探討LED散熱器最佳設計及其排列之研究

Study of LED Heat Sink Optimal Designs and Thermal Effect of LEDs Arrangement

王苑婷(Yuen-Ting Wang)

指導教授 ： 朱紹舒

共同指導教授 ： 孫書煌

崑山科技大學/工程學院/機械工程研究所/碩士(2010年)

摘要

近年來發光二極體(Light Emitting Diode, LED)發光效率不斷提昇，尤其白光LED逐漸成為未來照明應用主要元件。LED具有使用元件壽命長、高發光流明、省能及環保等優點，但是這些優點必須該元件的晶粒(die)接面溫度在容許工作溫度下操作才能得以實現；由於LED的封裝型式，其散發的熱量多以熱傳導與熱對流形式向外釋出，而隨著發光流明與驅動電流提升，高功率LED熱管理如何維持LED接面溫度(Tj)在容許的範圍內，以確保元件性能成為極重要議題。
本研究以田口方法為最佳化工具及有限元素法分析軟體COMSOL對LED散熱設計進行分析，最後再以LED間距進行調整對LED散熱模組進行微調，使LED接面溫度能有效下降，以維持LED正常工作。最佳化僅針對散熱器及LED載板進行研究，散熱模擬對流環境乃假設熱對流係數為常數以簡化分析模式，由於僅考慮熱傳導及自然對流，因此溫度控制將與散熱器材質和表面積大小及使用載板有相當的影響，本研究主題為檯燈設計，在有限空間及最佳的散熱效益間必須取得平衡，整體而言，以最佳化分析後7.2瓦的LED模組使用散熱器最高溫度63~64 ，而LED間距調整至最大18mm時最高溫度可再下降1~2 ，模擬結果其接面溫度也符合廠商規範容許範圍內，而最佳化所求得之總貢獻率比較下提升1.8%，並達到最佳化設計的改善。

關鍵字

發光二極體 ； 田口方法 ； 熱管理 ； 接面溫度 ； 熱對流係數

並列摘要

Recently, the luminous efficiency of light emitting diode (LED) is continuously been improved. The white-light LED becomes a major element for the application of illuminating devices in the future. LEDs contain several advantages such as long life-time, high luminous intensity, green energy and environmental safety. To achieve those advantages LED chips are necessary to operate under a limited of junction temperature (Tj). As the LED package types, its heat is dissipated by the heat conduction and the convection. However, the lumen and the drive current are increasing to enhance of lighting output; the thermal management of high power LED become an extremely important issue to ensure devices performance.
In this study, Taguchi method and Finite Element Analysis are used to optimal the heat sink and LED thermal designs, respectively. Base on the optimal and thermal analyses, LEDs on the module can be adjusted which led the junction temperature of LED to drop in order to maintain LED under a well operating conditions. Optimized the LED heat sink module to study its thermal characteristics, numerical simulation of for a constant convection coefficient is assumed to simplify the analytical model. Because the heat conduction and convection are included, the temperature control related with the material of heat sink, the surface area, and the type of substrate has a considerable impact. In this research, the desk lamp design is proposed because of the limited space and the thermal efficiency of heat sink; therefore, both constraints must be compromised each others. A 7.2 watts LED modules is used to analyze and the maximum temperature of heat sink is 63 to 64 . Then, LEDs spacing rearranged to 18mm which will cause the maximum temperature to further descend by 1 to 2 . The results show that the junction temperature is consistent with manufacturer specifications and the optimal design increases the rate of total contribution about 1.8 %.

並列關鍵字

light emitting diode (LED) ； Taguchi method ； Thermal management ； Junction temperature ； convection heat transfer coefficient

參考文獻

【19】經濟部智慧財產局，http://www.tipo.gov.tw/ 。

【25】“COMSOL MULTIPHYSICS 多重物理量耦合分析 訓練手冊”，皮托科技股份有限公司。

【1】呂宗蔚，“高亮度LED散熱系統之熱傳及效益研究”，國立成功大學機械工程學系，台南、台灣，2007。

【2】Nadarajah Narendran and Yimin Gu, “Life of LED-Based White Light Sources”, IEEE/OSA J. of display technology, Vol. 1, NO. 1, 2005.

【3】M. Arik, J. Petroski, S. Weaver, “Thermal Challenges Facing New Generation Light Emitting Diodes(LEDs) for Lighting Applications”, ASME/IEEE International Packaging Technical Conference,Hawaii, 2001.