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|其他題名: ||Optical and Thermal Performance Enhancement of InGaN Blue High-Power LED via Graphene Doped Silicone Encapsulant and Silver Paste|
Graphene;Alignment;Silicone Encapsulate;Silver Paste;Blue High Power LEDs;Optical Properties;Thermal Properties
|Issue Date: ||2018-11-13 10:56:15 (UTC+8)|
|Abstract: ||本論文討論將石墨烯(Graphene)分別摻雜在封裝矽膠與固晶銀膠中，應用於氮化銦鎵藍光高功率發光二極體(LED)封裝，對LED光熱特性的影響。研究分為兩個實驗進行：實驗一：探討封裝矽膠中摻雜不同濃度Graphene，其排列對LED光取出與熱特性的影響。實驗二：於固晶銀膠中摻雜不同濃度的Graphene，並探討對LED光取出與熱特性的影響。實驗一是透過外加電場改變封裝矽膠中不同摻雜濃度Graphene的排列，以提升LED的光輸出通量(Light Output Power, LOP)，外加電場強度為37 V/mm。以超音波震盪分散封裝矽膠中的Graphene，增加震盪時間可以提升Graphene分散效果，震盪超過50分鐘之後分散效果達到飽和。比較有/無施加電場改變Graphene的排列，發現除了摻雜濃度0.10 wt%外，其它摻雜濃度0.01 wt%、0.05 wt%均能提升LED LOP。當摻雜濃度為0.01 wt%時，經電場排列Graphene的LED LOP平均值為289.2 mW (@ 0.35 A)，相較沒加電場排列Graphene的LED，平均LOP提升4.97%；而且根據變電流對應LED LOP結果，具有較高的飽和電流值3.0 A，對應LOP為1,151 mW，而沒加電場排列Graphene的LED飽和電流僅為2.7 A。透過均勻外加電場排列Graphene，可以有效提升LED的LOP與散熱特性。實驗二是透過加入不同濃度的Graphene於固晶銀膠中，探討對LED光取出與熱特性的影響。比較摻雜濃度0 wt%、0.01 wt%、0.10 wt% Graphene的銀膠，發現0 wt%的LED，具有最高的LOP平均值530 mW( @ 0.35 A)，而0.01 wt%相比0 wt%的LED LOP下降約1%。根據變電流對應LED LOP結果，0.01 wt%相較於0 wt%的LED，有較高的飽和電流(增加0.10 A)，因此具有較佳的散熱特性。藍光晶片透過背鍍金屬，晶片正面反射率應可達99%以上。Graphene摻雜銀膠的濃度0 wt%、0.01 wt%、0.10 wt%，量測其光吸收率分別為4.21%、4.24%、4.22%且差異不大，量測其光反射率分別為0.75%、0.68%、0.50%，推論Graphene摻雜銀膠導致光輸出通量減少，可能主要來自光反射率差異的影響。比較不同摻雜濃度銀膠的LED熱特性，以摻雜濃度0.01 wt%最佳，接面溫度76.7℃，熱阻為9.9℃/W。在室溫下，相較於濃度0 wt%的LED，摻雜濃度0.01 wt%、0.10 wt% Graphene的平均熱/冷比可提升至0.96。且Graphene摻雜濃度0.01 wt%具有最佳平均推力值1.07 kgf，但晶片結構無法承受推力已先損毀，故Graphene摻雜銀膠後銀膠仍具有足夠的固晶性能。以超音波震盪分散封裝矽膠中的Graphene，取得最佳的處理時間(50 分鐘)，可以提供後續研究參考。即使透過排列Graphene可改善LED的出光量，因為Graphene會吸光，因此不適合安排在光路徑中，但可應用在導熱路徑。因為銀膠中的銀可以提供光反射，所以Graphene的吸光效應較不明顯，有機會把Graphene與銀膠混合搭配，應用在各式光電元件的固晶。|
This paper has demonstrated the effects of graphene doped in silicone encapsulate and silver paste respectively for InGaN blue high-power light-emitting diode (LED) package on the optical and thermal properties of the LEDs.The research is divided into two experiments. In Experiment 1, the alignment effects of graphene with different concentrations in silicone encapsulate on the optical and thermal properties of the LEDs were investigated. In Experiment 2, the effects of graphene with different concentrations in silver paste on the optical and thermal properties of the LEDs were investigated.In Experiment 1, the alignment of graphene with different doped concentrations in silicone encapsulate was changed by applied an electric field (37 V/mm) for increasing the light output power (LOP) of LEDs. The dispersion of graphene in silicone encapsulate increases with the increasing duration of ultrasonic vibrations and reaches saturation after the duration exceeds 50 minutes. The LOP of LEDs with graphene doped silicone treated by electric field is larger than that without electric field treatment, except that the graphene doping concentration of 0.10 wt%. The average LOP of LEDs with the doping concentration of aligned graphene 0.01 wt% in the silicone encapsulate is 289.2 mW with the injection current at 0.35 A and it has increased by 4.97% compared with that of unaligned graphene under the same doping concentration. The LOP of LEDs for different variable currents is measured. The doping concentration of aligned graphene 0.01 wt% was aligned or not aligned in the silicone encapsulate of the LED, and the saturation currents of the LED are 3.0 A and 2.7 A, respectively. The graphene in the silicone encapsulate was aligned by applying a uniform electric field then the LOP and heat dissipation properties of the LEDs were efficiently improved.In Experiment 2, the effect of graphene with different concentrations in the silver paste on the optical and thermal properties of LEDs was demonstrated.The doping concentration of the graphene was 0 wt% in the silver paste of the LED. The operating current of the LED was 0.35 A and the corresponding average LOP was 530 mW. The doping concentration of the graphene was 0.01 wt% in the silver paste of the LED, the LOP of the LED decreased by about 1% compared to the doping concentration of 0 wt%. The LOP of LEDs for different variable currents was measured. The doping concentration of the graphene was 0.01 wt% in the silver paste of the LED. The saturation current of the LED was 0.9 A. The doping concentration of the graphene was 0 wt% in the silver paste of the LED. The saturation current of the LED was only 0.8 A. Blue LEDs with metal mirror on the back of the chip, its frontal optical reflectance can theoretically reach over 99%. The doping of the graphene in the silver paste coated to glass and measures its optical absorption rates and optical reflectance. As the doping of the graphene was 0 wt%, 0.01wt%, and 0.10 wt% in silver paste, the difference of silver paste is not significant and it is respectively 4.21%, 4.24%, and 4.22% on optical absorption rates. As the doping of the graphene was 0 wt%, 0.01wt%, and 0.10 wt% in silver paste, and it is respectively 0.75%, 0.68%, and 0.50% on optical reflectance. The effect of graphene with different concentrations in the silver paste on thermal properties of LEDs was compared. Excellent heat dissipation properties when graphene doping concentration is 0.01 wt%. The junction temperature of the LED was 76.7°C and the thermal resistance was 9.9°C/W. The hot/cold ratio of LOP is increased 0.96 for LEDs with the graphene doping concentrations of 0.01 wt% and 0.10 wt% in the silver paste compared to that of LED without the graphene doping in the silver paste at room temperature. The silver paste with the graphene doping concentrations of 0.01 wt% can afford a maximum shear force of 1.07 kgf. Therefore, after doping of graphene, the silver paste still has sufficient bonding strength. However, the chip structure has been damaged under the shear force. Therefore, the adhesive strength of silver paste will be greater. After ultrasonic vibration, the graphene is well dispersed in silicone encapsulate. As the dispersion time is 50 min, the dispersion effect is the best. Graphene absorbs light, although the LOP of LED with graphene doped silicone encapsulate can be improved by aligning graphene, but graphene is still not suitable appearance in the light path. However, graphene doped silicone is suitable to be placed on the heat conduction path and play the role of heat dissipation / thermal conductive adhesive. The high reflectance of the silver in the silver paste, the effect of optical absorption by graphene is not obvious. Mixing graphene into silver paste is a suitable grain adhesive for using in a variety of optoelectronic device die-bonding processes.
|Appears in Collections:||[光電工程系所] 博碩士論文|
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