Phosphor Temperature Reduction by Optimizing the Phosphor Configuration in White Light-emitting Diode Package

Thermal management for white light-emitting diode (LED) packages is of great importance. Conventional thermal management methods mainly focus on the outside of LED package, but we, in this study, focused on the thermal management inside the LED package. Besides the heat generated in LED chips, we also consider the phosphor heat generation, which is calculated by Kubelka-Munk theory. We analyzed the effect of phosphor particle distribution on the thermal behaviors of LED packages. Two kinds of phosphor sizes, i.e. 5 mu m and 7 mu m, were applied for configuration optimization. Finite-element method (FEM) was adopted to simulate three cases. It is found that when the upper phosphor layer has larger concentration, the phosphor temperature is higher but the light extraction efficiency (LEE) is lower; when the lower phosphor layer has larger concentration, the phosphor temperature is lower but the LEE is higher. The phosphor temperature uniformity can be enhanced by 0.22% when the concentration of the lower phosphor layer is larger. Phosphor sedimentation, although deteriorates the optical performance, benefits the thermal behaviors on the contrary. There is a compromise that the thermal behaviors and optical performance seem to be inconsistent for different phosphor configurations.