Predictive Cohesive Zone Prediction of Delamination at Potting-PCB Interface Under Dynamic Loading and Sustained High-Temperature Exposure

Defense and Aerospace electronics widely use commercial components that may be subjected to high thermo-mechanical loading in addition to shock and vibration during transport, operation, and handling. Electronic components are reinforced with potting materials to protect them from harsh environments. Potting offers protection against shock, vibration, corrosive agents, and moisture. Component failure on electronic assemblies is often preceded by delamination of the potting material PCB interface. Determination of interfacial fracture toughness of the potting-PCB interface is critical to assess the reliability of potting assemblies. The potting material properties may evolve with sustained exposure to high-temperature exposure, which has the propensity to deteriorate interfacial properties. The evolution of potting-PCB interfacial properties and its effect on the reliability of potting is the focus of the study presented in this paper. Bi-material specimens of potting-PCB interfaces are prepared with a notch in the center to measure the effect of the sustained high-temperature operation on interfacial robustness. The samples are tested under dynamic four-point bending loads to compute the interfacial fracture toughness. Five potting materials under sustained high-temperature exposure to 100°C and 150°C for durations of 30 days, 60 days, 90 days, 120 days, 180 days, 240 days, 300 days, and 360 days have been studied. Variations in crack initiation and failure modes with respect to sustained isothermal exposure have been characterized. The interfacial stress intensity factors and strain-energy release rate have been computed for each testing condition. A cohesive zone model has been developed to predict the interfacial delamination behavior of the potting-PCB interface. The damage accumulation is predicted using the fracture parameters obtained from the experiment for both pristine and aged test conditions.