Environmental stress screening (ESS) refers to the process of exposing a newly manufactured or repaired product or component (typically electronic) to stresses such as thermal cycling and vibration in order to force latent defects to manifest themselves by permanent or catastrophic failure during the screening process. The surviving population, upon completion of screening, can be assumed to have a higher reliability than a similar unscreened population. Overview Developed to help electronics manufacturers detect product defects and production flaws, ESS is widely used in military and aerospace applications, less so for commercial products. The tests need not be elaborate, for example, switching an electronic or electrical system on and off a few times may be enough to catch some simple defects that would otherwise be encountered by the end user very soon after the product was first used. Tests typically include the following: Temperature variations Vibration tests Pressure Flexibility tests ESS can be performed as part of the manufacturing process or it can be used in new product qualification testing. An ESS system usually consists of a test chamber, controller, fixturing, interconnect and wiring, and a functional tester. These systems can be purchased from a variety of companies in the environmental test industry. The stress screening from this process will help find infant mortality in the product. Finding these failures before the product reaches the customer yields better quality and lower warranty expenses. Associated military terminology includes an operational requirements document (ORD) and ongoing reliability testing (ORT). Standardized Definitions and Methods The following is extracted from a paper on ESS testing prepared by the U.S. Air Force to provide standardized definitions and methods. Introduction The purpose of this paper is to provide standardized definitions and a roadmap of test processes for the Environmental Stress Screening (ESS) of replacement and repaired components used on Air Force systems. The term “component” is used interchangeably with the term “unit” and includes Line-replaceable unit (LRU) and sub-units (SRU). A component selected for testing is a Unit Under Test (UUT). Operational Safety, Suitability, and Effectiveness (OSS&E) policy and instructions require consistency in the disciplined engineering process used to ensure that activities such as maintenance repairs and part substitutions do not degrade system or end-item baselined characteristics over their operational life. Baselined characteristics are highly dependent on reliability, which is verified and maintained by ESS testing. OSS&E policy and instructions also require consistent engineering processes to ensure