Assessment and Comparison of Interface Fracture Toughness in Potting/Substrate Material Systems using ENF and CNF Bi-material Specimen

Electronics in aerospace and defense applications may be subjected to harsh environments during storage, transport, handling, and over a prolonged use life of the system. Reliable operation of electronics in such harsh environments is needed under high-g acceleration loads, high temperature, and high humidity. Potting compounds are often used to mitigate the harmful environmental effects by providing an additional element of structural support to the electronic assemblies. Interfacial delamination of potting is often a precursor to system failure. In this paper, the interfacial strength evolution has been quantified using a product-design agnostic test specimen. Two different specimen geometries have been studied to assess the effect of mode-mixety including the end-notch-flexure (ENF) and central notch flexure (CNF). The fracture toughness has been measured under monotonic and fatigue loads. Paris constants were developed for potting/substrate assemblies. The effect of mode-mixety has been on the measured fracture toughness.