Bonding interface materials evolution of intermediate In/Ag layers for low temperature fluxless solder based MEMS wafer level packaging

Abstract

In this paper, we proposed new intermediate bonding layers (IBLs) of Ag-rich composition in In-Ag solder systems in contrast to previous studies mainly based on eutectic composition. The intermetallic compounds (lMCs) at the bonding interface were investigated with respect to the bonding condition, post-bonding room temperature storage and post-bonding heat treatment. The IMCs of Ag21n and Ag2114 with high temperature resist to postbonding process are derived under process condition of wafer bonding at 180°C, 40mins and subsequent 120°C-130°C annealing for 24 hours. Based on our results, we can design proper packaging process flow so as to get reliable wafer level packaged MEMS devices. © 2008 IEEE.