A study on electrochemical effects in external capacitor packages
Exposing semiconductor devices with external capacitors to harsh environmental conditions may lead to electrical failures with the formation of conductive paths. This paper presents examples of the analysis of modules with the purpose to understand the respective failure modes. Appropriate sample preparation, sensitive analytical methods like micro-X-ray fluorescence spectroscopy (?XRF), ToF-SIMS, SEM/EDX, X-ray-microscopy as well as micro computed X-ray-tomography (?CT) have been applied to identify the root causes of the electrical failures. As a main conclusion of these investigations, we found that electrolytes can easily penetrate thermoplastic overmold materials which are typically used by module manufacturers. This can lead to either reversible electrical failures which can be eliminated by drying or irreversible electrical failures because of material migration. The effective failure mode depends on mechanical and climate conditions inside the module which could not be simulated up to now under laboratory but only under application conditions.
electrochemical migration failure analysis water drop test silver migration