用于LED的微透镜阵列的光学性能研究

功率发光二极管(LED)的发展迫切需要提高取光效率,微透镜阵列的二次光学设计是改善其光强分布的有效途径.建立了一种大功率LED的封装结构,二次光学设计采用了微透镜阵列技术,运用光线追踪法研究了这种封装结构的光学性能.分析结果表明,利用微透镜阵列技术能显著改善LED的光学性能,改变其光束分布,将LED的照度衰减降低12%以上,从而得到更加均匀的照明系统.     

带有TSV的硅基大功率LED封装技术研究

介绍了一种带有凹槽和硅通孔(through silicon via,TSV)的硅基制备以及晶圆级白光LED的封装方法。针对硅基大功率LED的封装结构建立了热传导模型,并通过有限元软件模拟分析了这种封装形式的散热效果。模拟结果显示,硅基封装满足LED芯片p-n结的温度要求。实验结合半导体制造工艺,在硅基板上完成了凹槽和通孔的制造,实现了LED芯片的有效封装。热阻测试仪测得硅基的热阻为1.068K/W。实验结果证明,这种方法有效实现了低热阻、低成本、高密度的LED芯片封装,是大功率LED封装发展的重要方向。     

Heat dissipation design and analysis of high power LED array using the finite element method

High-power Light Emitting Diode (LED) technology has developed rapidly in recent years from illumination to display applications. However, the rate of heat generation increases with the LED illumination intensity. The LED chip temperature has an inverse proportion with the LED lifetime. High-power LED arrays with good thermal management can have improved lifetime. Therefore, for better optical quality and longer LED lifetime it is important to solve the LED thermal problems of all components. In particular, Metal Core Printed Circuit Board (MCPCB) substrate heat sink design and thermal interface materials are key issues for thermal management. This paper presents an integrated multi-fin heat sink design with a fan on MCPCB substrate for a high-power LED array using the finite element method (FEM). The multi-fin heat sink design and simulation results provide useful information for LED heat dissipation and chip temperature estimation.     

Status and prospects for phosphor-based white LED packaging

The status and prospects for high-power, phosphor-based white light-emitting diode (LED) pack-aging have been presented. A system view for packaging design is proposed to address packaging issues. Four aspects of packaging are reviewed: optical control, thermal management, reliability and cost. Phosphor materials play the most important role in light extraction and color control. The conformal coating method improves the spatial color distribution (SCD) of LEDs. High refractive index (RI) encapsulants with high transmittance and modified surface morphology can enhance light extraction. Multi-phosphor-based packaging can realize the control of correlated color temperature (CCT) with high color rendering index (CRI). Effective thermal management can dissipate heat rapidly and reduce thermal stress caused by the mismatch of the coefficient of thermal expansion (CTE). Chip-on-board (COB) technology with a multi-layer ceramic substrate is the most promising method for high-power LED packaging. Low junction temperature will improve the reliability and provide longer life. Advanced processes, precise fabrication and careful operation are essential for high reliability LEDs. Cost is one of the biggest obstacles for the penetration of white LEDs into the market for general illumination products. Mass production in terms of CoB, system in packaging (SIP), 3D packaging and wafer level packaging (WLP) can reduce the cost significantly, especially when chip cost is lowered by using a large wafer size.     

功率LED柔性封装结构的设计与热特性分析

根据功率LED的柔性封装要求,提出了基于贴片式(SMD)封装的功率型LED柔性封装结构。对各层结构进行了优化设计,采用有限元分析(FEA),模拟了柔性封装结构LED的热场分布。对比研究了柔性LED与传统封装结构LED的热特性,并对弯曲状态下柔性衬底材料对芯片的应力进行了分析。结果表明,采用金属Cu箔衬底的柔性封装结构,其散热特性较好;Cu/超薄玻璃复合衬底替代Cu箔衬底,可以减少弯曲的应力,减少幅度达到2.5倍,散热特性基本相同。SMD柔性封装的LED不仅具有较好的热稳定性,且具有柔性可挠曲特性,其应用潜力很大。     

大功率LED低热阻封装技术进展

散热是大功率LED封装的关键技术之一,散热不良将严重影响LED器件的出光效率、亮度和可靠性。影响LED器件散热的因素很多,包括芯片结构、封装材料(热界面材料和散热基板)、封装结构与工艺等。文章具体分析了影响大功率LED热阻的各个因素,指出LED散热是一个系统概念,需要综合考虑各个环节的热阻,单纯降低某一热阻无法有效解决LED的散热难题。文中还对国内外降低LED热阻的最新技术进行了介绍。     

大功率白光LED封装设计与研究进展

封装设计、材料和结构的不断创新使发光二极管(LED)性能不断提高.从光学、热学、电学、机械、可靠性等方面,详细评述了大功率白光LED封装的设计和研究进展,并对封装材料和工艺进行了具体介绍.提出LED的封装设计应与芯片设计同时进行,并且需要对光、热、电、结构等性能统一考虑.在封装过程中,虽然材料(散热基板、荧光粉、灌封胶)选择很重要,但封装工艺(界面热阻、封装应力)对LED光效和可靠性影响也很大.     

Development of a thermal resistance model for chip-on-board packaging of high power LED arrays

The performance of high power LEDs strongly depends on the junction temperature. Operating at high junction temperature causes degradation of light intensity and lifetime. Therefore, proper thermal management is critical for LED packaging. While the design of the heat sink is a major contributor to lowering the overall thermal resistance of the packaged luminaire, another area of concern arises from the need to address the large heat fluxes that exist beneath the die. In this study we conduct a thermal analysis of high power LED packages implementing chip-on-board (COB) architecture combined with power electronic substrate focusing on heat spreading effect. An analytical thermal resistance model is presented for the LED array and validated by comparing it with finite element analysis (FEA) results. By using the analytical expression of thermal resistance, it is possible to understand the impact of design parameters (e.g., material properties, LED spacing, substrate thickness, etc.) on the package thermal resistance, bypassing the need for detailed computational simulations using FEA.     

基于微通道致冷的大功率LED阵列封装热分析

采用微通道致冷技术,设计了大功率LED阵列封装的微通道致冷结构,并应用热分析软件模拟了其热性能,探讨不同鳍片结构尺寸、流速、功率等参数对LED多芯片散热效果的影响.文中提出了采用交错通道以提高LED封装的散热能力,模拟结果显示,交错微通道致冷的封装结构能很好地满足大功率LED阵列的散热需要.     

基于COB技术的LED散热性能分析

当前,散热问题已成为影响LED寿命、光效、光衰和色温等技术参数的重要因素。文章在综合分析散热技术和LED封装对散热性能影响的基础上,利用COB(板上芯片)封装技术,将LED芯片直接封装在铝基板上,研制成了一种基于COB封装技术的LED。与SMD封装LED进行比较,分析了其散热性能。分析结果表明:基于COB封装技术的LED减少了LED器件的结构热阻和接触热阻,使其具有良好的散热性能。     

A Microjet Array Cooling System for Thermal Management of High-Brightness LEDs

In this paper, a microjet-based cooling system is proposed for the thermal management of high-power light-emitting diodes (LEDs). Preliminary experimental investigation and numerical simulation on such an active cooling system are conducted. In the experiment investigation, thermocouples are packaged with LED chips to measure the temperature and evaluate the cooling performance of the proposed system. The experimental results demonstrate that the microjet-based cooling system works well. For a 2 times 2 LED chip array, when the input power is 5.6 W and the environment temperature is 28degC, without any active cooling techniques, the temperature of 2 times 2 LED chip array substrate reaches 72degC within 2 min and will continue to increase sharply. However, by using the proposed cooling system, when the flow rate of micropump is 9.7 mL/s, the maximum LED substrate temperature measured by the thermocouples will remain stable at about 36.7degC. As for the numerical optimization, the comparison between the simulation and experimental results is presented to confirm the feasibility of the simulation model. By using the simulation model, the effects of microjet diameter, top cavity height, micropump flow rate, and jet device material on system performance are numerically studied. According to the preliminary test and numerical optimization, an optimized microjet cooling system is fabricated and applied in thermal management of a 220-W LED lamp. The temperature test demonstrates that the cooling system has good performance.     

基于热电制冷的大功率LED散热性能分析

提出了一种新型的基于热电制冷的大功率LED热管理方法。这种大功率LED阵列模块采用板上封装技术制造。为了解决散热问题,采用了热电制冷器将LED芯片产生的热量转移到周围的环境中。利用热电偶测量了大功率LED阵列模块在不同工作条件下的温度分布,LED的光学性能则通过光强分布测试仪来测试。结果表明,这种采用热电制冷的大功率LED阵列封装模块能够显著降低器件的工作温度,与不采用热电制冷器相比,基板温度能够降低36％以上,光学性能测量表明LED阵列模块的发光效率达到30．18lm／W。     

用于室内照明的自由曲面均匀配光透镜设计

以非成像光学为基础,设计了一种在大发散角范围内均匀配光的大功率LED室内照明二次配光透镜方案。采用划分网格法建立光源LED和接收面的映射关系,推导透镜自由曲面面形的一般方程,采用差分法求解透镜面形方程获得面形轮廓数据,再用三维软件建立透镜模型,通过光学仿真软件对所建模型进行光线追迹。结果表明:此方案适用于40°～140°配光角度要求的均匀配光;仿真配光角度120°的照明系统,当透镜的口径与LED发光面直径之比大于等于10时,照明系统的均匀性优于0.9,能量利用率大于92%,且照明效果不受接收面高度的影响。该设计方法为实现大功率LED室内均匀照明系统的小型化和简单化提供了一种有效的途径。     

大功率LED封装有限元热分析

介绍了有限元软件在大功率LED封装热分析中的应用,对一种多层陶瓷金属(MLCMP)封装结构的LED进行了热模拟分析,比较了不同热沉材料的散热性能,模拟了输入功率以及强制空气冷却条件对芯片温度的影响.结果表明当达到热稳态平衡时,芯片上的温度最高,透镜顶部表面的温度最低,当输入功率达到3 W时,芯片温度超过了150℃,强制空冷能显著改善器件的散热性能.     

基于有限元方法的光纤加速度计灵敏度仿真分析

散热是大功率LED封装的关键技术之一,散热基板的选用直接影响到LED器件的使用性能与可靠性。文章详细介绍了LED封装基板的发展现状,对比分析了树脂基板、金属基板、陶瓷基板、硅基板的结构特点与性能。最后预测了今后大功率LED基板的发展趋势及需要解决的问题。 更多还原     

Study of Phosphor Thermal-Isolated Packaging Technologies for High-Power White Light-Emitting Diodes

A novel packaging configuration for high-power phosphor-converting white light-emitting diodes (LEDs) application is reported. In this packaging configuration, a thermal-isolated encapsulant layer was used to separate the phosphor coating layer from the LED chip and the submount. Experimental and finite-element method simulation results proved that this thermal management can prevent the heat of LED chip from transferring to the phosphor coating layer. The surface temperature of the phosphor coating layer is a 16.8degC lower than that of the conventional packaging at 500-mA driver current for 1-mm power GaN-based LED chip. Experimental results also show that this packaging configuration can improve the light-emitting power performance and color characteristics stability of the white LED, especially under high current operating condition.     

白光LED封装用蛾眼化荧光玻璃制备及光学性能

针对荧光玻璃封装白光LED存在的全反射损耗问题,制备了一种蛾眼化荧光玻璃用于提高白光LED光学性能。采用光刻和刻蚀工艺在蓝宝石基片的单面上制作出蛾眼阵列结构,再利用丝网印刷和低温烧结工艺在蓝宝石的另外一面制备YAG∶Ce^3+荧光玻璃层,最后将制备的蛾眼化荧光玻璃用于白光LED封装。通过控制荧光层厚度可以有效调节白光LED发光性能,当荧光层厚度为40μm时,白光LED光效为77.8 lm/W,色温为6024 K,显色指数为69.5。与平面荧光玻璃封装结构相比,在100 mA电流下蛾眼化荧光玻璃封装结构的光效提高了24.9%。结果表明,蛾眼化荧光玻璃提高了白光LED光效,有利于促进荧光玻璃封装白光LED的实际应用。     

基于板上封装技术的大功率LED热分析

根据大功率LED板上封装(COB)技术的结构特点,提出三种COB方法.第一种方法是把芯片直接键合在铝制散热器k(COB-III型),另外两种方法是分别把芯片键合在铝基板上和铝基板的印刷线路板上(COB-II和COB-I型),并对三种COB的热特性进行有限元模拟、实验测量和对照分析.结果表明:在环境温度为30℃时,采用第...     

全铜通孔柔性LED封装热学性能仿真分析

柔性基板封装(COF)是一种新型LED封装形式。本研究在柔性基板中的高分子绝缘层(PI)中添加全铜通孔,通过有限元仿真分析全铜通孔对LED封装热学性能的影响。研究结果表明：在柔性LED封装中,PI层热阻最大,是导致芯片结温高的主要因素。PI层中全铜通孔的添加使PI层热阻大幅降低,显著提升LED封装的垂直散热能力。基于仿真计算结果,建立了PI层中添加全铜通孔数量与LED封装热阻间的对应关系。针对本研究中的封装结构,采用8*8 的全铜通孔阵列对LED封装的热学性能提升效果显著。     

大功率LED的热阻测量与结构分析

热阻的精确测量与器件结构分析是设计具有优良散热性能的大功率LED的前提。本文研究了大功率LED的光功率、环境温度和工作电流对热阻的影响规律,论述了积分式结构函数和微分式结构函数的推导过程及其主要性质,提出了大功率LED热阻的精确测量方法,并利用结构函数分析及辨识大功率LED器件的内部结构、尺寸、材料、制造缺陷和装配质量。