發光二極體陣列構裝之熱傳與光學分析

Thermal and Optical Analysis for LED Array Package

林佳筠(Jia-Yun Lin)

指導教授 ： 陳文華 ； 鄭仙志

國立清華大學/工學院/動力機械工程學系/碩士(2009年)

摘要

LED (lighting emitting diode, LED)用途廣泛，其陣列(array)更具商業價值，可作為面板背光源、一般照明及車頭燈等應用。唯其照明效果及壽命，受晶片接面溫度高低影響甚鉅，故建立一準確有效之LED陣列構裝熱傳及光學分析方法，以掌握其出光及散熱效能，極為重要。
本論文首先以有限單元分析軟體ANSYS®，建立包含熱傳導、熱對流與熱輻射之三維有限單元熱傳分析模型，以計算LED陣列構裝之溫度分佈。為準確獲得發熱功率，本論文並利用積分球量測輸入LED陣列構裝功率中轉換為光能之部分。本論文接著利用光學軟體lighttool®分析光線於構裝內部不均勻漫射對出光效率及散熱效果產生之影響。
於自然對流下，本論文並以紅外線熱像儀(infrared thermometer，IR)量測LED 陣列構裝表面溫度場，進而探討LED陣列構裝透明模封材料表面是否塗敷黑漆之差異，以獲得模封材料表面正確之表面放射率(emissivity)，並以熱電偶量測驗證及以紅外線熱像儀拍攝、校正後之LED陣列構裝之表面溫度場。此外，為準確求得晶片接面溫度，本論文亦進行了LED構裝內晶片溫度敏感(temperature sensitive parameters, TSP)曲線之量測。上述三維有限單元熱傳分析模型結果經與各項實驗量測結果相比較，顯示此分析模型之準確性。
於確立LED陣列構裝之熱傳與光學分析模型後，本論文最後以較佳之LED陣列構裝散熱陣列擺置為對象，針對不同模封材料外型，建立其流明(lumens)度之回應表面 (response surface)，進而以最適化法(optimization)求解在特定觀察面上出光及亮度最佳之表面，以有效獲得LED陣列構裝最佳之散熱與出光設計。

關鍵字

發光二極體 ； 陣列 ； 紅外線熱像儀 ； 放射率 ； 溫度敏感曲線 ； 回應表面 ； 最適化法

並列摘要

LED (lighting emitting diode, LED) has been widely used. Its array package specially has high commercial value and can allow various applications to liquid crystal display (LCD) backlight source, general lighting, and automobile instrument, etc.. However, the LED’s illumination performance and lifetime depend on the chip junction temperature distinctly. Thus, to control the thermal and extraction efficiency, the development of an effective thermal and optical analysis method on LED array package is extremely imperative.
Based on the ANSYS® finite element analysis program, this work first establishes a rigorous three-dimensional finite element heat transfer model for the computation of temperature fired of the LED array package, concerning heat conduction, convection and radiation conditions. To get the accurate power of heat, an integrating sphere is adopted to measure the part of photon energy transformed from the input power. Also, this work uses the optical analysis program lighttool® to analyze the influence of nonuniform rays diffusing inside the package thermal and extraction efficiency.
Under natural convection condition, this work uses the IR (infrared thermometer) to measure the temperature distribution on the surface of the LED array package. To obtain the correct surface emissivity of epoxy the difference with optical glass surface painted or not is investigated. The temperature of LED array package which has been measured and calibrated is also verified by thermal couple measurement by IR. In addition, to accurately obtain the chip junction temperature, the temperature sensitive parameter (TSP) curve of the LED array package is also established. To demonstrate the accuracy of the analysis model, computed results obtained from the above mentioned three-dimensional finite element heat transfer model are compared with various experimented results.
After verifying the thermal and optical analysis model, this work finally choose a LED array package with better thermal dissipation for analysis. The response surface of lumen for different shapes of modeling component is developed. The best brightness and most uniform extraction of the specific surface is obtained by an optimization scheme. The methodology achieved can be effectively implemented for the best thermal and optical design of LED array package.

並列關鍵字

LED ； array ； infrared thermometer ； emissivity ； temperature sensitive parameters ； response surface ； optimization

參考文獻

[1]. Akos Borbely and Stephen G. Johnson, , “2005 Performance of phosphor-coated light-emitting diode optics in ray-trace simulations”, Optical Engineering Vol.44

[2]. Arik, M. Petroski, J. and Weaver, S., 2002, “Thermal Challenges in the future generation solid-state lighting application: Light Emitting Diodes”, Pro. Of the ASME/IEEE ITHERM-Conference, San Diego, pp. 113-120.

[3]. Arik, M., Becker, C., Weaver, S. and Petroski, J., 2004 a, “Thermal Management of LEDs: Package to System”SPIE Vol. 5187, pp. 64-57.

[4]. Arik, M. and Weaver, S.,2004 b“Chip Scale Thermal Mangement of High Brightness LED Packages”SPIE Vol. 5530 pp. 214-223.

[7]. Chen, W. H., Cheng, H. C., and Lin, C. H., 2004(a), “On the Thermal Performance Characteristics of Three Dimensional Multichip Modules,” ASME, Vol. 126, pp. 374-383.