An Au-rich, eutectic Au/Sn alloy was fabricated by sequential electroplating of Au and Sn, and reflowing the as-deposited Au/Sn/Au triple-layer film at 320–350 °C. Microstructures and phase compositions for the as-deposited Au/Sn/Au triple-layer film and the reflowed Au-rich, eutectic Au/Sn alloys were studied. Two Si wafers, each with the Au-rich, eutectic Au/Sn alloy solder, were bonded together. For the deposited Au/Sn/Au triple-layer film, reaction between Au and Sn occurs at room temperature leading to the formation of AuSn and AuSn4. After reflowing at 320 °C, two phases remain, AuSn and Au5Sn, with the AuSn particles distributed randomly in the Au5Sn matrix.