大功率LED用封装基板研究进展

LED被称为第四代照明光源及绿色光源,近几年来该产业发展迅猛.由于LED结温的高低直接影响到LED的出光效率、器件寿命和可靠性等,因此散热问题已经成为大功率LED产业发展的瓶颈.文章阐述了大功率LED基板的封装结构和散热封装技术的发展状况,从基板的结构特点、导热性能及封装应用等方面分别介绍了金属芯印刷电路基板、覆铜陶瓷...     

大功率LED照明系统的热管理设计

由于大功率LED工作时所产生的大量热量,使得大功率LED照明系统中的热管理成为一个非常重要的议题.文中分析了在大功率LED照明系统中热传导、热对流和热辐射这3种热传递方式的应用,并分别提出了优化的方案.对于大功率LED照明系统的热管理设计,我们提出要系统考虑热通路的每个环节,通过分配温度梯度预算来选取适当的方案,以达到良好的散热效果.     

集成式大功率LED路灯散热器的结构设计

LED作为新一代绿色光源,正在被广泛的应用于照明行业.对于LED灯具来说,正常工作的前提是要具备良好的散热能力.利用CAE并结合正交分析法模拟分析了集成式大功率LED路灯散热器结构.通过分析翅片的高度、厚度、个数以及基板的长度、厚度、宽度等六个参数对其温度场的影响,得出较优的结构参数组合,使LED工作温度降低到要求温度以下,并使散热器的质量较轻.     

太阳能照明系统光源的选择

为了探究太阳能照明系统光源,验证LED用于太阳能照明的可行性,文章对不同批次的大功率白光LED进行了相关测试,并介绍了太阳能照明系统的组成,对不同使用场合的光源进行了比较,为太阳能照明系统光源的选择及进一步研究提供了参考。     

大功率LED照明灯具的光学及散热技术的研究

大功率LED照明灯具的光学及散热技术主要通过研发一种大功率LED照明灯具通过对LED模组的内部结构、发光特性、散热特性及电源连接控制等方面的研究,优化大功率LED生产工艺,改进现有生产的技术不足,研发出具有大照射角度、高散热长寿命的大功率LED灯具,降低了生产成本,提高大功率LED灯具的可靠性,提高其光学品质和光输出效率。     

大功率LED照明灯具的配光与散热的研究

本文通过对大功率LED照明灯具的配光与散热的研究,了解大功率LED照明灯具的使用寿命、光输出定向性、大功率LED灯珠的发光效率、散热系数等相关参数。对本公司现有的大功率LEDN明灯具产品的一次配光、二次配光、大功率LED灯珠散热进行了改进设计。大功率LED照明灯芯片加速老化、工作寿命减短等问题,因此散热是制约其发展的一个至关重要的因素。本文介绍了目前广泛运用的大功率LED灯散热技术、散热产品以及热分析工具,应用ANSYS软件针对一款大功率LED进行了热分析,求得各个部分的温度场分布,巴超出了结温的最大允许值。通过热分析,对该LED灯散热结构进行改进,将芯片最高温降为51．1226℃,仿真分析结果表明在允许范围之内,验证了改进方案的可行性。     

太阳能照明系统LED驱动器的优化研究与设计

太阳能照明已成为一项重要的研究课题,应运而生的LED照明光源的驱动技术也成为被研究的主要对象,文中对大功率LED的驱动方法进行了研究与分析,设计和制作了基于恒定导通时间控制的LED驱动器,并对高效驱动LED的恒流驱动电路进行了优化改进,使其与太阳能照明系统实现最优组合。     

10W COB集成LED光源的性能分析

随着发光二极管(LED)的发光效率、寿命、可靠性等性能的逐步提高,特别是大功率LED的发展备受人们关注,已经开始作为光源应用于普通照明领域中。但是大功率LED的散热问题是阻碍其迅速发展和推广普及的难题之一。从光色电热等性能方面,详细介绍了10W COB集成LED光源的研究进展,通过封装材料的选择和封装工艺的改善,可以有效改善LED的热阻性能,实测器件热阻值Rth=4.6K/W。     

基于LED照明灯具的散热片设计与分析

新一代大功率白光LED光源具有很多优点,如节能、环保、寿命长等,但大功率LED的散热也是一个至关重要的问题。如果LED散热问题解决不好,LED灯具工作一段时间后就会输出光功率减小,芯片加速老化,工作寿命缩短。文章从LED散热问题着手,详细介绍了目前广泛商用的大功率LED器件结构及导热途径、所用散热基片的特点,以及LED所用的散热片设计和计算方法。另外介绍了一种大功率LED在散热片上不同位置温度变化的测试结果,并推导出用于计算LED器件散热的有效公式。     

基于大功率LED的汽车多椭球前照灯设计

传统光源卤素灯泡用于前照灯照明,在节能和寿命上存在不足.研究了使用半导体LED光源和多椭球面反射镜的前照灯设计方法.基于前照灯近光配光标准和LED光源特点,建立了LED前照灯的设计模型,包括LED光源模拟单元、反射器设计单元、透镜设计单元和光路追迹算法.提出三维多椭球面作为反射镜的方法,实现了LED光源多椭球面前照灯的照明计算机仿真.分析了实验结果,并指出LED前照灯的优势和未来大功率LED汽车前照灯发展的关键技术.     

Status and Future of High-Power Light-Emitting Diodes for Solid-State Lighting

Status and future outlook of III-V compound semiconductor visible-spectrum light-emitting diodes (LEDs) are presented. Light extraction techniques are reviewed and extraction efficiencies are quantified in the 60%+ (AlGaInP) and ~80% (InGaN) regimes for state-of-the-art devices. The phosphor-based white LED concept is reviewed and recent performance discussed, showing that high-power white LEDs now approach the 100-lm/W regime. Devices employing multiple phosphors for "warm" white color temperatures (~3000-4000 K) and high color rendering (CRI>80), which provide properties critical for many illumination applications, are discussed. Recent developments in chip design, packaging, and high current performance lead to very high luminance devices (~50 Mcd/m² white at 1 A forward current in 1times1 mm² chip) that are suitable for application to automotive forward lighting. A prognosis for future LED performance levels is considered given further improvements in internal quantum efficiency, which to date lag achievements in light extraction efficiency for InGaN LEDs     

Correlated Color Temperature Tunable Multi-chip Light Emitting Diodes Light Source Design

One of the methods to derive white light from light emitting diodes（LEDs） is the multi-chip white LED technology, which mixes the light from red, green and blue LEDs. Introduced is an optimal algorithm for the spectrum design of the multi-chip white LEDs in this paper. It optimizes the selection of single color LEDs and drive current controlling, so that the multi-chip white LED achieves the target correlated color temperature （CCT）, as well as high luminous efficacy and good color rendering. A CCT tunable LED light source with four high-power LEDs is realized based on the above optimal design. Test results show that it maintains satisfactory color rendering and stable luminous efficacy across the whole CCT tuning range. Finally, discussed are the design improvement and the prospect of the future applications of the CCT tunable LED light source.     

大功率LED有源温控系统的开发

由于大功率LED供电时其大部分能量转化为热能,如果热量不能有效散出,将严重影响其光照亮度及其使用寿命。为了大功率LED散热的实际需要,提出并实现了一种LED有源温控系统的开发,采用热电制冷效应,使用LED驱动器本身作为制冷器的驱动电源,同时建立基于半导体传感器的温控监测电路,通过内部数字PI调节器形成一个完整的闭环控制系统,最后获得LED有源温控系统的具体配置方式,并分析测试的数据结果,展示了有源温控系统的准确性和可靠性。     

LED封装中的散热研究

文章论述了大功率LED封装中的散热问题,说明它对器件的输出功率和寿命有很大的影响,分析了小功率、大功率LED模块的封装中的散热对光效和寿命的影响。对封装及应用而言,增强它的散热能力是关键技术,指出对大功率LED和LED模块散热设计很重要,因为大功率白光LED的光效和寿命取决于其散热。目前大功率LED的重点是提高散热能力,说明封装结构和封装材料在提高大功率LED散热中的影响,LED模块的散热是未来的重点。通过选用高热导率材料可以使温度得到显著控制,重点论述了封装的关键技术,最后指出了未来LED封装技术的发展趋势。     

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.     

Designing Uniform Illumination Systems by Surface-Tailored Lens and Configurations of LED Arrays

Light-emitting diodes (LEDs) are gradually becoming the preferred choice for many lighting applications that require uniform illumination distribution. LED sources are usually composed of several individual LEDs which must be mounted on a panel as a lighting module. Therefore, the design is quite important for achieving a good uniform illumination distribution before a LED lighting module is produced. This paper presents a theory and design method by systemic concepts and focuses on the study of optical properties. We can design, efficiently, a LED lighting module and achieve a satisfactory uniformity by this theory and method, the design of a uniform LED illumination system. By this method, we not only obtain the maximally flat illumination distribution but also the emitting angle of the system can be designed at will. This method and theory will offer a preferable choice when LED lighting modules become the main stream for the lighting market in the future. Here, the light source is approximately defined as a point light source with cosine irradiance distribution.      

Code Division-Based Sensing of Illumination Contributions in Solid-State Lighting Systems

Light-emitting diodes (LEDs) have emerged as a prime candidate for the light source of the future. To enable easy user interaction with a future lighting system consisting of many LEDs, this paper proposes a method to accurately measure and estimate the local light contributions of a large set of LEDs. This is enabled through tagging the light of each LED with an unique identifier. To this end, we propose a new family of modulation and multiple access schemes in this paper, named code-time division multiple access-pulse position modulation (CTDMA-PPM) and CTDMA-pulse width modulation (CTDMA-PWM). These schemes satisfy illumination constraints, are compatible with the commonly used PWM dimming of LEDs, and meet the multi-signal separation requirements for simultaneous measurement of illumination strengths. Based on these modulation methods, the paper develops algorithms to estimate illumination. Finally, performance analyses show that even for a very large number of LEDs, the sensing performance of the proposed system satisfies the requirements up to an adequate range.     

多芯片集成大功率白光LED照明光源

通过对自行设计的集成功率型1W白光LED进行测试，发现当持续点亮900h时，其光通量衰减只有12％，比传统支架型封装的白光LED明显慢，而色温飘移也不明显。1W白光LED的色温可以覆盖2700～13000K，并且显色指数均可做到80以上，完全能够满足普通照明对光性能指标的要求。通过对多颗小功率芯片(60mW)进行不同的串并联组合，可以实现不同的额定电压与电流，可以更好地匹配驱动器的设计，提高整体发光效能，降低成本，并满足不同场合的需求。最后给出了3个典型LED驱动设计实例。     

大功率发光二极管的寿命试验及其失效分析

以GaN基蓝光LED芯片为基础光源制备了大功率蓝光LED,并通过荧光粉转换的方法制备了白光LED.对大功率蓝光和白光LED进行了寿命试验,并对其失效机理进行了分析.结果表明,大功率LED的光输出随时间的衰减呈指数规律,缺陷的生长和无辐射复合中心的形成,荧光粉量子效率的降低,静电的冲击,电极性能不稳定,以及封装体中各成分之间热膨胀系数失配引起的机械应力都可能导致大功率LED的失效.     

LED路灯热分析及散热结构设计

LED作为第四代照明光源已被广泛应用于显示和照明系统设备,但由于其光电转化率较低,大部分电能实际转化成了热量,所以如何提高其散热能力是大功率LED实现产业化亟待解决的关键技术之一。文章以某公司LED路灯为模型,采用ANSYS有限元软件对其进行参数化建模及热分析,得出了其稳态的温度场分布,在此基础上通过设计正交实验,分析了铝制热沉不同结构参数对其温度场的影响情况。由最终的结果可知,在合适的范围内使散热器翅片的厚度和间距较小一些,可得到较为理想的优化结构,既能控制芯片的最高温度,又有效地减小了散热器的质量。文章LED路灯算例得到优化的质量为原质量的33．40％。