Thermorheological analysis of high voltage electronic module potting

The purpose of this paper is to present the application of MARC viscoelastic finite element techniques to the evaluation of the long-life adequacy of potted electronic modules. Potting (encapsulation) systems in current designs for long life space applications are sensitive and vulnerable to temperature extremes in spacecraft thermal environments. Past electrical failures have been attributed to poor material selection for the encapsulation system. However, a recent significant technical development has uncovered the actual failure mechanism, and has shown it to be a slow crack propagation due to stresses which have been unknowingly built-in to the design. Presented in the subsequent sections are the results of linear elastic MARC analyses for a traveling wave tube design, and of the corresponding linear viscoelastic MARC analysis which showed a 25 percent stress reduction from the linear elastic stress state after 13.3 minutes of load application.