【作者】 杨贵；

【导师】 申长雨； 苏凤梅；

【作者基本信息】 郑州大学 ， 材料加工工程， 2021， 硕士

【摘要】 随着5G时代的到来,电子设备朝着小型化、集成化、多功能化、高功率密度化发展,随之而来会产生大量的热,如果这些热不能及时散去,热积累会影响电子器件的性能,甚至导致电子器件不能正常工作或损坏,因此对电子设备的散热性能提出了更高的要求。聚合物基导热材料因具有电绝缘性能、柔韧性、重量轻、强度高等优点而备受关注,在微电子封装领域有巨大的应用潜力。然而,聚合物的本征导热系数一般较低,无法满足散热要求。引入高导热填料,如氧化铝（Alumina,Al₂O₃）、氧化镁（Magnesium Oxide,Mg O）、氮化铝（Aluminum Nitride,Al N）、氮化硼（Boron Nitride,BN）、碳化硅（Silicon Carbide,Si C）等,是提高聚合物导热系数的有效途径,并且具有低成本、易加工、易工业化等优点。然而,采用传统加工方法进行共混,填料在复合材料内部随机分布,填料和填料之间不能互相搭接形成导热网络,填料和基体之间存在较大的界面热阻,这限制了聚合物导热复合材料的发展。因此,通过合理的填料结构设计,尽可能在聚合物基体中形成连续的传热导通路,是实现聚合物复合材料高导热率的关键。基于该研究思路,本论文开展了以下两方面的工作,具体如下:（1）采用静电纺丝-静电喷涂-热压的方法制备了高导热的聚乙烯醇（Polyvinyl Alcohol,PVA）/氮化硼纳米片（Boron Nitride Nanosheets,BNNS）复合材料。该PVA/BNNS复合材料具有高的面内导热系数。一方面是因为我们通过硼酸（Boric Acid,BA）辅助球磨的方法得到了少层的和大的侧向尺寸的BNNS。另外一个重要的因素是BNNS选择分布在PVA纤维表面,热压之后,BNNS互相连接并沿着面内方向取向,在复合材料内部构成良好的导热通路。此外,纳米复合材料的面内导热系数表现出明显的厚度依赖性,即导热系数随着复合材料厚度的降低而提高。当BNNS含量为40 wt%,复合材料厚度为30μm时,面内导热系数达到19.99 W/（m·K）。本工作可以提供一种实用的方法制备高导热复合材料用于高功率密度的电子器件散热。（2）以PVA为基体,以BNNS和银纳米线（Silver Nanowire,Ag NW）为填料,通过静电纺丝-喷涂-热压的方法制备了PVA/BNNS-Ag NW高导热复合材料。利用静电纺丝技术可以使BNNS沿着一维PVA纤维排列,在PVA/BNNS纤维膜上喷涂Ag NW后,一维Ag NW搭接BNNS,热压之后,Ag NW-BNNS在PVA/BNNS-Ag NW复合材料内部构建了沿着面内方向取向的杂化网络。实验结果表明,在喷涂少量Ag NW的情况下,该复合材料的面内导热系数明显提高。此外,该复合材料还表现出良好的电绝缘性。实验结果表明,PVA/BNNS-Ag NW复合材料在LED灯的散热应用方面表现出好的散热能力,在高性能电子器件的散热方面有很大的应用潜力。更多还原

【Abstract】 With the advent of the 5G era,electronic devices are developing towards miniaturisation,integration,multi-function,and high power density,resulting in the generation of excessive heat,which puts forward higher requirements for the heat dissipation performance of electronic devices,as the accumulation of heat seriously affects their performance and even leads to their failure.Polymer-based thermal management materials have drawn much attention as they possess advantages in electrical insulation performance,flexibility,lightweight,high strength,etc,which have great application prospects in the field of microelectronic packaging.However,the intrinsic thermal conductivity of polymers is generally low and cannot meet the requirements of heat dissipation.Incorporating high thermally conductive fillers,such as alumina（Al₂O₃）,magnesium oxide（Mg O）,aluminum nitride（Al N）,boron nitride（BN）,silicon carbide（Si C）,etc.,is an effective way to enhance the TC of polymers;it has the advantages of low cost,easy processing,industrial applicability,etc.The conventional method with randomly dispersed composite leads to heat flow in unintended directions in the composite,and limits the enhancement of thermal conductivity,due to the low probability of contact between fillers,and the high interfacial thermal resistance between fillers and polymer matrix.Forming continuous heat transporting paths of fillers in a polymer matrix as much as possible by rational structure design of fillers,which is believed to be the key to achieving high thermal conductivity composites.Based on this research idea,two aspects of work are carried out in this paper,the main contents are as following:（1）In this study,polyvinyl alcohol（PVA）/boron nitride nanoplatelets（BNNS）composites were fabricated with high in-plane TC via the combination of co-electrostatic spinning and spraying and hot-pressing technique.The high in-plane TC of the composites was due to the large lateral size of 2D BNNS,which was obtained via boric acid-assisted ball milling.Another paramount structural factor is the selective distribution of these BNNS on the surface of 1D PVA fibres.These interconnected BNNS are oriented along the in-plane direction after pressing,which construct continuous heat conduction pathways in the composites.Additionally,the in-plane TC of the composites shows obvious thickness dependence,that is,the in-plane TC increases with the decrease of the thickness of the composites.The in-plane TC reachs 19.99 W/（m·K）with a thickness of 30μm at BNNS fraction of40 wt%.Thus,this work provid a practical approach to fabricate ultrahigh in-plane TC composites,which will be used for the thermal dissipation of high power density electronic equipment.（2）Here,PVA/BNNS-Ag NW composites were fabricated with high in-plane TC via the combination of electrospinning and spraying and hot-pressing technique.Typically,BNNS can be arranged along fibers by electrospinning technique.Then spraying Ag NW on PVA/BNNS fiber film,a hybrid network oriented along the in-plane direction was constructed by Ag NW bridged BNNS in PVA/BNNS-Ag NW composite after hot pressing.The in-plane TC of the composites is significantly improved when a small amount of Ag NW is sprayed.In addition,PVA/BNNS-Ag NW composite exhibit good electrical insulation.The results demonstrated that PVA/BNNS-Ag NW composite show good heat dissipation capacity in the heat dissipation application of LED lights,so it has a great application potential in the heat dissipation of high-performance electronic devices.更多还原