层压封装平面LED光源的耐候实验

研究了层压封装的平面LED光源在高温高湿与水下环境的可靠性。平面LED光源采用标准层压工艺封装,对封装后的LED模组进行高温高湿耐候试验与水下环境试验,并与未封装的LED模组进行对比实验。实验结果表明,在环境温度为80℃、相对湿度为80%,模组工作电流为300 mA,连续33天高温高湿条件下,层压封装的平面LED模组的照度变化和温度均高于未封装的LED模组。在40℃水下环境下连续工作400 h,层压封装的平面LED模组的照度略有变化,且光衰小于1%。因此,层压封装能有效阻断外界高温高湿环境对LED模组可靠性的影响,更适合在常温水下照明应用。     

基于石墨嵌入式结构的SiC功率模块热仿真与优化

SiC器件相比于Si器件,具有更高的功率密度,表现出高的器件结温和热阻。为了提高SiC功率模块的散热能力,提出了一种基于石墨嵌入式叠层DBC的SiC功率模块封装结构,并建立封装体模型。通过ANSYS有限元软件,对石墨层厚度、铜层厚度和导热铜柱直径进行分析,研究各因素对散热性能的影响,并对封装结构进行优化以获得更好的热性能。仿真结果表明,石墨嵌入式封装结构结温为61.675℃,与传统单层DBC封装相比,结温降低19.32%,热阻降低27.05%。各影响因素中石墨层厚度对封装结温和热阻影响最大,其次是铜柱直径和铜层厚度。进一步优化后,结温降低了2.1%,热阻降低了3.4%。此封装结构实现了优异的散热性能,为高导热石墨在功率模块热管理中的应用提供参考。     

基于烟囱效应的集成封装半导体照明光源散热结构优化设计

针对基于集成封装发光二级管(COB LED)的半导体照明光源,研究了引流孔的形状、尺寸和位置等对基于烟囱效应的散热器的散热特性的影响。CFD仿真模拟表明,对于50W热功率的COB LED散热结构,在导热板上形成两个面积为15cm2、以光源中心对称的矩形引流孔,可在保持COB LED最高温度小于52℃的条件下,将基于烟囱效应的散热器的重量进一步降低15%。实验结果与模拟结果基本一致。     

两种热电分离式基板导热性能的对比研究

基于热电分离式设计理念，开发出FR4/Cu与FR4/AlN两种高导热散热基板，并利用SMT工艺将13Ｗ的Osram S2W型LED灯珠分别与上述两种散热基板焊接后组装成LED模组，利用半导体制冷温控台恒定散热基板底部温度后，使用结温测试仪对LED的结温进行了测试，同时借助直流电源和积分球分别对LED的总功率和光功率进行了测量后得到了模组的热功率值。最后根据LED结温测试结果与热功率值计算得出了模组的热阻值，并在此基础上对两种基板的散热性能进行了对比研究。结果表明，FR4/AlN基板的散热性能较之FR4/Cu基板稍逊，当使用FR4/Cu基板散热时，LED的结温和热阻分别是49.72 ℃ 、2.21℃ /Ｗ，当使用FR4/AlN基板散热时LED的结温和热阻分别是51.32 ℃、2.32℃/Ｗ。     

基于ANSYS分析温度对荧光粉发光性能的影响

采用有限元方法模拟了LED集成封装光源和LED远程荧光集成封装(LED RPIP)光源各部分的热量分布。通过结合模拟和实验数据分析得到:随着LED结温升高,荧光粉温度随之上升,发光性能不断衰退,LED硅胶板和LED远程荧光板温度从室温35℃分别升高到73.794和73.156℃,光源光通量分别降低了30.53和22.39lm。最后得出硅胶板和远程荧光板中荧光粉发光性能分别下降了0.943%和0.78%。     

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...     

提高小功率白光LED热特性的新方法

在传统直插式LED封装方法的基础上,提出了一种在环氧树脂中添加氮化硼(BN)填料的改进LED封装工艺。测量了BN填料质量分数与导热系数的关系,利用有限元分析软件ANSYS分析和实验测试了采用改进封装工艺φ5 mm白光LED的芯片结温、热阻等参数,并与传统封装方法的白光LED进行比较。结果表明:采用改进封装结构φ5 mm白光LED结温比传统封装方法下降4.5℃,热阻下降了17.8%,同时提高了初始光通量,降低了光衰。     

一种新型LED模组设计及工艺创新

设计了小功率多芯LED COB(Chip on Board)封装结构,制作了多芯LED模组并在实验中进行了多芯片固晶、焊线关键封装工艺创新研究,测量了多芯COB LED模组的光通量、色温、工作电压等参数。测试结果显示:在直径为65 mm的圆形镀金基板上采用COB技术焊接88颗发光功率为0.06 W的蓝色小功率LED芯片,涂覆黄色荧光粉合成白光,抽样样本10个模组平均功率达到5.1 W,光通量为468.26 Lm,正向电压为13.6 V,色温为5 986 K,显色指数为89;工艺过程表明由镀金基板做过渡层把原来两个芯片间正负极单根长引线由两根短引线替代,创新工艺有效。     

大功率集成LED光转换光源的研制

介绍了一种应用远程激发技术的大功率集成LED光转换光源,通过使用固晶区无绝缘层的镜面铝基板进行集成封装蓝光LED光源,即COB光源。所制蓝光光源与远程激发荧光粉模块结合制成LED光转换光源。利用镜面铝基板的高导热系数,解决多种LED封装形式下芯片点亮温度过高、光源衰减快的问题。采用LED荧光高分子模块与蓝光芯片分离结合的远程激发技术制成白光光源,解决荧光粉分布不均、热老化、色偏移问题。通过与传统粉胶封装方式制得的大功率集成LED器件比较测试,该种光源具有防眩光、光色均匀度高、长寿命、节能和环保的优点,从而具有更广泛的用途。     

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%。     

Minimum-time thermal dose control of thermal therapies

The problem of controlling noninvasive thermal therapies is formulated as the problem of directly controlling thermal dose of the target. To limit the damage to the surrounding normal tissue, the constraints on the peak allowable temperatures in the selected spacial locations are imposed. The developed controller has a cascade structure with a linear, constrained, model predictive temperature controller in the secondary loop. The temperature controller manipulates the intensity of the ultrasound transducer with saturation constraints, which noninvasively heats the spatially distributed target. The main nonlinear thermal dose controller dynamically generates the reference temperature trajectories for the temperature controller. The thermal dose controller is designed to force the treatment progression at either the actuation or temperature constraints, which is required to minimize the treatment time. The developed controller is applicable to high and low-intensity treatments, such as thermal ablation and thermoradiotherapy. The developed approach is tested using computer simulations for a one-dimensional model of a tumor with constraints on the maximum allowable temperature in the normal tissue and a constrained power output of the ultrasound transducer. The simulation results demonstrate that the proposed approach is effective at delivering the desired thermal dose in a near minimum time without violating constraints on the maximum allowable temperature in healthy tissue, despite significant plant-model mismatch introduced during numerical simulation. The results of in vitro and in vivo validation are reported elsewhere.     

Compact thermal models for stochastic thermal analysis

An effective approach is proposed for constructing compact thermal models for the stochastic thermal analysis of electronics components and packages. This approach exhibits high levels of accuracy for small state space dimensions of the model. The achieved compact thermal models can be used to accurately approximate the stochastic properties not only of junction temperatures but also of the whole space–time temperature rise distribution within the electronics component or package.     

用扫描热显微镜研究材料表面微区热导分布

从集总参数模型出发,初步分析了热敏电阻型热探针的热传导机制和热物性测量机理,说明了扫描热探针的信号与样品表面温度、样品与探针间的热阻以及样品热导率等因素有关。在不同的工作条件下,可分别用以进行表面的温度分布和微区热导分布等热参数的测量。选定Ｓｉ－ＳｉＯ２标准样品,定性地讨论了表面形貌和样品热导率对测量结果的影响。把扫描热显微镜用于复合材料研究,得到的热像图提供了微区热导分布的信息。     

Carbon-black thixotropic thermal pastes for improving thermal contacts

This paper addresses thermal interface materials for thermal conduction of excess heat for microelectronic applications. Carbon black (30 nm) thixotropic paste based on polyol ethers is comparable to carbon black fluidic paste based on polyethylene glycol (PEG) in its effectiveness as a thermal paste, and in its dependence on pressure history. Prior pressure (up to 0.69 MPa) application is helpful. The optimum carbon black content is 2.4 vol.% for the thixotropic paste. The thermal contact conductance across copper surfaces is 30 × 10⁴ and 11 × 10⁴ W/m²-°C for surface roughness of 0.05 μm and 15 μm, respectively. The volume electrical resistivity is 3 × 10³ Ω-cm. Boron nitride (BN) (5–11 μm) and graphite (5 μm) thixotropic pastes are less effective than carbon black thixotropic paste by up to 70% and 25%, respectively, in thermal contact conductance, due to low conformability.     

Transient thermal analysis of sapphire wafers subjected to thermal shocks

Rapid heating and cooling are commonly encountered events in integrated circuit processing, which produce thermal shocks and consequent thermal stresses in wafers. The present paper studies the heat transfer in sapphire wafers during a thermal shock as well as the dependence of the wafer temperature on various process parameters. A three-dimensional finite-element model of a single sapphire wafer was developed to analyze the transient heat conduction in conjunction with the heat radiation and heat convection on the wafer surfaces. A silicon wafer was also investigated, for comparison. It was found that the rapid thermal loading leads to a parabolic radial temperature distribution, which induces thermal stresses even if the wafer is not mechanically restrained. The study predicted that for sapphire wafers the maximum furnace temperature of 800 /spl deg/C should be held for two hours in order to get a uniform temperature throughout the wafer.     

高导热电封装复合材料界面热传导的扫描热显微镜分析

本文利用扫描热显微镜（SThM),以微米级的空间分辨率,测量了SiC/Cu和SiC/Al电封装复合材料增强相－基体的界面特征和界面导热性能,SThM热图显示出材料界面导热性能的差异,对形貌数据和热数据进行统计分析和转换,确定了复合材料的界面宽度和界面导热率。     

Integrated-circuit thermal modeling

The static heat-flow problem has been solved analytically in three dimensions for a two-blocks structure. The computer program calculating the temperature maps is simple and fast. Examples are given of temperature profiles on the chip surface of a high-power IC.     

一种新型的高耐热、高阻燃、低介电损耗的热固性树脂的开发

文章介绍了马来酰亚胺与三嗪环改性的酚醛树脂通过MICHAEL加成反应形成的新型热固性树脂。这种新型热固性树脂与环氧树脂一起形成了二元共混体系,这个二元共混体系应用于覆铜板,使得覆铜板具有高耐热、高阻燃、低介电损耗的特点,而且机械性能和吸湿后耐焊性有很好的平衡。     

Influence of thermal contact resistance on thermal impedance of microelectronic structures

The thermal impedance Z_th(jω) has been calculated numerically for a silicon chip glued on a ceramic substrate. The non perfect thermal contact is taken into account by modelling the chip-substrate interface as a thermal contact resistance r_c. If Z_th is represented as a Nyquist plot, mainly two circular arcs are observed. The high frequency arc is found to be almost independent from r_c, whereas the low frequency part is largely influenced by r_c. The thermal resistance R_th = Z_th(jω = 0) increases linearly with r_c, as known from the literature. Additionally, our simulations have shown that similar conclusions can be drawn for the real and imaginary part of Z_th at a fixed frequency ω ≠ 0.