INTRODUCTION

The debate concerning the merits of using plastic-encapsulated microcircuits (PEMs) in place of hermetically sealed microcircuits (HSMs) in defense systems has been going on for more than a decade. For the past two years, the shrinking defense budget has increased the pressure to reduce program costs, thereby increasing the focus on the economic benefits of using commercial PEMs. Over the past decade PEM technology, manufacturing, and quality have advanced to the point where PEMs will yield reliability levels equivalent (and in some ways superior) to their hermetic counterparts in many applications. The military should be able to share in the benefits of PEMs, such as potential lower cost, greater product variety, smaller size, lighter weight, and mechanical ruggedness.

PEMs will provide the desired reliability in military applications if the application is correctly understood in relation to the strengths and limitations of PEMs, and the industry's best practices are employed by both the supplier and user. The intent of this paper is to address the means for achieving these ends. It is to be acknowledged that the quantitative bounding of all of the variables affecting a given application, enabling a definitive envelope for total risk elimination, does not exist. The material presented is based on available data, best collective engineering knowledge, and long experience as a major supplier of both commercial PEMs and military HSMs.