Effect investigation of delamination on optical output of high power LEDs

In this work, the accelerated aging experimental tests of LED samples packaged with different kinds of LED chips were carried out under 85°C/85% relative humidity (RH) moisture condition. It was found that the optical output of these LED modules declines at different speeds during the aging experiments. Water was observed at the interface between PC lens and silicone glue in the modules. Based on the experimental results, optical modeling was established for these LED modules packaged with vertical LED chip and conventional chip. It was found that delaminations inside the LED packaging module play very important role for optical output decrease. The light extraction efficiency decrease induced by the delamination at the interfaces between PC and silicone glue is rather small, but delamination between phosphor and chip has big effect on LED optical output. It was also found that the effect of delamination on light extraction efficiency of LED module is different for modules packaged with vertical chip and conventional chip. The relative mechanisms for such a difference were given.