An improved substrate structure for high angular color uniformity of white light-emitting diodes

Angular color uniformity (ACU) is a key optical property of white light-emitting diodes (LEDs) and high ACU is strongly demanded in illumination applications. In this paper, we proposed an improved substrate structure to enhance the ACU of phosphor-converted white LEDs. Compared with the conventional substrate, the improved structure has an inverted trapezoid on the top of the substrate. We adopted the volume-of-fluid (VOF) model to simulate the phosphor gel spreading processes. Optical simulations were also carried out by the Monte Carlo ray-tracing method. The results show that a hemispherical geometry could be obtained with present structure. Compared with the traditional substrate, the ACU of LED module with improved substrate increased from 1148K to 196K at the average CCT of about 4000K.