Degradation Model for Device Reliability

The model assumes that, under a constant or cyclic stress, device degradation rate is proportional to the existing degradation. The proportionality constant is a positively distributed random variable. The distribution of the amount of degradation tends to be asymptotically lognormal. The general form of the life distribution is derived. Application of this model has been made in analyzing degradation data in thermal resistance, diode leakage, and transistor gain.