LED封装荧光粉涂覆的流动热成形建模与实验研究

White light light-emitting diodes (LEDs), which are considered as the next generation of green light sources, have been widely applied in our daily life. Phosphor dispensing coating is one of the most important processes in LED packaging, which determines the final optical and thermal performance of LED devices. Since phosphor coating is a natural flow process with heating solidification on a small chip, its essence is a process coupled with flow and heat transfer on a small scale, if we can find out the law of phosphor flow and heat solidification, we can instruct and propose new processes theoretically. Based on this idea, in this proposal, we will build the models of phosphor coating processes by fluid dynamics and Lattice-Boltzmann methods. In these models, the temperature-induced variation of material properties and stress of phosphor silicone matrix, heat exchange during the solidification process and other characteristics such as small dimension and complex boundary conditions will be considered. We will also set up a test platform for measuring and monitoring the phosphor coating process. Through experimental data, we will compare, confirm and modify the proposed models. Based on the above results, the effects of the parameters (geometry, physics, material, etc.) on the final morphology of phosphor silicone matrix will be investigated. This proposal covers a typical fundamental problem abstracting from the processes and applications. By such a research, we hope to instruct and realize some low-cost and high-reliability phosphor coating processes and promote the LEDs indeed penetrating the general lighting market.

白光发光二极管（LED）被誉为新一代绿色照明方式，在日常生活中已得到广泛应用。荧光粉点涂成形是白光LED封装中最重要的工艺方法之一，它决定了最终LED产品的光学和热学性能。由于点涂成形是流体在小尺度芯片上自然流动铺展并受热固化成形的过程，其本质是在小尺度物体上的耦合流动传热过程，如果能了解其流动成形规律，那么就可以从理论上指导新工艺设计。本项目基于这一想法，通过流体动力学和格子玻尔兹曼两种方法来建立模型，模型中考虑如下特性：荧光粉胶的粘度和表面张力等随温度变化、固化过程中伴随着热量交换、特征尺寸较小及边界条件复杂等。同时构建流动成形控制和检测实验台，通过实验来比较、验证和修正模型。在此基础上，研究温度、表面特征和材料等参数对流动与传热过程和荧光粉硅胶最终形貌的影响规律。本课题是一个典型的从工艺和应用中提出的基础问题，期望研究结果能指导实现低成本高可靠性涂覆工艺，促进LED真正迈向通用照明。

白光发光二极管（LED）被誉为新一代绿色照明方式，在日常生活中已得到广泛应用。荧光粉硅胶涂覆是白光LED封装中最重要的工艺之一，它决定了最终LED产品的光学和热学性能。荧光粉硅胶涂覆的本质是微流体在小尺度表面上的流动热成形过程，如果能了解其流动传热规律，那么就可以从理论上指导新型荧光粉硅胶涂覆工艺设计。基于上述背景，本项目展开了以下四部分研究内容：(1)建立荧光粉硅胶耦合流动与传热模型。通过流体动力学和格子玻尔兹曼两种方法来建立模型，模型中考虑如下特性：荧光粉硅胶黏度等随温度和时间变化、固化过程中伴随着热量交换、特征尺寸较小及边界条件复杂等。(2)开展荧光粉硅胶涂覆流动成形过程实验。搭建了以高速摄像机为核心的荧光粉硅胶流动铺展综合实验平台并通过实验来比较、验证和修正模型。结果表明基于两种方法建立的荧光粉硅胶耦合流动传热模型均能准确的预测荧光粉硅胶的流动成形过程，和实验观测结果对比，形貌偏差小于10%。(3)研究典型参数对流动传热过程和荧光粉硅胶形貌的作用规律。基于模型和实验探究了探究了涂覆高度、荧光粉浓度、基板温度和基板结构的影响规律。结果表明基板温度和基板结构是影响荧光粉硅胶流动和传热过程以及最终形貌的关键因素。(4)开发荧光粉涂覆工艺。基于模型预测结果和实验测试结果，提出三种新型荧光粉涂覆工艺。这些新型荧光粉涂覆工艺有效的提高了LED的空间颜色均匀性，并将光效提升了10%以上。本项目对荧光粉硅胶涂覆流动成形的一些基础问题进行了系统的研究，有助于指导实现低成本高可靠性荧光粉硅胶涂覆工艺，促进LED真正迈向通用照明。