提升高功率白光發光二極體光取出效率封裝技術之研究

Abstract

本論文的主旨在於探討如何藉由改善LED模組外在封裝的方式，加以增進整體 LED模組之光取出效率(extraction efficiency)及增進白光LED的光學特性：包括光均勻性或增進單位立體角光強度。主要利用TracePro光學軟體進行整體LED模組的設計與模擬，並輔以部份實際實驗量測結果來確認模擬結果的正確性與可靠性。 研究中首先成功的於TracePro軟體中建立了YAG:Ce螢光粉的散射模型與光波長轉換機制模型。之後我們藉由設計不同的凹杯以及取光鏡的形狀，搭配不同形式螢光粉的塗佈方式來嘗試提升LED模組的總光通量；另外藉由設計不同形式的反射杯及聚光透鏡來使LED達成高單位立體角光強度的目的。 在增進整體LED模組光取出效率方面，根據模擬結果，擁有最高光通量強度的組合為利用上直徑4.2 mm、下直徑3.2 mm、深度1 mm形式的凹杯，搭配上螢光粉遠離塗佈的技術，再加上型狀為半圓取光鏡的LED模組。預計可讓裸片發光強度為170 mW的藍光晶片經由封裝過後發出173.27 mW、相對色溫為6500K的白光，換算出的流明值則約為54流明。此光通量值為應用相同凹杯配合上傳統封裝形式(螢光粉均勻塗佈以及未加上取光鏡)時所能獲得的1.38倍。 在增進LED模組單位立體角光強度方面，比較利用反射杯及聚光透鏡兩種聚光方式：利用反射杯形式可獲得更高的單位立體角光強度值，其中心單位立體角光強度為未加反射杯LED模組的6.36倍，但卻伴隨較高的光損耗(6.33%)而造成較低的總光通量;而利用聚光透鏡可在光損耗較小(小於2%)的情況下達成聚光的目的，但能達成的單位立體角光強度值為未加聚光透鏡LED模組的5.27倍，小於利用反射杯形式聚光所能達成的值。

In this thesis, we changed the LED packaging to improve the light extraction efficiency and light characteristic of a white light LED module. The optical software TracePro was used to design the LED module. The radiant flux was optimized by designed different cups, phosphor applying methods, and lens shapes of LED modules. Higher radiant intensity was obtained by designing the reflector or the condensing lens of a LED module. At first we successfully established the simulation model by TracePro software for the white light LED using a blue LED chip with Ce:YAG phosphor. In the study of high extraction efficiency of a LED module, the highest radiant flux was obtained by using remote phosphor on type B cup (top diameter 4.2 mm, bottom diameter 3.2 mm, depth 1 mm) with a semi-sphere shape lens. The efficiency enhancement was 38% compared with the conventional LED structure. In the study of high radiant intensity of LED module, higher radiant intensity was obtained by using the LED module with a designed reflector. The radiant intensity of the LED module with a designed condensing lens was enhanced by a factor of 6.36 compared with the radiant intensity of a LED module without a reflector, but high light radiant flux loss was caused (6.33%) at the same time. Another method to get higher radiant intensity was using the condensing lens. The radiant intensity of the LED module with a designed condensing lens was enhanced by a factor of 5.27 compared with the radiant intensity of a LED module without a condensing lens. However, lower light radiant flux loss caused by the LED module with a condensing lens was lower than the value got from the LED module with a reflector.