Test method of life-time and reliability evaluation for high-power LED

The development history of the light-emitting diode (LED) is introduced. Several factors influencing LED reliability are put forward, among which the material defectiveness of LED and the heat dissipation during packaging are the main factors. The reliability evaluation of LED is analyzed by testing the LED lifetime, which is usually derived from the accelerated test. The testing methods to evaluate LED lifetime according to the accelerated stress (single and composite accelerated stresses) are listed and introduced. The reliability of high-power LEDs was tested and several mathematical models of the LED lifetime were derived under different accelerated stresses. The mathematical formula for deriving the LED lifetime is given based on some examples.