Abstract: Based on the stable Ivey non-cyanide Au-Sn alloy plating solution at room temperature,a new stable non-cyanide Au-Sn alloy plating solution at high temperatures was developed which could kept stable at 50 ℃ for 5 h without decomposition,using EDTA which was instead of ammonium citrate as gold ion complexing agent,potassium pyrophosphate as tinion complexing agent and adjusting the plating solution pH value from 6.0 to 8.0.The effects of NaAuCl4·2H2O concentration and current density (D) on the solution stability,coating composition and the growth rate of the non-cyanide plating solution were investigated.The results show that at 45 ℃ and kept the other composition as well as the concentration of the solution stable,the fastest growth rate of the coating was obtained and its stability was good when the NaAuCl4·2H2O concentration was 10 g·L-1.When the D value was in the range of 6-10 mA·cm-2 ,with the increasing of D the grain size of the coating increased and the growth rate of the coating increased first and then decreased.When the D value was 7 mA·cm-2,the growth rate was the fastest which increased to 24 μm·h-1.Au-Sn bumps electroplated on Si substrate (vapor plating with Au seed layer) in the plating solution had regular shape,and the composition was homogeneous.