Improved angular color uniformity and hydrothermal reliability of phosphor-converted white light-emitting diodes by using phosphor sedimentation.

We investigated the effect of phosphor deposition methods on the correlated color temperature (CCT), luminous flux and thermal characteristics of packaged white light-emitting diodes (WLEDs) for use in mobile display products. For both the samples, the CCT decreased with increasing viewing angle. Phosphor sedimentation samples displayed much better angular color uniformity than phosphor dispersion samples. The phosphor sedimentation sample had higher luminous flux and luminous efficacy at 20 mA than the phosphor dispersion sample. The phosphor sedimentation sample displayed much better high-temperature/humidity (85 °C/85%) reliability and lower package temperatures compared with the phosphor dispersion sample.