The Power Light-emitting Diode Phosphor Coating Technology

As the increasing development in white LEDs had been made, i.e. continuously increase of efficiency and decrease of price, the semiconductor lighting had been a newly high technology of great economic and social importance worldwide.The dissertation was focused on the packaging technology of the fabrication of white power LEDs in lighting application. The current research worked on the development of new planar coating technology of phosphor, which was of great importance on the fabrication of white power LEDs had been presented here.This thesis was organized as follows:Firstly, the structure and mechanism of white LEDs, and currently applied packaging process, especially phosphor coating technique for fabrication of power white LEDs were briefly introduced. The limitation of this traditional technology was analyzed.Secondly, the matching of the spectrum of the blue LED chips and that of the yellow conversion phosphor was studied to improve the conversion efficiency and the output light quality of white LEDs. The measurement of different LED chips and phosphors had been carried out on the emission spectrum of LED chip and the emission & excitation spectrum of phosphors to optimize the conversion effect of white LEDs.Thirdly, the uniformity of output light of different LED samples with traditional phosphor coating technology had been measured and analyzed statistically. Chromaticity deviation within the light spot and among those samples suggested that the non-uniformity of phosphor layer was main causes for this inherent disadvantage of those power white LEDs with traditional coating processes.Fourthly, conformal and planar phosphor coating structure was adopted to develop a shape controllable and uniform phosphor layer. Two new methods, the slurry method and electrophoretic deposition (EPD) were applied here. Feasibility studies were carried out. The conformal phosphor coating structures were realized with slurry methods i.e. the white power LEDs samples with phosphor layer of the thickness and shape uniformity. The improving output performance had been achieved with this newly developed coating technology.The work had been done here in this dissertation are helpful to improvement of output light quality of white power LEDs. The developed planar phosphor coating technology has the potential advantage in the mass production of white power LEDs.