SOME RISKS OF UNLIMITED THERMAL CYCLING ESS

摘要

A common practice in thermal cycling Environmental Stress Screening (ESS) is to require the last cycle, or the lastrntwo or three cycles, to be failure free, with no limit placed on the maximum number of cycles to which the product isrnsubjected. This results in a risk of overstressing, and thereby taking life out of, the product. The pitfalls of unlimited thermalrncycling ESS are:rn1. Reducing the time before the first expected random failure of the delivered system.rn2. Producing a risk of a random failure during ESS.rnThis paper describes, and illustrates by example, the pitfalls.