Electroless Ni plating solutions for reproducible black pad analyses

摘要

A large-scale black pad of electroless nickel (EN) plated films were reproduced using pure chemicals:NiCl_2·6H_2O as the Ni source, NaH_2PO_2·H_2O as the reducing agent, CH_3COONa·3H_2O and aminoacetate as thecomplexing agent and the buffer, respectively, and thiourea as the stabilizer. Plating baths with varyingconstituent compositions were investigated, and chemical compositions most suitable to the black pad studywere 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 typicalcharacteristics of the black pad phenomenon after the immersion gold (IG) process. Additions of a low level ofThiourea (0.6mg/L), slightly larger amounts of glycine (1～1.25x) and the complexing agent (1.25x) weresuggested from the standpoint of the black pad formation of Ni-P films.