Understanding the interface charge behaviors at narrow scale induced by square-wave electric stress in metal/epoxy resin structure

Abstract Detecting the space charges within micro-regions (less than several μ m) at metal/insulation interface induced by high-frequency voltages is challenging for the design and stability of power electronic devices. This study fabricated a novel embedded metal-epoxy insulation micro configuration using a mask magnetron sputtering method to simulate the interface structure under square-wave electric field. An improved Kelvin probe force microscope with probe vibration mode optimization and lateral pressure electrode was employed to detect the interface charges in the interface microregion. A high electric potential occurs at the insulation side of the interface after high-frequency square-wave field excitation. A transition zone of potential distribution is found at the interface within 5 μ m, which contributes to the electric field distortion at the interface. Interestingly, significant charge accumulations occur at the interface region less than 10 μ m. It decreases initially and then increases with the voltage frequency. It is indicated that the competition of charge injection and the charge recombination at the interface cause the reduction of charges and electric field less than 5 kHz. The study is useful for guiding the design and application of insulation in high power density electronic devices.