Sealed chip-on-board circuit protection

Results from sealed chip-on-board developmental studies for digital, analog, and microwave circuits are presented. This includes environmental screening of hermetic passivation coatings for chips and their interconnects, epoxies and silicone gel as encapsulation for mechanical protection of the assembly, and films for protecting the soft gels. A test plan generated by the Reliability Analysis Center was used as the basis of a factorial design of experiments to conduct military environmental tests on samples comprising large triple track resistors mounted on high-density, fine-line, polyimide aluminum circuits. This resulted in selection of one passivation for hermetic protection and one epoxy and two silicone gels for mechanical protection. Application criteria for military systems are presented.<
>