基于石墨烯复合材料的散热结构温度场分布有限元分析

高导石墨烯复合材料具有优异的热物理性能,与铜等传统热管理材料相比,具有密度低、导热性能好的优势,是非常理想的电子封装材料。但由于其高成本、低强度的缺点,严重制约了这类材料的应用。本文以课题组制备的石墨烯高导热复合材料为基础,采用复合材料作为关键散热部件材料,既利用了复合材料的定向高导热特性又解决了成本高、力学强度差的问题,并且通过ANSYS软件进行温度场模拟,成功将热源表面温度降低11.5℃,证明了在特殊区域,采用新型高导热石墨烯复合材料代替传统材料的手段,可以改善整个结构导热性能。研究成果为新型热管理材料在相关领域的应用提供了技术支撑。     

高频高速印制板材料导热性能的研究进展

随着电子技术的发展,对高频高速印制板导热性越来越高的要求。除了开发高成本的高导热性聚合物材料外,在聚合物中填充高导热性的无机材料也是提高高频高速印制板基材导热性能的有效方法,而且填充型复合材料可以用理论模型预测其导热系数。主要综述了填料的形貌、分布与表面改性对填充型复合材料导热系数的影响等方面的研究进展。     

电磁防护材料专题

题目：环氧树脂基导热复合材料的研究进展 作者：李冰、张晓伟 摘要：介绍了环氧树脂基导热复合材料的导热机理和导热模型,概述了国内外近年来在环氧树脂复合材料导热方面的研究开发和应用情况。     

聚合物基热界面材料的研究现状北大核心CSCD

热界面材料可以有效地改善两个固体界面间的热传导,对于电子器件的性能、寿命和稳定性起着至关重要的作用。近年来,小型化、集成化已经成为电子器件的发展趋势,电子器件的功耗不断提升,所产生的热量越来越高,对热管理提出了更高的要求,所以,热界面材料的创新与优化也备受关注。因此,综述了热界面材料的研究进展,包括导热填料的种类、填充量和性质对于复合材料性能的影响,特别介绍了复合材料中导热填料链状及网状结构制备,包括模板法制备填料导热网络、静电纺丝构建链状填料、外加电磁场控制填料的取向。最后总结了现阶段热界面材料研究的问题,展望了未来热界面材料的研究方向。     

环氧树脂/氧化铝复合材料的制备及导热模型

采用浇注成型法制备了环氧树脂/氧化铝复合材料,研究了氧化铝含量对所制复合材料导热、介电以及力学性能的影响.结果显示:当氧化铝含量小于体积分数0.3时,所制复合材料导热系数与Maxwell方程的计算值比较吻合,而混联模型更适合于预测氧化铝含量较高时的导热系数;该复合材料的介电常数随着氧化铝含量的增加而增加,弯曲强度随氧化...     

聚合物基复合封装材料导热性能的参数仿真

鉴于聚合物基复合封装材料导热性能传统研究方法的不足(效率低、预测模型不合理等),提出了一种基于VC++结合ANSYS和MATLAB联合编程的方法,对聚合物基复合材料的导热性能进行参数化有限元分析。用户只需要在由VC++开发出来的人机交互界面上输入复合材料的相关导热参数,即可由ANSYS与MATLAB相互协作完成导热模型的构建、模型导热率的数值仿真、结果输出的可视化处理等一系列工作。通过分析氮化铝填充环氧树脂复合材料的导热性能,检验了该方法的可靠性。研究结果表明,该方法不仅能够有效地预测实验结果,而且还方便易用。     

电子封装用高导热金属基复合材料的研究

高导热金属基复合材料具有优异的热物理性能,且密度较低,是非常理想的电子封装材料。但是由于其本身高的脆性和硬度,使得该材料很难通过二次机械加工成所需要的形状,严重制约了该材料的应用。本文总结了本实验室在第三代SiCp/Al电子封装材料以及第四代金刚石/Cu（或Al）电子封装材料的近净成形制备方面所取得的一些突破性成果,并就相关的关键工艺进行了讨论,论文最后对电子封装用高导热金属基复合材料未来的发展做出了展望。     

内嵌金属导热通道环氧模塑料导热性能与模拟

设计了垂直与水平两种导热结构,用高导热金属铜为填料在环氧模塑料（EMC）中进行填充,通过热模压法制备了样品。采用双热流计稳态法对样品导热系数进行了测试,采用ANSYS软件对EMC的热传导规律进行了模拟,并与实验结果进行比较分析。研究发现,随着铜填充量的增加,EMC的导热系数随之提高,填充量仅为25vol％时垂直导热结构试样导热系数高达104．62W／m·K。相同填充量下,垂直导热结构样品的导热系数远高于水平导热结构样品,垂直导热结构样品随着铜填充量的增加导热系数增加速度也明显快于水平导热结构样品,并出现明显的渗逾效应。模拟结果与实验结果符合较好。     

一类新型高导热环氧模塑料的制备

采用Si3N4陶瓷作填料,制备了一类新型高导热的环氧模塑料,研究了Si3N4的含量、分布及其形态对复合材料的导热性能及介电性能的影响。结果表明:随着Si3N4粉末体积填充量的增加,复合材料的热导率显著提高,当填充量体积分数为60%时,复合材料的热导率达到2.3W/(m·K),其介电常数随体积填充量的增加亦有所增加,但仍然维持在低水平。采用Agari模型进行理论计算的结果表明,该体系导热性能的提高与Si3N4填料之间热传导网络的形成有关。     

纳米添加剂对LED铝基板散热性能的影响

LED铝基板绝缘层的导热能力是影响大功率LED基板应用的主要因素.通过在环氧树脂中添加纳米级高导热填充物氧化铝、碳化硅、二氧化硅来提高绝缘层的导热能力,重点探讨填料种类、含量对基板绝缘层性能的影响,优化了填料配方.采用红外热像仪分析基板表面温度分布情况,通过散热实验测试铝基板的散热效果,结果证明导热效果良好.     

Thermal conduction at the nanoscale in some metals by MD

Miniaturization of electronic devices leads to nanoscale structures in the near future. As the system size decreases the heat dissipation density increases rapidly and the heat conduction becomes an important problem. Moreover, in very small systems the conduction is a size dependent phenomenon—conductivity decreases as the size decreases. We study the thermal conduction by phonons and its size dependency in seven metals, most of which are important in electronics. We use the molecular dynamic method with embedded atom potentials.     

Thermal properties of diamond/copper composite material

Thermal considerations are becoming increasingly important for the reliabilities of the electronics parts as the electronics technologies make continuous progress such as the higher output power of laser diodes or the higher level of integration of ICs. For this reason the desire for improving thermal properties of materials for electronics component parts is getting stronger and the material performance has become a critical design consideration for packages. To meet the demands for a high performance material for heat spreader materials and packages, a new composite material composed of diamond and copper was successfully manufactured under high pressure and high temperature. The effects of diamond particle sizes and the volume fractions of diamond on both thermal conductivity and the coefficient of thermal expansion (CTE) were investigated. The thermal conductivity of the composite material was dependent on both the particle size and the volume fraction of diamond, while the CTE was dependent only on the volume fraction of diamond. At the higher diamond volume fraction, the experimentally obtained thermal conductivities of the composite materials were above the theoretically expected values and the experimentally obtained CTE were between the two theoretical Kerner lines. This may be due to the fact that at the higher diamond volume fraction the diamond particles are closely packed to form bondings between each particle. The composite of diamond and copper have a potential for a heat spreading substrate with high performance and high reliability because not only its thermal conductivity is high but its coefficient of thermal expansion can be tailored according to a semiconductor material of electronics devices.     

An Anisotropically High Thermal Conductive Boron Nitride/Epoxy Composite Based on Nacre‐Mimetic 3D Network

Polymer‐based thermal interface materials (TIMs) with excellent thermal conductivity and electrical resistivity are in high demand in the electronics industry. In the past decade, thermally conductive fillers, such as boron nitride nanosheets (BNNS), were usually incorporated into the polymer‐based TIMs to improve their thermal conductivity for efficient heat management. However, the thermal performance of those composites means that they are still far from practical applications, mainly because of poor control over the 3D conductive network. In the present work, a high thermally conductive BNNS/epoxy composite is fabricated by building a nacre‐mimetic 3D conductive network within an epoxy resin matrix, realized by a unique bidirectional freezing technique. The as‐prepared composite exhibits a high thermal conductivity (6.07 W m^?1 K^?1) at 15 vol% BNNS loading, outstanding electrical resistivity, and thermal stability, making it attractive to electronic packaging applications. In addition, this research provides a promising strategy to achieve high thermal conductive polymer‐based TIMs by building efficient 3D conductive networks.     

Anisotropic Thermal Conductive Composite by the Guided Assembly of Boron Nitride Nanosheets for Flexible and Stretchable Electronics

Owing to the growing demand for highly integrated electronics, anisotropic heat dissipation of thermal management material is a challenging and promising technique. Moreover, to satisfy the needs for advancing flexible and stretchable electronic devices, maintaining high thermal conductivity during the deformation of electronic materials is at issue. Presented here is an effective assembly technique to realize a continuous array of boron nitride (BN) nanosheets on tetrahedral structures, creating 3D thermal paths for anisotropic dissipation integrated with deformable electronics. The tetrahedral structures, with a fancy wavy shaped cross‐section, guarantee flexibility and stretchability, without the degradation of thermal conductivity during the deformation of the composite film. The structured BN layer in the composites induces a high thermal conductivity of 1.15 W m^?1 K^?1 in the through‐plane and 11.05 W m^?1 K^?1 in the in‐plane direction at the low BN fraction of 16 wt%, which represent 145% and 83% increases over the randomly mixing method, respectively. Furthermore, this structured BN composite maintains thermal dissipation property with 50% strain of the original length of composite. Various electronic device demonstrations provide exceptional heat dissipation capabilities, including thin film silicon transistor and light‐emitting diode on flexible and stretchable composite, respectively.     

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.     

A review of selected thermal management solutions for military electronic systems

Thermal management of electronics is vital to the successful design, manufacture, and tactical operation of a variety of military electronic systems. Designs employ all modes of heat transfer including: conduction, natural and forced convection, aerodynamic heating, radiation, and two-phase heat transfer. A variety of heat sinks and heat exchange devices are employed, including the use of cold plates, electronic chassis coldwalls, compact heat exchangers, air-cycle and vapor-cycle refrigeration systems, phase change materials, thermoelectric devices, and heat pipes. This paper describes several military electronic systems on a variety of platforms and discusses the thermal management issues involved in the design of the thermal control systems. Specific examples are employed in the paper to emphasize the variety of thermal management problems encountered and the solution techniques employed.     

Development of conducting adhesive materials for microelectronic applications

Electrically and/or thermally conducting adhesive materials are classified into two categories depending on their conduction modes: isotropic and anisotropic materials. Silver-particle filled epoxy is the most common example of the class of isotropic materials which are conductive in all directions. This material has been long used in the electronic applications as a die-bonding material, where its good thermal conduction rather than its electrical conduction property is utilized. The silver-filled epoxy material has several limitations for high performance electrical interconnections, such as low electrical conductivity, increase in contact resistance during thermal exposure, low joint strength, corrosion issue due to silver migration, difficulty in rework, and so forth. The anisotropic conducting material provides electrical and/or thermal conduction only in one direction. An anisotropic conducting film (ACF) is used for interconnecting TAB mounted chips to a liquid crystal display panel, where fine pitch interconnection and low temperature assembly are required. In this paper, a brief review of the state-of-art conducting adhesive technology is provided. Subsequently, development of new conducting adhesive materials is presented for several different applications, which include high temperature materials for ceramic substrates, and low temperature materials for organic substrates.     

Thermal Conductivity of Amorphous Materials

Thermal conductivity is one of the most fundamental properties of solid materials. The thermal conductivity of ideal crystal materials has been widely studied over the past hundreds years. On the contrary, for amorphous materials that have valuable applications in flexible electronics, wearable electrics, artificial intelligence chips, thermal protection, advanced detectors, thermoelectrics, and other fields, their thermal properties are relatively rarely reported. Moreover, recent research indicates that the thermal conductivity of amorphous materials is quite different from that of ideal crystal materials. In this article, the authors systematically review the fundamental physical aspects of thermal conductivity in amorphous materials. They discuss the method to distinguish the different heat carriers (propagons, diffusons, and locons) and the relative contribution from them to thermal conductivity. In addition, various influencing factors, such as size, temperature, and interfaces, are addressed, and a series of interesting anomalies are presented. Finally, the authors discuss a number of open problems on thermal conductivity of amorphous materials and a brief summary is provided.     

Prospects of manufacturing organic semiconductor-based integratedcircuits

The driving force for developing organic thin-film transistor (OTFT)-based electronics is the fact that they are flexible, lightweight and have the prospect of low-cost manufacturing. Major barriers in the practical realization of OTFT-based electronic systems are the need for larger power supplies, lower gain, lower switching speeds and reliability problems. New directions leading to changes in the design of transistors, materials used in the fabrication, and processing techniques are warranted for developing process and equipment that can lead to the manufacturing of OTFT-based electronics. For developing dense OTFT-based electronics, the low thermal conductivity (as compared to silicon) of organic semiconductors is a fundamental problem. The use of nanodimension polymers with homogeneous microstructure, transistors operating in subthreshold region and the use of new materials (high and low dielectric constant dielectric materials as well as Cu as the conductor for interconnections) for fabricating transistors and a novel rapid photothermal processing technique for depositing thin films of organic semiconductors as well as for reducing the defects introduced during processing are some of the proposed directions that may lead to the manufacturing of OTFT based electronics     

高导热聚合物基复合封装材料及其应用

微电子封装密度的提高对传统环氧塑封料的导热性能提出了更高的要求,将高导热的陶瓷颗粒/纤维材料添加到聚合物塑封材料中可获得导热性能好的复合型电子封装材料。文章结合高导热环氧塑封材料的研究工作,评述了高热导聚合物基复合封装材料的材料体系、性能特点和在微电子封装中的应用情况。分析讨论了影响聚合物基复合电子封装材料导热性能和介电性能的因素,提出了进一步提高聚合物基复合电子封装材料导热性能的途径。