Phase Formation in
Gold-Tin Alloys Electroplated from a Non-cyanide
Yahui Zhang and
Douglas G. Ivey
Department of
Chemical and Materials Engineering,
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.