Effects of small amount of active Ti element additions on microstructure and property of Sn3.5Ag0.5Cu solder

The present work investigated the effect of adding a small amount of Ti on the microstructure, physical and mechanical properties of Sn3.5Ag0.5Cu (SAC) solder. The results indicated that adding a small amount of Ti can slightly decrease both the melting temperature and melting range of the SAC solder alloy and that it can also effectively refine the microstructure. The eutectic colony becomes rather narrower with the addition of Ti into SAC, and the microhardness, YS, and UTS are significantly higher than to those of the other commercially available SAC solder alloys. Microstructural analysis revealed that the origin of change in mechanical properties was due to refined β-Sn grains and the formation of new Ti2Sn3 inter-metallic compounds (IMC) in the SAC-XTi solder alloys. However, when the concentration of Ti exceeded 1.0 wt%, the benefits of elongation were reduced due to the small amount of coarse Ti2Sn3 in the eutectic colonies.