UC Irvine

Upon the dawn of the new millennium, a new generation of energy revolution is incoming. With the advent and development of wide bandgap (WBG) semiconductor materials, i.e., silicon carbide (SiC) and gallium nitride (GaN), the figure of merits of high-temperature power electronics have been largely improved by breaking the fundamental physical boundaries set by traditional silicon-based semiconductor devices. In order to fulfill the full potential of WBG-based technology, it is indeed essential and necessary to develop compatible electronic packaging materials that can sustain high operating temperature. Silver-indium (Ag-In) solid solution is such one of the promising candidates of metallic material for high-temperature and power electronics.

In the content of this dissertation, the author had systematically investigated multi-physical material properties of the Ag-In and other Ag-based solid solution. First of all, the author had discovered that Ag-In solid solution possessed the superior mechanical properties, i.e., low yield strength, high mechanical strength, and high ductility, which had proved to be an ideal combination for solid-state bonding applications. Secondly, the author had also discovered that Ag-In solid solution exhibited a great anti-tarnishing property, which could potentially solve the problematic tarnishing issues involved in Ag and its alloy applications. Moreover, a quantitative and theoretical model had been established by the author to explain the underlying anti-tarnishing mechanism within the context of HSAB principle, conceptual DFT formalization and Hammer-Nørskov (HN) d-band model, using an original semi-quantum-mechanical approach. Furthermore, the abnormal phenomenon that had been found in Ag-In system, namely, solid solution softening, was further studied and discussed in Ag-Al, Ag-Ga, and Ag-Sn binary systems. In addition, various physical properties of Ag-In alloys, i.e., thermal, electrical and optical properties, were studied to enable to the multi-physical co-designs, leading to Ag-In alloys potential various applications. Based on the findings above, an advanced solid-state bonding technology had been proposed using Ag-In solid solution for high-temperature power electronics applications. Finally, the concluding remarks and future research perspectives were discussed, where a unified multi-physical theorem and material co-design principles for electronic packaging could be developed in the future study.