High Field Dielectric Spectroscopy for Epoxy Moulding Compound Used in Power Electronics

Epoxy Molding Compound (EMC) is a material that is widely used in electronics. The characterization of the EMC is instrumental in providing information regarding the reliability of power electronic devices. This work aims to comprehend humidity's role in EMC's dielectric breakdown. Several studies have been conducted regarding filler's effect on EMC's dielectric characteristics at low voltages. However, the test will focus on high electric fields and their relationship to conductivity, permittivity, and dielectric loss. Dielectric spectroscopy is utilized here to determine the dielectric properties of a commercial-grade EMC and its linkage to frequency, temperature, and humidity. The test is done on the interdigitated capacitor with five different temperature points, from -25°C, 25°C, 80°C, 100°C, and 130°C, with increasing electrical fields, from 13 kV/ mm to 78 kV/mm and 84 kV/mm with the largest value not too far away from the breakdown strength measured during slow ramp breakdown measurements and a frequency range from 0.1 Hz to 10 kHz. This test obtained some exciting results, which can be the basis for further research regarding the EMC. A first observation is that a high electric field affects the relaxation of the material, with relaxation peaks becoming evident only at very high fields. Considering the complex AC conductivity, deviations Jonscher Power Law were observed at high fields and frequencies of around 100 Hz. These deviations seem associated with the onset of secondary peaks at the highest fields. Eventually, a decline of the real permittivity was observed at the highest fields when the frequencies became lower than 1 Hz. This decline is probably associated with the onset of homo-charge in the dielectric.