Dielectric Characteristic Analysis and Insulation State Evaluation of Packaging Material for Power Module With Different Aging Degrees

Epoxy resin (EP) exhibits excellent electrical and mechanical properties, which make it a promising material for insulation in high-voltage power modules. However, prolonged exposure to high temperatures can lead to thermo-oxidative aging of EP, ultimately resulting in irreparable damage to the insulation. This study aims to analyze the impact of aging on EP dielectric properties and establish a model for assessing the aging state. First, the surface morphology of EP before and after thermo-oxidative aging was observed, followed by testing the frequency domain spectroscopy (FDS) curves of the sample. Subsequently, the electric field stress distribution and overall dielectric loss characteristics of the power module were studied under different aging degrees and voltage frequencies. Through decomposing FDS curves, the study revealed how thermo-oxidative aging affects the dielectric properties, and an evaluation model of aging state was constructed. The results indicate that aging can significantly increase the total dielectric loss and space charge polarization loss of the power module. The dielectric characteristic parameters corresponding to the space charge polarization were selected to establish an aging evaluation model, and the evaluation error is less than 0.064.