Masters Theses

Date of Award

5-1998

Degree Type

Thesis

Degree Name

Master of Science

Major

Aviation Systems

Major Professor

Robert Richards

Abstract

Plastic Encapsulated Devices (PEDs) have historically been banned from most military systems, This is due to their perceived lower reliability than their counterpart, the Hermetically Sealed Device (BSD). In 1965 the Department of Defense (DoD) accounted for over 95 percent of all US manufactured semiconductor purchases. Currently DoD accounts for about one percent of their purchases. Although the total demand for semiconductors in DoD has increased dramatically it has paled in comparison to the consumer electronics and automotive demand for semiconductors. The market has shifted from one where DoD had significant input to one that is virtually driven by the consumer electronics and automotive demand. Recent DoD mandated acquisition reform initiatives have given Program Managers flexibility to incorporate non-military grade parts into their systems. As budget constraints put pressure on Program Managers to make system cost reductions, the use of PEDs was seriously considered. Numerous military programs have evaluated the use of PEDs in their systems. Extensive research into the history and manufacture of PEDs, their advantages and disadvantages has been conducted.

Problems with PEDs in missile systems predominately result from moisture and temperature. Moisture has the potential to cause long term storage problems from corrosion and to cause cracking of the encapsulant material during soldering processes. Temperature extremes can cause part failure from different coefficients of thermal expansion of the parts of the FED or thermal breakdown,

Through proper process controls the risks associated with FED use can be reduced to an acceptable level. The proper use of process controls will allow the use of FEDs and mitigate the risks associated with them. These process controls involve; reviewing the environment the part must be used in, part selection, analyzing the reliability of the part in the intended application and environment, understanding logistics impacts, establishing partnerships with part manufacturers, detailed review of the part manufacturing processes, and ensuring the part is properly qualified.

Prospects for future improvements in the application of FEDs in missile systems are discussed. These include the elimination of most government oversight and control of the detail process controls through-the use of effective warranties. Another prospect is the use of common parts databases across multiple programs both within a given contractor and across multiple contractors. The impact of future microcircuit technology advancements is also addressed.

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