基于纳米复合的超低介电材料

发布时间：2018-01-30 08:15

本文关键词： 超低介电常数纳米复合界面作用相结构成型工艺　出处：《西南科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着微电子工业的飞速发展,电子器件和集成电路正向着小型化、高密度化发展。元件密度和功能的不断提升对低介电技术提出了更多更高的要求。向材料中引入纳米孔洞可以降低介电常数(k),但k每降低0.1,至少需引入10%左右的孔隙率,因此达到超低介电往往需引入大量孔洞结构,牺牲材料的力学性能。近几十年来,纳米复合作为聚合物材料的改性手段,已经得到了广泛的应用。纳米复合的突出特点是可通过极小含量的纳米粒子显著改变聚合物的力学、热学、光学、电学等性质,其内在作用机制是通过纳米粒子大比表面积和强界面作用,诱导聚合物链在纳米粒子表面排列,产生受限作用,从而极大程度地改变聚合物性质。纳米复合的这一效应有望在调控低介电性质上发挥重要作用,同时相对于传统的化学或者多孔方法,纳米复合技术制备低介电材料还可进一步提高材料力学性能,也更为简单、高效,展现出显著的性能优势。基于上述思路,本课题采用几个典型的纳米复合体系,研究了纳米复合效应对材料低介电性能的影响并得到了超低介电常数(k=1.77)、低损耗(10-3)的纳米复合材料。以典型的纳米复合体系,线性低密度聚乙烯(PE)/二氧化硅纳米粒子(SNP)复合材料,为研究对象,研究纳米复合对介电性能的影响。采用直径为20 nm的SNP作为纳米填料粒子,通过热压成型复合得到一系列不同二氧化硅体积含量的纳米复合材料(PE/SNP)。介电测试发现,当二氧化硅体积含量为3.58%,复合材料的介电常数从2.43降低到k=1.93(10MHz),在这一测试频率(远高于1000Hz)下,介电常数主要由电子和分子极化决定,受定向极化、界面极化较小,因此主要与偶极子数量及排列方式有关。介电常数随着SNP含量增大,呈现先减小后增大的趋势。扫描电镜及密度测试结果表明PE/SNP纳米复合材料中仅存在极少量孔或缺陷,从而排除了多孔结构对材料介电性能的影响。DSC及XRD结果证明SNP对PE存在成核结晶作用,但SNP含量对成核作用影响较小,难以解释介电常数的变化规律。通过SEM对纳米复合体系相态进行了深入分析,发现PE在热压作用下呈现出各向异性的趋层状结晶结构。而SNP引入会引发PE围绕SNP成核生长,由此形成的PE/SNP聚集体会进一步团聚形成球形相结构,从而降低了材料的各向异性,研究还表明这一球形结构的规整性和含量与介电性能间呈现出直接关联,揭示了相结构及内在聚合物链排列对介电性能的影响和调控机制。通过调控纳米复合结构(纳米粒子的改性、成型压力及温度、填料尺寸、种类及维度),进一步研究纳米复合对材料介电性能的影响。首先,通过纳米粒子表面接枝及改变填料尺寸和种类直接调控界面效应,发现表面接枝聚苯乙烯的二氧化硅(G-SNP)与PE复合(PE/G-SNP)在二氧化硅体积含量为3.58%时介电常数为2.02,略高于PE/SNP。填料尺寸越大,纳米复合体系介电常数相对较高。球形纳米粒子相对于纳米棒粒子,降低介电常数效应更为明显。以上结果揭示了纳米粒子界面效应对介电性能有着重要影响,界面面积越大,作用越强,介电常数越低。另一个重要发现是,PE/SNP介电性能和相态结构与热压压力直接相关,在一定成型压力下,SNP才可产生显著的界面诱导作用,产生规整的球形相态结构,与之对应产生低介电效应。这一结果进一步证实了纳米复合效应对介电性能的作用机制。通过成型工艺筛选,获得较为理想的成型条件,当成型温度为155oC,成型压力2MPa时,复合材料介电常数最低,达到1.77,实现了良好的超低介电性能。
[Abstract]:With the rapid development of microelectronics industry, electronic devices and integrated circuits towards miniaturization, high density development. The density of components and function continuously put forward more requirements on low dielectric materials to introduce technology. Nano pores can reduce the dielectric constant (k), but the K is reduced by 0.1 each, at least the need to introduce about 10% porosity, so as to achieve the ultra low dielectric are often required to introduce a large number of holes, at the expense of the mechanical properties of materials. In recent decades, as a means of nano composite polymer materials, has been widely used. The outstanding feature of nano composite is mechanical, the minimum content of nanoparticles significantly change the polymer thermal, optical and electrical properties, its intrinsic mechanism is through the nanoparticles large surface area and strong interfacial interaction, induced polymer chain arranged on the surface of nanoparticles, have limited effect, Greatly change the properties of polymer nano composite. This effect is expected to play an important role in the regulation of low dielectric properties, and compared with the traditional chemical method or porous, nano composite preparation technology of low dielectric materials can also further improve the mechanical properties of the materials, but also more simple, efficient, showing significant performance advantages. Based on the above ideas, this thesis adopts several typical nano composite system, studied the effect of nano materials on the composite effect of low dielectric properties and obtain ultra low dielectric constant (k=1.77), low loss (10-3) nano composite material with nano composite system. The typical linear low density polyethylene (PE) / silica nanoparticles (SNP) composite material as the research object, effect of nano composite on the dielectric properties. The diameter of 20 nm SNP as the nano filler particles by hot pressing composite was The nano composite material to a series of different size silica content (PE/SNP). The dielectric tests show that when the silica content is 3.58%, the dielectric constant of the composite is reduced from 2.43 to k=1.93 (10MHz), in the test frequency (far more than 1000Hz), dielectric constant is mainly determined by the electronic and molecular under the direction of polarization, polarization, interface polarization is small, it is mainly related with the dipole number and arrangement of the dielectric constant with the increase of SNP content, decreased first and then increased. Scanning electron microscopy and density test results show that the defects of very small holes or only PE/SNP nano composite materials, eliminating the influence on the porous structure the.DSC and XRD dielectric properties of materials shows that the SNP of the existence of PE nucleation and crystallization, but has little effect on the content of SNP nucleation, difficult to explain the variation of dielectric constant of nano composite system by SEM. The phase is analyzed, showing a trend that PE crystalline layered anisotropic structure under the effect of heat and pressure. The introduction of SNP will lead to PE around the SNP nucleation and growth, resulting in the formation of PE/SNP aggregates further aggregated to form spherical phase structure, thereby reducing the anisotropy of the material, the study also showed that the spherical structure the regularity and content and dielectric properties are directly related, reveals the phase structure and the internal arrangement of polymer chains on the dielectric properties and regulation mechanism. Through the regulation of nano composite structure (modified nanoparticles, molding pressure and temperature, filler size, type and dimension), further study on effect of nano composite on the dielectric properties of the composites. Firstly, the grafted nanoparticles surface and changing the filler size and type of direct control interface effect, found the surface of silica grafted polystyrene (G-SNP) and PE composite (PE/G-SNP) in silica content is 3.58% the dielectric constant is 2.02, slightly higher than the PE/SNP. filler size, nano composite system relatively high dielectric constant. The spherical nanoparticles to nanorods particles, reduce the dielectric constant effect is more obvious. The above results reveal that the nanoparticle surface effect has an important effect on the dielectric properties. The interface is bigger, the stronger, lowerdielectricconstant. Another important finding is that the dielectric properties of PE/SNP and the phase structure and the pressure is directly related to the molding pressure, induced by SNP can create a significant interface, spherical regular phase structure generated, and the corresponding have a low dielectric effect. This result further confirmed that the mechanism of nano composite effect on dielectric properties. The forming process of screening, molding ideal conditions, when the molding temperature is 155oC, pressure molding When force 2MPa, the dielectric constant of the composite is the lowest, reaching 1.77, and good ultra-low dielectric properties are achieved.

【学位授予单位】：西南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33;TN04

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