Performance Validation of Voltage Blocking Technologies for Direct Cooling of High-Density Power Electronics

Abstract

The voltage shielding capacity of a hydrofluoroether type fluid, specifically HFE7500 along with that of Parylene C based conformal surface coatings are explored. Both voltage blocking technologies demonstrated an ability to maintain good voltage blocking capacity even when exposed to field strengths as high as 16.8kV/mm in the case of the dielectric fluid and 33.5 kV/mm for 2μm-thick layers of Parylene C. To potentially improve voltage blocking characteristics while minimizing thermal resistance, this study also explores the combined voltage shielding capacity of HFE7500 coupled with thin Parylene C coatings deposited via chemical vapor deposition (CVD). Breakdown tests on point-point electrodes coated with a 10μm film of this coating returned results that showed diminished breakdown voltage compared to bare electrodes. This may be attributed to several factors including the ionization of the coating that initiates breakdown at a reduced field strength.