Status and prospects for phosphor-based white LED packaging

Abstract

The status and prospects for high-power, phosphor-based white light-emitting diode (LED) packaging have been presented. A system view for packaging design is proposed to address packaging issues. Four aspects of packaging are reviewed: optical control, thermal management, reliability and cost. Phosphor materials play the most important role in light extraction and color control. The conformal coating method improves the spatial color distribution (SCD) of LEDs. High refractive index (RI) encapsulants with high transmittance and modified surface morphology can enhance light extraction. Multi-phosphor-based packaging can realize the control of correlated color temperature (CCT) with high color rendering index (CRI). Effective thermal management can dissipate heat rapidly and reduce thermal stress caused by the mismatch of the coefficient of thermal expansion (CTE). Chip-on-board (CoB) technology with a multi-layer ceramic substrate is the most promising method for high-power LED packaging. Low junction temperature will improve the reliability and provide longer life. Advanced processes, precise fabrication and careful operation are essential for high reliability LEDs. Cost is one of the biggest obstacles for the penetration of white LEDs into the market for general illumination products. Mass production in terms of CoB, system in packaging (SiP), 3D packaging and wafer level packaging (WLP) can reduce the cost significantly, especially when chip cost is lowered by using a large wafer size.

Keywords

light-emitting diode (LED) / packaging / phosphor / silicone / optical / thermal / reliability / cost

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Acknowledgements

This work was supported by the National Natural Science Foundation of China (Grant No. 50835005). The authors would like to acknowledge the help from Pei Wang and the supports of Science and Technology Department of Guangdong Province and Guangdong Real Faith Enterprises Group Co., Ltd.

RIGHTS & PERMISSIONS

2014 Higher Education Press and Springer-Verlag Berlin Heidelberg