Abstract: A polyimide film, and a preparation method and a use thereof, where the polyimide film has a thickness of greater than or equal to 250 ?m, and includes a film layer A and at least one-layer film layer B in contact with each other; a surface roughness Rz of the film layer A is less than or equal to 1.0 ?m; the number of micropores with a size greater than 0.1 mm in the film layer B is less than or equal to 1/m2; the film layer B has a density of greater than or equal to 1.45 g/cm3, and a surface roughness Rz of greater than or equal to 1.2 ?m. The polyimide film provided in the present application has the characteristics of large thickness, small linear thermal expansion coefficient, high pressure resistance and low gas permeability.

Abstract: A high-frequency fast recovery diode that includes a diode chip set, solder lugs, lead wires, lead terminals, a silicone coating layer and a plastic package body. The diode chip set includes n-diode chips arranged in the same polarity order sequentially, a part of the n-diode chips can be fast recovery diode chips and others can be conventional. Solder lugs are placed on both sides of, and connected with, each diode chip. Lead wires are connected with the solder lugs on the ends of the diode chip set, respectively. The silicone coating layer is provided around the diode chip set and the lugs. The plastic package body is provided around the lead terminals and the silicone coating layer. The shape of the plastic package body can be a cylindrical or square column. The reverse recovery time of the high-frequency fast recovery diode can be shortened, and the voltage resistance performance improved.