Effects of Bi addition on interfacial reactions and mechanical properties of In-3Ag-xBi/Cu solder joints.

In this study, the effects of Bi addition on the interfacial reactions and mechanical properties of In-3Ag-xBi/Cu joints were investigated. Better wettability was obtained with increased addition of Bi (0-2 wt%), but further additions up to 3 wt% decreased the beneficial effects. The intermetallic compounds (IMCs) formed at In-3Ag-xBi/Cu interfaces were (Ag,Cu)In in all cases. With the increase of Bi addition, the interfacial IMC grains coarsened and the IMC layers got thicker. The EPMA mapping revealed that Bi addition reacted with neither In or Ag to form intermetallics, it dissolved as solid solution in Indium matrix uniformly. In addition, the shear strength of the soldered joints were improved by Bi addition, with the peak shear strength occurring at 2 wt% Bi addition. The fracture mode also changed from typical ductile fracture mode to mixed ductile-brittle fracture mode with increased amount of Bi addition. [ABSTRACT FROM AUTHOR]