Polyimide film

A polyimide film having inorganic particles prepared by a process including the steps of:

• (a) mixing a plurality of inorganic particles with a solvent, and stirring the inorganic particles and the solvent to form a suspending liquid, wherein each of the inorganic particles has a particle size of about 0.1 μm to about 5 μm;
• (b) mixing and string a diamine monomer and a tetracarboxylic dianhydride monomer with the suspending liquid to polymerize the diamine monomer and the tetracarboxylic dianhydride monomer, and thus forming a polyamic acid mixture containing the inorganic particles;
• (c) coating the polyamic acid mixture on a substrate and then performing a drying process to form a dried layer of polyamic acid mixture on the substrate;
• (d) separating the dried layer of polyamic acid mixture from the substrate to form a polyamic acid mixture film;
• and (e) uniaxially stretching and heating the polyamic acid mixture film simultaneously to convert the polyamic acid mixture film into the polyimide film;
• wherein the polyimide film is about 12 μm to about 250 μm in thickness, a difference between two thermal expansion coefficients in any two mutually perpendicular directions on the film surface is less than 10 ppm/° C., the two thermal expansion coefficients are equal to or less than 30 ppm/° C., the Young's modulus of the polyimide film is greater than about 4 GPa in any direction, and the dimensional stability of the polyimide film measured by the standard of IPC-TM-650 is less than 0.10% in any direction.