隨著LED的亮度不斷提升，汽車頭燈採用LED是未來的趨勢。因引擎室周圍為一高溫的環境，溫度在80℃以上，過高的溫度會使LED的發光效率降低，且使用壽命會大幅下降，如何設計出高效率的散熱系統，是LED頭燈在應用上必須解決的問題。
本研究藉助ANSYS分析軟體探討高亮度LED應用於汽車頭燈上的熱傳特性，並以晶片接面溫度的變化，探討LED的熱傳導效益，使晶片維持在固定的操作溫度下，以維持元件的可靠度。探討之參數包含LED排列形式、Heat sink的面積與厚度以及改變Slug、Substrate、Heat sink材料等。結果顯示，均勻分布型與環型這兩種不同的排列形式，並沒有明顯的溫度差異，改變Heat sink的面積與厚度時，加大與加厚的Heat sink，在對流係數小於50W/m2‧K時，有較明顯的溫度差異；將Slug及Substrate改為高熱傳導係數之材料，可有效降低LED之接面溫度。實驗部分評估4種現有之散熱模組，在使用3W LED，環境溫度80℃，散熱條件為自然對流的情況下，都能滿足LED接面溫度低於135℃之要求

Following the improvement in light intensity of light emitting diodes(LEDs), the automobile headlamp using LEDs is becoming a trend. The engine compartment is a high temperature environment. The temperature around is above 80℃. High temperatures will reduce the luminous efficiency and lifetime of LEDs. Thus, designing a high efficiency thermal module is important in LED headlamp application in automobiles.
In this study, the ANSYS finite element software is used to study of the thermal characteristics of an automobile headlamp using high brightness LEDs as its light source. The parameters investigated include two LED layouts (ring and distributed types), LED heat sink area, thickness and different connecting conditions. The simulation results show that different layouts exhibit nearly the same temperature distributions. The heat sink areas and thickness effect are significant only when the convective coefficient is less than 50W/m2‧K. Using high thermal conductivity slugs and substrates can lower the junction temperature. Experimental results show that using four kinds of thermal modules lead to satisfactory junction temperature which is less than 135℃ in natural convection with an ambient temperature of 80℃.

[1]M. G. Craford, “Visible Light-Emitting Diodes: Past, Present, and Very Bright Future”, MRS Bulletin, October 2000.
[2]K. Eichhorn, “LEDs in Automotive Lighting”, Proc. of SPIE, Vol. 6134, pp 613405.1-613405.6, 2006.
[3]N. Narendran and Y. Gu, “Life of LED-Based White Light Sources”, IEEE/OSA Journal of Display Technology, Vol.1, No.1, pp 167-170, September 2005.
[4]K. Eichhorn, “LED Frontlighting”, Proc.of SPIE, Vol. 5663, pp 7-14, 2005.
[5]http://www.lexus.com/models/LSh/
[6]http://www.audi.com/audi/com/en2/models.html
[7]M. Arik and S. Weaver, “Chip Scale Thermal Management of High Brightness LED Package”, SPIE Proceeding, Vol. 5530, pp 214-223, 2004.
[8]M. Sayers, “Performance Considerations for LED Automotive Signal Lamps”, SAE Tech. Paper No.2002-01-0381.
[9]A. Cvetkovic, O. Dross, J. Chaves, P. Benitez, J. C. Miñano, and R. Mohedano, “Etendue-Preserving Mixing and Projection Optics for High-Luminance LEDs, Applied to Automotive Headlamps”, Optics Express, Vol. 14, No.26, pp. 13014-13020, 2006.
[10]P. Albou, “LED Module for Headlamp”, SAE Tech. Paper No.2003-01-0556.
[11] J. T. Hsu and W. L. Wang, “Automotive Forward Lighting with Use of High Flux Light-Emitting-Diodes”, SAE Tech. Paper No.2006-01-0104.
[12]A. Mednik, “Automotive LED Lighting Needs Special Drivers,” Power Electronics Technology Magazine, Vol. 31, No.8, pp. 22-28, 2005.
[13]P. Greenland and W. Berns, “Powering Next-Generation Solid-State Lighting”, Power Electronics Technology, Vol. 30, No.5 pp. 34-40 May 2004.
[14]J. Y. Tsao, “Light Emitting Diodes (LEDs) for General Illumination”, An OIDA Technology Roadmap Update 2002.
[15]F. Wall, P. S. Martin and G. Harbers, ” High Power LED Package Requirements”, Third International Conference on Solid State Lighting, Proc. of SPIE, Vol. 5187, pp.85-92, 2004.
[16]L. Sardi and R. Ackermann, “Integration of LEDs in Forward Lighting”, Proc. of SPIE, Vol. 5663, pp.1-6, 2005.
[17]Y. Lai and N. Cordero, “Thermal Management of Bright LEDs for Automotive Applications”, Thermal, Mechanical and Multiphysics Simulation and Experiments in Micro-Electronics and Micro-Systems, EuroSime, Vol. 2006, pp.1643953-1643957, 2006.
[18]Y. Lai, N. Cordero, F. Barthel, F. Tebbe, J. Kuhn, R. Apfelbeck, and D. Wurtenberger, “Liquid Cooling of Bright LEDs for Automotive Applications”, FLOTHERM Technical Papers, T382 ,2006.
[19]K. Kikuchi, Y. Hamashima, and Y. Kobayashi, “An Approach to Predicting LED Junction Temperatures with Fluid and Thermal Analysis”, SAE Tech. Paper No.2005-01-0864.
[20]M. Arik, J. Petroski, and S. Weaver, “Thermal Challenges in the Future Generation Solid State Lighting Applications: Light Emitting Diodes”, 2002 Inter Society Conference on Thermal Phenomena, pp. 113-120, 2002.
[21]J. Petroski, “Thermal Challenges Facing New Generation Light Emitting Diodes (LED) for Lighting Applications”, Solid State Lighting II, Proc. of SPIE, Vol. 4776, pp. 215-222, 2002.
[22]F. M. Steranka, J. Bhat, D. Collins, L. Cook, M. G. Craford, R. Fletcher, N. Gardner, P. Grillot, W. Goetz, M. Keuper, R. Khare, A. Kim, M. Krames, G. Harbers, M. Ludowise, P. S. Martin, M. Misra, G. Mueller, R. Mueller-Mach, S. Rudaz, Y.-C. Shen, D. Steigerwald, S. Stockman, S. Subramanya, T. Trottier, and J. J. Wierer, “High Power LEDs – Technology Status and Market Applications”, Physica Status Solidi (A) Vol. 194, No. 2, pp. 380–388 ,2002.
[23]M. Arik, C. Becker, S. Weaver, and J. Petroski, “Thermal Management of LEDs: Package to System”, Proc. of SPIE, Vol. 5187, pp. 64-75, 2004.
[24]S. Haque, D. Steigerwald, S. Rudaz, B. Steward, J. Bhat, D, Collins, F. Wall, S. Subramanya, C. Elpedes, P, Elizondo and P. S. Martin, “Packaging Challenges of High-power LEDs for Solid State Lighting”, Proc. of SPIE, Vol. 5288, pp. 881-886, 2003.
[25]Z. Ma, X. Wang, D. Zhu, and S. Liu, “Thermal Analysis and Modeling s of LED Arrays Integrated with an Innovative Liquid-cooling Module”, 6th International Conference on Electronic Packaging Technology, IEEE , pp.542-545, 2005.
[26]G. J. Sheu, F. S. Hwu, S. H. Tu, W. T. Chen, J. Y. Chang, J. C. Chen, “ The Heat Dissipation Performance of LED Applied a MHP”, Fifth International Conference on Solid State Lighting, Proc. of SPIE, Vol. 5941, pp. 1 - 8, 2005.
[27]K. Sazuka, “LED Headlamps”, SAE Tech. Paper No.2004-01-0437.
[28]M. Sivak, B. Schoettle, T. Minoda, and M. J. Flannagan, “Short Wavelength Content of LED Headlamps and Discomfort Glare”, Leukos, Vol.2, No.2 , pp.145-154, 2005.
[29] J. Petroski, “Spacing of High-brightness LEDs on Metal Substrate PCB’s for Proper Thermal Performance,”IEEE Inter Society Conference on Thermal Phenomena, Vol.2, pp.507-514, 2004.
[30]F. S. Tse and I. E. Morse, “Measurement and Instrumentation in Engineering”, Marcel Dekker, Inc, 1989.
[31]Technical Datasheet DS46, “Luxeon III Star”, www.lumiled.com
[32]李輝煌, “ANSYS工程分析-基礎與觀念”, 高立圖書有限公司, 2005.
[33]ANSYS User’s Manual, Release 11.0, 2006.
[34]Reference Design RD25, “Luxeon Reliability”, www.lumiled.com
[35]康淵,陳信吉, “ANSYS入門(修訂四版)”, 全華圖書股份有限公司, 2007.
[36]R. R. Tummala, “Fundamentals of Microsystems Packaging”, The McGraw-Hill Companies, Inc, 2001.
[37]MatWeb, http://www.matweb.com
[38]張正平, 周榮華, 趙守嚴, “LED汽車頭燈散熱分析”, 中華民國汽車工程學會車輛工程學刊, Vol.5, pp. 131-141, 2008.