Effect of the LaNd Addition on Melting Point and Spreading Properties of Bi5Sb8Sn Solder Alloy

Bi5Sb8Sn solder alloy is the most promising alternative to existing high-Pb solder as high-temperature lead-free soft solder alloy series whose melting point is about 264°C and have better conductivity and mechanical properties, but its wettability need to be improved. In this paper a novel Bi5Sb8SnLaNd quaternary alloy have been developed by adding a small amount of mixed rare earth LaNd elements into Bi5Sb8Sn solder alloy to improve the technological properties of Bi5Sb8Sn alloys. The experimental results showed that adding 0.1～0.3wt.% LaNd into Bi5Sb8Sn solder alloy made the melting point changed slightly, but resulted in the wettability of the solder alloy significant improvement. Compared with the matrix of Bi5Sb8Sn, the spreading area of solder alloy was about 20% bigger when the content of LaNd is 0.1wt.%. With increasing the content of rare earth LaNd, the spreading area of solder alloy decreased, but it was still higher than that of the matrix of Bi5Sb8Sn. This may be mainly attributed to the formation of new phases with rare earth and the thickness of the substrate intermetallic compounds in the Bi5Sb8Sn solder alloy.