由於高亮度LED發光效率高、壽命長且環保特性優良，一直被視為在下世代照明光源中將扮演重要角色，從LED的封裝結構來看，可分為晶片、銀膠（固晶材料）、支架（導線架）與介面材料所組成；每個部份都有其熱阻抗，而LED整體的熱阻值為個別材料熱阻值的加總，可視為串連的關係。熱阻值越低表示能快速把廢熱引導至元件外部，越不易使介面溫度升高；經驗顯示若介面溫度升高10℃，則LED壽命將會降低一半，所以如何正確又快速得知介面溫度將是很重要課題，有鑑於此，本研究將利用LED的特性去量測介面溫度。由於LED的操作電壓（Vf）會因環境溫度升高而產生近似線性的下降，本研究將LED置於恆溫箱中，待LED光源（包含LED晶片溫度）與環境溫度達到熱穩定狀態後，再以微小電流與脈衝方式即可得到一對應之操作電壓；如此將環境溫度逐步升高，等取得足夠的實驗數值，就可利用這些數值劃出操作電壓與介面溫度的對應曲線；值得注意是此步驟要注意到LED晶片之溫度是否已與環境溫度一致，故必須確認已達到熱穩定狀態才能進行量測。有了此對應曲線後，再令LED光源在正常環溫下點亮，先以微小電流與脈衝方式得到一電壓，接著通以正常電流值等到熱穩定後，再藉由脈衝方式記錄LED當時的操作電壓，最後再利用外插法或內插法即可得到所對應LED之介面溫度。
為了應證此量測方式具有可信與準確度，本文利用電子熱傳分析軟體Icepak，以數值模擬的方法探討LED光源之溫度變化，並將其實驗數據與模擬值作一比較；結果可得知模擬數值顯示LED的介面溫度為97.34(℃)，而實驗樣本取其平均值為96.3(℃) ，二者之相差值只有1.04(℃)，足以證明本實驗方法具有可信度。綜合來說，本研究所發展的量測方法，可以快速、準確及有效率地得知LED之介面溫度，也不會破壞到原本LED封裝的相關物理特性，例如色溫、色座標、演色性及發光效率等，且也不會因為溫度感測器黏著位置不同，而產生極大之誤差。最後把此量測方式應用於坊間的LED照明燈具，以證明本量測方法能直接運用於LED照明燈具，量測出介面溫度與一些對應的溫度監控點，進一步確認所規劃的量測方法具有準確度與實用性

Due to its high efficacy, long life, and environment-friendly characteristics, the high-brightness LED is considered as the most promising candidate for next generation light source. However, it is actually not heat-resistant. When the junction temperature approaches its endurance limit, LED starts to dim out and finally gradually extinguish. Experiments indicate that LED life span is cut into half for a 10-degree increase on junction temperature. Hence, accurate and fast measurement of the junction temperature is an important task for the LED industry and becomes the topic of this research. Measuring the junction temperature directly via sensor is a difficult challenge because of the complicate LED package. Therefore, this study proposes a scheme to obtain the junction temperature via an indirect and quick manner, which is based on the relation between LED’s operation voltage and the junction temperature.
At first, the LED operating voltages are recorded under various environmental temperatures after LED chip reaches thermal equilibrium inside an isothermal chamber, which ensures the equivalence of junction and ambient temperatures. Then, the correlation between operating voltage and junction temperature can be identified and served as the measuring base for LED junction temperature. Note that, to prevent the temperature increase resulting from LED dissipation heat, a small current pulse, such as 10 mA, is selected while measuring the operation voltage. In order to verify the credibility and accuracy of this proposed method, this research uses CFD software Icepak to perform the numerical calculation on the same LED chip. As a result, the outcome indicates that CFD calculation (97.34℃) agrees well with the experimental data (96.3℃). In summary, this rigorous, indirect scheme for measuring LED junction temperature has been successfully established and verified via comparing those CFD and test results. Furthermore, this study also utilizes the new measurement method to a commercial LED street lamp for demonstrating its validity to the practical LED lighting devices.

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