Thermal-Resistance-Based Reliability of TIM1 Materials in a Lidded Thermal Test Vehicle Under Active Thermal Load-Cycling

The reliability of thermal interface materials (TIM1) in lidded high-power flip-chip packages is investigated using a thermal test vehicle (TTV) under active power cycling. Two TIM materials with different thermal conductivities were evaluated by combining continuous thermal resistance monitoring with transient thermal measurements at defined cycling intervals. The results show that degradation of TIM1 is highly localized and strongly influenced both by assembly-related factors such as warpage and tolerances, and by the intrinsic material behavior under thermo-mechanical stress. Clear differences in spatial thermal resistance evolution were observed: TIM-A exhibited corner degradation, whereas TIMB showed more pronounced changes in central regions. Complementary accelerated grease pump-out tests confirmed material-dependent tendencies for void formation and displacement. The findings underline the need for location-sensitive assessment to predict TIM1 reliability in large-area dies for high-performance computing applications.