Abstract
This is the final installment of a series of three articles under the general topic โOff the bathtub onto the rollerโcoaster curveโ. A short version was presented at the 1988 Annual Reliability and Maintainability Symposium in the U.S.A. The first article was entitled โThe bathtub does not hold water any moreโ, and the second was entitled โThe rollerโcoaster curve is inโ. The three articles provide detailed discussions of the findings leading to the conclusions on the rollerโcoaster characteristics for the hazard rate curve for electronics. The first article discussed the problems with the bathtub and the second explored the shape of the hazard rate curve in view of some recent observations. This article suggests some plausible physical reasons for the formation of the rollerโcoaster shape. The generation of the shape starts with the basic failure mechanisms, which leads to the generally decreasing hazard rate. The humps could be caused by changing hazard conditions, wearโout failure distribution of flawed items, distribution of flaw sizes or residue small size flaws left in the equipment because of test and inspection limitations.