiSnP films with Sn content above 50 wt%. In particular, the plating bath using nickel hydroxide instead of nickel sulphate as the Ni source increased bath stability and obtained high Sn content. The effects of Ni source in the bath on the deposition films were studied. The bath using nickel hydroxide as the Ni source was almost unaffected by the bath ratio. Furthermore, the amount of dissolved oxygen (DO) in the plating bath also varied depending on the Ni source, affecting the composition of the deposited film and the bath stability. It was confirmed that electroless plating baths using nickel hydroxide have excellent bath stability and can be applied to a relatively wide range of plating operation conditions to obtain high Sn-containing films. In addition, the corrosion resistance was improved by increasing the Sn content in the film. It was also confirmed that the NiSnP with high Sn content does not dissolve in nitric acid.