Optimising thermal management of MEMS element with thermoelectric-cooler

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
$70\ {}^{\circ}\mathrm{C}\pm 0.2\ {}^{\circ}\mathrm{C}$
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
$1\ \text{mm}\times 1\ \text{mm}\times 2\ \text{mm}$
dimension (
$\mathrm{l} \times \mathrm{w}\times \mathrm{h}$
). 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 and tested various scenarios in a climate chamber. The tests confirmed to a large degree the simulations of behaviour at constant current. Two regulation algorithms were tested and optimised for of keeping the temperature as constant as possible during temperature changes. The best result kept the TTC temperature within 0.2 °C during temperature cycling. The power consumption during heating mode was reduced by decreasing the heat sink thermal transfer, but such a configuration would not work in cooling mode.