Materials and process optimizations for fabricating digital AM temperature and relative humidity sensor system circuits for use in high thermal stress environments

Abstract Additive manufacturing (AM) has experienced rapid growth across various industries owing to the advantages of AM technologies. However, the adoption of AM for sensor integrated circuits (ICs) in harsh environments remains limited due to insufficient high-temperature materials and lack of reliability data. This work demonstrates a wireless, conformal temperature and humidity sensor fabricated via multi-material AM using high-temperature-capable materials. Off-the-shelf components, including a microcontroller and sensor, are embedded in a 3D-printed SLA interposer with conformally printed silver interconnects and protective encapsulation. Additionally, these circuits were designed to communicate wirelessly via Bluetooth low energy (BLE) protocols. Process optimizations were made to manufacture AM sensor circuits efficiently and with high yield. The AM circuits were then electrically, thermally, and mechanically characterized to further optimize the performance of the sensors compared to those manufactured and connected via traditional methods. Key novelties of this approach include (1) fully conformal printing around a QFN-packaged IC, (2) an encapsulation strategy that enhances mechanical resilience of mounted components, and (3) integration of wireless data transmission into a rugged additively manufactured package. The AM sensor’s performance was also characterized and compared to conventional assemblies: results show stable operation from 25 °C up to 100 °C under cyclic humidity and significantly improved mechanical robustness of component interconnections due to encapsulation. This AM sensor demonstrates, to our knowledge, the first combination of conformal printed electronics, encapsulated packaging, and wireless communication for reliable operation in harsh environmental conditions.