The Light Emitting Diode (LED) has many advantages compared to traditional lamps, such as a long lifetime, color rendering and energy saving. It requires good thermal management, since as the temperature increases, the lifetime decreases. Furthermore, the presence of cracks in the Solder Joint of an LED (SJL) compromises the correct dispersion of heat and causes the joint fatigue. This can lead to a decrease in the lifetime of the assembled LED. In this study, we validated that an SJL can be considered faulty if the Forward Voltage (Vf) acquired before and after thermal cycles increases by more than 2%. The voltage measurement method was validated by comparing the results with the techniques commonly used to evaluate the defects of a solder joint as the X-ray analysis and the metallographic section. The failure analysis results present the probability of failure and the lifetime of the SJL achieved by analyzing the data using the Norris–Landberg Model. The lifetime calculated over 1800 SJLs considered in the validation process is greater than 20 years for 95.9% of the tested LEDs.

中文翻译：

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估计大功率LED焊点裂纹的正向电压方法的验证

与传统灯相比，发光二极管（LED）具有许多优势，例如使用寿命长，显色性强和节能。它需要良好的热管理，因为随着温度的升高，寿命会缩短。此外，LED（SJL）的焊点中存在裂纹会损害热量的正确散布并导致焊点疲劳。这可能导致组装的LED寿命缩短。在这项研究中，我们验证了如果热循环前后获得的正向电压（Vf）增加2％以上，则可以将SJL视为故障。通过将结果与通常用于评估焊点缺陷（如X射线分析和金相截面）的技术进行比较，验证了电压测量方法的有效性。失效分析结果显示了通过使用Norris-Landberg模型分析数据而获得的SJL失效概率和寿命。对于95.9％的被测试LED，在验证过程中计算出的1800 SJL以上的寿命超过20年。