Abstract Silicone is commonly used in light-emitting diode (LED) package as lens and/or encapsulation owing to its high light transmittance, large refractive index, and good thermal stability. However, the effect of silicone lens aging on the lumen decay and color shift of LED package is a considerable concern for package level reliability. This study empirically investigates the effects of silicone lens aging on lumen decay and color shift of LED package under three accelerated tests, namely, the constant stress-accelerated degradation test, step-up stress-accelerated degradation test, and step-down stress-accelerated degradation test (SDSADT). Results reveal that silicone lens aging substantially contributed to lumen decay and color shift of LEDs and considerably influenced the degradation kinetics of LED package. The color coordinates of LED package covered with aged silicone specimen in three testing methods exhibit a steady yellowing shift law at the same 45-degree direction. Silicone lens aging primarily reduces its transmittance to blue light as accumulated thermal oxidation and hydrolysis reaction, and its effect on the blue peak intensity of LED is independent of the stress-loaded order of step stress-accelerated degradation testing (SSADT). In addition, the effect law of silicone lens aging on LED lumen and color shift could be presented with the exponential and power function models, respectively. Lumen decay and color shift are mostly independent of the historical stress and loaded order in SSADT. The SDSADT testing manner more effectively distinguishes the color shift effect of thermal stress level compared with other accelerated tests. These findings are assumed to benefit the design and reliability assessment of LED products.

中文翻译：

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硅胶镜片老化对各种加速试验中发光二极管封装降解动力学的影响

摘要 有机硅由于具有高透光率、大折射率和良好的热稳定性，常用于发光二极管 (LED) 封装中作为透镜和/或封装。然而，硅胶透镜老化对 LED 封装的流明衰减和色偏的影响是封装级可靠性的一个相当大的问题。本研究通过三种加速试验，即恒定应力加速降解试验、升压应力加速降解试验和降压应力加速降解试验，实证研究了硅胶透镜老化对 LED 封装流明衰减和色移的影响。降解试验（SDSADT）。结果表明，硅胶透镜老化对 LED 的流明衰减和色移产生了重大影响，并显着影响了 LED 封装的降解动力学。在三种测试方法中，老化硅胶样品覆盖的 LED 封装的颜色坐标在相同的 45 度方向上表现出稳定的黄变规律。硅胶透镜老化主要是由于累积的热氧化和水解反应降低了其对蓝光的透射率，其对 LED 蓝色峰值强度的影响与步进应力加速退化测试 (SSADT) 的应力加载顺序无关。此外，硅胶透镜老化对LED流明和色偏的影响规律可以分别用指数函数模型和幂函数模型表示。流明衰减和颜色偏移大多与 SSADT 中的历史应力和加载顺序无关。SDSADT 测试方式与其他加速测试相比，更有效地区分了热应力水平的色移效应。