Research on the degradation mechanism of Stacked Aluminum Polymer Capacitors in Humid Environments

Stacked Aluminum Polymer Capacitors (SAPCs) exhibit high operating voltage, large capacitance, ultra-low equivalent series resistance (ESR), and stable performance across a wide temperature range. These characteristics position SAPCs as a strong candidate for high-reliability electronic systems. Despite their advantages, the absence of systematic studies on their failure mechanisms under humid stress limits further reliability improvements. This study integrates experimental analysis with first-principles simulations to clarify the degradation mechanisms of SAPCs in moist environments. Increased leakage current is primarily governed by defect-assisted electronic leakage in the γ-Al₂O₃ dielectric, while under humid conditions hydration-related phase transformation further accelerates this same process through local phase transformation and weak-point formation. The increase in ESR is associated with moisture-induced swelling of the cathode, compositional alterations, and interfacial mismatches. Based on these results, a cyclic voltammetry based rapid screening and preconditioning approach is proposed for SAPCs exposed to humid environments.The research provides a theoretical explanation for understanding the impact of moisture ingress on SAPCs’ performance and offers practical recommendations for managing reliability throughout production, storage, transportation, and testing.