Effects of Electroless NiSnP Plating Bath Composition with High Sn Containing Deposited Film

Abstract

Many studies have investigated Ni-Sn alloy because it has good luster and excellent corrosion resistance. Electroplating methods have already reached a practical level of applicability, but electroless plating methods have not reached such a degree of utility because they present difficulties such as insufficient film thickness and low Sn content in the deposited film. Therefore, we fixed the bath temperature and stirring under the operating conditions and studied details of the plating bath composition to deposit a film with a high Sn content of 50 wt% or more using electroless plating.

Results confirmed that the Sn contents in the deposited films differed depending on the complexing agent concentration, metal ratio, bath pH, and especially the metal source. Citric acid and sodium gluconate were suitable as complexing agents for each metal source. In the plating bath using Ni（OH）₂ as the Ni metal source, high contents of Sn were co-deposited stably. Moreover, Sn^4＋ was more suitable than Sn^2＋ as the Sn metal source. Because Sn^4＋ formed stable complex ions, the plating bath was stabilized. A film with high Sn content was deposited. Therefore, films with 50 wt% or more Sn contents were obtained even when using electroless plating.