The invention discloses a high-frequency covering film with a high
electromagnetic shielding function and a preparation method thereof. The high-frequency covering film sequentially comprises an insulating layer, a bonding layer, a
copper foil layer, a first high-frequency bonding layer, a high-frequency insulating layer and a second high-frequency bonding layer from top to bottom, the high-frequency insulating layer is an insulating layer of which the
dielectric coefficient is lower than 4.0 and the
dielectric loss is lower than 0.015 (@ 10GHz); and the first high-frequency bonding layer andthe second high-frequency bonding layer are both
resin adhesive layers with the
dielectric coefficient being lower than 4.0, the
dielectric loss being 0.002-0.010 (@ 10 GHz) and the water absorption being 0.001-0.5%. According to the invention, the shielding rate can be up to more than 100dB; the dielectric property is good, the
dielectric loss is 0.003-0.010 at 10 GHz, and the dielectric coefficient is lower than 4.0; the
mechanical property is good, and
machining processes such as drilling and hole filling can be coped with; a thick
dielectric layer can be designed within a large thickness range, so that
signal transmission loss under
high frequency is reduced; and
soldering tin is good in
heat resistance, plate explosion is avoided in the FPC and PCB assembling process, and gas escape is facilitated and plate explosion is avoided through drilling, hole filling and other process designs.