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Effects of Phosphor Layer Structure on Performance of White Light-Emitting Diodes
Remote Phosphor Structure
|引用:|| 許榮宗, “白光LED 製作技術走勢,” 工業材料雜誌220期, 台北,台灣, pp. 148~149, 2005.  S. Shionoya, and M. Y. William, “Phosphor handbook,” CRC Press LLC. New York, p. 4, 1998.  劉如熹, 林益山, 廖秋峰, “LED 照明光源展望(一)：從藍光紫外光到白光,” 工業材料雜誌220期, 台北, 台灣, p. 139, 2005.  楊素華, “螢光粉在發光上的應用, ”科學發展358期, 台北, 台灣, pp. 66-71, 2003.  D. A. Skoog, and J. J. Leary, “Principles of instrumental analysis,” Saunders College Pub. pp. 176-177, 1992.  J. A. DeLuca, “An introduction to luminescence in inorganic solids,” J. Chem. Educ, Vol. 57, Number 8, pp. 541-545, 1980.  R. C. Ropp, “Luminescence and the solid state,” Elsevier Science Publishers. p. 245, 1991.  H. C. Lee, “Introduction to Color imaging science,” Cambridge, UK, New York Cambridge University Press, p. 272, 2005.  鄭佐柏, “色彩理論與數位影像,” 新文京開發出版股份有限公司, pp. 60-66, 2004.  LEDTRONICS, INC. 網站： http://www.ledtronics.com/datasheets/Pages/chromaticity/097b.htm  鄭州大學包裝工程系網站： http://big5.cgan.net/book/books/print/packcolor/link/5-4-2.html  UNCC網站： http://personal.uncc.edu/lagaro/cwg/color/AdditivePri.gif http://personal.uncc.edu/lagaro/cwg/color/ SubtractivePri.gif  K. Murakami, T. Taguchi, and M. Yoshino , “White illumination characteristics of ZnS-based phosphor materials excited by InGaN-based ultraviolet light-emitting diode,” Proc. SPIE Vol. 4079, pp.112-119, 2000.  T. Taguchi, “ Japanese semiconductor lighting project based on ultraviolet LED and phosphor systems, ” Proc. SPIE Vol. 4445, pp. 5-12, 2001.  Y. Uchida and T. Taguchi, “ Theoretical and experimental luminous characteristics of white LEDs composed of multiphosphors and near-UV LED for lighting,” Proc. SPIE Vol. 4996, pp. 166-173, 2003.  H. Lee, Y. Park, M. Chang, G. Kim, S. Hong, H. Won, J. Lee, and Y. Oh, “ The enhancement of light efficiency using modified phosphor that is coated sub-micro size sulfonated polystyrene beads,” Proc. SPIE Vol. 6321, pp. 1-6, 2003.  Y. Gu and N. Narendran , “A noncontact method for determining junction temperature of phosphor-converted white LEDs ,” Proc. SPIE Vol. 5187, pp. 107-114, 2004.  C. C. Miller, Y. Zong, and Y. Ohno , “LED photometric calibrations at the National Institute of Standards and Technology and future measurement needs of LEDs,” Proc. SPIE Vol. 5530, pp. 69-79, 2004.  N. Narendran, Y. Gu, and R. Hosseinzadeh, “Estimating junction temperature of high-flux white LEDs,” Proc. SPIE Vol. 5366, pp. 158-160, 2004.  N. Narendran, “Improved performance white LED,” Proc. SPIE Vol. 5941, pp. 1-6, 2005.  S. Fujita, S. Yoshihara, A. Sakamoto, S. Yamamoto, and S. Tanabe, “ YAG glass-ceramic phosphor for white LED (I): background and development,” Proc. SPIE Vol. 5941, pp. 1-7, 2005.  S. Fujita, S. Yoshihara, A. Sakamoto, S. Yamamoto, and S. Tanabe, “ YAG glass-ceramic phosphor for white LED (II): background and development,” Proc. SPIE Vol. 5941, pp. 1-6, 2005.  W. Falicoff, J. Chaves, and B. Parkyn, “PC-LED luminance nhancement due to phosphor scattering,” Proc. SPIE Vol. 5942, pp. 1- 15, 2005.  B. Braune, H. Brunner, J. Strauss, and K. Petersen , “Light conversion in opto semiconductor devices: from the development of luminous materials to products with customized colors ,” Proc. SPIE Vol. 6013, pp. 1-8, 2005.  B. Parkyn, J. Chaves, and W. Falicoff , “Remote phosphor with recycling blue-pass mirror”, Proc. SPIE Vol. 5942, pp. 1-12, 2005.  H. Y. Chou, T. H. Hsu, and T. H. Yang , “Effective method for improving illuminating properties of white-light LEDs ,” Proc. SPIE Vol. 5739, pp. 33-41, 2005.  E. Radkov, Z. Brown, I. Hausmann, and J. Reginelli , “Performance of white PC-LEDs based on violet chips, ” Proc. SPIE Vol. 6337, pp. 1-4, 2006.  D. Kan, E. Wu, and D. M. Wang, “Design optimization and experimental verification of white-light-emitting diodes using multiple phosphor films, ” Proc. SPIE Vol. 6337, pp. 1-8, 2006.  Lambda Research Corporation. Trace pro 4.0 使用手冊, p. 4.14, 2007.|
本論文藉由螢光粉置於支架表面之封裝方式，探討發光效率及壽命和傳統封裝之差異。由於背向光被藍光晶片吸收的減少，提高光取出效率，實驗結果顯示其光輸出及發光效率比傳統方式提升17 % 以上；另外在相同色度座標下，螢光粉置於支架表面之封裝方式，所需要的螢光粉濃度較高。故當晶片工作電流上升時，大部份的螢光粉均被藍光光子激發成黃光，並混合成白光，當注入電流由20 mA提升至70 mA時，白光發光二極體之CIE色度座標x, y值只分別偏移0.002及0.004，遠小於傳統封裝方式(x, y值變動範圍各約-0.01)，此結果顯示此螢光粉構裝方式具有較穩定的色溫表現，並能簡化白光二極體封裝產業之測試流程。
在本論文中我們同時利用光學模擬軟體Trace Pro來驗證實驗理論及結果，藉由實驗參數，建立光學模擬模型，分析模型觀察面之平面照度圖及燭光分佈圖得到40 %的光輸出提升，在冷熱衝擊試驗及壽命測試，照度及發光效率衰減較傳統封裝減少5 %以上，由此可知螢光粉置於支架表面的封裝概念確實能提升其發光效率及可靠度。|
Recently, high-efficiency white light-emitting diodes (LEDs) have become an important issue in developing practical solid-state lighting applications. Among the methods available for creating white-light LEDs, the phosphor-converted (pc) structure is the most popular packaging. Generally, the phosphor is dispersed within the silicone surrounding the LED die in a white LED package. A portion of the blue light emitted from the InGaN chip is converted by the phosphor to produce the yellow light. The combination of blue and yellow emissions achieves the white light. In this thesis, the effects of remote phosphor structure on the efficiencies and lifetimes of white LED lamps have been investigated. Since the blue light reflected from the remote phosphor layer and absorbed by the chip is reduced, the light extraction efficiency of the LED lamp can be improved. From the measurement result, a 17% improvement in light output has been achieved as compared that of the conventional white LED package. Under the same CIE coordinate, it was found that the LED sample with a remote phosphor package should possess higher phosphor concentration. When the injection current increased from 20 to 70 mA, the CIE (x, y) values shifted only 0.002 and 0.004, whereas both the CIE (x, y) values of conventional LED package shifted about 0.01. This could be due to the fact that more phosphor particles will be excited by the blue photons due to the higher phosphor concentration. These results indicate that the remote phosphor structure has higher stability in color temperature performance which can simplify the test process in the LED packaging line. In the simulation works, we have used a Trace-Pro software based on the ray tracing theory to correlate the experiment results. According to the experimental parameters, a setup of the LED structure model can be established. The incident flux map and cadela distribution plots can then be calculated. It is found that a 40% improvement in light output was obtained as compared with that of the conventional white LED package. This exhibits that the simulation trend can coincide with our present experimental results to some extent. Furthermore, from the results of temperature shock and ambient life tests, the luminance decay rates can be improved over 5% as compared with those of the conventional LED package sample. These results suggest that the remote phosphor structure can authentically increase the efficiency and reliability of white LED lamps.
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