Trap characterization at inaccessible dielectric interface: experimental approach and implementation

The insulation lifespan of multilayer insulation materials largely depends on the interfacial insulation performance, especially trap characteristics. However, their inaccessible limits the investigation of trap parameters. Here, we propose a non-invasive measurement system based on the Pockels effect, combined with an inversion algorithm to obtain the interface charge decay process. Furthermore, we establish a calculation path for interface traps based on an emission function that describes the detrapping process. The coefficients and validity of the proposed method are corrected and verified using the trap solution of Al₂O₃ ceramic surface traps obtained from isothermal surface potential decay (ISPD). The Al₂O₃ ceramic and silicone gel interface encapsulation structure in power modules is used to analyze the equivalence between the trap solution obtained by the proposed method and the actual trap distribution. The results indicate that adjusting the injected charge density can significantly affect the trap solution. The further application of the proposed method reveals spatial differences in the charge trapping capability of interface traps in the encapsulation structure through trap parameters. In conclusion, this letter provides an effective method for investigating the characteristics of traps at inaccessible interfaces.