Intermetallic compound formation and growth behavior at the interface between indium and Au/Ni(V) metallization

Pure indium (In) solder is promising as the thermal interface material (TIM) for efficient heat dissipation and as the Pb-free solder for cryogenic joining applications. In this study, liquid/solid and solid/solid reactions between In and Au/Ni(V) surface finish on a Si chip are investigated to explore the formation of intermetallic compounds (IMCs) formed at the In/Au/Ni(V) interface and their growth kinetics. Two IMCs, (Ni,Au)28In72 and Ni-V-In, are formed at the interface in the liquid/solid and solid/solid reactions performed at 220-260 degrees C and 100-150 degrees C, respectively. The growth of the (Ni,Au)28In72 crystalline phase follows the parabolic law and the underlying NiV-In amorphous phase is formed as a result of phase transformation from original Ni(V) due to outward diffusion of Ni and inward diffusion of In. This phase transformation proceeds at a faster rate in the liquid/solid reaction. The Ni supply is exhausted once the Ni(V) is completely transformed into the Ni-V-In phase, accelerating the ripening reaction of (Ni,Au)28In72 and its spallation into the molten In matrix.