Sorry, I totally forgot the electroplating and I remember that we need to add three kinds of chemicals to the plating bath and one of the chemical is organic sulphur compound for covering.
I search from Google and get the following information:
"Detailed Product Description
M (2-meracapto-benzimidazole) Chemical name: 2-meracapto-benzimidazole Molecular formula: C7H6N2S CA No. 583-39-1 Appearance White crystal Assay >= 95% Melting Point ( C) 303-304 Level of addition 0.6-1.0 mg/l Application: It is soluble in alkaline solution, M is used as brightener for copper plating, which can brighten and level the deposit. Furthermore, it can improve working current density."
"A little ambiguity? Are you talking about a brightener additive for an acid copper plating bath or an acid dip to brighten parts made of copper?
Red Sky Plating - Albuquerque, NM, USA
Have you tried thiourea? Use it sparingly. Be very careful, this thing will give you pancreatic cancer and damage your bones.
- Aurora, CO, U.S.A."