新型封装材料与大功率LED封装热管理

高效散热封装材料的合理选择和有效使用是提高大功率LED(发光二极管)封装可靠性的重要环节。在分析封装系统热阻对LED性能的影响及对传统散热封装材料性能进行比较的基础上,阐述了金属芯印刷电路板材料、金属基绝缘板材料、陶瓷基板材料、导热界面材料和金属基复合材料结构特点、导热性能及其封装应用实例。指出了封装材料的研究重点和亟待解决的问题。     

大功率 LED 汽车前照灯散热系统设计

针对大功率发光二极管(Light-emitting diode, LED)对结点温度要求严格控制的特点,提出一种基于导热板+热沉的散热技术来满足LED 前照灯散热封装的需求。通过数值模拟和试验方法研究了芯片的结温随环境温度、导热板长度、散热器倾斜角度、芯片封装深度的变化规律,试验值与数值模拟值基本吻合。结果均表明,环境温度及散热器的倾斜角对芯片结温有较大影响,芯片结温随环境温度基本呈线性变化关系,散热装置水平放置的散热效果最高。     

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。     

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...     

基于金刚石散热结构的超高功率LED光源

金刚石是自然界导热率最高的材料,具备极佳的耐热和导热性能。基于金刚石导热的散热结构,大大提高了超高功率LED的散热能力。介绍了三种金刚石散热结构:氮化镓与金刚石直接结合实现GaN-ondiamond光与热集成的结构;在传统的LED光源中增加金刚石薄膜作为高导热层的散热结构;以金刚石复合材料做成的LED热沉结构。理论上,三种结构中第一种结构的散热效果最好,与目前最先进的碳化硅衬底LED相比,其结温降低了40%~45%。     

LTCC微波一体化封装

文章介绍了采用LTCC技术制作微波一体化封装,重点研究了X波段LTCC一体化封装的微带穿墙结构及其微波特性。同时对封装的散热结构进行了研究,根据不同的散热要求采用不同的散热结构。采用导热孔散热的方式,其热导率与导热孔的排列方式(孔径和间距)有关,热导率可达50W(m·K)-1。封装的气密性与导热孔的结构有密切关系,热沉的焊接可大大提高封装的气密性。     

多颗粒LED封装警示灯热特性数值与实验研究

针对一款新型LED旋转警示车灯,选取了三个不同的关键参数(灯柱半径r,散热底座半径R及散热底座高度H),基于有限元理论及热电偶测量法,研究了多颗粒LED封装灯具结构的热特性。结果表明:最高温度点处于LED颗粒的中心处,最高温度可达67.31℃(仿真时),64.95℃(实验时)。散热底座半径对结构的最高温度影响最大。可以通过散热底座的设计来提高LED颗粒的热可靠性及车灯的使用寿命;亦为LED灯具结构设计提供了设计基础。     

COB塑料基板和玻璃封装的LED灯具双通道散热分析

提出了一种新的LED灯具封装方式,使用高导热玻璃壳和惰性气体替代传统的环氧树脂进行封装,使用塑料散热器代替传统铝基板,以达到双通道散热的效果。采用ANSYS有限元热分析软件,优化惰性气体层厚度,并通过改变LED个数和单灯功率与传统的陶瓷基板COB封装方式进行热仿真对比分析。研究表明,惰性气体层厚度为1.5 mm时散热效果较好,双通道散热灯具的热阻远小于单通道散热灯具热阻。由于玻璃与传统的环氧树脂相比,透光性高、不易老化、抗紫外线效果好,在大功率、密集型封装和紫外LED灯具大发展的市场环境下,这种新的封装方式应用前景广阔。     

大功率LED模组散热基板结构研究

大功率LED模组散热直接影响其光效和使用寿命。通过建立相应的有限元模型,运用有限元(FEM)分析方法,对大功率LED模组温度在散热基板内的分布进行模拟计算,采用嵌入高导热环的基板结构,提高大功率LED模组的散热效率。在此基础上,结合实际工艺,对高导热环结构参数的影响进行了详细分析,使导热环的尺寸和基板的散热效率达到最优。     

应用石墨片导热层压封装COB LED光源及其热性能

研究了加石墨片导热层的层压封装COB LED光源的热性能和水下环境运行的可靠性。采用COB技术制备了COB LED光源,并在COB LED光源和平面铝基板散热器之间加石墨片进行真空层压封装,然后对层压封装的COB LED光源模组进行了光谱和热性能实验。在900 mA恒流驱动条件下,测得COB LED光源的电压温度系数为-0.3 mV/K;对石墨片导热层层压封装的COB LED光源模组和未加石墨片的模组在水温25℃水环境下进行了运行对比实验,结果发现运行结温分别为49.28℃和63.67℃。实验结果表明,层压封装COB LED光源用石墨片导热层能有效降低运行结温,并适合在常温水下照明应用。     

Improving thermal conductivity of polymer composites in embedded LEDs systems

Polymer embedding of LEDs increases safety and waterproof levels in LED based lighting systems. The embedding allows for mechanical flexibility of these systems. The increase of polymer thermal conductivity has been a research challenge for decades. Here, we suggest materials for enhancing thermal conductivity in polymer embedded LED systems. We demonstrate that thermally conductive fillers into the polymer matrix to form a composite improved heat transfer from the LEDs to the environment. Non metallic boron nitride with a high intrinsic thermal conductivity is a good candidate. Thermal conductivity of basic polymer PDMS with various filler size and polymer ratios is reported here. Here, an in situ measurement tool to fast evaluate the quality of the composites in LED applications is demonstrated. Future work will focus on further increasing the thermal conductivity of the composites by using different mixtures.     

Design methodologies for reliability of SSL LED boards

This work presents a comparison of various LED board technologies from thermal, mechanical and reliability point of view provided by an accurate 3-D modelling. LED boards are proposed as a possible technology replacement of FR4 LED boards used in 400 lumen retrofit SSL lamps. Presented design methodology can be used for other high power SSL lamp designs. The performance of new LED board designs were evaluated by numerical modeling. Modeling methodology was proven by measurement on reference FR4 LED board. Thermal performance was compared by extracting of LED boards thermal resistances and thermal stress has been inspected considering the widest temperature operating range according to standards (−40 to +125 °C). Thermo-mechanical and reliability analysis have been performed to study parameters of each LED board technology, using thermal boundary conditions extracted from the thermal simulation of a whole LED lamp. Elastic–plastic analysis with temperature dependent stress–strain material properties has been performed. The objective of the work is to optimize not only the thermal management by thermal simulation of LED boards, but also to find potential problems from mechanical failure point of view and to present a methodology to design SSL LED boards for reliability.     

基于LED的校园照明节能控制系统

设计了一套适用于高校校园的LED照明节能控制系统,包括LED恒流驱动电源、光照度检测模块、红外热释电传感模块、计数模块和GPRS无线通信模块等。配套了18 W T8型LED灯管和50 W面板型两种LED灯具,分别用于替换教室荧光灯和校园道路路灯。驱动电源通用性好,支持12 V和24 V两种直流输入电压,最大输出功率可达150 W,且输出电压自适应,使其能够兼容多种串并方式的LED灯具。该系统同样适用于博物馆、大型酒店、地下停车场等照明需求量大的应用场合。     

一种高功率LED射灯的散热设计与实验研究

以一款MR16 LED射灯为模型,采用ANSYS有限元软件进行热分析。以散热器翅片保持60℃为标准,通过实验与仿真相结合的方法,分析了LED射灯的热流功率、散热器基座厚度、LED芯片间距、对流面积对整个系统散热性能的影响。结果表明,散热器对流面积是影响灯具散热性能的最重要因素;对一定的散热器,存在一个有效的最大芯片输入功率。现有MR16 LED射灯的散热器最大散热功率只能达到2.5 W左右,要使散热功率增大并且发挥散热器最佳性能,必须增加散热器的对流面积。对该结构散热器散热性能的定量研究对今后高功率LED灯具的生产具有一定的指导意义。     

大功率LED热特性测试评价方法研究

分析了大功率LED的热阻特性,结果表明不同厚度和热导系数的粘接材料热阻不同,而不同热阻的粘接材料对于LED热特性的实际影响一直缺乏有效的测量手段。采用热像仪拍摄热图的方法对粘接材料对LED热特性的影响进行了测试,测试结果表明热像仪成像可以作为大功率LED热特性测试评价的有效手段。     

Experimental and numerical approach on junction temperature of high-power LED

The understanding of thermal resistance and junction temperature is important in the area of designing efficient, long-lasting high-power Light Emitting Diodes (LEDs) and diode stacks. This paper developed a systematic evaluating program for investigating the effect of location and thickness on the thermal resistance and junction temperature of LED on an aluminum substrate. Structure function measurements were implemented by Thermal Transient Tester (T3ster) and Integrating Sphere on LED placed on an aluminum plate. The temperature distribution of LED was analyzed to understand the relationship between thermal resistance and location of the LED on the aluminum base. Meantime, to evaluate the validity of the test, the simulation is developed by considering structure properties. The simulation curve basically has a similarity with the experimental curve in the overall. It implies that the evaluating method can provide guidance in understanding thermal reliability of LED lamps and designing thermal management techniques.     

Lifetime assessment of Bisphenol-A Polycarbonate (BPA-PC) plastic lens,used in LED-based products

In this investigation, the accelerated optical degradation of two different commercial Bisphenol-A Polycarbonate (BPA-PC) grades under elevated temperature stress is studied. The BPA-PC plates are used both in light conversion carriers in LED modules and encapsulants in LED packages. BPA-PC plates are exposed to temperatures in the range of 100–140 °C. Optical properties of the thermally-aged plates were studied using an integrated sphere. The results show that increasing the exposure time leads to degradation of BPA-PC optical properties, i.e. decrease of light transmission and increase in the yellowing index (YI). An exponential luminous decay model and Arrhenius equation are used to predict the lumen depreciation over different time and temperatures. Accelerated thermal stress tests together with the applied reliability model are used to predict the lifetime of plastic lens in LED lamps in real life conditions.     

LED灯具在加油站照明中的模拟分析

本文探讨了LED灯具应用于加油站照明中的可行性与优越性。根据加油站的平面布局及不同功能区域的划分,选择合适的LED灯具并用专业的照明模拟软件进行了照明设计。模拟结果表明合理布置LED灯具的位置,不仅能满足各个区域的照度要求,并且能大大提高照明的均匀性。     

Thermal design for the high-power LED lamp

This paper summarizes different kinds of heat sinks on the market for high power LED lamps.Analysis is made on the thermal model of LED,PCB and heat sink separately with a simplified mode provided.Two examples of simulation are illustrated as a demonstration for the thermal simulation as guidance for LED lamp design.     

Thermal design for the high-power LED lamp

This paper summarizes different kinds of heat sinks on the market for high power LED lamps. Analysis is made on the thermal model of LED, PCB and heat sink separately with a simplified mode provided. Two examples of simulation are illustrated as a demonstration for the thermal simulation as guidance for LED lamp design.