Electroless Ni plating solutions for reproducible black pad analyses.

Abstract

A large-scale black pad of electroless nickel (EN) plated films were reproduced using pure chemicals: NiCl2·6H2O as the Ni source, NaH2PO2·H2O as the reducing agent, CH3COONa·3H2O and aminoacetate as the complexing agent and the buffer, respectively, and thiourea as the stabilizer. Plating baths with varying constituent compositions were investigated, and chemical compositions most suitable to the black pad study were sought. Cross-sectional scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses showed that the nickel-phosphorus (Ni-P) film made out of the #5 bath best demonstrated the typical characteristics of the black pad phenomenon after the immersion gold (IG) process. Additions of a low level of Thiourea (0.6mg/L), slightly larger amounts of glycine (1∼1.25x) and the complexing agent (1.25x) were suggested from the standpoint of the black pad formation of Ni-P films.