The Use of Potting Materials for Electronic-Packaging Survivability in Smart Munitions

Potted electronics are becoming quite common in precision artillery applications due to demands for increased structural-robustness of these miniaturized smart-munitions. In field artillery applications, the potted electronics are inactive for most of their lifetime where they may have been stored in a bunker without environmental (temperature and humidity) controls for up to 20 years. In contrast, the electronics for most commercial applications tend to be active for most of their lifetimes and the operating environment here is more predictable. This difference makes the thermal management task for the artillery application very challenging. The ability to accurately analyze these designs also requires the use of fully-coupled thermal-stress transient analysis methods and also accurate material properties and strain rates over the full temperature range to be analyzed. To highlight the thermal-stress transient effects the potted configuration of a typical electronics assembly is analyzed. In addition, the structural dynamic responses of un-potted and potted assemblies, subjected to gun launch environments, are analyzed. The results indicate that for the potted design the dynamic response of the processor board is attenuated by the potting material during gun launch, and also some unexpected results, for a hollow cavity device which, fortunately, can be mostly resolved by using some commonly used manufacturing/assembly steps.