電鍍銅基板應用於高功率LED之光電特性與熱效應之研究

Analysis of Optoelectronic properties and thermal effects on high power LEDs with copper substrate by plating

王萬煒(Wan-Wei Wang)

指導教授 ： 陳隆建

國立臺北科技大學/電資學院/光電工程系研究所/博士(2014年)

摘要

高功率氮化鎵GaN基(GaN-based LEDs) (45 mil×45 mil)發光二極體由於具有各項特點，諸如省電、最佳光學設計、使用壽命長、環保，目前廣泛被應用在室內照明、室外空間和路燈照明；但因熱逸散導致高功率GaN基發光二極體功能衰減的問題，對產業界和科學研發界而言，是一個必要解決的挑戰。
藉由研究高功率GaN基發光二極體之連接裝置的組件和特性，此研究發現熱能損失很高，這個熱能損失是由於高功率GaN基發光二極體前後端，邊緣接觸面的傳導效能差而造成熱效應升高所致；首先我們採取的方法是, 高功率GaN基發光二極體以雷射鑽孔連結前後兩端的連接裝置，用電鍍銅改善它的熱逸散問題。其二利用雷射剝離Laser Lift-Off (LLO)技術置換藍寶石基板以電鍍銅基板取代。量測兩種電鍍銅基板的光電效應及熱效應，均能有效提高熱能損失率。
為了使用銅基板電鍍技術改善GaN發光二極體在固態照明方面的應用，在製程中採用準分子雷射剝離技術，而此準分子雷射剝離技術卻需加添額外的程序，因此反而導致業者受苦於低的產能，和高的成本；為了解決這樣的負面後果，研究使用雷射鑽孔作為在GaN基LED生產製程中的取代方法，讓熱傳導經由LED裡面的雷射鑽孔，從前端、後端、到散熱板然後散逸。然而，因為邊緣接觸面的傳導效能差，前端與後端有時候連結得並不好，在電子顯微鏡下顯示了鑽孔內的連結不良現象。以濺鍍銅及電鍍銅改善此連接不良現象。
電鍍銅改善它的熱逸散問題，結果顯示，當輸入電流500 mA時，電鍍過的連接裝置光輸出功率54.36 mW 比傳統式LED的45.12 mW高出20.5%。接面溫度的量測由傳統式LED輸入電流500 mA溫升至96 oC，鑽孔電鍍後降低到54.1 oC。
因此，在這份研究報告裡，研究並檢視GaN基發光二極體連接裝置組件的光電特性及熱效應，用銅電鍍基板技術處理建立前、後端以期有更好的連結，以達成更好的熱傳導效能。

關鍵字

電鍍 ； 銅 ； 氮化鎵 ； 高功率LED ； 雷射剝離技術

並列摘要

With all the positive features such as superior power consumption, optimal optical design, operational longevity, and the fact of being eco-friendly, high-powered gallium nitride-based light-emitting diodes (GaN-based LEDs, with 45mil x 45mil of spec.) have been wildly applied to light up the space in and around the buildings and the streets. However, the performance decay caused by the heat dissipation of high-powered LEDs posts a challenge to scientists and manufacturers, an issue yet to be resolved.
Through studying the fabrication and characteristics of the copper substrate in a gallium-based light diode (GaN-based LED), we have found a high yield loss which resulted from the poor surface conductivity on the copper substrate of the both ends in the GaN-based LEDs. To improve the heat dissipation, our first step was to copper plate the substrate going through the front- and back-ends of the GaN-based LED and laser drill a hole on it. Secondly, we replaced sapphire substrate with copper-plated one, using Laser Lift-Off(LLO) Technology. The new measurement on both Optical-Electrical efficiency and thermal efficiency, taken from the copper substrate, showed a satisfactory improvement on the yield loss.
In order to use the plating technology to improve the performance of GaN-based LEDs in solid-state lighting applications , the manufacturers incorporate Laser Lift-Off (LLO) technology in the LED fabrication procedure. While the LLO technology requires an extra process in manufacturing, the LED manufacturers suffer from low yield, and high cost. To remove this unpleasant consequence, the previous studies have introduced a laser drilling methods to replace the LLO method in manufacturing GaN-based LED. Through a laser-drilled hole within the LED, the thermal conduction is directed from the front-end, the back-end, the heat sink slug, and then dissipates.
Nonetheless, the front- and the back-ends of the copper substrate are sometimes poorly connected because of the bad surface conductivity on the edges, as shown in a scanning electron microscope (SEM) image of the poor connection in the through hole. We adopted sputter coating method to copper plate the substrate and established a better surface conductivity. The copper substrate improved the heat dissipation. When in-flow current was at 500 mA, the output power measured from GaN-based LED with the copper substrate read 54.36 mW, 20.5% increase from 45.12 mW from the traditional LED. The junction temperature went down from 96 oC to 54.1 oC.
Therefore, in this study and analysis, we examined the fabrication and the characteristics of the GaN-based LED. We use Sputter Coating Technology to copper plate the substrate to establish a better surface conductivity on the edges of the front- and the back-ends for a better thermal effect through a laser-drilled hole.

並列關鍵字

GaN-based LEDs ； Electroplating ； Connecting plug ； laser lift off

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