Effects of dopants on wettability and microstructure evolution of Lead-Free solder joints

In this study, the synergy effects of Sb and rare earth (RE) element addition on the wettability and microstructure evolution of Lead-Free solder joints are investigated. Experiment results indicate that Sb and RE element possibly had synergy effect on improving the wettability of lead-free solder. It is found that Sn-3.0Ag-0.5Cu-0.8Sb-XY, with X ranging between 0.05 and 0.1, has the best wettability on Cu substrate. The thickness of IMC increases as the amount of yttrium increase from 0wt% to 0.25wt% in the SAC-0.8Sb-Xwt%Y/Cu system.When the yttrium concentration is increased from 0.25wt% to 0.5wt%, the IMC thickness decreases. Further increase in the RE concentration just results in a slightly increasement of the IMC thickness. Considering the wettability and IMC growth, it is found that the optimal composition of the Y is about 0.5wt%. Results in this study just reveal that simutenuasly adding 0.8wt% of Sb and some Y does not have obvious effect on suppression of the IMC growth of the SAC-0.8Sb-Xwt%Y/Cu solder joints.