This is just an Excerpt from a larger document, click here to view the entire document.Summary and Conclusions
Derating of electronic and electromechanical components to reduce the stresses applied can be one of the most important design related actions that a manufacturer of a product can take. Every component has limitations on its performance capabilities and extreme stresses reduce this capability. If the product has a defect, even a minor one, the extra applied stresses will reduce the time until degraded performance or failure occurs. By decreasing mechanical, thermal, electrical and other environmental stresses and increasing component strengths, the possibility of degradation or catastrophic failure is lessened. Because all the operating characteristics of components cannot be guaranteed by the component manufacturer, it is good policy to derate generously to provide adequate margin of safety and reduce actual component failure rates.