Electroless plating solution containing thiodiglycolic acid and arylsulphonic acid condensate with formalin

摘要

An electroless plating solution comprises nickel ion, a chelating agent for nickel ion, a reducing agent eg dimethylamine borane, one or more soluble salts of a condensate of an arylsulphonic acid with formalin, and thiodiglycolic acid. The solution may further contain a propynesulphonate. The arylsulphonic acid used in the condensate is preferably a naphtholenesulphonic acid. The nickel film formed may have a thickness of 5-200 mu m. The substrate to be coated may be immersed while it is rocking or while barrel processing is carried out. Alternatively the immersion is conducted while the electroless plating solution is subjected to continuous filtration. The substrate may be a substrate which has previously been subjected to an electroless plating with Ni-P alloy. The electroless plating solution has a high bath stability and is capable of forming an excellent thick deposit free from pits and cracks.