Influence of indium on wetting behaviors of Sn-8Zn-3Bi lead-free solders

The wetting behaviors of the Sn-8Zn-3Bi-(0-5)In alloys on Cu substrate were tested by an area-of-spread method. The spreading areas of these alloys increase with the addition of In before In content reaches 0.5wt%, which indicates small addition of In can improve the wettability of Sn-8Zn-3Bi based alloys. Bubble's largest pressure method was applied to measure the surface tensions of the Sn-8Zn-3Bi-(0-1.5)In melts. Adding 0.5wt% In into the foundry alloy, the surface tension of the alloy is lower than that of the other alloys. But more addition of In causes degradation of the surface tension. Wetting balance method was used to evaluate the wetting forces of these solders on Cu substrates. With addition of 0.5wt% In, wetting force reaches the maximum, which results from decrease of the solder/Cu interfacial tension.