Copper Pyrophosphate/PY61H Plating Bath: Chemical Variables, Synergism, and Electrodeposition Mechanism. Topical Report

摘要

The study identified chemically PY61H, a proprietary agent used in copper pyrophosphate baths for its brightening and leveling properties for plated through-holes of printed wiring boards (PWBs). Numerous weapons programs incorporate printed wiring boards. PY61H consisted primarily of the dipotassium salt of 2,5-dimercapto-1,3,4-thiadiazole. Laboratory-scale prototypes of production baths demonstrated that the dimercaptothiadiazole salt can produce a bright plate analogous to the PY61H mixture. The effective brightener concentration for both PY61H and dimercaptothiadiazole was determined by cyclic voltammetry performed at a rotating platinum disk electrode. New peaks attributed to brightener degradation products became evident from the voltammograms of prototypes that have undergone successive electrolysis and brightener addition steps. Scattering of the points from plots of brightener concentration varying with voltammetric response revealed the need to operate the bath within narrower ranges for the inorganic constituents, especially ammonia. This report describes the mechanism postulated to be responsible for the leveling in the copper pyrophosphate bath. (ERA citation 07:004952)