GaN基白光LED可靠性研究与失效分析

针对LED样品检测中的样品短路失效、LED光源黑化、光通量下降和芯片表面通孔异常现象，采用金相切片、机械微操、静电测试等方式结合扫描电镜和能谱仪（EDS）等表征手段对失效机制进行了分析，揭示了LED失效原因。包括镀层银离子与杂质硫离子导致光源黑化；芯片抗静电电压低，部分样品发生静电击穿；失效芯片通孔下面的Ni-Sn共晶层存在大量空洞，使得复杂结构的芯片通孔应力不均，样品工作时芯片表面开裂破碎，从而导致PN结短路失效；封装胶中残存的杂质离子腐蚀芯片负电极导致电极脱落而出现漏电、光衰和死灯等现象。

Invalid Analysis and Dependability Research of GaN-based White LED

The phenomenon of LED sample detection and its failure mechanism were reported. This phenomenon included the short-circuit failure, LED light source, the flux decreased and blackening the surface of the chip hole anomaly. We used many methods, including metallographic, mechanical micro and static test, combining with many instruments, including optical microscope, scanning electron microscope and X-ray analysis characterization. The analysis reveals that LED abnormalities and failures are caused by the following reasons. First, the coating of silver ion and impurity sulfur ions lead to blackening of the light source. Second, the antistatic voltage of the chip is low. Some samples were subjected to electrostatic breakdown. And in addition, a large number of voids exist in the Ni-Sn eutectic layer beneath the view of the chip. It causes the uneven stress of the chip through the complex structure, the thermal conductivity decreases, and the chip surface cracks and breaks while the sample is working. This results in short-circuit fault of PN junction. Third, residual impurity ions in the encapsulation adhesive corrode the negative electrode of the chip. It causes the electrode to fall off. It leads to leakage, light weak and dead lights.