| Summary: | 碩士 === 國立清華大學 === 動力機械工程學系 === 104 === In recent years, Light emitting diodes (LEDs) has become more and more popular because of their low power consumption, low-pollution and long-life. Currently, the common lumen maintenance test of LED follows IES LM80-08 standard, which costs at least 6000 hours for measurement and prolongs the time-to-market schedule.
There are some stress will influence the lifetime of LEDs, such as temperature stress, current stress and humidity stress. In our previous researches, a modified accelerated aging test algorithm using different high temperature stress without input current was successfully proposed. In this research, we will process an accelerated aging test with current stress and temperature stress. The purpose of this research are (i) observing the lumen degradation in current and temperature loading aging test, (ii) investigating the current stress and temperature stress accelerated factor in the test, (iii) finding the appropriate life prediction model to predict the accurate lifetime and (iv) proposing an available method to shorten the reliability test standards, promoted the light-emitting diode industry.
First of all, we use a validated finite element thermal analysis model and thermal resistance of LED to predict the junction temperature and find out the ambient temperature of experimental conditions. Then use the forward voltage method to measure the junction temperature and validate the prediction result. Finally, we set up the accelerated aging test experimental conditions. In our experiment result, the same junction temperature with different current stress will cause the lumen maintenance decay similarly. So that in this experimental conditions that could use Arrhenius model which only consider high temperature stress without input current to prediction the lifetime of LED. Moreover, during the experiment we found out the heating type of oven will influence junction temperature of LED seriously. In the future, when we do the aging test of LED should consider about the oven to make sure whether the measurement result is correct.
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