Effect Of Nano Dielectric Materials Of Molybdate And Tungstate On The Properties Of Polyimide-based Polymer Films

Polyimide?PI?,as a high performance polymer,has been widely used in microelectronics and other industrial fields.However,at present,the pure polyimide materials has not fully meet the requirements of the development of the electronic device for excellent properties.Therefore,modification of PI has been very active.The modification of polyimide with nano dielectric materials of tungstate and molybdate has not been reported by the domestic and overseas researchers.Besides,tungstate and molybdate are typical materials of low dielectric constant ceramic.Therefore,in this study,thermosetting polyimide was modified by epoxy resins?EP?,nano-CaMoO₄ and nano-CaWO₄.The thermostability,dielectric properties,insulating property of PI have been improved.The effect of EP,nano-CaMoO₄ and nano-CaWO₄on the properties of PI and its internal mechanism was studied.The curing temperature of PI has been decreased to 170?from 220?,with E44used as modifier.PI/EP composite material,which meets the requirement of applied process,was obtained.IR spectra reveals that during the curing process,the active functional groups of PI react with those of EP,which is the reason of the decrease in the curing temperature of PI.The XRD,SEM,IR results of PI/EP/CaMoO₄ composite material reveals that the particles grow bigger with the increase of CaMoO₄ content.The TGA shows the thermostability of PI/EP/CaMoO₄ composites is improved significantly,which may be attributed to the improvement of three-dimensional network with the introduction of nano-CaMoO₄.The measuring results of relative dielectric constant show that in the frequency range of 0.1-150 kHz,with the increase of CaMoO₄,the relative permittivity of PI/EP/CaMoO₄ composites decrease first and then increase.The relative dielectric constant of PI/EP/CaMoO₄ composites is lower than that of PI,when the CaMoO₄ content is 1 wt%and 2.5 wt%.The measuring results of dielectric loss reveal that the dielectric loss of all the samples of PI/EP/CaMoO₄ composites is less than that of PI,when the frequency is in the range of 1-150 kHz.The uniform design was performed to investigate the effect of content of nano-CaMoO₄,KH550,EP on the volume resistivity of PI matrix composites.The analyses of results show that in the experimental domain,there is a positive correlation between volume resisitivty??_v?and CaMoO₄ content(m_{Ca MoO4})and a negtive correlation between?_v and the usage amount of KH550(m _KH550),the EP content(m_EP),and m²_CaMoO4,respectively.There is a parabola relationship between?_v and m_{Ca MoO4}.With the increase of CaMoO₄ content,?_v increases first and then decrease quadratically.?_v has a linear relation with m _EP and m_KH550,respectively.The effects of m²_CaMoO4,m _CaMoO4 and m_EP on responses of?_v are relatively remarkable,while the effect of m_KH550 is most insignificant.The best conditon for highest?_v is:m _CaMoO4=3.97,m_KH550=1,m_EP=15.The relation between dielectric constant of PI/EP/CaWO₄ composites and frequency is similar to that between dielectric constant of PI/EP/CaMoO₄ composites and frequency.It is the same with the relationship between dielectric constant of PI/EP/CaWO₄ composites and CaWO₄ content.However,it should be noticed that at the same frequency,the permittivity of PI/EP/CaWO₄ composite is lower than that of PI/EP/CaMoO₄ composite containing the same content of nano materials and EP.