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

An Erratum to this article was published on 19 October 2010

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.

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Funding from the Natural Sciences and Engineering Research Council (NSERC) of Canada and support of Micralyne Inc. are greatly acknowledged. The authors would also like to thank R. Eslahpazir for help with TEM imaging and the Alberta Centre for Surface Engineering and Science (ACSES) for providing access to XPS facilities.

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Correspondence to Douglas G. Ivey.

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An erratum to this article can be found at

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Dalili, N., He, A., Liu, Q. et al. A Cryo-XPS Study of Triammonium Citrate-KAuCl4-Na2SO3 Electroplating Solutions for Pb-Free Solder Packaging. Journal of Elec Materi 39, 1554–1561 (2010).

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  • Cryogenic XPS
  • Au electroplating solution
  • Au+ complexes
  • citrate
  • sulfite