Low-Drift MEMS Thermal Wind Sensor With Symmetric Packaging Using Plastic Injection Molding Process

Abstract

In this article, a novel micro-electromechanical systems (MEMS) thermal wind sensor using the plastic injection packaging method was proposed. Compared with previous devices suffering from packaging asymmetry, the presented design can relieve the drift phenomenon and improve the accuracy of wind detection. Lumped parameter model and finite-element method (FEM) simulation were developed, and the sensor's improvement was validated. By means of plastic injection molding process, the MEMS sensor chip based on ceramic substrate was encapsulated in a plastic carrier with low thermal conductivity of 0.96 W/( m ·K). In addition, individual packaging was implemented by laser cutting, which ensures that the geometric center of the chip is almost coincident with that of packaging. The sensor, operated in the constant temperature difference (CTD) mode, was tested in the wind tunnel. The experimental results show that wind speed is measured up to 30 m/s with an accuracy of ±7%, while the direction is characterized over the full range of 360° with errors less than ±5°. Compared with the device in our previous work, the measurement accuracy of the proposed prototype sensor was improved by more than two times because of effective benchmark drift suppression.