Preparation And Study On Polyimide/Alumina/Boron Nitride Nanocomposite Films

Due to the rigid structure including imide ring and aromatic ring,polyimide film has high and low temperature resistance,radiation res istance,corrosion resistance and high insulation performance.Polyimide films are widely used in flexible printed circuit boards,flexible displays,integrated circuits,semiconductor packaging,solar cell substrates,and insulating materials.In the field of insulation materials,with the development of high frequency,miniaturization and integration of electrical,frequency conversion technology is widely used due to its high efficiency and energy saving characteristics.Frequency conversion motors generally use pulse width modulation(PWM)drive technology.The output PWM voltage has the characteristics of steep rising edge and high frequency,which will be accompanied by corona discharge.Therefore,the polyimide film is required to have better corona resistance.In addition,in the fields of circuit board substrates or cover films,with the development of microelectronic technology,electronic circuits are gradually densely packed,requiring materials with certain thermal conductivity,otherwise it will cause short circuit,ablation and other damage due to overheating,which affects Normal use.Therefore,improving the thermal performance of polyimide films has become a hot research topic.In order to improve the corona resistance and thermal conductivity of the polyimide film,alumina particles and boron nitride particles were used to modify the polyimide film.The basic mechanical properties,dielectric properties,thermal stability,corona resistance,and thermal conductivity of polyimide composite films are studied by using a universal material testing machine,a precision impedance analyzer,a thermal conductivity coefficient analyzer,a thermogravimetric analyzer,Corona resistance tester,thermal conductivity tester.The research shows that the addition of alumina particles greatly improves the corona resistance of the composite film.When the content of alumina particles is 18wt%,the corona aging time of the composite film reaches 530min,which is 260 times that of pure polyimide film.With the addition of alumina particles,the dielectric constant of the composite film has increased,the volume resistivity and breakdown strength have decreased slightly,and the thermal stability has been well maintained.Further research on the corona resistance mechanism of the composite film revealed that the improvement of the corona resistance of the film is closely related to the injection of space charge and the transport of electrons.The corona aging process of the film basically meets the trap theory model.With the addition of boron nitride particles,the mechanical properties and thermal stability of the composite film are slightly reduced.As the content of boron nitride increases,the thermal conductivity of the PI/BN composite film first decreases and then increases.With the increase of BN,the interface between polyimide and boron nitride increases,and it is also the process of establishing a thin film thermal network chain.When the content of boron nitride is less than 15wt%,the interface effect occupies the main position,and the thermal conductivity of the composite film decreases.When the content of boron nitride is higher than 15wt%,the thermal conductivity network is a factor that affects the thermal conductivity of the material.As the content of boron nitride increases,the thermal conductivity of the composite film increases.When the boron nitride content is 30wt%,the thermal conductivity of the PI/BN composite film reaches 0.72 W/(m·K).