Development of compression molding process for Fan-Out wafer level packaging

Abstract

The present study deals with the investigation of compression mold processes and materials to enable a high-density chip-first multi-die Fan-Out assembly. Wafer warpage, die shift and mold filling are investigated on 300mm wafers using various Epoxy Mold Compounds (EMC) with a target mold cap thickness of 200 mu m. Compression molding steps are first conducted on bare silicon, secondly on wafers coated with Temporary Bonding Material (TBM) and finally with populated dies on the TBM. The impact of TBM, and EMC materials along with Post-Mold-Cure (PMC) profiles have been explored in order to optimize the wafer warpage. The combination of the optimum material and process enabled ultra-low bow values below 200 mu m on 300mm silicon wafers. In addition, the ability for mold materials to fill narrow gaps specifics to Fan-out assemblies was also addressed. Furthermore, factors such as the die density and mold material distribution impact on die shift are also discussed.