Annular-Encapsulation Packaging to Realize High-Performance MEMS Thermal Wind Sensor

In this paper, an annular-encapsulation packaging method is proposed to develop high-performance micromachined thermal wind sensor. The sensor used for demonstrating the feasibility of this design is composed of a central heater and eight thermistors. It measures the wind speed and direction through detecting the airflow-induced temperature distribution on the chip surface. Unlike the conventional self-packaging, epoxy resin is only utilized to encapsulate the bonding wires between the sensor pads and the PCB (print circuit board), while the front surface of the sensor is in contact with the air in this annular-encapsulation packaging. Based on this approach, the unwanted heat loss from the sensor to the epoxy resin is minimized, and more efficient heat exchange between the sensor and the airflow is realized via the backside of the chip. The experimental results show that the sensitivity of the sensor with this annular packaging at the wind speed 3.3m/s is 44.29 mv/ms −1 , achieving improvement of 50.8%, compared with the sensitivity 29.37 mV/ms −1 of the conventional self-packaged sensor.