| Summary: | Light emitting diode (LED) offers high efficiency and energy saving alternative to
current light solution. It is believed to have a longer lifespan and higher reliability than
conventional incandescent and fluorescent lamps.
In this project, the High Brightness White LED from Osram went through accelerated life
testing. Under the accelerated environmental condition, namely, temperature and
humidity cycling, degradation caused by these 2 factors need to be investigated. Prior to
that, the preparation for reliability test had to be careful considered. One consideration
was the junction temperature which would vary if self heating exited in the LED during
operation. The optical result was sensitive to the junction temperature. In order to avoid
this phenomenon, a method used to determine an optimized pulse setting has been found
in this project.
The Total luminous flux was taken to determine the time to degradation (TTD).Others
parameter such as the Scotopic to Photopic flux(SP) ratio and the blue to yellow emission
intensity ratio was computed as well. With all these data, a failure analysis could be
conducted to determine the underlining failure mechanisms
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