Effects of small amount addition of rare earth Er on microstructure and property of SnAgCu solder

In the present work, effect of adding small amount of Er on the microstructure, physical and mechanical properties of Sn3.8Ag0.7Cu solder has been investigated. The purpose is to understand if the heavy rare earth Er has similar effect as light rare earth Ce or La on improving properties of SnAgCu lead-free solder. The results indicated that adding small amount of Er can evidently improve the wettability, mechanical strength and creep rupture life of the Sn3.8Ag0.7Cu solder alloy. It is pointed out that proper Er content in the Sn3.8Ag0.7Cu solder alloy should be in a range of 0.05–0.25 wt%. Moreover, the size of intermetallic compounds (IMC) was measured quantitatively for the Sn3.8Ag0.7Cu solder alloys with various Er contents. It is felt that the increase in mechanical strength may be related to the refining of IMCs of the solder due to the addition of small amount of Er.