电视背光LED灯失效机理和分析方法

基于直下式LED发光电视,从封装失效、芯片失效、热应力失效、电应力失效等方面分析了电视背光系统中发光二极管(LED)器件的失效机理和改进措施,同步提出安全性失效和可靠性失效的理论概念,并对电视整机系统的LED温升控制和LED驱动电流控制方面进行了分析,提出了实用的LED失效分析流程.     

光电耦合器封装及相关失效机理

与一般的半导体器件相比,光电耦合器的工作原理、结构和封装设计独具特色。光耦的失效机理除与单独的LED、三极管相同外,还有它独有的失效机理。在简单介绍光耦的工作原理与封装结构的基础上,重点分析了几种与光耦封装有关的失效机理:导光胶或反射胶工艺控制不佳导致胶开裂、起皮;光耦内部材料间热膨胀系数不匹配,内部电连接开路;内部沾污产生腐蚀;塑料和内部有机胶吸潮发生"爆米花效应";外部电路异常导致光耦失效。并针对各种失效机理提出了改进措施。     

50例微波器件失效分析结果汇总与分析

对约50例微波器件失效分析结果进行了汇总和分析,阐述了微波器件在使用中失效的主要原因、分类及其分布。汇总情况表明,由于器件本身质量和可靠性导致的失效约占80%,其余20%是使用不当造成的。在器件本身的质量和可靠性问题方面,具体失效机理有引线键合不良、芯片缺陷(包括沾污、裂片、工艺结构缺陷等)、芯片粘结、管壳缺陷、胶使用不当等;在使用不当方面,主要是静电放电(ESD)损伤和过电损伤(EOS),EOS损伤中包括输出端失配、加电顺序等操作不当引入的过电应力等。     

电池保护电路中MOSFET器件常见失效机理研究

受限于电子设备的内部空间,电池保护电路中MOSFET器件通常采用晶圆级芯片规模封装（WLCSP）。由于WLCSP的特点,电池保护电路中的MOSFET器件在生产、使用中会出现各种类型的失效模式和失效机理。介绍了采用WLCSP技术封装的MOSFET器件常用的分析方法与设备,结合相关的失效案例,论述了芯片开裂、芯片工艺缺陷、芯片腐蚀和过电应力这4种常见的失效机理,为MOSFET器件及其他电子元器件的失效分析和问题解决提供一定的参考。     

金属陶瓷封装器件安装中典型失效及注意事项

文章对金属陶瓷封装器件安装使用中与封装有关的三种典型失效模式进行了分析。安装使用中过多的热积累导致壳体引脚脱落;安装区域线胀系数差异过大造成的额外应力,导致壳体引脚拉断;安装位置不平整或受挤压,致使壳体内部芯片、陶瓷电路片开裂。并且根据这三种失效机理提出了金属陶瓷封装器件安装使用中的相关注意事项,对提高金属陶瓷封装器件的使用可靠性具有一定的参考价值。     

铜丝键合在实际应用中的失效分析

研究并总结了铜丝键合塑封器件在实际应用环境中工作时发生的几种不同失效模式和失效机理,包括常见封装类型电路的失效,这些封装类型占据绝大部分铜丝键合的市场比例。和传统的实验室可靠性测试相比,实际应用中的铜丝失效能够全面暴露潜在可靠性问题和薄弱点,因为实际应用环境存在更多不可控因素。实际应用时的失效或退化机理主要包括:外键合点氯腐蚀、金属间化合物氯腐蚀、电偶腐蚀、键合弹坑、封装缺陷五种类型。对实际应用中的数据和分析为进一步改善铜丝键合可靠性、提高器件稳定性提供了依据。     

SiP组件中芯片失效机理与失效分析

由于分析手段与分析设备的限制,系统级封装（SiP）组件的芯片在失效分析的过程中带有一定的盲目性。结合故障树分析方法,以PM O S芯片失效为例,讨论了SiP组件常见的管芯失效机理：电应力失效、热应力失效、机械损伤和环境应力失效以及相应的失效现象;最后从设计和工艺角度提出了降低各种失效机理发生的改进措施。     

密封封装内部水汽含量判据研究

密封封装内部的水汽对于半导体器件的可靠性是一种威胁,由此导致的硅表面铝金属线的腐蚀是一种主要的失效机理。为了防止密封封装内部发生腐蚀失效,从而提高器件的可靠性,美军标和我国国军标均给出了内部水汽含量的试验流程和判据。然而另一些研究表明,水汽的单独存在并不会导致铝线腐蚀失效。研究了水汽在密封器件的腐蚀失效机理中的作用,对硅表面铝线的腐蚀过程进行了数学描述,分析了目前标准中内部水汽含量判据,并给出了防止密封器件腐蚀失效的建议。     

二极管器件漏电失效分析及改进措施

通过外观检查、开盖检查、 I/V曲线测试、微光显微镜观测和扫描电子显微镜检查等分析手段,结合芯片结构,对漏电失效的二极管器件进行分析,定位器件的失效位置,确定器件漏电失效的机理。形成一套针对半导体分立器件的失效分析流程,并对漏电失效模式提出了相应的优化改进措施。     

塑封双极型功率晶体管的失效与案例分析

由于其自身的结构与封装形式,塑封双极型功率管存在很多可靠性问题.介绍了塑封双极型功率晶体管可靠性问题及失效机理,包括封装缺陷、粘结失效以及由于温度变化而引起的热应力失效和由于吸入潮气而导致的腐蚀失效.通过剖析一晶体管的失效机理,给出了对此类晶体管失效分析的方法和思路.讨论了晶体管存在异物、芯片粘结失效和热应力失效等失效模式.     

LED夜景照明工程的质量检测与评价

LED光源的独特优势使其在城市夜景照明工程中得到越来越广泛的应用。本文通过厦门市LED夜景工程的建设实例，介绍了应用于夜景照明的LED器件部件的质量检测标准和夜景工程的施工验收规范，指出了现行的夜景工程质量测评方法存在的问题和今后的改进方向。     

视觉检测系统LED光源照度优化方法

针对当前视觉检测系统LED光源照度优化研究中存在的照度效果评价因素单一、照度优化方法通用性不足等问题,以芯片封装质量视觉检测为例,提出一种基于改进樽海鞘算法的LED光源照度优化方法。该方法在单个LED光源照度数学模型基础上,建立标准条形LED阵列光源照度数学模型,获取条形LED阵列在任意空间位姿与被测面的照度值;基于照度均匀度、照度梯度变化与对中度、平均照度、目标与背景区分度等因素建立平面照度效果评价函数;提出改进樽海鞘算法,通过改进算法收敛系数、速度、领导者与追随者位置等更新策略,增强区域搜索的多样性;应用改进樽海鞘算法对平面照度效果评价函数进行优化求解,获取具有最优照度效果的空间位姿参数。实验结果表明:考察优化区域的相对照度分布,文中提出的LED光源照度优化方法所得照度分布与实际测量所得照度分布结果基本一致,目标区域理论照度均匀度在98.78%以上,误差在5.57%以内。因此文中提出方法优化目标合理,可用于视觉检测系统具有最优照度效果时光源位姿信息参数的获取。     

Failure modes and effects analysis for high-power GaN-based light-emitting diodes package technology

In this study, nondestructive test is developed to analyze the structure failure of LED package. The relationship between thermal resistance analysis and LED package failure structure is build with T3Ster thermal transient tester and scanning electron microscope (SEM). The failure LED device with defect in the attaching layer and gap between LED chip and copper are designed advisedly. The failure factors of LED package have been measured with thermal resistance analysis and SEM cross-section images. The thermal dissipation performance of LED with defect in the attaching layer is indicated by thermal resistance analysis combined with SEM cross-section images. The blister in attaching layer results in 4.4 K/W additional thermal resistance. The gap between LED chip and copper also makes high additional thermal resistance with 8.6 K/W. Different failures of LED packages are indicated obviously using thermal transfer analysis. The LED package failure structure such as interface defect between solder and cup-shaped copper is able to forecast without destructive measurement.     

Reliability test and failure analysis of high power LED packages

A new type application specific light emitting diode(LED) package(ASLP) with freeform polycarbonate lens for street lighting is developed,whose manufacturing processes are compatible with a typical LED packaging process.The reliability test methods and failure criterions from different vendors are reviewed and compared.It is found that test methods and failure criterions are quite different.The rapid reliability assessment standards are urgently needed for the LED industry.85℃/85 RH with 700 mA is used to test our LED modules with three other vendors for 1000 h,showing no visible degradation in optical performance for our modules,with two other vendors showing significant degradation.Some failure analysis methods such as C-SAM,Nano X-ray CT and optical microscope are used for LED packages.Some failure mechanisms such as delaminations and cracks are detected in the LED packages after the accelerated reliability testing.The finite element simulation method is helpful for the failure analysis and design of the reliability of the LED packaging.One example is used to show one currently used module in industry is vulnerable and may not easily pass the harsh thermal cycle testing.     

Analysis of electrical parameters of InGaN-based LED packages with aging

As the light-emitting diode (LED) becomes a mature technology in the general illumination space, there is a tendency to operate LEDs at high current densities and temperatures in order to gain higher light output at lower cost. Further, there is interest among intelligent-lighting platform developers to offer predictive maintenance capabilities to users. The existing useful life prediction model defines LED lifetime based on parametric failure; however, there is a need for a useful life prediction model based on catastrophic failure, which can occur with the degradation of components in an LED package. Electrical parameters, especially package series resistance, are good indicators of LED package health (i.e., remaining useful life) and could potentially be sensed real-time in an application. In this study, the series resistance variation pattern until catastrophic failure was measured at different current and temperature stress conditions. The degradation mechanisms at each phase of variation were explained and, using available models, activation energies and exponents were extracted. The experimental data suggest electromigration-induced metal migration from the contact metallization layer to the semiconductor is the cause of short circuit catastrophic failure of LED packages. The variation patterns of ideality factor and reverse leakage current support this hypothesis. The information presented can be used to develop a catastrophic life estimation model for LED packages under current and temperature stress.     

功率型白光LED可靠性的实验及仿真建模研究

快速推广LED产品到照明市场最主要的障碍在于长期的可靠性测试问题。由于长期的LED可靠性测试不符合快速且低成本的要求,因此本实验对白光LED进行步进式加速寿命老化测试,步进式环境温度从55oC到145oC变化。同时,对LED进行结温测试,并使用COMSOL仿真软件进行温度场分布仿真来模拟器件的发热情况,结果表明荧光胶处的温度高于LED芯片温度。在长期老化之后,对LED的光度进行测量,可以对LED的失效机理进行分析。通过研究温度对LED的光谱功率分布衰减的影响及光通量衰减的影响,发现在经过近3500 h的老化之后,LED的光衰很严重,表明电流及高温对LED的影响是极大的。     

LED道路照明装置在低温运行环境下的特殊技术要求

LED路灯作为道路照明的发展趋势已经得到普遍认同,但产品研发过程中却忽略了在寒地应用环境下的特殊技术要求。文章讨论了冷热冲击的温度变化可能引起LED器件的失效问题和LED驱动装置低温运行的可靠性保障,并依据大量实验和应用数据,总结了LED道路照明装置在低温运行环境推广应用的特殊技术要求和设计指导意见,并提供了详细的指导性规范准则。     

Light emitting diodes reliability review

The increasing demand for light emitting diodes (LEDs) has been driven by a number of application categories, including display backlighting, communications, medical services, signage, and general illumination. The construction of LEDs is somewhat similar to microelectronics, but there are functional requirements, materials, and interfaces in LEDs that make their failure modes and mechanisms unique. This paper presents a comprehensive review for industry and academic research on LED failure mechanisms and reliability to help LED developers and end-product manufacturers focus resources in an effective manner. The focus is on the reliability of LEDs at the die and package levels. The reliability information provided by the LED manufacturers is not at a mature enough stage to be useful to most consumers and end-product manufacturers. This paper provides the groundwork for an understanding of the reliability issues of LEDs across the supply chain. We provide an introduction to LEDs and present the key industries that use LEDs and LED applications. The construction details and fabrication steps of LEDs as they relate to failure mechanisms and reliability are discussed next. We then categorize LED failures into thirteen different groups related to semiconductor, interconnect, and package reliability issues. We then identify the relationships between failure causes and their associated mechanisms, issues in thermal standardization, and critical areas of investigation and development in LED technology and reliability.     

LED组件寿命评估方法的研究

由于LED技术的飞速发展,其应用产品不断扩大到人们生活的各个方面,因此LED产品的可靠性问题也日益受到人们的关注。在可靠性工程常用的寿命分布中,指数分布是应用广泛的一种分布,进入偶然失效期以后都可以认为产品失效分布是指数分布。LED产品的寿命试验有定时截尾和定数截尾2种方式,由于定数结尾需要较长的试验时间,因此采用定时截尾的试验方法来获取试验数据。给出了LED组件的寿命评估方法,该方法对LED模块和应用产品同样适用。