Application of (Electrochemical) Impedance Spectroscopy to Investigate the Degradation of Epoxy Mold Compounds for Plastic Encapsulation of Power Electronics—A Feasibility Study

ABSTRACT The present work investigates the suitability of impedance spectroscopy to characterize typical plastic encapsulation materials in electronic packaging. In a first approach, a commercially available epoxy mold compound (EMC) after processing to millimeters thick free‐standing samples is studied. The use of free‐standing samples avoids any influence of substrate/encapsulation interaction and enables the investigation of the intrinsic properties before and after harsh conditions of exposition in a Pressure Cooker Test (PCT). The change of properties of the mold material and the uptake of water is characterized with impedance spectroscopy in a 2‐electrode design. Complementary material diagnostic (FTIR) confirms the results of the impedance spectroscopy. The free‐standing mold failed dramatically and degraded under the conditions of the PCT due to embrittlement of the polymer and a fast water uptake. The study impressively demonstrates the (electrochemical) impedance spectroscopy as a powerful tool for qualifying and characterizing materials with extremely high impedance, such as plastic encapsulations.