功率LED驱动电源高温通断及COB温度循环可靠性研究

发布时间：2018-04-10 21:01

本文选题：LED驱动电源 + COB　；参考：《北京工业大学》2015年硕士论文

【摘要】：LED是人类文明历程上的一个重要的发明,是追求节能减排、低碳环保的有力保障。由于寿命长、效率高、环保、可靠性高、亮度高等优点,LED照明已经广泛应用于照明显示等领域。在未来将会进一步代替传统照明方式,因此市场上升空间还很大,人们对LED照明关注的热度也不会减弱。与之而来的是不可忽视的可靠性问题。本文针对路灯照明系统对其中的LED驱动电源和COB光源进行可靠性研究。LED因不能直接使用市电所以必须有专门的驱动电源为其供电,因此LED驱动电源质量的好坏不仅直接影响整个照明系统的使用情况,还会给灯珠带来额外的应力。COB是高功率和小尺寸发展的结果,但散热问题也随之而来,如何有效地将热量及时散发出去是一个难题。本文针对电解电容在LED驱动电源失效率高和COB焊料层可靠性的问题,设计了LED驱动电源高温通断可靠性实验和COB温度循环可靠性实验。主要有以下工作:一、LED驱动电源主要包括EMC滤波、PFC转换、PWM控制和DC/DC变换模块,其中最薄弱的环节是DC/DC变换模块中的滤波电解电容。电解电容在长期的工作中电解液会损耗,进而导致电容量下降,滤波功能退化,出现失效现象。LED驱动电源一直缺乏统一的标准,这给驱动电源的考核带来了难题。本论文在实验过程中对LED驱动电源重要参数进行记录,得出变化情况,从整体上对驱动电源做出评估。实验后针对重点部位解剖驱动电源,取出电解电容,对电解电容重要参数进行考核,分析出主要退化原因,对后续的研究具有重要意义。二、对于COB封装形式的LED进行了不同温升和不同功率的退化对比研究。给实验样品施加循环温度应力来进行加速实验,用不同的电流控制温升,每组实验进行了12000次左右的循环。实验循环过程中对光通量和热阻进行了测量,发现光通量降低,热阻增加。实验后采用非破坏性的结构函数方法确定了退化的部位,实验后用X射线、超声波测量和SEM对内部结构进行验证,发现芯片外部的引线有烧毁的现象,芯片和热沉之间的焊料层出现空洞。这与结构函数方法得出的结论一致。引线的断裂是光通量急剧下降的原因,焊料层出现的空洞是热阻增加的原因。
[Abstract]:LED is an important invention in the course of human civilization.Due to long life, high efficiency, environmental protection, high reliability, high brightness and other advantages, LED lighting has been widely used in lighting display and other fields.In the future will further replace the traditional lighting, so there is still a lot of room for market growth, people's attention to LED lighting heat will not weaken.In contrast, there is a problem of reliability that cannot be ignored.In this paper, the reliability of LED driving power supply and COB light source in street lighting system is studied.Therefore, the quality of LED drive power not only directly affects the use of the whole lighting system, but also brings extra stress to the bead. It is the result of the development of high power and small size, but the problem of heat dissipation also follows.How to effectively release heat in time is a difficult problem.Aiming at the problems of high failure rate of electrolytic capacitor in LED driving power supply and reliability of COB solder layer, the high temperature on-off reliability experiment and COB temperature cycle reliability experiment of LED drive power supply are designed in this paper.The main work is as follows: 1. The main driving power supply includes EMC filter converter PWM control module and DC/DC conversion module. The weakest link is the filter electrolytic capacitance in the DC/DC conversion module.Electrolytic capacitors will lose electrolyte in a long period of work, which will lead to the decrease of capacitance, the degradation of filtering function, the failure phenomenon of LED driving power supply and the lack of uniform standard, which brings problems to the examination of driving power supply.In this paper, the important parameters of LED drive power are recorded in the experiment process, and the changes are obtained, and the overall evaluation of the driving power supply is made.After the experiment, the main parameters of the electrolytic capacitance are examined, and the main reasons of degradation are analyzed, which is of great significance to the subsequent research.Secondly, the degradation of COB LED with different temperature rise and different power is studied.The cyclic temperature stress was applied to the experimental sample to accelerate the experiment. The temperature rise was controlled by different current. About 12000 cycles were carried out in each group of experiments.The luminous flux and thermal resistance were measured during the experimental cycle. It was found that the luminous flux decreased and the thermal resistance increased.After the experiment, non-destructive structural function method was used to determine the degenerated site. After the experiment, X-ray, ultrasonic measurement and SEM were used to verify the internal structure, and it was found that the lead wire outside the chip was destroyed.Holes appear in the solder layer between the chip and the heat sink.This is consistent with the conclusion of the structural function method.The fracture of the lead is the reason of the sharp decrease of luminous flux, and the hole in the solder layer is the reason of the increase of thermal resistance.
【学位授予单位】：北京工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN312.8

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