Advanced Methodologies for Developing Improved Potted Smart Munitions for High-G Applications

Abstract

Potted electronics are becoming more common in precision-guided smart munitions designs due to the requirements for miniaturization and structural-robustness. In most of these applications, the potted electronics are inactive for most of their lifetime and may be stored without environmental (temperature and humidity) controls for up to 20 yr. The uncontrolled environment for smart munitions however makes the thermal management task especially difficult due to the coefficient of thermal expansion (CTE) mismatch that can exist between the potting material and the electronic components. In this paper, we will do the following: (1) present a methodology being developed for reducing the thermal stresses to the potted electronics used in uncontrolled environments by encapsulating the circuit board assembly (CBA) with a thin polymer layer which has been precisely formed to conform to the imprecisely shaped, as-populated, CBA. The protective polymer layer will be both flexible and soft enough to protect the CBA components from damage caused by thermal expansion mismatches, but not degrade the structural support that the potting provides during high-g force projectile launches, (2) discuss how the protective polymer layer methodology can also be used to lessen in-circuit board crosstalk, improve shielding from external RF interference, control tin-whisker growth, and enhance moisture barrier properties and thermal management for CBAs, and (3) demonstrate how to improve the smart munitions survivability under extreme high-g applications through the use of syntactic foams and material characterization before and after accelerated temperature-cycling and thermal-aging tests.