LED構裝溫度量測與熱傳分析

Temperature Measurement and Heat Transfer Analysis for LED Package

王焜雄(Kung-Hsiung Wang)

指導教授 ： 陳文華

國立清華大學/工學院/動力機械工程學系/碩士(2008年)

摘要

發光二極體(Lighting Emitting Diode, LED) 具有體積小、耗電量小、壽命長及色彩豐富等優點，主要應用於液晶顯示器(Liquid Crystal Display, LCD)背光源、指示燈、汽車儀表版、煞車燈與交通號誌等，當功率及效率提升後，將很有機會取代傳統之照明設備。在此情形下，LED構裝之散熱效能將更為重要，而需予以深入研究。
本論文旨在提出一方法來分析LED構裝之散熱效能。首先利用紅外線熱像儀進行LED構裝表面溫度之量測，其結果並以熱電偶之量測結果予以驗證，而LED構裝表面之發射率係數並得藉以校正。接著建立了LED溫度敏感參數(temperature sensitive parameters, TSP)曲線之量測技術，並藉之可間接量得晶片接面溫度Tj。
本論文並利用有限單元分析軟體ANSYS®建立一精確之LED構裝三維有限單元熱傳分析模型，並採用了適當之發射率係數及熱對流/熱輻射邊界條件。由LED構裝晶片接面溫度及表面溫度分佈之比較，顯示本論文之模擬及實驗結果頗為脗合。
最後，本論文並利用發展之有限單元模型探討不同參數對於LED構裝散熱效能之影響，其中包括輸入功率、模封材料/引線框架之熱傳導係數及引線框架之幾何尺寸等。結果顯示若選擇LED構裝內適當之各項參數，將可有效降低晶片接面溫度，增加其使用壽命。

關鍵字

發光二極體 ； 溫度量測 ； 熱阻

並列摘要

LED (Lighting Emitting Diode) has various advantages, such as small size, less power consumption, long lifespan and variegated colors, which can extensively be used as LCD (Liquid Crystal Display) backlight source, indicator lamp, automobile instrument, tail light and traffic light, etc.. LED can probably replace traditional light as its power and efficiency increase. In such situation, however, the heat dissipation of LED package becomes more important and needs to be thoroughly studied.
This study presents a methodology for investigating the thermal dissipation of the LED package. The IR (infrared) thermography measurement is first performed to investigate the thermal disposition on the surface of the package. The results are verified by the thermal couple measurement and the emissivity coefficients on the surface of the LED package can be thus calibrated. The technique for establishing the TSP (temperature sensitive parameter) curve of the LED is demonstrated and the chip junction temperature Tj can be indirectly measured thereafter.
A rigorous three-dimensional finite element model for the heat transfer analysis of the LED package is also constructed by ANSYS® program with proper emissivity coefficients and appropriate heat convection / radiation boundary conditions. Good correlations of the simulated and experimental results are found by comparing the chip junction temperature and temperature distribution on the surface of the LED package.
Finally, this study also investigates the influence of various parameters on the thermal performance of the LED package by the finite element model developed, including the input power, thermal conductivity of epoxy lens / lead frame and sizes of lead frame. The results show that appropriate choice of the parameters in LED package studied will decrease the chip junction temperature and increase the application lifespan effectively.

並列關鍵字

lighting emitting diode ； temperature measurement ； thermal resistance

參考文獻

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