Phase Formation in Gold-Tin Alloys Electroplated from a Non-cyanide Bath

Yahui Zhang and Douglas G. Ivey

Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, Canada T6G 2G6

Email: yahui@ualberta.ca; Phone: (780) 492-6192

 

Keywords: Au, Sn, intermetallics, non-cyanide solution, co-electroplating.

 

Abstract

Au-Sn alloys are commonly used as solder materials in semiconductor industries. In this work, gold-tin alloys have been electroplated from a non-cyanide bath. The effects of bath composition and PC plating factors on compositions of Au-Sn deposits, intermetallic phase formation, and plating rates have been investigated. The transition current density for plating the two different gold-tin intermetallics, Au5Sn and AuSn, was shifted to lower current densities at lower ammonium citrate dosage. In addition, deposits plated from solutions with lower ammonium citrate concentrations were denser. Thin film x-ray diffraction analysis showed that only Au5Sn or/and AuSn phases are plated out in the deposits. The growth of either Au5Sn or AuSn phases showed no preferred orientation.

 

 

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