Film capacitors have a self-healing capability and can clear faults in the film such as pores or impurities while under a voltage. The metal coatings, vacuum-deposited directly onto the plastic film, are only 20nm to 50nm thick. A dielectric breakdown occurs when the field strength is exceeded locally at a weak point. The high temperatures reached (up to 6000K) in the breakdown channel transform the dielectric into a highly compressed plasma that forces its way out.