Typical failure mechanism of LED package

Traditional epoxy filled with quartz sand cannot be used as plastic packaging materials of LED, as it is a kind of optoelectronic device. Its plastic packaging materials must be those with high light transmission rate such as epoxy and silicone. But these packaging materials also have the following weak points: big thermal mismatch coefficient with chip and lead frame, poor air tightness, easy to thermal aging or corrosion aging, etc. These weak points would greatly increase the failure rate of LED devices, because of their high heat exchanging efficiency. As expected, during the process of LED device failure analysis, combining with the analysis method of polymer materials, these weak points are proved to be the fundamental reasons of the failure. The failure mechanism including: the electrochemical corrosion of chip and lead frame caused by moisture permeability, chemical corrosion of lead frame and bonding wire and other metallic materials caused by corrosive gas permeation, the corrosion and aging of encapsulant, etc. According to these failure mechanisms, more specific suggestions are offered to increase LED device quality.