Verification, Validation, and Testing of Engineered Systems

5.6 BLACK BOX—ENVIRONMENT TESTING

5.6.1 Environmental Stress Screening (ESS) Testing

Purpose

The purpose of Environmental Stress Screening (ESS) is to pre­cipitate and eliminate latent defects in systems which are introduced either during the design of the system or during the manufacturing, assembling and packaging processes. ESS tests, also known as “burn-in,” attempt to catch “infant mortality” failures. Such failures rarely emerge during normal testing or visual inspection.

The topic of ESS is highly specialized and we will describe it in a very superficial manner. Interested readers are directed to the references identified in this section for more information. They describe the historical evolution of ESS and its basic concepts as well as statistical and physical quantification of ESS phenomena. By and large, the references concentrate mainly on environmental stress screening of electronic equipment, which typically includes ESS conditions, durations of exposure, procedures, equipment operation, actions taken upon detection of defects and screening documentation.

Rationale

The rationale for conducting environmental stress screening is for effectively disclosing manufacturing defects in systems, mainly electronic equipment caused by poor workmanship and faulty or marginal parts. ESS can also identify design problems if the design is inherently fragile or if qualification and reliability growth tests were not effective. The objectives of ESS testing is, therefore, to improve ...