Design, Simulation, and Reliability for LED Mobile Flash Based on Illuminance Homogeneity, Angular Color Uniformity, and Color Stability

To improve the performance of Flash LED for obtaining good picture quality, a novel ceramic packaging structure was designed and optimized based on illuminance homogeneity and angular color uniformity (ACU) for meeting the requirement of mobile flash products. The illuminance homogeneity was analyzed via both near-field optical measurement and optical simulation by Monte-Carlo method according to nine dots measurement method. Their results matched well. The target package includes vertical chip, Al₂O₃ substrate, phosphor conformal coating layer, and silicone molding as encapsulation. Through the layer print approach and layer transfer method, the thickness of phosphors layer was optimized by finite element analysis method to improve the temperature distribution and eventually the reliability of LED units. In addition, good Delta CCT was obtained by optimizing the phosphor layer. The design methods were characterized by electrical-optical testing.