摘要
采用0603封装的GaN基白光LED作为灯源,制作成空封结构的LED显示器。在温度为85℃和湿度为85%的环境下,对LED显示器进行了240 h的通电老化试验。试验后,测试发现LED出现了正向电压增大。在显微镜下观察到LED芯片表面P电极脱落处和P电极附近存在疑似烧伤异常。采用扫描电子显微镜(SEM)和能谱分析仪(EDS)对LED芯片进行了表面形貌表征和微区成分分析,发现LED芯片表面P电极脱落处和P电极附近有部分区域呈现粗糙状,可见颗粒状物质,在P电极脱落处生成的颗粒为Al、Cr和Au等金属颗粒,在P电极附近烧伤位置存在异常元素氯。分析认为,LED正向电压增大的主要原因是:P电极中的Al、Cr和Au等金属发生了电迁移以及电迁移至P电极附近的铝发生了电化学腐蚀,导致P电极与LED芯片的外延层之间的电流通道上的电阻增加,表现为LED的正向电压增大。最后,根据分析结果,提出了控制方案,对于提高LED显示器的质量与可靠性具有一定的指导意义。
The 0603 packaged GaN based white LED is used as the lamp source to fabricate an LED display with an air-sealed structure.In the environment with a temperature of 85℃and a humidity of 85%,the LED display is subjected to a power aging test for 240 h.After the test,it was found that the forward voltage of the LED increased.Under microscopy,suspected burn abnormalities are observed at the drop-off position of P-electrode and near P-electrode on the surface of the LED chip.Scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS)were used to characterize the surface morphology of the LED chip and to analyze the micro-area components.And it is found that the drop-off position of P-electrode and part of the area near the P-electrode on the surface of the LED chip are rough,and granular substances are visible.The particles formed at the drop-off position of P-electrode are metallic particles such as Al,Cr and Au.The abnormal element chlorine is detected at the burned position near the P-electrode.The analysis shows that the main reasons for the increase of the forward voltage of LED are:the electromigration of Al,Cr and Au in the P-electrode and the electrochemical corrosion of Al near the P-electrode,which results in the increase of the resistance in the current channel between the P-electrode and the epitaxial layer of the LED chip,and the increase of the forward voltage of the LED.Finally,based on the analysis results,a control scheme is proposed,which has certain guiding significance for improving the quality and reliability of LED display.
作者
曾友华
ZENG Youhua(Xiamen Hualian Electronics Co.,LTD.,Xiamen 361008,China)
出处
《电子产品可靠性与环境试验》
2023年第5期65-70,共6页
Electronic Product Reliability and Environmental Testing
关键词
高温
高湿
正向电压增大
白光LED
失效分析
腐蚀
high temperature
high humidity
forward voltage increase
white LED
failure analysis
corrosion
