Research On Dielectric Properties And Microstructure Of Nanohybrid Polyimide Film Induced By External Field

The development of nanoscience and technology provide new ideas and ways to the exploitation of new materials and the modifying of present materials,and the appearance of nanodielectrics also open a new application field for the dielectrics. Polyimide/inorganic materials have been widely used in the electronic,electrical and other fields by its excellent heat-resistance,mechanical properties and corona-resistant performance. PI/Al₂O₃ material has gradually become the focus of the study at domestic and abroad.In this paper, the influence of inorganic nanoparticles on dielectric properties and breakdown characteristic of polyimide hybrid films are studied. The PI hybrid films are prepared by sol-gel and Al₂O₃ components are 0%, 5%, 10%, 20% and 0%, 4%, 8%, 12%, 16%, 24% respectively, (two groups samples), which are used as the experimental films. The effect of Al₂O₃ components and external field on the dielectric properties and morphologies of the breakdown holes have been studied. Under the condition of high DC field, permittivity, loss tangent and breakdown voltages have been measured. The relationship of breakdown time and transmittance of film under the laser irradiation have been studied. The surface morphology and element distribution around the breakdown hole are investigated by scanning election microscope. By the above experiments, we explore the dielectric properties and the breakdown characteristics of PI hybrid films and the roles of nanoparticles in the films. The changes of electric field and the performance change of PI films by laser irradiation also have been analyzed.The experimental results show that the samples with 5%,10% and 20% components PI hybrid films have the same process on the absorption of laser. PI films absorb the laser energy and the temperature rise. When the injection power density of laser gets to the damage threshold of PI hybrid films, the film will be breakdown. By controlling of laser irradiation intensity, the nanoparticles can be induced to improve the performance of thin film under the precondition of the films without being breakdown. Under the condition of temperature 20°C, the humidity 20% and the frequency range 10²-10⁵Hz, the permittivity and loss tangent of the films with Al₂O₃ different components are inversely proportional to the relationship with the frequency. Under the fixed-frequency condition, for the 5% components sample, the dielectric constant has the biggest growth rate. The loss tangent has a drastic change for the 10% components sample. PI hybrid films produced a large number of Joule heat in the breakdown process, which is the process of high-temperature melting, breakdown and gradual erosion process. Accompanied the action of heat transmission, the films are damaged by thermal stress finally.