Evolution of Thermal Interface Material-to-Copper Interfacial Fracture Toughness Subjected to Monotonic and Fatigue Loading After Thermal Cycling

Abstract Automotive electronics increasingly use high-performance semiconductors to enable a number of advanced driver assistance systems. Thermal management in chip-based electronic systems is quickly becoming one of the most significant impediments to enhanced performance and integration density. The ongoing downsizing and integration of semiconductor devices have increased by heat generated per unit volume of the chip. Thermal interface material (TIM) facilitates heat dissipation from chip to package and from package to heat sink. Exposure to the wide temperature ranges typical in automotive conditions may result in the early propagation of fractures at the TIM-to-Copper contact, leading to high thermal resistance and device thermal runaway. In this paper, bimaterial samples have been created by dispensing TIM materials onto the copper surface and curing them based on the specified conditions. A total of three different TIM materials are used in this study. Two types of samples are prepared, namely with and without pre-crack. The samples are tested in four-point bend monotonic and fatigue loading conditions. The pre-cracked samples are used for fatigue four-point bend loading, and the no-pre-crack samples are used for monotonic four-point bend loading. Before testing, to calculate the bi-material samples’ KIC and KIIC fracture toughness values, they are subjected to automotive-grade thermal cycling from −40°C to +125°C for up to 1000 cycles. Interfacial crack initiation, propagation, and failure mechanisms are investigated. The interfaces’ strain-energy release rate and fracture toughness are assessed.