The effect of Cu particle additions on the microstructure and melting point of Sn-Bi solder for die attachment

This study aims to produce high temperature joints by using relatively low processing temperature eutectic Sn-Bi solder. By the addition of 30 mass %Cu particles to the eutectic Sn-Bi solder, this research produces a new in-situ phase with a higher remelting point. The microstructure of eutectic Sn-Bi and Sn-Bi with Cu particles addition were investigated where added Cu particles converted almost all Sn phase to new phases. The microstructure analysis shows that increasing the heat input accelerates the reaction between Sn phase and Cu particles. The differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and electron probe microanalyzer (EPMA) proved that almost all Sn phases is converted to new phases resulting in a higher melting point.