Evolution of the Interface Critical Stress Intensity Factors Between TIM Copper Substrates due to High-Temperature Isothermal Aging

Modern computing platforms used in data centers or harsh environment platforms would be exposed to sustained high temperatures over an extended period of time. Thermal interface materials are extensively used to transport heat from the die surfaces to the Cu-heat spreader. The TIM interface may be exposed to compression in addition to thermal mismatch during power cycling and environmental temperature cycling. Failure of the interface may be a precursor of system failure owing to the subsequent temperature rise. Reliability assurance in the use case scenario requires a fundamental understanding of the interface’s robustness and evolution under operational loads. In this study, the TIM-Cu interfaces were subjected to high temperatures prior to measuring the interface’s critical stress intensity factors. Four-point bend specimens were fabricated and subjected to sustained high temperatures for 15 days, 30 days, 45 days, 60 days, 90 days, and 120 days at temperatures of 100°C, and 150°C. Tests were conducted to determine interfacial delamination of the sample specimen and identify the critical steady-state energy release rates. A digital image correlation approach was also employed to comprehend the progression of crack growth and the crack tip opening displacement (CTOD) to assess the deterioration of various TIM interfaces at various aging durations.