Effects of Ti addition to Sn–Ag and Sn–Cu solders

► Ti additions to Sn–Cu and Sn–Ag solders can effectively reduce the undercooling. ► Increasing the cooling rate will increase the hardness of Ti-added solders. ► Ti2Sn3 networks stabilize the morphology of β-Sn even in a severe aging condition. ► The orientation distribution of β-Sn can be preserved after a minor addition of Ti. ► Ti-added solder may be a superior candidate for enhanced electromigration resistance. Minor alloying addition to solders has been an important strategy to improve the integrity and reliability of Pb-free solder joints. In this study, a small amount of Ti was added to Sn–Cu and Sn–Ag solders, and their microstructures, solidification behaviors, mechanical properties, and high temperature aging characteristics were investigated. Thermal analysis confirmed Ti addition being very effective in reducing the undercooling. Correlations between cooling rates, microstructure, and microhardness were established. One pronounced feature of Ti addition was that Ti-added solders had microstructures very stable against extreme aging conditions.