Tin-rich, Sn-Au solder films were fabricated using electrodeposition, from a suspension composed of a Sn electrolyte with suspended Au particles. The Sn-rich eutectic alloy offers a potentially cheaper alternative to the Au-rich eutectic for optoelectronic and MEMS device packaging and may be applicable as a Pb-free solder for microelectronic packaging. Eutectic and near-eutectic deposits, with uniform thicknesses and compositions were fabricated. Gold content in the deposits increased with increasing Au particle loading in the electrolyte and increasing current density. Room temperature aging led to the formation of AuSn_4 at the Au particle-Sn matrix interface. Reflow of deposits with near-eutectic compositions resulted in the formation of the two eutectic phases, Sn and AuSn_4.
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