功率电子散热技术

现代功率电子设备功耗越来越大,体积越来越小,对散热的要求也越来越高。文章介绍了目前常用于功率电子设备的风冷、水冷、微管道散热器、热管技术等散热技术,阐述了各种散热技术的原理、特点,并介绍了最新的国内外学者的研究成果。     

一种雷达发射机散热系统的设计及改进

根据热源分布情况和发热元器件的散热要求，本发射机散热分强迫风冷与强迫水冷两种形式。目前，发射机内两冷却水回路压力损耗之差较大，因而要求水冷机柜水泵出口压力较大，这样就增加水泵的驱动功率。本文提出了一种较为合理的冷却回路联结方式，这对于降低回路压力损耗、提高系统可靠性具有重要意义。     

铜-硼/金刚石复合材料翅片热沉散热研究

采用气压浸渗法制备了热导率为850 W ? m-1 ? K-1的铜-硼/金刚石复合材料翅片热沉,测试了其在自然冷却、强迫风冷和强迫水冷三种冷却模式下的散热效果.结果表明,热源功率越高,铜-硼/金刚石复合材料的散热效果越显著.在强迫水冷模式下,当加热片的输入功率为80 W时,使用铜-硼/金刚石复合材料翅片热沉时加热片的最高温度比使用铜翅片热沉时低14℃,比使用铝翅片热沉时低23℃.Icepak热模拟发现,在强迫水冷模式下输入功率为80 W时,与铜和铝翅片热沉相比,铜-硼/金刚石复合材料翅片热沉的整体温度更低且温度分布更均匀.研究结果证实,铜-硼/金刚石复合材料是一种高效的散热材料,在大功率电子器件散热中具有广阔的应用前景.     

电子设备散热技术研究

随着微电子技术的发展,使得电子器件的热流密度不断增加,这样势必对电子器件有更高的散热要求,因此有效地解决散热问题已成为电子设备必须解决的关键技术.针对现代电子设备所面临的散热问题,就自然对流散、强制风冷散热、液体冷却、热管、微槽道冷却、集成热路、热电致冷等常用的电子设备散热技术及某些前沿的研究现状、发展趋势及存在问题分别予以阐述,希望对同行能有所帮助.     

CPU风冷散热器散热性能的实验测试

CPU风冷散热器作为最传统的散热方式,现在仍被广大PC机用户使用.按散热片材料分为全铝、全铜和铜铝复合式三种,其中铜铝复合式是现今主流产品.为对其散热性能进行测试,设计测试散热器散热性能的实验装置.通过改变输入电压,改变风道、风速和模拟芯片的发热功率,测试目前PC机使用最多的放射状铜铝复合式风冷散热器在不同风速、不同加热功率下强迫风冷时的散热性能.从它的瞬时储热能力、热阻及CPU表面温度三个方面分析其散热性能,得出这款散热器能较好地满足CPU发热功率在120 W以内的散热需求.实验测试装置具有通用性,实验结果有助于对此款散热器的改进,以提高其散热性能.     

高压大功率串级调速系统中斩波IGBT水冷散热系统的设计

针对直流升压斩波模块中IGBT的散热问题,提出一种较为实用的IGBT功率损耗的计算方法,并针对该问题设计出一套工程实用的水冷散热系统。首先对其水冷散热系统的热路等效分析,由相似理论得到散热系统的整体热阻的求解公式。然后对冷媒温度变化进行分析,得到散热系统内的热阻分配规律。最后得到水冷散热系统的一、二次冷却结构的有效的参数设计方法。以DYNEX的DIM800ECM33-F000型IGBT的水冷散热系统设计为例,理论计算结果以及工程实际应用情况证明,此设计方法切实有效。     

基于CAE技术的大功率磁控管散热系统设计

运用流体分析软件对大功率磁控管模型进行风冷流场和温度模拟,完成了输出功率为1．5kW和2kW的大功率磁控管散热系统设计。分别对磁控管内部叶片结构、散热片数量、厚度、材质及应用风压等级等参数进行计算,得到磁控管温升对以上各参数变化的敏感程度,结果显示磁控管温度在考察功率范围内与耗散功率呈线性关系,而散热系统设计参数的提高受到各种因素的限制。因此,在允许空载的情况下,对于输出功率超过2kW的大功率磁控管,风冷方式已经难以满足磁控管的冷却需求。     

行波管强迫风冷散热设计

本文利用流体仿真软件Fluent对一高功率螺旋线脉冲行波管进行散热器模拟计算,通过分析比较两种散热方案,表明在相同散热条件下,强迫风冷的散热能力明显优于传导冷却的方案;因此在条件许可时尽可能使用强迫风冷设计,利于提高行波管工作可靠性。     

一种基于水冷系统的先进IGBT散热模块设计

以磁悬浮列车牵引变流器中的单个IGBT模块为研究对象,鉴于目前IGBT模块功率越来越大,传统风冷散热模块难以满足其散热要求,设计了一款新型热管嵌入式IGBT水冷散热模组。通过Ansys Icepak软件对该冷却系统和设计的水冷模组的压力损失进行仿真分析,研究了增加圆柱形翅片和扁平翅片与不同入口流量对模块性能的影响。结果表明：与传统水冷模组相比,新型热管嵌入式IGBT水冷散热系统使IGBT模块芯片最高温度从81.51℃降低到75.34℃,降低约7.4%;最大温差从12.81℃降低到9.92℃,进一步提高了IGBT模块的芯片温度均匀性,验证了新型水冷系统具有良好的散热性能,满足IGBT模块的要求,为后续先进的水冷系统设计奠定基础。     

浅谈变频器散热技术的发展现状

随着变频器的越来越广泛的应用,变频器的散热技术的研究变得越来越重要。目前电力电子设备常用的散热技术有自然空气散热、强制风冷、水冷和热管等,本文阐述了这几种散热技术的工作原理及其特点。     

Pump Uniformity and Temperature Profile Measurements in a Planar Waveguide Nd:YAG Laser by a Beam Deflection Method

A planar waveguide laser using a large-core Nd:YAG waveguide and face-pumping by diode bars has produced a multimode power up to 160 W, with direct-contact water-cooling across the largest faces of the waveguide in the lateral direction. A method is reported that measures the nonuniform heat dissipation in the waveguide core and nonuniform water-cooling through deflection of a helium-neon laser beam passing through the waveguide claddings. Temperature gradients resulting from the varying heat transfer coefficient to the coolant are quantified, together with lateral thermal lens effects associated with edge-cooling and nonuniform pumping. The heat flux in the claddings is compared for two different waveguide structures, giving information on multipass face-pumping efficiency and uniformity.     

Towards a Thermal Moore's Law

Thermal design power trends and power densities for present and future single-core microprocessors are investigated. These trends are derived based on Moore's law and scaling theory. Both active and stand-by power are discussed and accounted for in the calculations. A brief discussion of various leakage power components and their impact on the power density trends is provided. Two different lower limits of heat dissipation for irreversible logic computers that have previously appeared in the literature are discussed. These are based on the irreversibility of logic to represent one bit of information, and on the distribution of electrons to represent a bit. These limits are found to be two or more orders of magnitude lower than present-day microprocessor thermal design power trends. Further, these thermal demand trends are compared to the projected trends for the desktop product sector from the International Technology Roadmap for Semiconductors (ITRS). To evaluate the thermal impact of projected power densities, heat sink thermal resistances are calculated for a given technology target. Based on the heat sink thermal resistance trends, the evolution of a consistent air-cooling limit is predicted. One viable alternative to air-cooling, i.e., the use of high-efficiency solid-state thermoelectric coolers (TECs), is explored in detail. The impact of different parasitics on the thermoelectric figure of merit (ZT) is quantified.     

Ultrasound applicators with internal water-cooling for high-powered interstitial thermal therapy

Internal water-cooling of direct-coupled ultrasound (US) applicators for interstitial thermal therapy (hyperthermia and coagulative thermal therapy) was investigated. Implantable applicators were constructed using tubular US sources (360 angular acoustic emittance, approximately 7 MHz) of 10 mm length and 1.5, 1.8, 2.2, and 2.5 mm outer diameter (OD). Directional applicators were also constructed using 2.2 mm OD tubes sectored to provide active acoustic sectors of 90 degrees and 200 degrees. A water-cooling mechanism was integrated within the inner lumen of the applicator to remove heat from the inner transducer surface. High levels of convective heat transfer (2100-3800 W/m2K) were measured for practical water flow rates of 20-80 mL/min. Comparative acoustic measurements demonstrated that internal water-cooling did not significantly degrade the acoustic intensity or beam distribution of the US transducers. Water-cooling allowed substantially higher levels of applied electrical power (> 45 W) than previous designs (with air-cooling or no cooling), without detriment to the applicators. High-temperature heating trials performed with these applicators in vivo (porcine liver and thigh muscle) and in vitro (bovine liver) showed improved thermal penetration and coagulation. Radial depth of coagulation from the applicator surface ranged from 12 to 20 mm for 1-5 min of sonication with 28-W applied power. Higher powers (41 W) demonstrated increased coagulation depths (approximately 9 mm) at shorter times (15 s). Thermal lesion dimensions (angular and axial expanse) produced with directional applicators were controlled and directed, and corresponded to the active zone of the transducer. These characteristic lesion shapes were also generally unchanged with different sonication times and power, and were found to be consistent with previous coagulation studies using air-cooled applicators. The implementation of water-cooling is a significant advance for the application of ultrasound interstitial thermal therapy (USITT), providing greater treatment volumes, shorter treatment times, and the potential for treatment of highly perfused tissue with shaped lesions.     

不同冷却速度对SMT焊点热循环寿命的影响

采用水冷、空冷和炉冷的不同冷却方式，对焊点的热循环寿命进行了初步研究，结果表明，对ＳｎＰｂ６０／４０钎料，空冷焊点的热循环寿命最高，水冷的最差。焊点的断面均是沿晶和穿晶的混合断口，并伴有疲劳辉纹，呈现蠕变和疲劳交互作用的断裂特征。     

钕玻璃激光器热容方式运行的能量特性研究

钕玻璃激光器采用双灯对称紧耦合非聚焦泵浦腔,先后以热容及常规水冷方式运行10 s（重复频率10 Hz）,分别记录100个光脉冲的脉冲能量.通过对比实验分析脉冲能量变化趋势,热容方式运行的钕玻璃激光器的平均输出功率及单脉冲能量均高于常规运行方式,约为1.4倍.结合理论计算,验证了热容激光器在抽运阶段输出的全部脉冲串能量的理论值.该结果对进一步了解钕玻璃激光器热容运行方式的输出特性具有一定的参考价值.     

Investigation on the CPU nanofluid cooling

The small physical size of electronic equipment, space limitation for installing air-cooling systems and high heat flux produced from a single chip have attracted a great deal of interest in more efficient heat dissipation equipment such as high-performance liquid cooling systems and mini-rectangular fin heat sinks. In this study, the influence of nanofluids on the performance of heat sink for CPU cooling is investigated experimentally and numerically. The former is carried out for water and nanofluid CuO-water at two solid concentrations of 0.86 and 2.25 vol.%. While in the latter, numerical simulations are validated for the laminar flow model with the application of the commercial package ANSYS Fluent 13. For the investigated range of mass flow rate and heat load (115 and 130 W), up to 7.7% of thermal conductance improvement is observed in case of nanofluids in comparison to water. The results of this study pave the way for more credible designs of cooling systems of electronic devices to promote a high-performance and longer life cycle.     

大功率LED封装有限元热分析

介绍了有限元软件在大功率LED封装热分析中的应用,对一种多层陶瓷金属(MLCMP)封装结构的LED进行了热模拟分析,比较了不同热沉材料的散热性能,模拟了输入功率以及强制空气冷却条件对芯片温度的影响.结果表明当达到热稳态平衡时,芯片上的温度最高,透镜顶部表面的温度最低,当输入功率达到3 W时,芯片温度超过了150℃,强制空冷能显著改善器件的散热性能.     

Immersion-cooled heat sinks for electronics: insight fromhigh-speed photography

The development of effective heat sinks for the primary heat-dissipating component of a typical portable electronics device is an ongoing challenge. Thermal management using air-cooling is limited by the inherently limited thermal properties of the coolant. Other alternatives, including liquid immersion cooling, phase-change materials, and heat pipes, may merit consideration if the basic mechanisms can be reliably predicted. This study sheds light on the nucleation characteristics of an etched cavity-enhanced surface for use in an immersion-cooled heat sink. The target application is a high-density multichip module with several heat dissipating sources. High-speed photography was used to record parameters such as bubble interactions, bubble size, departure frequency and active site density while varying the cavity spacing and heat flux. The cavities, which have a characteristic dimension of approximately 40 μm, are arranged in a square cluster 12.7 mm on each side. It was determined that the contribution of latent heat as a heat dissipation mechanism is only minor (less than 16%). In addition, it is proposed that the latent heat dissipation percentage may be used as a thermal performance indicator. Interactions between neighboring heat sources were also studied. These interactions decreased the bubble departure frequency and thereby affected the latent heat contribution     

三维多芯片组件的散热分析

建立了一种叠层多芯片组件结构，应用计算流体动力学方法(CFD)，对金刚石基板的三维多芯片结构进行了散热分析，模拟了器件在强制空气冷却条件下的热传递过程和温度分布。此外，还探讨了各种设计参数和物性参数对3D-MCM器件温度场的影响。     

Evaporation-condensation cooling systems for electronic equipment

The paper shows that heat pipes with metal-fibrous capillary structures and evaporation-condensation cooling system based on heat pipes are highly efficient means of providing optimal thermal conditions for different electronic instruments and devices. Such cooling system combining the functions of effective heating conduit (equivalent heat conductivity is much higher than the heat conductivity of the best heat-conducting materials) and effective radiator with the possibility of passive heat dissipation is characterized by a high heat transport ability, low thermal resistance, relatively small size and weight, reliable performance at different orientation in space under exposure to mass forces action. The paper presents examples of developed designs and investigations of heat pipes and evaporation-condensation systems with metal-fibrous capillary structures aimed at cooling the different heat generating items of electronic equipment. In this case, special types and designs of systems are discussed. These systems operate under different conditions of heat removal to absorbing medium and feature both a high heat transport ability and specific dielectric properties. In addition, the thermotechnical characteristics of proposed cooling systems are also presented.