"220V AC Cooling Fan" derating component derating design is one of reliability design techniques must be used. The so-called derating, even lower than the rating of components used in the stress (such as heat stress, electrical stress) state. The reason must be because there is a certain degree of dependence between the stress intensity and its reliability "220V AC Cooling Fan" of electronic components. Stress, the lower the reliability. In addition, the performance characteristics of the parameters specified in the manual components are often based on specific criteria based on environmental stress nominal value, the actual use of occasions working conditions often exceeds the environmental stress conditions. Therefore, only when the "220V AC Cooling Fan" component derating enough to compensate for the increased environmental stress, in order to achieve the required reliability index.