Preparation And Properties Of Silver/Polyimide Composite Films With High Dielectric Permittivity

Since polymer-based high dielectric composites have very important applications in the micro-electronics field, to improve the dielectric permittivity of this kind of materials is of great significance to the development of dielectric industry. According to the percolation theory, a metal/polymer composite's dielectric permittivity will show a sharp increase when its metal particles' loading comes close to the percolation threshold. Silver particle, with its high electrical conductivity and stable chemical property, is an ideal choice to serve as the filling material. Polyimide has excellent performances such as outstanding thermostabilization, good dielectric and mechanical property, structure designability, etc., and can be used as high performance polymer matrix.In this paper, we prepared the Ag/polyimide (PI) high dielectric composite films and studied their dielectric and other properties. In the preparation of micron silver/PI composite films, the unmodified micron silver particles were equably dispersed with the PI matrix through in situ polymerization and Ag/polyimide high dielectric composite films with outstanding over-all properties were prepared. Under an applied voltage of 10~3Hz, the dielectric permittivity of the composite film reached 400. Besides, because of the stable structure of the polyimide matrix, the composites possessed excellent thermal and mechanical properties. In the preparation of nanometer silver/PI composite films, we first made nanometer silver particles through chemical reduction reactions and introduced modification to the silver particles using KH550. Due to the weak inter reaction between KH550 and the silver particles, the fillers showed a severe aggregation within the PI matrix, leading to a bad dielectric property of the composite films. In the end we drew a conclusion from the experiments that the micron silver/PI composite film possesses high dielectric permittivity as well as good thermal and mechanical properties and is an ideal choice for polymer-based high dielectric composites.