Constant failure rate—A paradigm in transition?
James A. McLinn · Quality and Reliability Engineering International · 1990
Abstract As a science, reliability has now entered middle age, having achieved almost 40 years of recognized modern practice. As we move into the new decade of the 1990s it is appropriate that we review the status of modern reliability. The history of science has lessons for us to learn concerning the nature of paradigm changes. Clearly some reliability practitioners have had difficulty changing their own world views as scientific knowledge has increased and the conditions of the profession have changed. The very first generalized model for reliability was based upon electron tube life data from the early 1950s. It was with these old types of complex and failure prone products upon which the original reliability model was developed and generalized. This first model dictated that the failure probability density of electronics follows the exponential law which implies that the electronics will show constant failure rates during their useful lives. To get to the constant failure rate period, an infant mortality was traversed and about 10 per cent failures observed. The reliability beliefs of the 1950s when combined with the product successes of the 1960s has created a reliability paradigm problem that first became apparent in the late 1970s. Improved quality and design effort with new technologies and knowledge about effective screening changed the conditions. Modern semiconductor electronic products do not follow the original electron tube reliability model. The applicability of this original model and the subsequent thinking that it led to must now be questioned. It is time to create a new and better paradigm to replace the defunct exponential law.