The step-down-stress accelerated storage testing evaluation methods of small sample electronic products based on Arrhenius model
Accelerated life testing (ALT) is used to obtain failure data quickly under high stress levels in order to predict product life performance under design stress conditions. Most of the previous work on designing ALT plans is focused on the application of step-stress. According to the advantages of step-down-stress accelerated life testing about its higher failure rate, less sample size and simpler test equipment, this paper develops a method of accelerated storage life evaluation method based on step-down-stress Type-II censored accelerated life testing data in engineering practice. Firstly, the failure data under accelerated stresses are converted to normal stress employing acceleration factors of Arrhenius model based on the theory of Nelson. This paper establishes the maximum likelihood function of the whole samples under normal stress after converting failure time. Then Arrhenius model parameters and average life of product under normal stress are obtained by parameters partial derivation of the maximum likelihood estimation. Subsequently, the confidence interval and confidence lower limit of average life under a certain confidence level are obtained by the Fisher matrix. Lastly taking the step-down-stress Type-Π censored accelerated life test of a small sample electronic products as an example for analysis, this paper compares and analyzes the result of step-down-stress accelerated life evaluation method based on the Arrhenius model with the average life expectancy, failure rate and reliability function of field data. This paper verifies the efficiency and accuracy of step-down-stress accelerated storage life evaluation method based on Arrhenius model specific to small sample.