Characterization of Potting Materials in Military Environments

Reliability expectations in mission-critical applications necessitate the understanding of survivability, failure mechanisms, and efficacy of supplemental restraints such as potting materials in mitigating the propensity for failure. Interfacial failure of the potting materials under high g shock loads is a dominant failure mechanism. Interfacial damage thresholds needed for predictive modeling or the effect of sustained high temperatures on the propensity for failure are largely absent in the state of the art. The research objectives of this study include investigating failure modes of potting-printed circuit board interfaces under the high-temperature exposure effect of mode mixity under end-notch and bi- material specimen geometries. The potting/PCB interfaces have been exposed to high temperatures at 100oC and 150oC. The fracture toughness parameters have been measured and used to calculate the cohesive zone parameters at the interface. The effect of shock orientation has been examined on the failure propensity under 30-degree and 60-degree shock orientation for pristine and 100oC, 180-days aged assemblies. A predictive model has been developed to assess interface and interconnect failure. The model has been validated with experimental data acquired from high-speed imaging in conjunction with digital image correlation for measurement of out-of-plane deformation and strains.