高显色LED白光芯片中湿-热-光耦合作用机理及非平稳退化模型研究

To fulfill the requirement on high efficacy, high color rendering, and small size, Light-emitting diode (LED) white chip, with the flip-chip LED and multiple-phosphor/silicone film preforming technology, has been proposed recently. However, unknown failure mechanisms, failure modes and reliability problems from new packaging materials and unconventional processes have become the critical barrier to their adoption. Therefore, this project is proposed to solve the critical scientific problems on the moisture-thermal-optical coupling mechanisms of LED white chip under the complex application environment, and the non-stationary degradation modeling for the LED white chip package by taking the multiple-materials, multiple-surfaces and multiple-physics into account. In details, the moisture-absorption mechanism and moisture-thermal-optical coupling model of multicolor phosphor/silicone composites will be studied firstly. Then, the failure cause identification, stress coupling and failure analysis methods for LED white chip aged under complex loads will be developed. Finally, according to the non-stationary degradation characteristic of the multiple-material system in LED white chip under complex loads, a stochastic process-based degradation model considering the joint failure probability distribution function for multiple failure modes will be established to increase the accuracy of degradation lifetime prediction for LED white chip. The major contributions of this project are to support the theoretical basics for the novel LED white chip packaging structures, materials and processes, and also to provide the technical guidance on the fast, accurate and cost-effective reliability assessment for high quality LED light sources.

面向高效、高显色、小尺寸应用需求，采用倒装LED芯片结合混色荧光薄膜预成型技术的LED白光芯片近期被提出。然而，新封装材料、非传统工艺以及复杂苛刻应用要求带来的新失效机理、失效模式和可靠性问题已经成为LED白光芯片推广的关键瓶颈。本项目围绕“复杂环境下LED白光芯片中湿-热-光耦合作用机理，以及其多材料、多界面封装体系在物理场中的非平稳退化过程建模”基础问题展开。首先，研究湿气环境下多基色混合荧光粉/硅胶材料的吸湿机理及湿-热-光耦合模型；其次，提出多应力条件下老化主因识别、应力耦合性分析和失效分析方法；最后，针对复杂负载下多材料体系的非平稳退化特征，构建随机退化模型和多失效模式的联合概率分布模型，最终实现准确的LED退化寿命预测。通过本项目研究，一方面为新型LED封装结构、材料和工艺的应用推广奠定必要的理论基础；另一方面也为高品质LED光源进行快速、准确的可靠性评估提供必要的技术支撑。

高显色白光LED是未来照明技术的重要发展方向。然而，高效高可靠荧光材料选择、封装结构设计和性能优化、多维度高精度可靠性评估等一直是制约高品质半导体照明产品制造和应用的关键技术瓶颈。本项目针对凝练的“高显色LED白光芯片多材料、多界面、多物理场作用下的失效机理、退化规律及可靠性评估方法”等关键科学问题，首先，建立了LED白光芯片封装的湿-热-光耦合模型和失效物理模型，全面分析了复杂环境下封装结构、材料和界面失效机理对LED白光芯片光-色性能的影响机制，为新一代高品质LED封装结构设计和材料开发提供了关键理论模型；其次，开展了温度-电流-湿度耦合因素，恒定/步进复杂应力加速老化试验和失效机理分析，为新产品应用环境选择提供了丰富的实验数据；最后，建立了复杂条件下LED非平稳退化模型及可靠性预测方法，为拓展半导体照明产品可靠性评估方法提供了重要理论支撑。研究成果在Laser Photonics Rev., OE, EAWA, IEEE TED/EDL等高质量期刊/会议上发表学术论文40篇；申请/授权发明专利13项；参与撰写Springer英文书籍2部中2个章节；牵头制定ISA-TCS技术推荐1项，参与制定CASA团体标准4项，CSAS团体标准1项；联合培养香港理工大学博士生1名，独立培养硕士生13名，其中获“江苏省优秀专业学位硕士论文”1篇；获江苏省科学技术奖、国际半导体照明突出贡献奖等；项目负责人入选上海市浦江人才计划（D特殊急需类）。