This study evaluates the reliability and cost-effectiveness of using commercial plastic-encapsulated microcircuits (PEM) in a typical military system, with a view to increasing their acceptability in military applications. The cost comparison indicates an average 6-fold decrease in cost when commercial devices are used. Assurance testing did not reveal any special problems with commercial parts. Thus, if commercial PEM were proven to be sufficiently reliable for an intended military application, large cost savings would be gained by using them instead of hermetic packages.
The 4.5-sigma enhanced inspection program and the process control methods suggested here would enhance the manufacturing yield of the PLGR (Precision Lightweight Global Positioning System Receiver) by encouraging improvements in the manufacturing process while simultaneously cutting the cost of a 100% rescreen to qualify the final product. Neither the requirements assurance tests (including the step-stress test-analyze-and-fix test), nor the reliability demonstration test, nor the operational test, showed more failures than are typical for any new development, and no problems unique to PEMs were observed. Thus, the use of PEM did not lead to any special problems that caused PLGR-use specifications to be violated.
Complete failure analysis of the isolated parts is in progress, and the results will help to understand the specific reliability issues involved with the use of PEM in military systems. These issues can then be addressed to improve the acceptability of such devices in future military applications.
*Rockwell international, Cedar Rapids
**Army Research Laboratory, Ft. Monmouth
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