Thermal conductivity of polyimide/AlN and polyimide/(AlN + BN) composite films prepared by in-situ polymerization

A series of polyimide/AlN composite films and polyimide/AlN/BN composite films with different contents were prepared by using polyimide as organic matrix, AlN and BN as inorganic fillers. The filling of the ALN + BN particles increases the dielectric constant, the breakdown strength, and the thermal conductivity of the film. After filling in 9 vol% AlN content, the thermal conductivity of the polyimide/AlN composite film was 0.675 W/(m·K), which was three times that of the pure PI film. The PI/AlN/BN composite film had a thermal conductivity of 0.711 W/(m·K) when the content of AlN and BN was 3 vol% and 6 vol%, When the inorganic packing particles are 3%, the tensile strength loss is small and the breakdown strength is increased to 180 kV/mm. The SEM image of PI film showed that when different contents of AlN particles were added to the matrix, whitening phenomenon may occur due to poor interface bonding ability, and the problem was improved after KH560 modification. The result showed that two fillers with different particle sizes formed a close-packing, which was beneficial to increase the number of thermal conduction paths, thereby improving the thermal conductivity. Overall, this paper prepared a series of PI thin films with high thermal conductivity and high insulation.