AbstractThis paper describes a class of reliability screens for use in the manufacturing process of electronic products which are directly related to the funcationality of the product being produced. The field reliability that was attained from using functional screening on an example product is presented. Because of the exceptionally low failure occurrence now possible in today's products, some simple alternative reliability monitoring statistics based on the binomial are suggested. Implications of this improved reliability on the effectiveness of screening methods is discussed, and the notion of field failures as screening escapes is introduced. Then some reasons to experiment with functional stress screens in place of a total reliance on the more traditional environmental stress screens are presented. Finally, the characteristics of functional screens are presented. Careful experimentation using appropriate statistical analysis in developing and comparing screening approaches is emphasized throughout this paper.