影响功率器件散热器散热性能的几何因素分析

型材散热器的几何结构由肋片和基座构成，主要几何参数包括肋片长、肋片厚，肋片数、基座厚、基座宽等，研究了型材散热器几何因素对其热性能的影响，通过改变散热器的几何参数，可以有效的降低散热器的热阻，获得好的散热效果。本文的研究为型材散热器的的选择及优化设计提供了依据。     

基于微通道散热的大功率LED阵列的热阻研究

采用微通道致冷技术,设计了大功率LED阵列的外部热沉.针对直鳍片微通道结构的散热器,理论分析了影响其热阻的因素,推导了热阻表达式,并对微通道散热器的结构参数进行了优化,指出当通道宽度取某一数值时,散热器的热阻可达到最小.利用MATLAB软件,对LED的热阻与微通道散热器的结构参数和冷却液的压力关系进行了仿真,给出了直观的关系曲线.     

LED导热胶片性能研究与评估

大功率LED器件的基座与散热基板之间的接触热阻会阻碍其芯片PN结与散热基板之间的热传导,从而影响到器件的光、色、电性能及寿命。导热胶片用于填充材料界面之间接合或接触时产生的微空隙及表面凹凸不平的孔洞,是减小接触热阻、降低芯片PN结温度的有效手段。文章主要通过测定热阻值来开展对导热胶片在实际应用中导热性能的研究。通过阻容...     

温度对压接型IGBT器件内部接触热阻的影响

温度是功率半导体器件备受关注的问题,不仅直接影响功率半导体器件的电气性能,而且还间接影响功率半导体器件的热学和机械特性.压接型IGBT器件内部是电磁场、温度场和结构场的多物理量耦合场,器件内部各组件间的接触热阻是温度场与结构场双向耦合的重要桥梁,也是器件可靠性的重要影响因素.通过单芯片子模组有限元模型分析了各组件间的接触热阻,重点研究了温度对接触热阻的影响,计算了热阻测量前后的接触热阻值,并进行了对比.鉴于目前接触热阻测量方法的局限性,通过测量单个快恢复二极管(FRD)芯片子模组结到壳热阻值与温度的变化关系间接得到接触热阻与温度的关系,并对有限元计算结果进行了验证.     

LDMOS热阻的电学法测试与分析

基于结构函数理论,运用电学测试法,提取封装LDMOS导热路径上各层材料的热阻值,以及管壳与恒温平台之间的接触热阻值。对各层热阻进行分析,发现焊料层的热阻远大于理论值,提出了一种减小焊料层热阻的方法。改变管壳与恒温平台的接触情况,分别测出不同接触情况下的热阻值,对比发现接触情况会影响结到壳热阻的大小,提出了减小接触热阻的方法。     

基于接触位置的扩散热阻研究

本文利用热瞬态分析仪T3ster测试了大功率LED封装阵列中不同阵列点热阻的变化,得到结论：在散热基板中心点处热阻最小,距中心点越远热阻越大,并且热阻与距离呈线性关系。通过分析得到热阻增加的部分为扩散热阻,所以扩散热阻应作为大功率LED封装阵列设计的考虑因素之一。     

集成电路封装热阻分析

集成电路热阻是集成电路特别是功率型电路的主要可靠性参数。在一定功率下,它决定了电路工作时的结温,在进行系统热设计、可靠性预计时都要考虑电路的热阻。集成电路热阻测试方法是我国微电子工业尚待解决的问题,也是当前研究重点之一。本文介绍采用统一热分布的标准芯片测试电路热阻的方法,并分析不同封装形式、不同粘片工艺、不同芯片面积以及不同生产厂对电路热阻的影响。     

提高晶闸管结温的途径

目的:本文分析了晶闸管结温温度上升的主要原因,探讨了如何提高晶闸管的结温温度。方法:通过分析晶闸管的结壳阻值、接触热阻和散热器热阻的各种影响因素来观察晶闸管结温温升的情况。结果:运用的分析方法对提高晶闸管结温温度具有研究意义。结论:可以尽量降低晶闸管的接触热阻和散热器热阻阻值,提高晶闸管的压接工艺,使用优质的接触介质,增大晶闸管的散热面积,提高散热器的风速风压,改变风流状态等,来提高晶闸管结温的温度。     

ANSYS 接触单元在接触热阻仿真中的应用

收集极的散热性能是对空间行波管稳定性和可靠性的一个重要影响因素。本文基于简化的单级收集极进行热 分析,提出了一种将接触热阻引入散热性能分析过程中的新方法,利用ANSYS 中自带的接触单元CONTA172 和 TARGE169 来模拟接触热阻的存在,较以前在模拟时采用仿真薄层的方法更加直接、简便,解决了利用仿真薄层划分 网格困难、计算量大的难题。     

扩散热阻对FR4/AlN复合材料导热性能的影响

首先,将AlN陶瓷表面金属化后分别切割成10 mm×10 mm×1.0mm、12 mm×12 mm×1.0 mm及15 mm×15 mm×1.0mm的方块,嵌入环氧树脂中制备成FR4/AlN复合材料;然后,利用SMT工艺将同款LED灯珠与上述内置三种不同尺寸AlN的复合基板材料组装成LED模组;最后,利用结温测试仪与半导体制冷温控台对三种LED模组分别进行了结温测试.同时,结合热仿真手段对复合材料水平面的温度分布情况进行了模拟研究.结果表明:上述三种尺寸陶瓷片对应LED的结温分别为96.95、92.94与91.81℃.热仿真结果显示,陶瓷片尺寸通过界面热阻对扩散热阻产生影响,增大陶瓷片尺寸有助于降低扩散热阻,进而改善FR4/AlN复合材料的整体散热性能.     

LED筒灯复合结构热管散热器的数值模拟

为解决LED筒灯使用单纯自然对流散热扩散热阻过大、温度分布不均的问题,提出一种基于平板热管和热虹吸管的复合结构热管散热器,并用数值模拟的方法研究了热功率、翅片高度、翅片数目、辐射换热对该散热器性能的影响。模拟结果表明应用于LED筒灯的复合结构热管散热器的热阻随着热功率的增加而减小,翅片高度和翅片数目存在一个最优值,使得散热器温度和热阻最小,自然对流情况下不可忽视辐射换热的作用。     

Performance of Isotropic and Anisotropic Heat Spreaders

Anisotropic heat spreaders (flexible graphite and continuous carbon fiber polymer-matrix composite) and isotropic heat spreaders (copper and aluminum) have been evaluated numerically in terms of thermal resistance. Anisotropic ones are attractive for their through-thickness thermal insulation ability. Flexible graphite is superior to carbon fiber composite in providing lower thermal resistance. Carbon fiber composite is advantageous in its superior through-thickness thermal insulation ability and its smaller critical thickness (the optimal thickness for maximizing heat spreading while minimizing thickness). The isotropic heat spreaders are superior to the anisotropic ones in providing low thermal resistance, provided that the thickness is large, but they do not have the through-thickness thermal insulation ability. A higher value of the in-plane thermal conductivity enhances the effectiveness of flexible graphite. As the heat source area decreases, the thermal resistance increases while the critical thickness decreases. For the same heat source area, a greater in-plane dimension of the heat source perpendicular to the intended heat spreading direction decreases the thermal resistance and critical thickness. Flexible graphite is comparatively more advantageous when the thickness is smaller and when the heat source area is larger. For the same thickness below 2?mm, flexible graphite with in-plane conductivity of 1500?W/(m?K) is superior to copper and that with in-plane conductivity of 600?W/(m?K) is superior to aluminum. The highest thermal conductance obtained is 6.1?×?10⁴?W/(m²?K) when the thermal interfacial resistance is neglected and 5.1?×?10⁴?W/(m²?K) when this resistance is included. The conductance increases with decreasing heat source area and with decreasing heat spreader length.     

Heat Flow Pattern and Thermal Resistance Modeling of Anisotropic Heat Spreaders

To ensure safe operating temperatures of the ever smaller heat generating electronic devices, drastic measures should be taken. Heat spreaders are used to increase surface area, by spreading the heat without necessarily transferring it to the ambient in the first place. The heat flow pattern is investigated in heat spreaders and the fundamental differences regarding how heat conducts in different materials is addressed. Isotropic materials are compared with anisotropic ones having a specifically higher in-plane thermal conductivity than through plane direction. Thermal resistance models are proposed for anisotropic and isotropic heat spreaders in compliance with the order of magnitude of dimensions used in electronics packaging. After establishing thermal resistance models for both the isotropic and anisotropic cases, numerical results are used to find a correlation for predicting thermal resistance in anisotropic heat spreaders with high anisotropy ratios.     

多孔侧肋双层微通道热沉构形优化

建立了多孔侧肋双层微通道复合热沉模型,选取最大热阻最小化为优化目标、热沉单元端面纵横比为优化变量,在热沉总体积和流体区域体积占比给定的条件下,对复合热沉进行了构形优化,并分析了冷却剂入口速度、多孔材料孔隙率、上下通道高度比、流体区域体积占比、肋厚比等参数对热沉最优构形的影响.结果表明:给定初始条件,优化热沉单元端面纵横比,可使最大热阻减小21.19％;在热沉单元端面纵横比较小时,减小孔隙率有利于降低最大热阻,而在热沉单元端面纵横比较大时,存在最优的孔隙率使得最大热阻最小;上下通道高度比和肋厚比的改变均未影响热沉最优构形.     

微通道液冷冷板散热特性研究

本文研究了3种典型构型微通道冷板的散热特性,分别为冷板盖板与翅片焊接、冷板盖板与翅片不焊接以及翅片双面插排形式。对比了3种不同构型冷板的散热能力并对3种构型冷板的流阻特性进行了研究,发现翅片排布越密集流阻越大,越不利于整个液冷系统的流量分配。研究了冷却液流量对功率芯片温度的影响,发现冷却液流量较小时,流量增加可大幅降低芯片温度,当冷却液流量足够大时,冷却液流量对芯片温度影响不大。通过对不同翅片高度和不同单边厚度的冷板进行研究,发现翅片高度6mm工况下当翅片和盖板间隙0.3mm时冷板散热能力最强,其余厚度冷板翅片盖板间隙0.2mm时散热能力最强。冷板单边厚度越小,传热热阻越小,功率器件温度越低。     

CPU散热器的优化设计及数值模拟

散热器的散热性能对维持中央处理器(CPU)的运行速率和使用寿命具有重要影响.通过对CPU散热器进行热设计,优化散热器的结构,采用热阻分析法建立CPU散热器的数学模型,利用CFD数值模拟方法研究不同肋片长度的CPU散热器的散热性能,并对肋长为21mm的CPU散热器进行案例分析.研究结果表明:实验范围内,加长散热器肋片长度到27mm可有效降低传热热阻,提高散热性能;超过该长度,肋片长度的增加对散热性能的影响不大.     

Heat spreading in a thin longitudinal fin

In view of the trend towards higher power densities in ever shrinking geometries, understanding heat spreading fundamentals is gaining importance. In this paper heat spreading in thin longitudinal geometries is considered. This geometry is of practical interest in one-dimensional Cartesian geometries. A characteristic length is derived and it is shown that this has physical significance for the distance that heat spreads, and for the total amount of heat cooled away. Furthermore, it is investigated when “thin” is a viable assumption. The use of the characteristic length is illustrated for the case of a line source cooling to a plate and for the case of the fins of a plate heatsink. The results are compared to numerical simulations. The work is an extension of the authors' earlier work on heat spreading in infinite longitudinal geometries and heat spreading in infinite and finite circular geometries.     

Heat transfer from square pin-fin heat sinks using air impingement cooling

Experimental and numerical results are presented for heat transfer from a C4 mounted organic land grid array (OLGA) thermal test chip cooled by air impingement. Five heat sink geometries were investigated for Reynolds numbers ranging from 9,000 to 26,000. The dimensionless nozzle-to-heat sink vertical spacing z/D was varied between 2 and 12. In this study, we investigate the interactions between heat sink geometry, flow conditions and nozzle setting and how they affect the convective heat transfer and overall cooling of the test chip as measured by total thermal resistance /spl theta//sub ja/. Optimizing fin arrays by minimizing the overall heat sink thermal resistance instead of focusing solely on maximizing the heat transfer from the fins is shown to be a better design criterion. We also provide results that show cooling performance gains can be obtained by inserting a deflector plate above the heat sink.     

Performance Analysis of Pin-Fin Heat Sinks With Confined Impingement Cooling

This work assesses the performance of pin-fin heat sinks with confined impingement cooling using numerical simulation. The extent to which the Reynolds number, the height and the width of the fins, the nozzle-to-heat sink distance, the thermal conductivity, the upper confining plate and the fin number affect the thermal resistance are considered. The work shows that increasing the Reynolds number reduces the thermal resistance, but the effect decreases slowly as the Reynolds number increases. Although increasing the fin height can reduce the thermal resistance, reduction decreases. The fin width that is associated with the minimum thermal resistance increases with the Reynolds number. The optimal nozzle-to-heat sink distance increases with the Reynolds number. The thermal resistance decreases with an increasing thermal conductivity; however, the drop in the thermal resistance becomes smaller. The presence of the upper confining plate increases the thermal resistance. Additionally, the thermal resistance initially decreases and then increases slowly as the fin number increases.     

直热管传热系统热阻的试验研究

对常温直热管传热系统的总热阻进行了试验研究,着重分析了真空和大气环境下该系统裸接并用不同的螺钉扭矩安装时热管的总热阻及热管与热端安装面、冷端安装面的热阻。研究表明,试验环境对该系统的传热能力有一定的影响,热端和冷端安装面在真空中的热阻均比在大气环境中的大。螺钉的安装扭矩会影响接触面的热阻。两种环境中,在一定的热负荷下,冷端安装面在扭矩为0.4 Nm时的热阻约是扭矩为1.2 Nm时的2.4倍。