Phase separation mechanism and property changes in In–41Sn–9Zn under the current stressing

Abstract

Phase separation mechanism and property changes in In–41Sn–9Zn solder was investigated with the current density of direct current 1.0 × 10³ A/cm². The results indicated that the phase separation was affected by the combination of electron wind force and back stress. The different degree of lattice distortion between different regions was one of the causes of the back stress. In the alloy, In-rich β phases and Sn-rich γ phases were segregated at the cathode side and anode side respectively, while Zn atoms didn’t migrate to the two poles significantly. Sn was the main diffusing atom $\left( {\left| {{\text{Z}}_{\text{Sn}}^{*} } \right| > \,\left| {{\text{Z}}_{\text{In}}^{*} } \right|} \right)$ in the alloy, so the volume change rates at the anode side was about four times higher than that of the cathode side. After 72 h electromigration, the cathode–anode difference in micro-hardness, melting point, thermal enthalpy and melting interval was about 0.3 Mpa, 2 °C, 4.18 J/g, and 0.9 °C, respectively.