Prediction of Crack Initiation at Die Corner of Molded Underfill Flip-Chip Packages Under Thermal Load by New Criteria

The present study provides solutions for the stress and strain fields near the junction formed at the intersection of the inclusion and matrix interfaces under thermal load. It further explores how the non-singular stress terms influence the stress field near the corner of the interface between the molded underfill (MUF) and the die in a typical flip-chip (FC) package subjected to thermal load. The results obtained indicate that achieving a comprehensive understanding of the stress field requires consideration of the dominant singular stress terms, the regular stress term (the first non-singular stress term) and the I-stress term (the second non-singular stress term), so as to offer a theoretical basis for accurate evaluation of the reliability of integrated circuit packages.