Thermal management of MEMS element with thermoelectric-cooler

Abstract

The accuracy of MEMS sensing devices can be greatly increased by controlling the operating temperature. This work is part of a project where the goal is to develop an active thermal control unit (TCU) capable of regulating a packaged MEMS device at 70°C ± 1 °C in the temperature range from -46 °C to 90 °C. To accomplish this, a thermoelectric cooler (TEC) is sandwiched between the MEMS package and a heat sink with a thermal interface material (TIM). An in-house tool has been used to calculate the optimum TEC parameters, ending up with 72 legs of 1 mm x 1 mm x 2 mm dimension (l x w x h). Simulations in COMSOL show that the TEC can reach the target temperature within the required time and power consumption. In this work we have built a full demonstrator using a thermal test chip (TTC) to represent a MEMS. Tests done in a climatic chamber show large performance discrepancies compared to the simulations. The TEC manages to keep the target temperature when the ambient temperature is below 70 °C, but does not manage when the temperature is 90 °C. This is due to the insufficient heat dissipation from the hot side of the TEC.