Effect of electric pulse incubation melt on solidified microstructures and mechanical properties of Sn58Bi alloy

Sn58Bi alloy is a typical low-melting point solder. However, the brittle Bi phase would lead to relatively low ductility and toughness, limiting its application in advanced 2.5D/3D electronic packaging. We presented a strategy to enhance the ductility of Sn58Bi alloy by electric pulse incubating (EPI) the liquid melt. Unique microstructures including pre-eutectic Sn, Bi-rich phase and fine Sn-Bi eutectic structure were obtained due to different size atomic clusters in melt incubated by electric pulse. It was found that the ductility of as-treated samples was improved significantly as the applied pulse voltage was increased. The enhancement should be attributed to cooperation deformation of a great number of pre-eutectic Sn and Bi-rich phases. This research could help to provide a new path for ductility and reliability improvement of Sn-Bi solder joints in advanced electronic interconnection.