We investigated the effect of selective coating of white silicone on the output and thermal performance of white LED packages for middle power lighting application. The LED package, where a Zener diode part was coated by TiO2 particles-mixed white silicone, exhibited lower surface temperature and heat flux than those with the uncoated Zener diode. The white silicone-coated packages resulted in lower thermal resistance (Rth) than the uncoated ones. For example, the Rth at 85 °C of the uncoated and coated white LED packages in the junction-PCB was 26.30 K W−1 and 21.98 K W−1, respectively. The coated blue and white LED packages yielded 6.5% and 4.5% higher luminous fluxes than the uncoated packages, respectively. Far-field emission patterns showed that the coated white LED packages had view angle of 118.06° and 118.10° along the two orthogonal directions, respectively, whilst the uncoated package gave 117.37° and 117.55°. After operation under 60 °C/80% relative humidity condition for 1000 h, the uncoated white LED package yielded maintenance rate of 96.85% whereas the coated packages gave 98.17%. At 85 °C under 200 mA, the thermal resistance of the white silicone-coated white LED packages was lowered by 17.7% than the uncoated packages.

中文翻译：

---

选择性涂覆白色硅胶以改善白色 LED 封装的光学和热特性

我们研究了选择性涂覆白色硅胶对中等功率照明应用的白色 LED 封装的输出和热性能的影响。LED 封装的齐纳二​​极管部分涂有 TiO2 颗粒混合白色硅胶，与未涂层齐纳二极管相比，其表面温度和热通量更低。白色有机硅涂层封装的热阻 (Rth) 低于未涂层封装。例如，在 85 °C 下，结 PCB 中未涂层和涂层白色 LED 封装的 Rth 分别为 26.30 KW-1 和 21.98 KW-1。有涂层的蓝色和白色 LED 封装产生的光通量分别比无涂层封装高 6.5% 和 4.5%。远场发射模式显示镀膜白光 LED 封装的视角为 118.06° 和 118°。沿两个正交方向分别为 10°，而未涂层封装则为 117.37° 和 117.55°。在 60°C/80% 相对湿度条件下运行 1000 小时后，未涂层的白光 LED 封装的维持率为 96.85%，而涂层的封装为 98.17%。在 85 °C 和 200 mA 下，白色硅胶涂层的白色 LED 封装的热阻比未涂层的封装降低 17.7%。