In the stage of rapid testing of flexible PCBs, many aspects need to be paid attention to: the manufacturer chemically deposits a very thin electroless copper layer on the entire surface of the panel (including the inside of the hole). Through the holes metalized in this way, an electrical connection is made from one side of the flexible circuit to the other.

Manufacturers of flexible PCB urgent proofing are now ready to apply conductive glue or circuit imaging boards, and the surface treatment can include chemical immersion in an acid bath. Then chemical cleaning, micro-etching and application of anti-corrosive agents are carried out. Image application is usually by using dry film. Screen printing process or use liquid photoimageable resist to complete. A heated roller is used to laminate the dry resist onto the panel, and then the film containing the negative image of the desired trace pattern is placed on the coated plate.

The flexible PCB expedited proofing manufacturer exposes the panel and the film to a UV light source to harden and fix the specific area of the resist under the transparent part of the film, so that the area that is not penetrated by the ultraviolet light is relatively soft and unexposed. The next step is the development process, which rinses off the unexposed soft resist and exposes the excess copper.

In the etching process, the flexible PCB anti-flash manufacturers use chemical solutions to dissolve the unwanted copper on the surface of the panel, leaving only the required copper circuits under the photoresist. Once hardened, the photoresist is chemically stripped. The required copper pattern will remain on the polyimide surface.

The inspection process involving visual and automatic optical inspection equipment is usually carried out after this stage, sometimes. Electrical testing procedures are also used, and emergency proofing of multilayer flexible PCBs is to drill holes in the substrate and glue each additional layer. Then perform the above-mentioned through-hole plating, imaging, development and etching processes, the manufacturer also pastes the rigid part of the board in the same way.

In the later stage of the flex PCB's urgent proofing, the manufacturer uses a cover layer to shield all the copper areas of the flex circuit that will not be soldered. This is an adhesive film made by drilling holes in appropriate locations, and the manufacturer laminates it onto the flexible PCB.