Performance enhancement of Au-Ge eutectic alloys for high-temperature electronics

Au-Ge eutectic has been used as a high temperature electronics interconnection material up to 250°C due to its favorable characteristics. However, both nano-indentation and shear testing, confirmed the loss of strength of the Au-Ge eutectic at a high temperature of 300°C due to the growth of the (Ge) phase. This coarsening has also resulted in the weakening of the (Au) phase due to the deterioration of the precipitation hardening of the (Au) matrix by the (Ge) dispersed phase. In this paper, various techniques for averting the coarsening of the (Ge) phase have been explored. It has been determined that Sn can dissolve in the Au-Ge and segregate in the (Ge) phase, resulting in restraining the coarsening of the (Ge) phase. The composition of the ternary Au-Ge-Sn alloy has been designed by taking into account; the compliance with the solidification criterion and precipitation of phases in the bulk solder. It has been ensured that no brittle intermetallic compounds (IMCs) precipitate in the matrix of the Au-Ge eutectic bulk solder, as a result of micro-alloying with Sn.