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A Cryo-XPS Study of Triammonium Citrate-KAuCl4-Na2SO3 Electroplating Solutions for Pb-Free Solder Packaging

Research paper by Neda Dalili, Anqiang He, Qi Liu, Douglas G. Ivey

Indexed on: 04 Jun '10Published on: 04 Jun '10Published in: Journal of Electronic Materials



Abstract

Cyanide-free Au plating baths, containing KAuCl4, triammonium citrate, and sodium sulfite, have been developed by the authors. The stability of these solutions depends on the order of mixing of the additives. The aim of this study was to employ turbidity measurements and cryogenic x-ray photoelectron spectroscopy (XPS) to identify the role of the additives and the complexes responsible for solution stability or degradation. Electron microscopy was used to characterize any precipitation products generated in the solutions. It was shown that the long-term stability of the solutions is due to the role of citrate and sulfite as complexing agents.