Electro-dissolution of the Bi second phase in Sn5Bi solder alloy

• The electro-dissolution of second phase in Sn5Bi solder alloy was investigated.
• The analysis through XRD and SEM shows evidence of electro-dissolution.
• The dissolution kinetics of second phase was proposed under current stressing.

This study investigated the electro-dissolution, supersaturation and recrystallization of the second phase Bi in the Sn5Bi solder under 4.0×103–6.0×103 A/cm2 current stressing at 25 °C. The ex-situ XRD analysis of the current stressed specimen, after being quenched with liquid nitrogen, reveals a reduction of the Bi orientation peaks. The SEM investigation shows the dissolution and supersaturation of the Bi phase during current stressing. The in-situ SEM investigation reveals that recrystallization of the Bi phase occurred in the unquenched specimen when the current stopped. The kinetics of the electro-dissolution were analyzed, and the results showed that the maximum dissolution rate occurred during the progress of current stressing.