1.1 PURPOSE & SCOPE
Environmental stress screening (ESS) is a cost-effective means of improving quality and reliability of electrical, electronic, electro-optical, electromechanical and electrochemical assemblies and systems at a time when defect removal is relatively inexpensive. This document provides guidance for implementing the ESS requirements in Part 6, Section C, Paragraph 3f(1) of DoD Instruction 5000.2 dated 23 February 1991. It will help program managers, project engineers, and contracting officers implement a successful ESS program. It explains to management the benefits of ESS, and when and how to implement it, and conveys ESS fundamentals, planning and execution to engineers. It focuses on ESS in development, production and overhaul, at levels of assembly from the printed wiring assembly to the system. ESS of parts is covered in other publications.
Random vibration and temperature cycling have proven to be the most successful forms of ESS in terms of effective flaw precipitation. The focus of these guidelines is on these forms, and an acceptable methodology for each is detailed herein and recommended for use. Other forms of ESS which may prove effective for specific hardware configurations and characteristics will require approval by the procuring agency.
1.2 BACKGROUND
The Department of Defense and its contractors have made great strides in recent years in learning how to design reliable weapon systems. Most failures in fielded systems today are traced to defective parts and improper workmanship during manufacturing.
In the 1950s, in order to reduce rework due to defective parts, functional testing of incoming parts was introduced. Because of the initial high failure rate experienced by equipment due to infant mortality of parts, burn-in at higher levels of assembly was instituted in the 1960s. None of these approaches, however, stressed the assemblies adequately to precipitate manufacturing defects. ESS was introduced in the 1970s to stimulate the identification of latent defects as early in the production process as possible and to correct the process to preclude their recurrence.
Each Service independently developed regulations and guidance on implementing ESS in their acquisitions. Among companies making products for tri-service use, this led to conflicts and confusion, increased acquisition costs through inefficient utilization of ESS screening equipment, increased configuration control efforts, and more complex logistics systems.
The Departments of the Army, Navy, and Air Force have collaborated in the preparation of this document to resolve this problem. By offering a single source of ESS management methods, engineering guidance, best practices and issues to be considered in preparing Statements of Work and contracts, this document will help to assure consistency in interpretation and implementation of ESS programs across all three Services.
1.3 DOCUMENT PREPARATION
The Tri-Service Environmental Stress Screening Guidelines acknowledges the Institute of Environmental Sciences (IES) and the Environmental Stress Screening of Electronic Hardware (ESSEH) Committee for their comments and for use of published information presented in the IES-ESSEH Environmental Stress Screening Guidelines for Assemblies dated March 1990. Major portions of the ESSEH Guidelines have been reprinted with permission from the IES. These guidelines have been developed by the ESSEH Technical Committee of the IES as a continuing series to advance the state of technical and engineering sciences.
