Effect of In Addition on Wetting Properties of Sn-Zn-In/Cu Soldering

Abstract

In this study, trace amounts (0.5–2 mass%) of indium (In) are added to the binary Sn-9Zn alloy to examine the effect of such addition on wetting properties of Sn-9Zn-In soldering. Results show that addition of In to Sn-9Zn alloy leads to decrease in eutectic temperature; and the greater the amount of In added, the larger the decrease is. On the other hand, the maximum wetting force, an indicator of wettability and solderability, increases with increasing mass% of In added. In addition, the higher the eutectic temperature, the better the wettability of solder is. Increasing In content in the solder also enhances the dissolution of Cu. Moreover, the higher the In content, the faster the dissolution rate is. At wetting temperatures of 220°C and 240°C, the wetting time achieved is shorter than 3 s, which can meet practical needs for industrial applications. In sum, the addition of 0.5 mass% of In is optimal in that it can achieve good wettability while maintaining low dissolution rate, which would also enhance solderability.