The polyimide film is most commonly used to fabricate the flexible copper clad laminates (FCCLs) and coverlays (CV...
The polyimide film is most commonly used to fabricate the flexible copper clad laminates (FCCLs) and coverlays (CVLs) for flexible printed circuits in high-precision electronics because of its outstanding comprehensive properties such as dielectric properties, mechanical properties, radiation resistance, thermal and wear resistance. Previously, we’ve discussed PI films’ application in FCCLs. Today, let’s take a look at adhesive coated polyimide film for flexible printed circuits (FPCs).
picture of polyimide coverlay for FPCs
Polyimide film for industrial use is generally attached to paper base with adhesive and made into rolls for storage. The PI coverlay for FPCs can be divided into one-sided adhesive coated polyimide film and double-sided adhesive coated polyimide film for multi-layered FPCs. Adhesive coated polyimide films mainly consist of PI base film, adhesive and release paper. Three kinds of adhesives are usually applied to the PI film: acrylate adhesive, epoxy adhesive, and polyimide adhesive. The release materials include polypropylene film, PET film, composite paper, and synthetic paper etc.
PI coverlays for single-sided or double-sided FPCs
Like the green solder mask for PCBs, PI covelays are mainly used for the following three aspects:
① protecting circuits from dust and pollution as well as electrostatic discharge(ESD) and avoiding oxidation and erosion of the copper foil;
② acting as the coverlay for the subsequent surface treatment in areas without gold plated;
③ being as the soldering-resistance layer in the surface mounting technology.