Parylene Coatings in Power Electronic Modules

Double sided cooling (DSC) of power electronic modules enables higher power densities and lower parasitics which can be advantageous, especially for using wide bandgap power semiconductor devices [1]. Therein, insulation materials possessing good gap filling capabilities are needed and Parylene coatings seem to be highly promising [2]. Parylene F-VT4 and F-AF4 coatings were studied for their suitability as insulation material in double sided power electronic modules. Gap penetration behavior, adhesion as well as electrical insulation were compared. For the latter two properties, the effect of aging via temperature shock testing (TST, Tmin: -40 °C, Tmax: 220 °C, 300 cycles) was studied. For both Parylene types the gap filling capability tests showed promising results. Partial discharge measurements before and after TST showed that the Parylene F-AF4 coated samples maintain their insulation strength in the chosen TST conditions, whereas the Parylene F-VT4 coated do not. Cross-cut testing of the Parylene F-VT4 coated samples before and after TST resulted in no or little reduction of the adhesion due to TST.