Environmental Stress Screen (ESS) is the process of accelerating the exposure of potential defects within electronic or electromechanical products by applying reasonable environmental stress (such as temperature cycling, random vibration, etc.) or electrical stress within the design range. Scientific and reasonable environmental stress screening can improve product reliability and reduce the rate of external repair. Environmental stress screening induces faults in products with potential defects and identifies early faults, as described in the bathtub curve below. For products with good performance without defects, it is non-destructive testing.

The main purpose of environmental stress screening is to eliminate defective components and introduced process defects used in the manufacturing process. Emphasis should be placed on strengthening the screening of components, but to ensure that the product has sufficient reliability, screening should also be carried out throughout all stages of the manufacturing process. It should be carried out at every assembly level as much as possible to eliminate defects introduced during the process of assembling low-level products into high-level products. For example, for electronic products, assembly should be carried out at various levels such as components, assemblies, and equipment. Although any higher-level screening can partially replace the screening on lower level components, the screening efficiency will be reduced and the cost of screening will be greatly increased.

Typical types of stress screening include temperature cycling, random vibration, high temperature, electrical stress, thermal shock, sinusoidal fixed frequency vibration, sinusoidal scanning vibration, low temperature, comprehensive environment, humidity, acceleration, altitude, etc. According to statistical analysis, faults caused by environmental factors account for 52% of total faults in electromechanical and electronic products, of which faults caused by temperature account for 40%, faults caused by vibration account for 27%, and faults caused by humidity account for 19%. For some special products, additional stresses should be added, such as low-pressure (vacuum degree) stress when highly sensitive. During the experiment, the product should also be powered on, that is, subjected to electrical stress.
There are three main methods for environmental stress screening: conventional screening, quantitative screening, and high acceleration stress screening.
Conventional screening is currently the most widely used method in engineering applications. Conventional screening refers to screening that does not require a quantitative relationship between the screening results and product reliability indicators and cost thresholds. The method used for screening is determined based on experience. The goal is only to screen out early faults. If the selection criteria are not appropriate, the screened product may not necessarily reach the stage of basic constant failure.
Quantitative screening is the development of conventional screening. Quantitative screening refers to the process of establishing a quantitative relationship between screening effectiveness, cost, and on-site fault repair costs for product reliability. Quantitative screening should only be carried out after the product structure design has been determined (including the selection of components) and information on the impact of screening stress on it has been obtained.
High acceleration stress screening is an excitation test method based on fault physics theory. Take product failures or malfunctions as the main research object, and improve product reliability by stimulating, analyzing, researching, and curing product defects.

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