环氧模塑料中导热通道的构造与导热性能

以低密度聚乙烯(LDPE)为原料,添加不同含量的高导热氮化硅陶瓷颗粒和短切玻璃纤维,熔融挤出不同直径的Si3N4/LDPE杆料。采用热模压法制备了环氧模塑料(EMC)。研究了杆料直径、陶瓷填充量对EMC导热性能、介电性能的影响。结果表明:在相同填充量下,杆料直径越大,样品热导率越大;5mm含玻纤杆料φ(填充量)为40%,热导率高达2.1W/(m·K)。样品的εr随杆料填充量的增大而显著减小,φ5mm含玻纤杆料填充量为40%时降至最低,为3.25(1MHz)。     

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。     

硅油及填料对导热硅脂接触热阻的影响

文中研究了不同种类硅油、不同金属氧化物导热填料及其颗粒直径大小分布、不同偶联剂种类等因素对导热硅脂产品的接触热阻、导热系数、界面厚度、粘度、耐渗油性等性能的影响。结果证明:二甲基硅油与球形氧化铝导热填料搭配使用可以获得更高的填料填充量,通过加入偶联剂可大大降低导热硅脂产品的粘度并提高导热硅脂的耐渗油性,而适中的导热填料颗粒大小分布以及较小的界面厚度可以得到高导热系数以及超低接触热阻的导热硅脂产品。     

无机导热粒子对铝基板导热性能的影响

随着电子信息产业的高速发展,对铝基板覆铜板导热性能的要求也越来越高,提升铝基板覆铜板导热率的关键在于提高绝缘层的导热率,绝缘层以环氧树脂为基体材料,填充的无机导热粒子间通过相互接触形成三维导热网络通路,从而提升铝基覆铜板的导热性能。实验结果表明,当基体材料与主要填充的三种无机陶瓷导热粒子的比例达到ＥＰ∶ＢＮ∶ＡｌＮ∶Ａｌ２Ｏ３＝ 1.9∶1∶3∶6时,绝缘层的导热系数最终可以达到2.8Ｗ/ (ｍ·Ｋ)。     

热管等效导热系数的数值模拟

为了分析热管简化模型的准确性,采用CFD(Computational Fluid Dynamics)软件Fluent对热管的等效导热系数进行了模拟,在导热系数的三种设定方式下,将简化模型热阻的模拟值与实验值进行了对比,结果表明各向异性模型比各向同性模型具有更高的精度。蒸发段和冷凝段的长度是影响模拟精度的主要因素,当蒸发段和冷凝段长度增大时,简化模型非传热方向上的导热热阻减小,适当减小该方向上的导热系数能更准确地模拟真实热管。     

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。     

基于激光热成像的局部导热系数测试

导热系数是表征材料传热能力的基本参数,与材料种类及成型过程中的温度、压力等工艺参数密切相关,因此制样测试可能无法反映真实产品特性,需要适用于不规则形状样品的局部导热系数测试技术。提出一种基于激光热成像的测试方法,通过减小传热时间来保证热响应仅对局部区域材料敏感,通过高分辨热像仪记录的温度场演变数据同时反演光斑分布和材料导热系数。使用粉末成型铁氧体样品进行实验验证,对规则样品进行10次重复实验,相对标准差为2.3 %,均值与Hot-Disk法测试结果的相对偏差为0.1 %;对不规则形状样品3个位置进行测试,最大相对偏差1.6 %。该方法有望用于不规则形状、小尺寸、非均匀材质部件的原位无损测试。     

激光闪射法测量双层材料导热系数的实验探索

通过设计不同厚度绝缘层的铝基板试样,使用激光闪射法测量其绝缘层及金属层的综合导热系数,并使用稳态热流法理论计算平均导热系数与之进行对比,指出两种测试方法存在的差异。分析了激光闪射法不适合用于测量双层材料综合导热系数的原因。最后引入平均导热系数与综合导热系数之间的计算关系式,说明激光闪射法测量双层材料导热系数的应用。     

精细水煤浆导热系数研究

对精细水煤浆的导热系数及测量方法进行了研究,给出了用热线法测量精细水煤浆导热系数的公式,并对精细水煤浆的导热系数进行了有效测量,测试结果的累计总误差小于±3％。     

高导热环氧模塑料的制备

介绍了导热系数大于3 W/(m·K)高导热环氧模塑料的制备。以低黏度多芳香环（MAR）环氧树脂和MAR酚醛树脂为基体,以偶联剂处理的球形氧化铝做导热填料,磷类做催化剂,经高速混合机混合、双螺杆挤出机挤出,合成高导热环氧模塑料。并研究了不同偶联剂类型对弯曲强度的影响。通过改变填充量至93%,导热系数最高可达5.6 W/(m·K),且有较好的弯曲性能和流动性能。     

Thermal Transport in Conductive Polymer–Based Materials

The demand for flexible conductive materials has motivated many recent studies on conductive polymer–based materials. However, the thermal conductivity of conductive polymers is relatively low, which may lead to serious heat dissipation problems for device applications. This review provides a summary of the fundamental principles for thermal transport in conductive polymers and their composites, and recent advancements in regulating their thermal conductivity. The thermal transport mechanisms in conductive polymer–based materials and up‐to‐date experimental approaches for measuring thermal conductivity are first summarized. Effective approaches for the regulation of thermal conductivity are then discussed. Finally, thermal‐related applications and future perspectives are given for conductive polymers and their composites.     

导热涂层对LED散热性能的影响

研究了导热涂层对不同发光颜色、不同封装数量的水下密闭环境下应用的发光二极管(LED)散热情况的影响,结果表明:红色LED的温度上升最慢,蓝色次之,绿色LED的温度上升最快;封装数量越多,LED的温升越快;在LED系统集成电路板上加入导热涂层能提高其散热效率,高导热率涂层的散热效果优于低导热率涂层.     

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.     

微波芯片元件的导电胶粘接工艺与应用

导电胶常用于微波组件的组装过程,其粘接强度、导电、导热和韧性等性能指标严重影响其应用范围.分析了导电胶的国内外情况和主要性能参数,总结了混合微电路对导电胶应用的指标要求.通过微波芯片元件粘接工艺过程,分析了导电胶的固化工艺与粘接强度和玻璃化转变温度的关系、胶层厚度与热阻的关系、胶点位置和大小与粘片位置控制等方面的影响关系.测试结果显示,经导电胶粘接的芯片元件的电性能和粘接强度等指标均满足设计和使用要求,产品具有较好的可靠性和一致性.     

Photopatternable Conductive PDMS Materials for Microfabrication

Conductive photodefinable polydimethylsiloxane (PDMS) composites that provide both high electrical conductivity and photopatternability have been developed. The photosensitive composite materials, which consist of a photosensitive component, a conductive filler, and a PDMS pre‐polymer, can be used as a negative photoresist or a positive photoresist with an additional curing agent. A standard photolithographic approach has been used to fabricate conductive elastomeric microstructures. Feature sizes of 60 µm in the positive photoresist and 10 µm in the negative photoresist have been successfully achieved. Moreover, as the conductive filler, silver powders significantly improve the electrical conductivity of the PDMS polymer, but also provide enhanced mechanical and thermal properties as well as interesting biological properties. The combined electrical, mechanical, thermal, and biological properties along with photopatternability make the PDMS‐Ag composite an excellent processable and structural material for various microfabrication applications.     

Highly Conductive Porous Graphene/Ceramic Composites for Heat Transfer and Thermal Energy Storage

A novel architecture of 3D graphene growth on porous Al₂O₃ ceramics is proposed for thermal management using ambient pressure chemical vapor deposition. The formation mechanism of graphene is attributed to the carbothermic reduction occurring at the Al₂O₃ surface to initialize the nucleation and growth of graphene. The graphene films are coated on insulating anodic aluminum oxide (AAO) templates and porous Al₂O₃ ceramic substrates. The graphene coated AAO possesses one‐dimensional isolated graphene tubes, which can act as the media for directional thermal transport. The graphene/Al₂O₃ composite (G‐Al₂O₃) contains an interconnected macroporous graphene framework with an extremely low sheet electrical resistance down to 0.11 Ω sq^?1 and thermal conductivity with 8.28 W m^?1 K^?1. The G‐Al₂O₃ provides enormous conductive pathways for electronic and heat transfer, suitable for application as heat sinks. Such a porous composite is also attractive as a highly thermally conductive reservoir to hold phase change materials (stearic acid) for thermal energy storage. This work displays the great potential of CVD direct growth of graphene on dielectric porous substrates for thermal conduction and electronic applications.     

非金属基导热材料对HPLED散热性能影响

由于光电转换效率较低,产生的多余熬已成为提升单位体积下大功率LED (HPLED)灯光输出量的主要瓶颈,使有效减少HPLED灯热流回路上各界面接触热阻成为重要课题.研究了不同的非金属基导热界面材料在不同环境温度条件下,应用于HPLED灯具模型中的第二界面处时对灯具散热情况的影响.结果表明,具有相变特征的非金属基导热界面材料.在其相变转化点位置之上的某一特定临界点后的热传导性能优于导热系数相对更高的非金属石墨基的界面材料.第二界面材料之间的接触热阻对发挥其导热能力有重要影响.