Research Progress in Anisotropic Thermal Conduction Behavior of Polyimide Films

Polyimide films are widely used in the fields of advanced integrated circuits, optoelectronic displays, flexible functional electronics, etc. With the further development of application, the poor thermal conductivity of polyimide film is unable to meet the rapid heat dissipation requirements of electronic devices. In order to improve the thermal conductivity of films and maintain the superior performance of polyimide materials, a new generation of anisotropic polyimide films with high thermal conductivity has become the focus of research. Due to the obvious anisotropy in the structure or properties of polyimides and thermally conductive fillers, the thermal conductivity behavior of both polyimide intrinsic films and polyimide-based composite films mostly shows significant anisotropy. The molecular structures and chain aggregation of polyimides, orientation arrangement of thermally conductive fillers, as well as the matrix morphology will all exert an important impact on the thermal conductivity and their anisotropic behavior of films. Here, we systematically summarize the research progress on anisotropic thermal conduction behavior of polyimide intrinsic films and polyimide-based composite films. The molecular structure design of polyimides, anisotropic heat conduction mechanism, filler orientation and matrix phase structures are discussed in detail. The effect of structural characteristics of polyimide intrinsic films on their thermal conductivity in different directions is presented, and the related research results of amorphous polyimides and liquid crystalline polyimides are respectively introduced. Composite films based on the orientation arrangement of thermally conductive fillers are described, and the other polyimide-based composite films with the matrix phase separation structures are also concluded. The relationship between the orientation or dispersed state of thermally conductive fillers in the matrix and the anisotropic thermal conduction behavior of two types composite films are particularly investigated. Finally, the challenges of polyimide-based film materials with high anisotropic thermal conduction are summarized and the prospects of the future work are outlooked.