Mechanical and thermal response of compliant Thermal Interface Materials under cyclic loading

Compliant Thermal Interface Materials (TIMs) or Gap pads are an important material set in many applications including automotive electronics. Commercially available Compliant TIMs exhibit significant time-dependent deformation under compression limiting their utility. While these materials are expected to enhance thermal transport by filling gaps, their (often viscoelastic) mechanical behavior is not well understood. Present work is aimed at the development of test procedures to identify time-dependent viscoelastic behavior of compliant TIMs and to correlate the mechanical response of the materials to experimentally measured effective thermal conductivity. Towards this end, a commercially available compliant TIM using dynamic mechanical tests on a specially constructed low-load mechanical tester at 25°C and 75°C. Sinusoidal displacement profiles are applied at frequencies ranging from 0.1/hr to 10/hr. The change in response as a result of cyclic loading, or softening due to cycling, is quantified over a period of 500 cycles. The eventual goal is to study the stresses transmitted to the solder joints through the TIMs as a result of applied pressures during heatsink assembly.