Study on LED devices step-stress accelerated degradation test

In this paper, the method of accelerated degradation test is used in order to get the degradation of LED devices in a relatively short period of time, In the accelerated degradation test for selected LED samples, the number of stress level is 3, the sample volume is m = 18, and test the selected sample the luminous flux of each 48h. At first LED devices work 168 hours under 85°C, then the temperature is increased to 95°C, and after 168 hours' work, and then the temperature is raised to 105°C, the LED devices work under stress conditions higher than normal state, which quickly exposed product failure, effectively shorten the time sample failure required. When all the samples reach the specified failure criterion, the test ends. Establish the relationship between the average life expectancy of the LED samples and temperature according to the Arrhenius model. Combined with the Nelson rules, set up the statistical models of LED samples life under lognormal distribution. According to the reliability parameters, using MATLAB software to get LED samples' life curve and average life.