How does photochemical etching work?

Photo chemical etching is a process where a photo-sensitive film, UV light, and chemicals are used to selectively remove certain areas of metal. The parts that remain after the removal process yield an accurate replica of the part design with minimal waste. 

Typically the process is accomplished as follows…

1. Phototool/Artwork Generation… Photo tooling becomes the master tool for all future production runs. Tooling or artwork is designed from a CAD file or drawn from a print if CAD file is not available. The process involves taking an exact replica of the part and compensating dimensions for etch factors such as material type and material thickness. Once drawn, the image is stepped and repeated on a set of mylar films. The films are then registered within .0005″.
2. Material Preparation… Material is cut to length based on part size and photo size and then thoroughly cleaned to remove all dirt, grease and mill oils from the surface so to ensure the adhesion of photoresist.
3. Photoresist Coating… Photoresist is a UV light sensitive coating that may be applied in a variety of ways. Tongjin’s custom manufactured liquid resist dip coater allows for coating of extremely thin materials, as thin as .0005″. In addition, our Western Magnum dry film laminator gives us the flexibility to increase material thickness by using a hot roll laminator for better adhesion when product calls for increased etching times.
4. Photoresist Exposure… After coating, material is put into the double sided photo tool and exposed to high intensity light on both sides. Timing and intensity of light is critical to cure the image onto the photoresist. Tongjin’s Colight exposure units allows us to develop both liquid resist and dry film resist without interruption.
5. Photo Developing… During exposure, the image is hardened onto the material, however, all remaining resist must be removed. A liquid chemical bath along with high pressure spray will remove all unwanted resist and leave only the exact image of the part.
6. Etching/Chemical Milling… Panels are then fed through one of our Chemcut etching lines. Typical etching bath consists of an aqueous ferric chloride bath maintained to a precise chemical composition to achieve a constant etching rate and the lowest environmental impact. The result, unwanted material is “etched” away leaving only the parts as designed on the photo tool. Photoresist is stripped away prior to inspection.
7. Inspection… Parts then go through a rigorous inspection process. Quality control is essential to the success of our company. Our Quality Management System (QMS) is certified to ISO 9001:2015 standards. Upon completion of inspection, parts are shipped as requested.