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...     

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。     

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。     

The Effects of Si Submounts Containing Cu Thermal Vias on the Heat-Dissipation Characteristics of a High-Power Light-Emitting Diode Package

We investigated the effects of Si submounts containing Cu thermal vias on the heat-dissipation characteristics of a high-power light-emitting diode (LED) package. Simulations were used to determine the optimum conditions for effective heat dissipation from the LED. The optimum thickness of the Si submount containing the Cu thermal vias was 250 μm. The optimum heat flux area ratio between the Si submount and the LED chip was 25. The thermal resistance of an Si submount 250 μm thick and 25 mm² in area was 1.85 K/W without Cu vias. This value decreased to 1.50 K/W on incorporation of the 400-μm-diameter Cu vias. In addition, the total thermal resistance of the LED package structure was improved from 9.7 K/W to 8.3 K/W on incorporation of the 400-μm-diameter Cu vias into the Si submount.     

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。     

一种回路热管对大功率LED散热的研究

针对大功率LED散热能力较其它照明灯具差这一问题,研制了一种应用在多芯片大功率LED散热上的回路热管装置,并研究了热负荷、倾角等对热管的起动性、均温性和热阻等的影响。试验结果表明,所设计的热管散热器的热阻在0.48～1.47K/W之间;在蒸发器倾斜角为0°和30°时,蒸发器的均温性分别被控制在1.5℃和4.3℃以内。因此,将这种结构的热管应用在大功率LED散热系统中时,首先应该对蒸发器倾斜角度对系统散热性能的影响进行测试评估。     

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。     

5.6-W Broad-Area Lasers With a Vertical Far-Field Angle of 31$^{circ}$ Emitting at 670 nm

Highly efficient 670-nm high-power broad-area laser diodes with a single InGaP quantum-well embedded in AlGaInP waveguide layers and n-AlInP and p-AlGaAs cladding layers are presented. The developed vertical layer structure leads to a vertical far-field angle of 31deg. At 15degC, 100 mu-m-wide broad-area lasers reach an output power of 5.6 W limited by thermal rollover. The conversion efficiency was 41% at 1.5 W. A 7600-h reliable operation at 1.5 W and a mean time to failure of about 37550 h will be reported.     

Design and Simulation of High-power LED Array Packaging

Thermal management is one of the key technologies for high-power Light emitting diode（LED） entering into the general illuminating field. Successful thermal management depends on optimal packaging structure and selected packaging materials. In this paper, the aluminum is employed as a substrate of LED, 3×3 array chips are placed on the substrate, heat dissipation performance is simulated using finite element analysis（FEA） software, analyzed are the influences on the temperature of the chip with different convection coefficient, and optical properties are simulated using optical analysis software. The results show that the packaging structure can not only effectually improve the thermal performance of high-power LED array but also increase the light extraction efficiency.     

一种利用有限元法模拟LED芯片结点温度的方法

提出了一种以有限元法估算发光二极管(LED)光源模块结点温度的方法,提出了较详细的计算步骤,最后以6只1 W大功率LED组成的光源模块为例,演示如何以实测为基础,实测与软件试算相结合来估算LED光源模块的芯片结点温度.结果证明该方法具有较好的预测性,可以用来研究LED光源模块的温度分布,从而为研究LED封装材料匹配性、系统可靠性提供一定的参照.     

Failure modes and effects analysis for high-power GaN-based light-emitting diodes package technology

In this study, nondestructive test is developed to analyze the structure failure of LED package. The relationship between thermal resistance analysis and LED package failure structure is build with T3Ster thermal transient tester and scanning electron microscope (SEM). The failure LED device with defect in the attaching layer and gap between LED chip and copper are designed advisedly. The failure factors of LED package have been measured with thermal resistance analysis and SEM cross-section images. The thermal dissipation performance of LED with defect in the attaching layer is indicated by thermal resistance analysis combined with SEM cross-section images. The blister in attaching layer results in 4.4 K/W additional thermal resistance. The gap between LED chip and copper also makes high additional thermal resistance with 8.6 K/W. Different failures of LED packages are indicated obviously using thermal transfer analysis. The LED package failure structure such as interface defect between solder and cup-shaped copper is able to forecast without destructive measurement.     

Thermal simulation and optimization design on a high-power LED spot lamp

In this paper, thermal characteristics of the high-power LED spot lamp are reported. The emphasis is placed upon optimizing design of the heat sink of LED spot lamp using the optimization module and the orthogonal-experiment method. Results demonstrate that the weight of the heat sink is decreased to 46.1% of that for the initial structure, and the influence of each factor on junction temperature and weight of the heat sink is acquired by range analysis. Finally, the influence of ambient temperature and natural convection coefficient on the LED maximum temperature is analyzed. The results and the optimizing methodology are of great importance to the thermal design of LED lamps.     

一种通用低成本大功率高亮度LED封装技术

提出了一种热传导高、热膨胀匹配良好、低成本、大功率、高亮度LED封装技术。该技术采用光电子与微电子技术相结合，利用背面出光的LED芯片，倒装焊接在有双向浪涌和静电保护电路的硅基板上。由于在封装中引入了热膨胀过渡层，在保证良好热膨胀匹配的同时，热阻增加少。采用该封装技术封装的白光LED，发光稳定，光衰小，长期寿命高。     

Study on High-power LED Heat Dissipation Based on Printed Circuit Board

In order to study the role of printed circuit board(PCB)in high-power LED heat dissipation,a simple model of high-power LED lamp was designed.According to this lamp model,some thermal performances such as thermal resistances of four types of PCB and the changes of LED junction temperature were tested under three different working currents.The obtained results indicate that LED junction temperature can not be lowered significantly with the decreasing thermal resistance of PCB.However,PCB with low thermal res...     

Analysis of thermal characteristics and mechanism of degradation of flip-chip high power LEDs

The purpose of this study is to investigate the thermal behavior at the die-attached interfaces of flip-chip GaN high-power light emitting diodes (LEDs) using a combination of theoretical and experimental analyses. The results indicate that contact thermal resistance increased dramatically at the die-attached interfaces with aging time and stress, degrading the luminous flux. The junction temperature and thermal uniformity of the flip-chip structure both strongly depend on the arrangement of gold bumps. Local hot spots effectively reduce light output under high electric and thermal stress, influencing the long-term performance of the LED device. The results were validated using finite element analysis and in experiments using an infrared and an emission microscope. A two-step thermal transient degradation mode was identified under various aging stresses. A simulation further optimized the bump configuration that was associated to yield a low junction temperature and high temperature uniformity of the LED chip. Accordingly, the results are helpful in enhancing the performance and reliability of high-power LEDs.     

Experimental study on high-power LEDs integrated with micro heat pipe

Micro heat pipe (MHP) is applied to implement the efficient heat transfer of light emitting diode (LED) device. The fabrication of MHP is based on micro-electro-mechanical-system (MEMS) technique, 15 micro grooves were etched on one side of silicon (Si) substrate, which was then packaged with aluminum heat sink to form an MHP. On the other side of Si substrate, three LED chips were fixed by die bonding. Then experiments were performed to study the thermal performance of this LED device. The results show that the LED device with higher filling ratio is better when the input power is 1.0 W; with the increase of input power, the optimum filling ratio changes from 30% to 48%, and the time reaching stable state is reduced; when the input power is equal to 2.5 W, only the LED device with filling ratio of 48% can work normally. So integrating MHP into high-power LED device can implement the effective control of junction temperature.     

大功率LED照明的驱动和散热设计

对大功率LED光源的驱动电源和散热特性进行了分析。通过对大功率LED驱动电源的应用效率和光源热量产生、热源传导方式及热流特性的研究,提出了优化改进驱动电路设计和结构设计方法,在驱动电路设计中通过升/降压恒流电路、采用工频变压整流设计提高电源的利用率,降低电源耗热;在结构设计中通过优化改进翅片材质及界面材料、改进翅片结构、加装热管和均温板几种方式进一步提高散热效果,从而使产品的质量和性能得到全面提升。     

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.     

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。