大功率LED荧光粉硅胶点涂工艺的实验及模拟研究

Experimental and Numerical Study of Phosphor Dispensing Process in Light Emitting Diodes

为得到白光LED照明产品,大功率LED封装工艺流程中,荧光粉硅胶混合物需通过点涂等方式涂覆于LED芯片上。荧光粉硅胶涂覆工艺的本质是一个两相流动过程,它直接决定了荧光粉硅胶层的几何形貌及物理特性,并最终影响LED产品的性能,因此准确描述这一成形过程特别重要。基于高速摄像机的实验平台,通过实验捕捉荧光粉硅胶形貌的动态成形过程。应用格子Boltzmann方法,建立荧光粉硅胶流动模型,对荧光粉硅胶点涂工艺进行模拟,得到荧光粉硅胶点涂成形过程及最终形貌。结果表明:荧光粉硅胶点涂工艺中,存在撞击、铺展及稳定成形三个阶段;格子Boltzmann方法能够正确模拟荧光粉硅胶点涂这一流动过程,并能够预测荧光粉硅胶层的最终形貌,为后续研究中对点涂工艺的优化提供了理论基础。

To get white light emission,it's common to use a blue LED(light emitting diode) chip covered with yellow emitting phosphor via a dispensing process.The phosphor coating process is a process of two-phase flow,which decides the morphology and the properties of the phosphor gel,thus strongly influences both optical and thermal performances of LEDs.It is important to describe the dispensing process accurately to improve dispensing quality.Based on the experimental platform with high speed camera,the dynamic phosphor gel morphology was captured.And using lattice Boltzmann method(LBM),a flow model of phosphor gel was established to simulate the dispensing process.Results show that the dispensing process can be divided into the collision stage,the spreading stage and the forming stage.And LBM can simulate the dispensing process of phosphor gel accurately and predict the morphology.