Interface Fracture Characterization and Prediction of Competing Risk-of-Failure in FCBGAs Under Automotive Sustained Humidity and Temperature Exposure

Automotive electronics are used for various functions, including guidance, navigation, and control. Flipchip ball grid array (FCBGA) architectures are increasingly used to enable advanced functionality. This paper focuses on the interface reliability of the chip-underfill, substrate-underfill, and thermal interface material-to-copper interfaces under the overlapping stresses of temperature and humidity. High temperature and moisture-induced failures are some of the major contributing factors to failure in underhood automotive electronics. Exposure to high temperature and moisture has been shown to deteriorate the interfaces in the FCBGA packages, which are often precursors to package failure. Past studies on package-level interfaces often concentrate on the effects of individual environmental factors. Yet, real-world automotive electronics encounter a multitude of harsh conditions. The presented work takes a platform-agnostic approach by studying the evolution of the fracture toughness of individual interfaces in a test specimen. Mode-1 and Mode-2 fracture toughness values have been measured after varying amounts of exposure to overlapping temperature and humidity loads. The measurements enable the assessment of the risk of packaging failure through the systematic assessment of the failure margin of each of the interfaces.