The main process is: dry film-exposure-development-etching-film removal... Dry film: Laminate a dry film on the substrate (copper on the surface). Some use a wet film (that is, ink). The wet film is coated. Because the ink is sticky, it must be pre-baked until it is not sticky. Regardless of dry film and wet film, they are all UV-sensitive materials.
Exposure-The equipment is an exposure machine with a UV light source. There are two types of flash and parallel light, the latter is better. When exposing, align the film prepared in advance with the substrate and fix it with the substrate, and place the substrate on the exposure machine platform for exposure. The specific operation is skipped here. The purpose of exposure is to transfer the graphics to the dry film. The transparent area on the film will transmit UV light to the dry film, causing the dry film to undergo photopolymerization. The black pattern of the film shields the UV light, and the dry film underneath Keep the original state, after the exposure of the dry film, you can clearly see the same graphics as the film.
Development-Rinse the exposed substrate in the developer solution. The unexposed dry film is soluble in the developer solution. The exposure is just the opposite, so the dry film pattern is formed after development.
Etching——The substrate is etched in an etching solution. The dry film is resistant to etching. The cover film protects the copper underneath, while the exposed copper is etched away, thus forming a dry film and a copper strip. Graphics.
Film removal——The substrate is rinsed in a film removal liquid. The dry film is soluble in this liquid. The final substrate will have a copper pattern complementary to the film pattern.
In fact, what was mentioned above is a simple negative etching process, also called a subtractive process. At present, the semi-additive method is more widely used. The film used is positive, that is, the copper pattern made is the same as that of the film.