Volume 37, Issue 4 (July 2009)
Reliability Life Prediction of VFD by Constant Temperature Stress Accelerated Life Tests and Maximum Likelihood Estimation
In order to obtain the life information of vacuum fluorescent display (VFD) in a short time, four constant stress accelerated life tests (CSALT) are conducted with the cathode temperature increased. Lognormal function is applied for describing the life distribution of VFD. Assuming an Arrhenius model, the lognormal parameters are computed by using the maximum likelihood estimation. Furthermore, a self-developed software is employed in predicting the VFD life. The statistical analysis of the results indicates that the test design of CSALT is correct and feasible, that the average life of VFD is over 30,000 h, and that the life-stress relationship satisfies linear Arrhenius equation completely. The precise accelerated parameter is shown to be particularly useful to predict the VFD life within shorter time. Thus, this work provides significant guidelines to help engineers make decisions in design and manufacturing strategy from the aspect of reliability life.