Low-temperature Metal Bonding for Optical Device Packaging

Low-temperature solid-liquid interdiffusion (SLID) bonding is an attractive alternative for the packaging of optical devices. It reduces global residual stress build up caused by differences in coefficient of thermal expansion (CTE) at elevated temperatures. This work applied the Cu-Sn-In-based SLID bonding method to bond silicon and optically transparent materials at 200 °C. Experimental results show a successful bonding with minor unavoidable misalignment from the CTE mismatch and major misalignment from the bonding alignment process. Microstructural analysis shows the intermetallic compound consists only of Cu
6
(Sn,In)
5
on the bond that is thermally stable up to 600 °C.