Enhancement of dielectric breakdown strength in glass using polymer coatings

Traditional polymer film capacitors used in pulsed power and power electronics applications have severe limitations in terms of high temperature reliability. Alkali-free glass is a promising material for high temperature and high power capacitors because of its low dielectric loss and high breakdown strength (12 MV/cm), resulting in energy density values exceeding 35 J/cm
³
. Several alkali-free glass compositions are commercially available with a permittivity range of 5 to 7 and low dielectric loss (tan δ <; 0.5%) up to 200°C. Polymer coatings, such as parylene-C and fluorinated polyester (FPE) significantly increase the breakdown strength of alkali-free glass sheets; in some cases, by over 50% at temperatures up to 125°C, compared to uncoated glass.