高功率發光二極體之溫度與電流加速老化效應分析

Study on Temperature and Current Stress Aging Effect for High Power Light Emitting Diodes

徐逢懋(Hsu, Feng Mao)

指導教授 ： 江國寧

國立清華大學/工學院/動力機械工程學系/碩士(2015年)

摘要

隨著科技的快速發展，環保意識逐漸抬頭，全球面臨暖化的問題。在日常生活照明中，發光二極體具有低汙染、低耗能與壽命長等特性，日漸普及於生活周遭。目前在發光二極體製造商普遍採用的測試規範為IES(Illuminating Engineering Society) LM80-08，此法規為人詬病的是測試時間冗長，影響產品的上市時程，嚴重阻礙發光二極體的發展。
本研究之目的在觀察溫度電流加速老化因子影響，研究旨在(一)預估光衰模型，提供準確的壽命預估，(二)找出溫度應力與電流應力在光衰老化試驗中的加速因子，(三)提出可用方法有效縮短長時間的測試規範，協助發光二極體展業發展。
本研究初步在常溫下進行晶片接面溫度的量測，藉由分析實驗樣本之封裝結構，建立有限單元熱分析模型，了解發光二極體內熱傳行為，輔助溫度電流加速老化試驗設計，將量測之實驗結果與有限單元模擬結果進行比較，驗證有限單元熱分析模型的正確性。溫度電流加速老化試驗實驗樣本為高功率白光及藍光發光二極體，目的為探討螢光粉光衰機制。利用有限單元熱分析模型預估加速老化實驗條件，預估環境溫度負載並通入工作電流達到目標溫度。根據LM-80-08規範進行試驗，使用TM-21-11預估光衰至70%之壽命值，分別針對藍光和白光樣本之試驗結果進行探討，提出電流效應對高功率發光二極體之影響。最後，與過去已提出之壽命預估模型比較分析，建議在壽命預估模型中需增加電流應力因子，達到更準確之壽命預估。

關鍵字

高功率發光二極體 ； 有限單元熱分析 ； 加速老化壽命試驗 ； 阿瑞尼士壽命預估模型

並列摘要

Through the technology developing rapidly, the concept of environmental friendly would be in our mind. The world faced the problem of globe warming. In daily life, light-emitting diode(LED) had characteristics of low pollution, low power consumption, and long lifetime. The reliability test of IES LM80-08 was in common use to the manufacturers of LED. It would cost too much time and prolonged the time-to-market. This situation can be regarded as an obstacle to the LED research and development.
The purpose of this research would observe the factor of current stress and temperature stress in accelerated aging test, and aimed at (i) fitting the appropriate life prediction model, propose the accurate lifetime, (ii) investigating the accelerated factor in the test with current stress and temperature stress. (iii) proposing an available method to shorten the reliability test standards, promoted the light-emitting diode industry.
The research would measure the junction temperature of LED at ambient temperature. Building the finite element model by the sample to understand the transportation of the heat in the packaging. The simulation model would assist the accelerated aging test design. The result of the simulation would compare with experimental junction temperature measurement to validate the model. The sample consist of white LEDs, and blue LEDs in order to separate the influence of phosphor. The test would use the finite element model to predict the target junction temperature which is consider both of temperature and current joule heating. The test would carry out based on the standard IES LM-80-08 and predict the lifetime by TM-21-11. The degradation of light output was detected during aging. The research analysis the experiment result in blue LEDs and white LEDs, respectively. It could propose the influence of current effect in HP-LEDs. Finally, the result would compare with the previous research which is only consider the temperature stress. The result reveal the current stress is an essential factor in life prediction model.

並列關鍵字

HP-LED ； Finite Element thermal analysis ； Accelerated aging test ； Arrhenius’s equation

參考文獻

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