Chuck Reusnow
Lockheed Martin Missiles and Fire Control

Brian Russell
Dow Corning 

Unlike commercial electronics, missiles are required to reliably operate after long-term dormant storage possibly longer than thirty years. Plastic encapsulated microcircuits (PEMs) are prone to failure mechanisms caused by moisture contamination and corrosion occurring long-term storage. PEMs also exhibit failure mechanisms related to extreme temperature cycles and even small temperature cycles over time long periods of time. These failure mechanisms are further perturbed by fractures caused by rapid high reflow temperatures during circuit card assembly. The problems are expected to get worse when regulations force the use of higher temperature lead free solders. Advanced packages further exacerbate the problem with the extremely thin layer of protection.

The defense industry is not the only industry that requires reliable operation in harsh environments. The automotive and communications industries require all weather outside operation. These environments equally initiate the same PEM failure mechanisms observed in military applications.

This tutorial covers materials, methods and processes for providing cost effective, reliable and rugged plastic packages. These packages demonstrate near hermetic capabilities surviving a rigorous 1000 hours of HAST at 140 deg C and 85% relative humidity. A pilot line for the process has been established and optimized to achieve maximized technical performance at minimal production costs. Small silicon technology production quantities have been fabricated on the pilot production line. The devices have been packaged in commercial plastic encapsulated configurations and have undergone extensive environmental and qualification testing with excellent results. GaAs devices have also been fabricated using this process and are exhibiting increases of 15% to 25% in performance.