Intermetallic formation mechanisms and properties in room-temperature Ga soldering

Abstract Ga and Ga-based alloys have received significant attention due to their potential applications as liquid metals and also for low temperature, or even room temperature, bonding in microelectronics. This study investigates the effect of In and Sn on the interfacial reactions between eutectic Ga-based alloys and Cu substrates at room temperature. The interfacial microstructures are characterised by electron microscopy and Synchrotron powder x-ray diffraction. In-situ heating observations are carried out to verify the thermal expansion properties of the intermetallic compounds formed with In and/or Sn additions in the Ga-based alloy/Cu reactions. The alloying elements are found to decrease the coefficient of thermal expansion of CuGa2 as the temperature increases. In and Sn are also examined with respect to their influence on the wettability of Ga-based alloys on Cu substrates under an argon atmosphere. The results are important to consider in the development of bonding processes involving Ga and Ga alloys.