Application of Field Grading Material for Power Device Insulation in PCB Embedded Environment

This paper presents the development of a Field Grading Material (FGM) to be applied for the insulation of high voltage wide bandgap power device embedded in printed circuit board (PCB) technology. This composite encapsulant is made up with an epoxy resin matrix and high permittivity particles (barium titanate:
$\text{BaTi}{\mathrm{O}}_3$
). The permittivity gradient is obtained through a gradient of particle concentrations achieved by the way of an electrophoresis process (i.e., application of a DC electric field to drift particles around the high potential electrode). The characterizations carried out include digital microscope and scanning electron microscope (SEM) observations to determine the morphology of the FGM layers and their particle density. The breakdown voltage of a test structure made with two FGMencapsulated copper tracks on top of a FR4 prepreg was also evaluated and has shown an insulation enhancement compared to control test chip (full FR4 or epoxy).