Thermal and structural response of pin fins for different interface conditions

Thermal management of electronic products relies on the effective dissipation of heat. Heat sink elements (e.g. a pin fin) are used for any effective heat dissipation network. Despite much optimized design of the heat sink element, the heat transfer may not be effective because the interface between power device and heat sink element is critical in the heat dissipation network. Thermal Interface Materials TIM (e.g. adhesive, solder, pads, or pastes) are employed at interface between power device and heat sink element to minimize the interface thermal resistance. However, several challenges need to be addressed before they can be successfully utilized because depending on the thermal interface conditions, the thermal stress level can attain undesirable values. This issue can be addressed by the optimization of the system design with the help of simulation methods. Generally the effects of interface conditions are studied on the thermal performance of the heat sink system whereas in this paper, a coupled-field (thermalstructural) analysis using FEM is performed to study the thermal as well as structural behavior of the heat sink system. Temperature variation and stress fields in the region of interface between pin fin and base plate are analyzed. Effects of various parameters (such as contact pressure, surface roughness, TIM thickness, and operating conditions) on the resulting thermal and structural response at the interface are presented. It has been found that different interface conditions may have comparable thermal performance with significant different stress fields at the interface. Therefore stress state must be known to ensure the structural integrity of the heat sink system for a given operating condition.