路燈用高功率發光二極體組件於臺灣熱環境下之壽命分佈與可靠度分析

Abstract

當今世界環保意識提升，高功率發光二極體大量被應用於照明產業，臺灣也提出並積極推動將傳統路燈汰換為高功率發光二極體的政策。就此，本研究提出一套路燈用高功率發光二極體組件於臺灣熱環境下之壽命分佈與可靠度分析評估流程，並探討組件與其封裝元件壽命與可靠度之關係。本研究首先未考慮環境因素之不確定性，以有限元素分析，獲得高功率發光二極體封裝元件在熱環境下之接面溫度，據以評估封裝元件壽命；而後，考慮特定街道路段與規範需求，估算需要之光通量，據以設計發光二極體組件之電路配置。本研究後半段考慮熱環境之不確定性，以蒙地卡羅法模擬同一樣本下之不同熱環境因素，而後依據前半段之分析模型，以及k-out-of-n redundancy之可靠度模型，分析、評估組件與封裝元件之壽命分佈與可靠度。本研究結果顯示，提高熱環境因素變異程度會使封裝元件與組件之壽命分佈變得分散，也發現組件的平均失效時間較封裝元件短，但組件壽命分佈比封裝元件壽命分佈集中。本研究結果可以提供路燈廠商做為參考以利投資決策與維護策略規劃。

With enhancing environmental awareness in recent years, high-power light emitting diodes (HPLED) have been applied extensively in lighting industry. The government of Taiwan also promotes and advocates the replacement of traditional street lights by HPLEDs. Owing to the above situations, this thesis proposes a procedure for analyzing and estimating the lifetime distribution and reliability of a typical HPLED assembly of street light under thermal environments in Taiwan. Furthermore, the relation of lifetime and reliability between the assembly and its package components is investigated. In the first part of thesis, it is done by finding the junction temperature of a single HPLED package component under a canonical thermal environment through finite element analysis without considering uncertainties of the environmental factors. The lifetime of the package component is estimated after the junction temperature is obtained. In the second part of thesis, the design of circuit configuration is addressed and discussed from the viewpoint of a assembly and its components.. The code requires luminous flux for a local street is considered as an illustrated example. To reflect real situation, the uncertainty of thermal environments is considered as well by assuming the mixed convection heat transfer coefficient a random variable. Under these assumptions, a mathematical model of k-out-of-n redundancy is established for the lifetime distribution and reliability estimation of the HPLED package components and their assembly used as a street light. Through numerical calculation, it is found that the more of the uncertainty of thermal environments does makes the lifetime distributions of the assembly and its package components more dispersed. However, the lifetime distribution of the assembly is more concentrated than that of its package components. The mean time to failure of assembly is shorter than that of its package components. It is asserted that the results of this thesis can provide information for a street-light contractor to decide its investment as well as plan an appropriate maintenance strategy in advance.