Preparation And Study On Dielectric Behavior Of Polyimide Composite Film

As the development of advanced technology on the fields of microelectronics,the integration degree of the ultra large scale integrated circuit is rapidly improved as well.Therefore,the requirements for the dielectric materials are getting higher and higher.It is known that polyimide(PI)have been researched heatedly for its advantages on excellent physical and chemical properties,including thermal,chemical stability,mechanical strength and low dielectric properties,making it a potential of the dielectric material.However,the dielectric constant of polyimide film is in the range of 3.0?3.6,when used as high dielectric material in integrated circuit embedded micro capacitor,it is too low;and used as a low dielectric material in integrated circuit,it is too high.In the study,PI materials were modified in dielectric properties to obtain high speed,low power consumption and high density integrated circuit.The main work is as follows.First of all,two anhydride monomer(BPDA,ODPA,PMDA,6FDA)and two amine monomer(ODA,PDA)were selected to synthesis series of different system PI films,and the effects of monomer on dielectric properties,mechanical properties and thermal properties of PI films were investigated.The results demonstrate that the dielectric constant of the common aromatic polyimide film is about 3.4,and the dielectric loss is 10-3.The dielectric constant decreased to 3 when the fluorine was introduced.In order to obtain high dielectric PI films,a three-phase composite film was produced by inserting multi-walled carbon nanotubes(MWCNTs)and BaTiO3 nanoparticles into PI.The combination of in-situ polymerization and water-based preparation involved in the experiment ensured fillers'homogeneous dispersion in the matrix,which led to flexible shape of the composite films.The dielectric properties of composite films as a function of the frequency and the volume fraction of MWCNTs were studied.Such composite film displayed a high permitivity(314.07),low loss tangent valu(1)and excellent flexibility at 100Hz in the neighborhood of percolation threshold(9 vol%)owing to the special microcapacitor structure.The experimental results were highly consistent with the power law of percolation theory.In order to obtain low dielectric PI films,a novel polyimide composite film containing sulfonated graphene fillers has been prepared using a water-based method.In order to improve dispersibility of SG in PI matrix,triethylamine(TEA)was applied to complex polyamic acid(PAA)the precusor in the form of PAA salt so that its water-solubility could be enhanced.Later,the aqueous SG was blended with the obtained PAA salt,and this water-based mixing facilitated fillers' greater dispersion in matrix.The dielectric properties and thermal properties of the composite films were studied,and their microstructures were analyzed by scanning electron microscopy.The dielectric measurement results indicate that the dielectric constant of the composite films reaches as low as 2.06 at 1000 Hz,while maintaining low dielectric loss at the level of 10-3.Scanning electron microscopy images reveal that the low dielectric constants of PI/SG composite films are related to the porous microstructure.