Breakdown Characteristics Of Inorganic Nano-Al₂O₃ Hybrid Polyimide Film

Polyimide/nano-Al₂O₃ films have been used widely in the electrical and electronic industry for its excellent heat resistance, mechanical and corona resistance properties. Modification of inorganic nano-particles in the composite material shows good prospect particularly. Therefore polyimide/nano-Al₂O₃ materials have been became the focus of research in the past few years at home and abroad.In order to research the effect of inorganic nano-particles on the electric characteristic of PI hybrid films, electrical strength, DC volume resistivity, DC conductivity, dielectric spectroscopy and infrared spectroscopy for four kind of different polyimide/nano-Al₂O₃ films were measured and analyzed by their own measuring system respectively. The surface morphology of polyimide/nano- Al₂O₃ films was observed by the scanning electron microscopy. In the use of Matlab software, the accurate value of area for the breakdown holes was obtained through morphology image processing and further calculations by the pixels as the basic computing unit.The results shown that the permittivity and dissipation factor of the hybrid films were increasing with ascending frequency at 20°C, humidity 20%, 10²-10⁵Hz frequency range. It's similar with the Dupont 100HN and 100CR films. At the specific-frequency, the permittivity and dissipation factor of hybrid films are increasing with ascending contents of nano-Al₂O₃ particles. The permittivity is higher than the others at the content of 10%, and the dissipation factor is changes drastically at the content of 5%. The breakdown strength of all hybrid polyimide films is linear with the contents of inorganic nano-Al₂O₃. The breakdown process of pure polyimide films accompanied with the process of decomposition of substances and heat release. In the breakdown process of hybrid PI film, there were a large number of Joule heat. It's reveal that the breakdown process of the hybrid films is process gradually of erosion with heat transfer. Finally, the area of breakdown hole was calculated respectively by three methods. The performances of these methods were evaluated at the same time. The obtained results and methods were analysed and evaluated in the perspective of deviation.