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In this paper, the design, fabrication, and characterization of a robust MEMS thermal wind sensor utilizing ceramic film packaging are proposed. The ceramic film is fabricated by means of low temperature co-fired ceramic (LTCC) technology, achieving the excellent adhesion between silicon substrate and ceramic film without any thermal adhesive. The most important is that the adverse effects of the packaging on the performance of the thermal wind sensor can be minimized by adjusting the thickness and thermal conductivity of the ceramic film during the preparation of the ceramic slurry. The influences of thickness and thermal conductivity of ceramic film on the performance of sensor have been simulated by finite element method, and the results are in reasonable agreement with theoretical analysis. The proposed sensors were tested and calibrated in a wind tunnel. Experiments results demonstrate that the sensitivity of the proposed sensor is decreased only 4.7%, compared with the sensor without ceramic film. The maximum measurement error of the proposed sensor in wind speed and direction is 0.66 m/s and 5°, respectively. Compared with the sensor packaged with $250\mu \text{m}$ ceramic carrier, the heating power of the proposed sensor is reduced by nearly 50% and the sensitivity is increased by an order of magnitude at the same time.

In this paper, we present a robust, low-power and wide-range MEMS thermal wind sensor, which is based on a glass reflow process. A general analytical model is first proposed for obtaining the heater’s temperature and the temperature distribution on the sensor surface. Based on this model, the effect of the sensor’s geometry and package on the sensor’s performance is investigated. These results demonstrate how the measurement range and the sensitivity of the sensor can be optimized with a change in structural geometries. Besides, it has shown that the package structure of the sensor is also important for obtaining the required performance. Then, calculated results are validated with 2-D finite element method (FEM) solver CMOSOL. It is found that although there is some deviation between theoretical and simulation results, the model can have good reference value for latter MEMS thermal wind sensor design. Finally, the sensor is characterized in a wind tunnel. At a constant heating power of 14.5 mW, measurement results show that the sensor can detect airflow speeds of up to 33 m/s, with an accuracy better than 0.5 m/s at low speeds and 5% Full-Scale at high speeds. Airflow direction can be determined in a 360° range with an accuracy better than 5°. In addition, the sensor also shows a good repeatability.

In this paper, a novel MEMS thermal wind sensor adopting vertical stacking thermistors is proposed for the first time. Compared with the traditional wind sensors, the novelty of this work is that eight thermistors, fabricated on two layers, can achieve improved sensitivity of wind detection. The sensor is tested in wind tunnel in calorimetric principle and the heater is supplied with constant voltage (initial power 210 mW). Experiments demonstrate that the sensitivity of the proposed senor is double that of the traditional one without increasing the chip size. Measuring range of wind speed from 0 m/s to 33 m/s and full range (360°) of wind direction detection have been achieved.

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.

In this paper, a micromachined silicon thermal wind sensor with improved sensitivity is demonstrated. Deep reactive ion etching (DRIE) trenches are fabricated to suppress the lateral heat conduction between the heater and the thermistors. Moreover, two Wheatstone full-bridges consisting of eight thermistors are designed to increase the output voltage by 50%. Based on these two methods, the sensitivity of the micromachined wind sensor can be improved remarkably, which is verified by the experiments. The results show that the measurement wind speed range can be up to 33m/s in constant voltage (CV) mode with the initial heating power of 256mW. The sensitivity is measured to be 29.37mV/ms−1 at the wind speed of 3.3m/s, achieving an improvement of about 226%, compared with the traditional wind sensor. The results also show that wind direction in a full range of 360° can be determined with an accuracy of ±5°.