The roller‐coaster curve is in

This is the second part of a three‐part article under the general heading of ‘Off the bathtub onto the roller‐coaster curve’, a short version 1 of which was presented at the 1988 Annual Reliability and Maintainability Symposium in the U.S.A. The first part was entitled ‘The bathtub does not hold water any more’, 2 and the last part, to be published in a later issue of this journal, is entitled ‘Physical basis for the roller‐coaster hazard rate curve’. This three‐part article provides detailed discussions of the findings leading to the conclusions on the roller‐coaster characteristics for the hazard rate curve for electronics. Part 1 discussed problems with the bathtub curve. This part explores the shape of the failure rate curve in view of some recent observations. For more than twenty years investigators studying semiconducting device burn‐in have subscribed to the concept of freak failures, which manifest themselves as a hump on the hazard rate curve. In addition to semiconducting device data several sets of screening data, as well as operational data dating all the way back to 1961, also showed that indeed one can expect electronic systems to have generally decreasing failure rate curves with failure humps on them. The author of this paper calls these curves the roller‐coaster curves.