In this study, we produced Au-Sn alloy electroplated from a single solution and optimized the composition. The composition of electroplated Au-Sn alloy was Au-31.02 at.% Sn at the condition of 6 ms on - 4 ms off pulse current, 50 °C and 10 mA/cm2. Results in XRD analysis showed that Au-Sn alloy electroplated at DC 10 mA/cm2 had AuSn phase (δ) only and Au5Sn phase (d) appeared with decreasing the pulsed current on time. Also micro-patterned Au-Sn solder bump was produced by photolithography. Though it’s composition of Au-35.98 at.% Sn was not optimum, we tried to bond between Au-Sn solder bump and Si wafer that was coated with Ti (100 nm)/Au (300 nm).