A Life Prediction Model for High-Reliability Products and Its Application to VFD Based on Constant-Stress ADTs

For many high-reliability and long-life products, the accuracies of some existing life prediction models are not high enough, which may limit their fast development. For this purpose, four groups of constant-stress accelerated degradation tests (ADTs) were carried out by increasing the temperature of a vacuum fluorescent display (VFD) cathodic filament, and the equivalent average luminance degradation model (EALDM) was proposed to predict VFD life. In this model, firstly, a two-parameter Weibull function was used to fit average test data at each accelerated stress, and the corresponding formula of luminance degradation was obtained. Secondly, a power function was determined to fit multi-groups of data points formed by an accelerated stress and time at different given luminance, and then the work time under normal stress was extrapolated. Finally, by reusing the Weibull function to fit the data points, including the work time and given luminance, the life prediction of products was achieved. The results indicate that the test design of constant-stress ADTs is correct and feasible; the Weibull function well reveals the VFD luminance decaying law at both accelerated and normal stresses, and the power function objectively reflects the relationship between work time and stress. It is found by comparing the predicted life with the reference value that EALDM has high precision, which paves the way for following research in life prediction methodology and acts as a guide for professional technicians.