可热交联的含氟聚硅氧烷的合成及性能研究

Polysiloxanes have been widely used in many areas such as electronic/electrical, microelectronic industries due to their high stability and excellent insulating properties. With the rapid development of large-scale integrated circuits (IC) and high-frequency communication technology, the application of polysiloxanes is facing a challenge. Because organic materials with low dielectric constant (Dk<2.5), low dissipation factor(Df) and good bonding strength are urgently required for insulting encapsulation resins for IC dies as well as a matrix for the fabrication of high-frequency printed circuit boards (PCB). Although polysiloxanes possessing good thermal stability and bonding strength, their Dk and Df are unable to meet the growing requirements. Polytetrafluoroethylene and polybutadiene are ideal dielectric materials used at high frequency, but their inert interaction to substrates greatly hinders their application. It is noted that introduction of fluoro groups to polysiloxanes can lower their Dk while keeping their good bonding strength. However, fluorinated polysiloxanes with low Dk and high thermal stability are rarely reported, thus developing this kind of fluorinated polysiloxanes is of great significance. In this project, we will explore the synthesis of new directly thermo-crosslinkable fluorinated polysiloxanes and study the relationship between their structures and properties to provide a new approach to obtain fluorinated polysiloxanes with low Dk and high thermal stability . This research will not only be instructive to molecular design of this kind of fluorinated polysiloxanes, but also can develop a series of new low Dk materials with good overall properties.

聚硅氧烷具有优良的耐热性、低介电性能等，被广泛应用于电子电气和微电子领域。然而，近年来随着大规模集成电路和高频通讯技术的发展，聚硅氧烷的应用面临挑战，因为高绝缘封装材料和高频印刷电路板的基体树脂对材料的要求苛刻，不仅要求介电常数<2.5、对介电损耗和粘结力也要求较高。聚硅氧烷的耐热性和粘结力较高，但其介电常数和介电损耗已满足不了发展要求。尽管聚四氟乙烯和聚丁二烯可以满足要求，但其结构的惰性使其与基材的粘附力较低。已知将含氟基团引入聚硅氧烷，既能降低介电常数，又能保留其良好的粘附性，然而迄今具有低介电常数且高耐热的含氟硅氧烷品种很少，故发展这类材料具有较高的学术和经济价值。因此，本项目通过分子设计，研究可热交联的含氟聚硅氧烷的合成及其结构与性能关系，为获得高耐热低介电含氟聚硅氧烷提供新思路。开展本项目的研究不仅对这类含氟聚硅氧烷的结构设计具有指导意义，还有望获得性能优异的新型低介电常数材料。

随着高频通讯技术的发展，迫切需要具有低介电常数（<2.5）和低介电损耗的材料作为高频印刷电路板的基体树脂。尽管聚四氟乙烯(PTFE)可以满足要求，但是PTFE的惰性使其很难与基材形成良好的附着力。因此，研究粘结力良好且介电常数和介电损耗低的高性能材料具有较高的学术价值和经济价值。聚硅氧烷与基材具有良好的粘附性，但传统的聚硅氧烷材料的介电常数为2.6-3.0，已不能满足使用需求。而将含氟基团引入聚硅氧烷，不仅可使材料的介电常数降低，而且能保持材料的粘附性。已知的含氟硅氧烷材料其耐热性较低，不能满足在较高温度环境下保持稳定的使用条件，因此发展高耐热的含氟聚硅氧烷才是使其能被作为超低介电常数材料得以应用的有效途径。为了获得高耐热的聚硅氧烷材料，一种重要的方法是发展可交联的硅氧烷，但这些硅氧烷往往需要添加催化剂或引发剂才能发生交联，这对其介电性能是不利的。因此，发展可直接热交联的含氟聚硅氧烷可以有效的解决这一问题。为了获得介电性能、耐热性、粘结性等综合性能优异的聚硅氧烷，本项目发展了新型的可直接交联的含氟聚硅氧烷。通过将三氟乙烯基醚、苯乙烯等热固性基团引入硅氧烷中，获得了新型的含氟硅氧烷单体及其简捷高效的合成方法。这些硅氧烷单体可直接热交联。所得含氟聚硅氧烷表现出优异的耐热性、粘结性、疏水性及绝缘性能。在5GHz或10GHz高频条件下，多种含氟聚硅氧烷具有较低的介电常数（2.37-2.56）和介电损耗（1.66×10−3-4.0×10−3）。其中，部分含氟聚硅氧烷的T5d高于450 oC，Tg可达到200 oC以上。这些含氟聚硅氧烷的优异性能可使其用作集成电路的高绝缘封装材料和高频印刷电路板的基体树脂，具有良好的应用前景。本项目不仅获得了高耐热低介电常数材料的新制备方法，而且可以为我国相关行业的发展提供新材料的支撑。