Research on Simulation Method for Failure of Micro-miniature Fuze in Hygrothermal Environment during Long-term Storage

Abstract To enhance the long-term storage reliability and safety of micro-miniature fuze, meet the technical requirements for rapid wartime deployment, this study conducts simulation research on the failure mechanisms of micro-miniature fuze in hygrothermal storage environments. Based on Fick’s second law, heat transfer theory, and the invariant failure mechanism of vulnerable materials in the micro-delay initiation circuit module, the process of external moisture diffusion into the circuit is analysed. A moisture diffusion simulation model analogous to heat conduction is established, revealing distinct hygroscopic kinetics: ABS plastic exhibits the highest moisture absorption rate, followed by potting compound and PCB. The durations required for each material to reach 90% of equilibrium moisture content under ambient humidity are quantified as 3 days, 7 days, and 70 days, respectively. Furthermore, by integrating thermal expansion and hygroscopic swelling strain models, a coupled hygro-thermal-stress simulation model is constructed based on the superposition principle. This establishes a hygrothermal-stress coupling simulation methodology, identifies plastic housing, potting compound, and semiconductor chip wire bonding as critical failure locations where induced hygrothermal stresses exceed material ultimate strengths. These components are determined to be pivotal in fuze failure during prolonged hygrothermal storage. Through coupled hygro-thermal-stress simulation analysis, this research resolves the issues of unclear hygrothermal stress mechanisms, unquantifiable failure risks, and undetermined failure modes. It provides an effective methodology for analysing long-term storage failures in fuze and enhancing their reliability and safety.