A dominant mechanism for thin film power capacitors going high or self-destructing

Abstract

Thin film capacitors typically degrade in use by exhibiting much increased dissipation factors and nominal capacitance values that fall off steeply with frequency. The cause of the increased loss is poorly explained in the literature and is often inferred to be probably due to changes in the properties of the dielectric film. However, it can be shown that the increase in losses can almost entirely be attributed to increased losses in the metal film due to increased path lengths brought on principally by corrosion. Further, the modification of the path lengths can result in localized heating and sporadic fusing of vestigial links during operation, greatly increasing the risk of catastrophic failure. Measurement and teardown inspection of degraded capacitors provide strong support for theoretical modeling involving the critical role of corrosion in capacitor degradation and failure.