Thermal Aging Induced Underfill Degradation and Its Effect on Reliability of Advanced Packaging

Reliability on 2.5D IC package is a big concern and challenge due to complicated packaging structure and high reliable requirement. Underfill failure such as delamination and cracking is one of common failure modes in 2.5D IC package when package is subjected to thermal aging condition. Underfill cracking occurs for 2.5D IC package with TSV interposer after high temperature storage (HTS) test. Failure mechanism is determined based on material characterization on underfill. Testing results show that underfill shrinkage increases with increasing HTS duration and interfacial strength of underfill/silicon decreases with increasing HTS duration. Thermal aging induced underfill shrinkage and interfacial strength degradation are main reasons resulting in failure. Finite element analysis (FEA) is conducted with modeling thermal induced shrinkage for 2.5D package under HTS condition. The predicted failure and location of underfill cracking is consistent with experimental observation when applying the developed new FEA model and material properties.