Transient Thermal Characterization and Assessment of Power Module With Encapsulated Phase Change Material Toward Overload Capability

To mitigate transient thermal surge induced by the overload conditions in diverse applications, phase change materials (PCMs) have been proposed as an effective thermal management solution, offering enhanced heat capacity to maintain the power module within the safe operating area. However, PCM-integrated power modules face significant challenges, including excessive cost, process complexity, and increased steady-state thermal resistance. Besides, the absence of thermal models, insufficient understanding of thermal interactive mechanisms, and the lack of standardized evaluation criteria constrain the advanced thermal design for the packaging and practical application of PCM-based modules. To fill these gaps, this letter proposes a cost-effective and process-compatible overload-enhanced power module by the in-situ replacement of silicone gel with paraffin wax. Considering the impact of phase change transient on the junction temperature during the overload conditions, an improved thermal model is created by introducing the temperature-dependent heat capacity. Moreover, the thermal impedance of paraffin wax-coated power modules is comprehensively investigated by the finite element simulations. To quantify the overload capability, evaluation metrics comprising the optimal overload duration and the overall overload capability are proposed. Finally, power modules encapsulated with paraffin wax are fabricated, experimentally characterized, and evaluated. It is demonstrated that the proposed design provides an additional phase-change thermal impedance of 0.006 K/W with the steady-state thermal resistance maintained at 0.12 K/W compared to its silicone gel-encapsulated counterparts, thus offering a novel packaging approach and a thermal impedance-oriented evaluation criterion for power modules with high overload capability.