Preparation And Properties Of Polyhedral Oligomeric Silsesquioxane/Polyimide Porous Composite Films With Low Dieclectric Constant

Polyimide(PI)has excellent comprehensive performance and is widely used in electronic and electrical industry.With the development of microelectronics industry,PI as interlayer material is required to have lower dielectric constant to meet the demand of miniaturization development of electronic devices.Common methods to reduce PI dielectric constant include reducing PI polarization and introducing hole structure.In this paper,the above two methods are combined.The organic solution containing polyhedral oligomeric silsesquioxane(POSS)and soluble fluorine-containing PI is used as the organic phase.The porous structure containing POSS is introduced on the surface of PI flat film by microemulsion droplet template method,which reduces the dielectric constant of PI film and improves its water resistance and other properties.POSS nanoparticles were added into the microemulsion system,and the POSS/PI porous composite film(S-POSS/PI)with single-layer and porous structure was prepared by microemulsion droplet template method.Due to the introduction of fluorine-containing groups,cage POSS structure and surface porous coating,the dielectric constant and water absorption of PI film decreased significantly,and the film still showed good mechanical properties.When the content of POSS increased from 0 wt % to 50 wt%,the dielectric constant decreased to 2.428,which was 27.63% lower than that of PI flat film.The water absorption rate decreased to 0.603%,which was 78.43% lower than that of PI flat membrane.In addition,the dielectric constant of S-POSS/PI composite film increased by 2.94%-4.83% after 24 hours in high humidity environment,while the dielectric constant of PI flat film increased by 9.43%,which proved the stability of low dielectric constant of S-POSS/PI in wet environment.In order to further improve the dielectric properties and water resistance of polyimide films,the above S-POSS/PI porous composite film was used as the substrate,and the microemulsion containing POSS was poured on the other surface of the film to prepare the sandwich POSS/PI porous composite film(DPOSS/PI)with porous structure on both sides of the polyimide film.The experimental results show that compared with S-POSS/PI,the introduction of the composite porous structure on both sides of D-POSS PI further reduces the dielectric constant and water absorption of the PI film.At the same time,the increase of the dielectric constant of D-POSS/PI after moisture absorption is only1.19%.Due to the symmetrical distribution of the porous structure on both sides of D-POSS/PI,the tensile strength is maintained or even improved.The POSS/PI composite film prepared by microemulsion droplet template method not only improves the dielectric properties and water resistance of the film,but also maintains its mechanical properties and improves the comprehensive performance of the polyimide film.The above research work provides a new idea for the preparation of low dielectric constant polyimide composite films.