Fluorescent SiC and its application to white light-emitting diodes

Fluorescent-SiC (f-SiC), which contains donor and acceptor impurities with optimum concentrations, has high conversion efficiency from NUV to visible light caused by donor-acceptor-pair (DAP) recombination. This material can be used as a substrate for a near UV light-emitting diode (LED) stack, and leads to monolithic white LED device with suitable spectral property for general lighting applications. In this paper, we describe basic technologies of the white LED, such as optical properties of f-SiC substrate, and epitaxial growth of NUV stack on the f-SiC substrate.     

Nitride-based cascade near white light-emitting diodes

An InGaN-GaN blue light-emitting diode (LED) structure and an InGaN-GaN green LED structure were grown sequentially onto the same sapphire substrate so as to achieve a nitride-based near white LED. In order to avoid thyristor effect, we choose a large 2.1×2.1 mm² LED chip size, which was six times larger than that of the normal LED. It was found that we could observe a near white light emission with Commission International de l'Eclairage color coordinates x=0.2 and y=0.3, when the injection current was lower than 200 mA. It was also found that the output power, luminous efficiency and color temperature of such a cascade near white LED were 4.2 mW, 81 l m/W, and 9000 K, respectively     

YAG:Ce~(3+)玻璃陶瓷白光LED的发光特性

用化学共沉淀法制备掺铈钇铝石榴石(YAG:Ce3+)前驱体,以B2O3-Al2O3-SiO2-Na2O为玻璃基质制作Ce3+掺杂YAG玻璃陶瓷,并封装成玻璃陶瓷白光发光二极管(LED)。改变玻璃陶瓷基片厚度和外形,测量玻璃陶瓷白光LED的光电色参数,并与常规涂敷YAG荧光粉方法制作的白光LED进行对照比较。结果表明,玻璃陶瓷白光LED发射光谱波形与普通白光LED光谱基本一致。玻璃陶瓷基片从0.50mm变化到0.90mm厚时,相关色温(CCT)从4 182 K增加到8862K。0.60mm厚平板玻璃陶瓷基片封装成的白光LED荧光能量转换效率约为20%,中心CCT为6396K,-85°和+85°视角CCT分别为5921K和5898K;而平凸玻璃陶瓷基片封装成的白光LED,-85°和+85°视角CCT变化范围可控制在150K范围内。     

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。     

一种色温可调LED的封装与性能研究

LED以其优良的性能结合智能控制系统,被越来越多地应用于室内外照明场合,但同时也对其色温、显色指数等色度指标提出了新的要求.为了应对这种挑战,设计了一种新型的色温可调LED,利用大功率LED芯片结合金属基板封装出了色温可调的暖白光高显色指数LED样品,对其发光光谱、色温和显色指数随电流的变化进行了测试,发现LED的光谱...     

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。     

Preparation of GaN-on-Si based thin-film flip-chip LEDs

GaN based MQW epitaxial layers were grown on Si(111) substrate by MOCVD using AIN as the buffer layer.High light extraction LEDs were prepared by substrate transferring technology in combination with thin-film and flip-chip design.The blue and white 1.1×1.1 mm~2 LED lamps are measured.The optical powers and external quantum efficiency for silicone encapsulated blue lamp are 546 mW,and 50.3%at forward current of 350 mA, while the photometric light output for a white lamp packaged with standard YAG phosphor is 120.1 lm.     

Light output improvement of GaN-based light-emitting diodes grown on Si (111) by a via-thin-film structure

This work reports the fabrication of via-thin-film light-emitting diode (via-TF-LED) to improve the light output power (LOP) of blue/white GaN-based LEDs grown on Si (111) substrates.The as-fabricated via-TF-LEDs were featured with a roughened n-GaN surface and the p-GaN surface bonded to a wafer carrier with a silver-based reflective electrode,together with an array of embedded n-type via pillar metal contact from the p-GaN surface etched through the multiple-quantum-wells (MQWs) into the n-GaN layer.When operated at 350 mA,the via-TF-LED gave an enhanced blue LOP by 7.8％ and over 3.5 times as compared to the vertical thin-film LED (TF-LED) and the conventional lateral structure LED (LS-LED).After covering with yellow phosphor that converts some blue photons into yellow light,the via-TF-LED emitted an enhanced white luminous flux by 13.5％ and over 5 times,as compared with the white TF-LED and the white LS-LED,respectively.The significant LOP improvement of the via-TF-LED was attributed to the elimination of light absorption by the Si (111) epitaxial substrate and the finger-like n-electrodes on the roughened emitting surface.     

国外白光LED技术与产业现状及发展趋势

近年来,LED技术与产业发展迅速,成为半导体制造行业的最大亮点.从技术和产业两个大的方面介绍了国外LED的发展现状、特点和趋势.介绍了产业化的两种衬底外延技术--蓝宝石衬底和SiC衬底,然后介绍了近年来出现的几种芯片技术、几大公司的芯片技术特点、常用的封装技术及其发展趋势目标等,最后介绍了LED器件的实验室水平和商业化生产的水平以及低成本LED的发展,总结了LED的技术发展趋势.产业方面、,主要介绍了LED生产线的分布、欧、美、日、韩等国的产业概况、公司封装产值排名及分析,最后总结了产业发展的特点与趋势.     

LED用PCB材料

概述了白色基板和白色阻焊剂等LED用PCB材料。     

Stable White Light‐Emitting Biocomposite Films

The demonstration of reliable and stable white light‐emitting diodes (LEDs) is one of the main technological challenges of the LED industry. This is usually accomplished by incorporation of light‐emitting rare‐earth elements (REEs) compounds within an external polymeric coating of a blue LED allowing the generation of white light. However, due to both environmental and cost issues, the development of low‐cost REE‐free coatings, which exhibit competitive performance compared to conventional white LED is of great importance. In this work, the formation of an REE‐free white LED coating is demonstrated. This biocomposite material, composed of biological (crystalline nanocellulose and porcine gastric mucin) and organic (light‐emitting dyes) compounds, exhibits excellent optical and mechanical properties as well as resistance to heat, humidity, and UV radiation. The coating is further used to demonstrate a working white LED by incorporating it within a commercial blue LED.     

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.     

大功率LED封装的热管理

建立了一种大功率LED照明灯具的实际封装结构,采用ANSYS有限元软件对其进行热分析,得出了其稳态的温度场分布,并通过实际测量与计算得出了原始模型LED的实际节温,在此基础上提出了几种优化方案,分别采用不同的LED封装材料以及不同的铝热沉结构尺寸,并且进行了模拟对比,对其中一种可行性方案进行了参数优化,在经济和效果之间达到了较好的平衡,获得了较好的优化效果.     

基于Si衬底的功率型GaN基LED制造技术

介绍了Si衬底功率型GaN基LED芯片和封装制造技术,分析了Si衬底功率型GaN基LED芯片制造和封装工艺及关键技术,提供了产品测试数据。Si衬底LED芯片制备采用上下电极垂直结构与Ag反射镜工艺,封装采用仿流明大功率封装,封装后白光LED光通量达80 lm,光效达70 lm/W,产品已达商品化。与蓝宝石和SiC衬底技术路线相比,Si衬底LED芯片具有原创技术产权,可销往任何国家而不受国际专利的限制。产品抗静电性能好,寿命长,可承受的电流密度高,具有单引线垂直结构,器件封装工艺简单,而且生产效率高,成本低廉。其应用前景广阔,是值得大力发展的一门新技术。     

无荧光粉转换白光LED的研究和进展

白光LED具有节能、环保、寿命长等优点,它的问世是人类照明史上一个重大的里程碑,标志着一种全新的照明光源的诞生。为了提高白光LED的各项性能,克服现有技术的壁垒及不足,各种无荧光粉转换的新型结构的白光LED应运而生。本文在分析LED发光机理的基础上,给出了目前白光LED常用的3种制备方法及优缺点,列举了无荧光粉转换白光LED的最新发展,指出了无荧光粉转换白光LED面临的问题,并对无荧光粉转换白光LED的未来发展进行了总结。     

Overdriving reliability of chip scale packaged LEDs: Quantitatively analyzing the impact of component

The objective of this study is to quantitatively evaluate the impacts of LED components on the overdriving reliability of high power white LED chip scale packages (CSPs). The reliability tests under room temperature are conducted over 1000 h in this study on CSP LEDs with overdriving currents. A novel method is proposed to investigate the impact of various components, including blue die, phosphor layer, and substrate, on the lumen depreciation of CSP LEDs after aging test. The electro-optical measurement results show that the overdriving current can lead to both massive light output degradation and significant color shift of CSP LEDs. The quantitative analysis results show that the phosphor layer is the major contributor to the failure in early period aging test. For the long-term reliability, the degradations of phosphor and reflectivity of substrate contribute significantly on lumen depreciation. The proposed reliability assessment method with overdriving loadings can be usefully implemented for LED manufacturers to make a cost- and effective-decision before mass production.     

荧光粉涂覆方式对白光LED光色指标的影响

文章采用TRACEPRO软件建立了三种白光LED的光学模型:(1)芯片直接涂覆荧光粉;(2)芯片涂覆硅胶后涂覆荧光粉层;(3)芯片涂覆荧光粉后涂覆硅胶层.通过改变荧光粉的摩尔浓度或硅胶厚度来考察白光LED的光色指标,如光通量、色温及显色指数的变化.研究结果表明:第一种和第二种涂覆方式中,光色指标随着荧光粉摩尔浓度或硅胶厚度的改变呈规律性变化;第三种涂覆方式中,色温及显色指数的变化趋势不稳定,第三种方式光通量高于前两种,最大值可达到87.31m.三种方式的显色指数在70左右.研究结论为白光LED工艺设计提供参考和依据.     

新型白光LED驱动电路

显示系统能够显示更多内容和更具功能性的前景预测，使绿色显示向更高分辨率的方向发展。白光LED由于所具有的低成本、长寿命和小体积的特性正在迅速成为照明和背光源的选择。但是由于白光LED（3．1～4．0V）相对于绿光LED（1．8～2．7V）具有更高的电压降，因而绿光LED可以直接由带有一个镇流电阻的线性稳压器来供电，而用于照明和背光的白光LED需要对电池电压进行升压。本文将着重讨论几种驱动白光LED的新方法，并分析每种方法的优点。     

深能级对白光LED的电致发光和I-V特性的影响

为了研究一种无荧光粉的单芯片白光发光二极管(LED)的光电性质,实际测量了它的升温电致发光光谱和升温电流-电压(I-V)特性,并测量了相似结构的蓝光LED以作对比。实验发现白光LED的电致发光光谱中有一个与有源区中的深能级相关的较宽的长波长发光峰,根据这个发光峰的强度与温度之间的依赖关系,通过数据拟合,得到了深能级的平均激活能,约为199 meV。由于有源区中存在大量深能级,也对白光LED的I-V特性产生一定影响,有源区中的深能级成为额外的载流子源,使白光LED的I-V特性表现出独特的性质。     

图形化蓝宝石衬底形貌对GaN基LED出光性能的影响

近年来,图形化蓝宝石衬底(PSS)作为GaN基LED外延衬底材料被广泛应用.通过干法刻蚀和湿法腐蚀制备了不同规格和形状的蓝宝石衬底图形,并进行外延生长、芯片制备和封装验证,采用扫描电子显微镜(SEM)和3D轮廓仪进行形貌表征,研究了不同规格和形状的衬底图形对LED芯片出光性能影响,并与外购锥形衬底(PSSZ2)进行对比.结果表明,在20 mA工作电流下,PSSZ2的LED光通量为8.33 lm.采用类三角锥和盾形衬底的LED光通量分别为7.83 lm和7.67 lm,分别比PSSZ2衬底低6.00％和7.92％.对锥形形貌进行优化,采用高1.69 μm、直径2.62 μm、间距0.42 μm的锥形衬底(PSSZ3)的LED光通量为8.67 lm,比PSSZ2衬底高4.08％,优化的PSSZ3能有效地提高LED出光性能.