High reliability and compression flow underfill encapsulant for flip-chip applications

We have developed a next generation underfill encapsulant material for a compression bonding chip assembly process that is based on epoxy resin. As it has a high moisture resistance, we selected phenol resin as the curing agent for epoxy resin. The underfill material can be very significant for improvement of the flip chip assembly process for chip scale packages (CSP), multichip modules (MCM), and typical small packages. This compression bonding chip assembly process is very significant for low cost realization with high level production. However, the conventional underfill material could not adapt to the new assembly process which has a fast-cure process with the polymerization of the underfill. In this paper, we present specific experimental results for our underfill in this new flip-chip assembly process.