通过对LED封装结构热模拟分析表明,模拟固晶胶粘贴部分失效的情况下,采用热导率为0.1 W/m·K的普通硅胶封装成的LED芯片最高温度为220.27°C,采用导热填料高热导率硅胶灌封的LED芯片最高温度可降低到122.71°C,大幅降低了芯片的温度。纳米ZnO导热填料高热导率硅胶,其填料颗粒的直径小于25 nm,透光率高,可适用于LED封装。高温加速老化结果表明,采用导热硅胶灌封的LED样品具有很好的热稳定性,LED高温老化2 000 h后,光通维持率保持在90％以上,避免了由于灌封材料和荧光粉老化产生的黑褐色覆盖层,提高热稳定性和器件使用寿命。

Thermally conductive silicone is developed to remove the heat to the ambient environment generated by LED chip in order to ensure the reliable operation of LED devices.Simulation model built by COSMOS shows the maximum LED chip temperature getting lower from 220.27°C to 122.71°C.After a 2 000 hours’ thermal stress test,the degradation of optical power with nearly exponential kinetics was observed.Package level analysis was carried out in order to clarify the role of degradation in optical properties.The browning took place on the LED Sample A with low thermal conductive silicone potting.Carbonization of normal silicone edge around the chip may affect the overall light emission. Thermal stability and device property are improved.