This work addresses the virtual investigation of a highly sensitive capacitive pressure sensor under the influence of mechanical loads and variable environmental boundary conditions such as temperature and humidity. This type of pressure sensor realized as a micro-electromechanical system (MEMS), with its small size and potential high accuracy, are possible drivers for a variety of new applications such as indoor navigation. To ensure the high accuracies required for specific applications, the design and material selection must be optimized. In the presented work, methods for characterizing and modeling the deformation behavior of MEMS are developed, implemented, and validated. The influence of mechanical loads, temperature, and humidity on the behavior over different system scales (assembly - PCB - sensor package - chip - membrane) is considered. In addition to semiconductors and metallic connections, the MEMS sensors consist of a combination of different polymer composites. These composites are partly insulating materials, adhesives, or also conductive connections. Depending on their macromolecular composition or the fillers used, they exhibit pronounced temperature and humidity dependencies. To determine these dependencies, a detailed characterization of the hygro-thermo-mechanical material properties was carried out as part of the work. The measured material data was then the basis for calibrating selected material models to describe the relevant dependencies. A particular challenge in modeling the influence of material moisture was the discontinuous change in moisture concentration across the material boundaries of the hybrid system. To account for these discontinuities, a solubility approach was chosen. Furthermore, the water activity method was implemented to describe dynamic moisture changes. Based on the material models, a combination of global and local models was implemented to describe the influence of external loads on the deformation behavior of the semiconductor's pressure membrane. The influence of temperature, humidity, and four-point bending load on the MEMS sensors' behavior was analyzed in a further step by experimental tests. The capacitance signals of selected MEMS pressure sensors were read during defined variable loads. The measured capacitance signals confirmed the results predicted by the simulations. The characterization and validated modeling of the MEMS sensor serve as a basis for further possible sensor design optimization. Different design and material variants can be investigated and evaluated against each other in a time-efficient manner, thus enabling more robust and accurate sensors for new applications.
|Publication status||Published - 2021|
Bibliographical noteembargoed until null
- pressure sensor
- Microeletronic packages
- four-point bending
- pressure sensitive membrane
- analytical methods