Substrate reflectivity study for high brightness LED package

Luminous efficacy is key performance index for LED package. Conventional LED used plastic compound and silver plating as reflective surface. In this paper, we discussed the relation between roughness and reflectivity and the relation between reflectivity of substrate surface and luminous efficacy. We used aluminum alloy A6063-T5 as LED package substrate. There are three surface treatments - diamond cutting, diamond cutting with anodizing treatment, and blue clay polishing that are used on LED package substrates. From substrate machining results, we found there is no relation between roughness and surface reflectivity. From optical simulation and LED packaging results, we found there is positive relation between substrate reflectivity and luminous efficacy. The reflectivity at 550~600nm dominates the LED luminous efficacy.