Ultra-thin moisture barrier coatings for passive components

Abstract

Polymer Multi-Layer (PML) capacitors have demonstrated excellent performance for numerous power electronics applications, particularly where high temperature stability is required. These capacitors are sensitive to high humidity, and if they are not protected from moisture exposure their performance degrades rapidly due to electrochemical corrosion. Conventional protective coatings, such as epoxies and polyurethanes, are extremely thick--usually over 1 mm. Previous work has shown that a thick coating leads to a large equivalent series inductance (ESL) of the capacitor, and negatively affects the capacitor performance. An ultra-thin moisture barrier coating is desirable to improve both electrical performance and capacitance density. This thesis focuses on developing coatings which are thinner than 200 tm and which adequately protect PML capacitors from humidity. Novel moisture barrier designs have been fabricated and tested.