High Out-of-Plane Thermally Conductive Polyimide Film for Electronic Thermal Management by the Incorporation of Core–Shell Ag/Polyimide Microparticles

Polyimide (PI) films with high out-of-plane thermal conductivity are highly desirable for effectively alleviating thermal failure in advanced flexible electronics. However, it is still a great challenge to achieve high out-of-plane thermal conductivity with a low filler content by a simple method. Herein, an Ag-coated PI microsphere (PIM@Ag) as a thermally conductive filler with a considerable heat-transfer path in the out-of-plane direction is prepared to improve the out-of-plane thermal conductivity of the PI film. Because of the introduction of thermal welding between Ag nanoparticles during thermal imidization further eliminating the interface thermal resistance, the resultant PI/PIM@Ag composite film exhibits a high out-of-plane thermal conductivity of 1.2 Wm–1K–1 with an ultralow Ag content of 6.08 wt % and a superior tensile strength of 124.0 MPa compared to 78.9 MPa of a pure PI film. Practical application and comsol simulation results verify that the PI/PIM@Ag composite film has excellent heat dissipation ability for a chip. This work provides an idea for improving the out-of-plane thermal conductivity of polymers with low filler contents.