Evolution of Viscoelastic Properties and Interface-Fracture Toughness Under Sustained High Temperature Operation Typical of Automotive Underhood for up to 1-year

A large portion of the automotive electronics that enables guidance, navigation and safety functions resides underhood in front of the firewall where operating temperatures are much higher than in traditional consumer applications. The incorporation of advanced driver assistance systems has resulted in the need for flip-chip ball-grid array (FCBGA) form-factors on the automotive platforms. In this paper, process-property-performance relationships have been characterized for a number of packaging materials used in FCBGAs including underfills and electronic mold compounds under sustained operation at high temperatures. Changes in material properties were studied for isothermal aging at three different temperatures which are above, near, and below the glass transition temperature of the material. Long-term exposure of four different underfill materials were investigated at three different isothermal aging temperatures. A fabrication method has been developed to prepare test specimen for DMA testing. The properties of underfill materials including storage modulus, loss modulus, glass transition temperature and tangent delta have been studied using a combination of dynamic mechanical analysis and tensile testing for durations up to 1-year of thermal exposure to temperatures in the range of 100C to 150C. In addition to the bulk properties the interfacial properties have been examined at the substrate-to-underfill interface and chip-to-underfill interface for sustained exposure to high temperatures. Material-based control indicators have been identified for each of the materials.