單晶片與複合微晶片發光二極體之熱電耦合模擬研究;The research on single chip LED and multiple microchips LED by the thermal-electrical coupling method

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Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/53822

Title:	單晶片與複合微晶片發光二極體之熱電耦合模擬研究;The research on single chip LED and multiple microchips LED by the thermal-electrical coupling method
Authors:	宋狄祥;Sung2,Ti-Hsiang
Contributors:	機械工程研究所
Keywords:	單晶片;複合微晶片;發光二極體;數值模擬;single chip;multiple microchips;numerical simulation;LED
Date:	2012-07-17
Issue Date:	2012-09-11 18:17:03 (UTC+8)
Publisher:	國立中央大學
Abstract:	近年來，發光二極體(LED)在固態照明中扮演著重要的地位，其中微製程技術的成熟，讓複合微晶片(Multiple Microchips)LED在近年來備受重視，複合微晶片是一種以陣列方式將多顆微晶粒連結而成的新式LED，如果將微晶粒以串聯陣列的方式做設計的話，除了可以提高在傳統單晶片LED中輸入電壓的限制以外，還可以配合在市面的交流電壓、透過全波整流器將交流電壓轉換成的全波電壓和直接使用直流電的三種方式來驅動點亮，但因為單晶片只能以直流的方式驅動，所以本研究將單晶片與複合微晶兩者在同樣尺寸和同樣磊晶的條件下，以直流式電流來驅動，並且針對不同瓦數時，複合微晶片的高電壓低電流特性在電性和溫度以及光三者的關係來和傳統低電流的單晶片做比較。另外本研究針對於LED發光層的物理機制中，利用光輸出功率量測的實驗結果來修正數值方法中的熱電耦合統御方程式。研究中先透過接面溫度及光學特性的量測實驗與數值模擬來相互驗證之後，再利用模擬結果來分析複合微晶片和單晶片的電流密度與溫度分布形態上的差異。由結果可以發現複合微晶片的電流分布是局部雍塞的形式分布在整塊晶片中和單晶片中的整體壅塞完全不同，這樣的差異,使複合微晶片在溫度能平均分布於晶片中，且還有降低接面溫度的效果。複合微晶片的設計除了在電流密度和溫度分布造成的影響以外，還有複合微晶片的串聯設計下所造成高電壓低電流的特性，會讓非活化層所製造的焦耳較低，尤其在越高瓦數下，傳統的單晶片與複合微晶片在焦耳熱的差異更加明顯，這也是複合單晶片在高瓦數下能讓溫度較低使光輸出功率較好的主要原因之一。最後本研究利用數值的方法，來模擬在實驗中可能會造成LED燒毀的高瓦數電功率。從模擬結果得到在高瓦數的8W下單晶片已達光飽和而複合微晶片的光輸出功率則因為溫度較低的影響所以並未出現光飽和的現象，此外還可以利用高瓦數的模擬結果來估計兩種LED在此封裝體下，大約可以承受電功率在5W左右所產生的溫度，如果繼續增加電功率可能會因溫度過高開始有封裝上的損壞產生，並大約在電功率到達8W時，兩種LED的接面溫度都會超出晶片所能承受的溫度極限。Recently, light-emitting diode (LED) has been playing an important role in solid-state lighting, especially the maturity of the micro process technology made the multiple microchips LED receive recognition in the market. The multiple microchips LED is a kind of new type LED which is connected by many multi-microchips in array way, if we design the multi-microchips in serial array, that we can not only raise the input voltage levels in the traditional single chip LED, but use the alternating current (AC), full-wave current and direct current (DC) these three ways to light up. However, the single chip only can drive in DC way. In my research, we put single chip and multiple microchips under the condition of same size and same epitaxy, driving with the DC. For different wattage, we can compare the difference of single chip and multiple microchips in the relation of electricity, temperature and light. Also, we use the result of light output power measurement to revise the governing equation of coupling of the thermal and electrical characteristics in the numerical methods. First, we use the measurement of junction temperature and optical characteristics to test and verify with the numerical analysis, then using the simulation result to analyze the different current density and temperature distribution between the single chip and the multiple microchips. According to the research, we found the electric distribution of the multiple microchips is partial-crowding, not alike the single chip is whole-crowding. This difference makes the multiple microchips is equally distributed and lower the junction temperature. Bacause of its series connection design, the multiple microchips turn into high voltage -low current and cause chip produce lower joule heat. Higher watts we use, the more different between the tradition single chip and multiple microchips. This is the reason why the multiple microchips can make lower temperature and better light output power. And last, we try to use numerical methods to simulate how high watts would caused LED destroy. From the result, we found the single chip under 8 watts has already reached Light saturation but the multiple microchips hasn’t because of its lower temperature. In addition, we can also calculate theses two LED can bear the temperature in about 5 watts . If we keep enhance the electric power may cause the package damaged and when the power reach about 8 watts, the junction temperature of these two chips would be unbearable.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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