Modeling and Analysis of SiC Capacitive Pressure Sensors Based on FEA Postprocessing With Infinitesimal Approach

In the design and reliability analysis of SiC capacitive pressure sensors (CPSs), the complex and harsh working environment causes irregular deformation of the sensors, which makes it difficult to analyze the capacitance. In addition, when finite element analysis (FEA) software is used for research, multi-physics coupling can be complicated, and different software adopts distinct capacitance analysis processes or even lacks related modules. Through applying the idea of the infinitesimal approach, this paper proposes a model of capacitance calculation for CPSs based on FEA postprocessing, including two mesh processing methods of reflection and densification. First, a SiC sensor is modeled and simulated under environmental stress by using Ansys Workbench. Afterward, the deformation results of the faces and edges of the insulating layers in the capacitor are exported. Then, MATLAB is used for processing the deformation data. Lastly, the capacitance value of the sensor is calculated in accordance with the concept of parallel plate capacitor. The research shows that within the pressure range of 0.5-100 kPa, the error of capacitance values between the proposed model and the theoretical calculation is less than 20%, which reduces to about 7% after the theoretical deviation is corrected; the error between the proposed model and the experiment of the fabricated SiC sensor is 4.7%, and that of capacitance ratio is 3.5%. This calculation model is validated to be suitable for all finite element software for analyzing the performance of different kinds of CPSs.