Investigation of key factors in thermal compression (TCB) NCF bonding process

Electronics with higher Input/Output (I/O) density and smaller package size challenge the fine pitch flip chip technology. Thermal compression bonding combined with pre-applied non-conductive film (TC-NCF) has the advantages of simplifying the process steps, protecting interconnects in situ, avoiding the flux residue and having no concerns of adhesive overflow issue. It is a promising process for fine pitch, thin die flip chip packages. In this study, a series of TC-NCF experiments using two types of NCFs were performed on both Chip-on-substrate (CoS) and Chip-on-chip (CoC) packages. Process factors affecting the bondability of TC-NCF interconnect such as bonding force, heating rate, bonding temperature and wetting time were investigated. The results were addressed from bondability evaluation criterions of solder wetting, NCF voids and solder shape. This investigation can serve as a reference for TC-NCF process development and failure analysis.