Abstract
Automotive under-the-hood electronics may reside on-engine, on-transmission, or in-wheel-well. Several high I/O advanced packaging architectures, including the flip-chip ball grid arrays (FCBGAs), enable much of the functionality. Underhood electronics in automobiles are an integral part of the critical and safety operations of the vehicle. Underfills significantly reduce the amount of plastic work during temperature excursions and offer mechanical support to the solder connections. One of the most common failure modes at chip/UF interfaces has been delamination. A critical characteristic in evaluating the chip/UF interfacial reliability is the interfacial fracture toughness of the chip/UF interfaces. The interfacial crack could rapidly spread to the solder joints, leading to system failure. The chip/UF interface properties may change over time in response to high-temperature exposure. In this study, bi-material specimens of Chip/UF interfaces have been fabricated and exposed to high temperatures of 100°C and 150°C for 30 days, 60 days, 90 days, 120 days, 180 days, 240 days, 300 days, and 360 days. The aged samples are subjected to four-point bend fatigue and monotonic loading. The interfacial fracture toughness values have been determined for each loading condition. The Paris constants (A, n) are computed from fatigue loading interfaces, which directly represent the evolution of interfacial properties with respect to sustained high-temperature exposure. A predictive finite element model of the FCBGA interfaces has been created.
