OVERVIEW

Emerged from a strong consumer movement within the military services and the Department of Defense [1], ESS has its origins in environmental testing; basically, a means of exposing samples of product assemblies to one or more simulated field conditions [2]. Driven by the military, environmental testing became prominent during World War II, when the proliferation of sophisticated weaponry, aircraft, and communications systems demanded a less costly and time-intensive method of demonstrating the reliability of equipment than by use-stress level testing. Laboratory experimentation with small-scale hardware was conducted. An insulated chamber, equipped with the technology to simulate environments such as temperature, humidity, altitude and others was used. These tests were performed during developmental stages to verify design, and on a manufacturing audit basis to measure design compliance.

After the war, new electronic technologies became available to the consumer market, a situation that created a different need. As products were downsized, their complexity increased, involving unique processing and assembly procedures. The accumulation of field failure data showed that design compliance was no longer sufficient evidence of reliability. It also led to the discovery that a number of unpredictable factors involved in parts design, product workmanship and manufacturing processes were contributing to higher than desired failure rates. As many of these failures were occurring during the product's infancy, it was determined that a testing methodology that could mimic the product's infancy stage would provide the cure.

In an attempt to pass products through infancy, a process of powering products for an...