Influence of Sustained High Temperature Exposure on the Interface Bond Strength between TIM-Copper Substrates

Modern CPUs have evolved from bulky die size and low power into high powered machines that requires a need for significantly improved thermal interface material to conduct heat from the die surfaces to the Cu-heat spreader. Automotive applications of these CPUs requires a high performance characteristics of TIMs since environment is extremely harsh and reliability of the materials becomes a primacy for the operation of the vehicle. TIM to Copper interfaces becomes one of the primary locations of failure and act as forerunner to the breakdown of the whole state of the art system. Assessment of reliability of end applicants requires an understanding of damage progression of the TIM-Copper interfaces as a function of operating temperature and times. Our study exposes the TIM-Copper interfaces to high temperature and then the interface fracture toughness is quantified. A four-point bend composite bend was fabricated and then the sample was kept at high temperature of 100°C, 150°C for aging time 10 days, 30 days, 60 days and 120 days. Quasi-static bending loads was used to observe and determine interfacial delamination of the sample specimen. A 2D- digital image correlation method was also employed to understand the progression of crack growth and the crack tip opening displacement (CTOD) to equate the degradation of various TIM interfaces at different aging schedules.