Monte Carlo simulations of gas flow and heat transfer in vacuum packaged MEMS devices

The flow and heat transfer in vacuum packaged MEMS devices is numerically studied by using the direct simulation Monte Carlo method. The problem is simplified as an enclosure with a hot surface at the bottom. If the bottom is considered at a completely uniform high temperature, flow will be induced by the thermal stress difference from discontinuous temperature distribution effect. The heat transfer is weakened by the rarefied gas effect when compared with the continuum-based solution. If the bottom temperature is partly high and continuously decreases besides the hot part, the gas flow near the bottom surface will be remarkably enhanced due to the temperature gradients. As a result, the heat transfer on the hot chip surface is also enhanced. The current research can improve the understanding of gas flow and heat transfer in vacuum packaged MEMS devices.