Taguchi Optimization of Wetting, Thermal and Mechanical Properties of Sn-1.0wt.%Ag-0.5wt.%Cu Alloys Modified with Bi and Sb

Abstract

This study was conducted on SAC105 (Sn-1wt.%Ag-0.5wt.%Cu) lead-free solder modified with Bi and Sb. The wetting, melting point, and mechanical properties were analysed with the addition of 1~5 wt.%Bi and 1~5 wt.%Sb for SAC105 base alloy. The wetting characteristics were assessed by wetting time (zero cross time, ZCT) obtained from wetting balance tests. The mechanical properties were analysed by tensile tests. Considering two factors (Bi, Sb), a three-level (0, 1, 2 wt.%) design of experiment (DOE) method array was applied for Taguchi optimization. The results indicated that the solder wetting increased as Bi content increased, while it decreased with Sb. The ZCT decreased with increasing Bi content up to 4 wt.%, while it increased proportionally to Sb content. The melting point, measured using a differential scanning calorimeter (DSC), showed that the melting point tended to decrease according to Bi increase, while it increases depending on the Sb content. Increase in Bi and Sb levels resulted in enhanced tensile strength in the mechanical properties tests, with Bi having a more noticeable impact. The Taguchi optimized conditions for the Bi and Sb studies were found to be 2 wt.%Bi and 2 wt.%Sb. This led to an optimal set of 0.9 s of wetting time, a 222.55 °C melting point, a 55 MPa tensile strength, and a 50% elongation.

Keywords

• lead-free solder
• SAC alloy
• wetting
• microstructure
• mechanical properties