Underfilling flip chip packages with transfer molding technologies

This work focuses on the exposed-die molded underfill (MUF) and overmold as underfill (OMUF) technologies for flip chip in the form of a molded matrix array package. A series of mold compounds were selected for this evaluation. MUF and OMUF parts were successfully assembled and subjected to reliability stress tests. All the materials have high MUF and OMUF assembly process yields. The evaluations showed that OMUF has a better reliability performance than that of MUF. Mold corner crack was observed in MUF. This work discusses the relationships between package configurations, assembly processes and material physical properties for high performance MUF/OMUF technologies.