Analysis of a failure in a molded package caused by electrochemical migration

Abstract

Electrical components can fail during their function in an electrical circuit, especially in a harsh environment. One of the possible failure reasons is the electrochemical migration, which leads to a short circuit or change of electrical parameters of components. This paper focuses on electrochemical effects and explains mechanisms leading to the formation of a conductive path within a component molded in a plastic package. Appropriate diagnostic methods - SEM/EDS and penetration tests have been chosen in order to find the root cause for short circuit creation. It was found that the conductive path appeared due to electrochemical migration of silver between the Electrically Conductive Adhesive (ECA) joints connecting the capacitor package. A tiny gap that was found between the molding compound and the leadframe of the package, showed to be the necessary condition for the electrochemical migration to appear. The main aim of this work was not just to identify the cause of an inadvertent conductive path creation, but also to identify the part of the manufacturing process, where similar problems can be prevented.