Experimental Studies on the Effect of Thermal Interface Material and Mounting Technique on the Thermal Resistance of Device Cooling Arrangement

For thermal management, power electronic devices are typically mounted on a heat sink with a thermal interface material (TIM) between the device tab and heat sink for the purpose of electrical isolation. Different thermal interface materials are available. The device can be mounted on to the heat sink with a screw or a special mounting clamp. Over the thermal resistances of the device, interface material and heat sink, the contact thermal resistances are also significant, but are challenging to be quantified. This paper presents experimental studies to evaluate the thermal resistance between the device junction and the heat sink, considering different thermal interface materials and different clamps at different mounting torques of the fastening screw. The device power dissipation, on state resistance and heat sink temperature are measured. Since the junction temperature cannot be measured directly, a procedure to estimate the same based on measured on-state resistance is presented. The experimental arrangement and techniques are reported along with comparative results for different mounting arrangements.