Photofabrication
Photofabrication allows for the production of high tolerance, precision and thin metal parts without subjecting the materials to forces which might cause the distortion, stress and raised burrs common with other metallurgical techniques. Stainless steel alloys, carbon, copper, brass, nickel, manganese, silver, zinc, aluminum and even glass products are commonly manufactured with this reduced stress process in a number of industries. In addition to electronics, aerospace, medical, automotive and publishing industrial applications, custom photofabrication is also common in commercial and domestic settings for its ability to create precise and personal designs, replicating even photographic imagery. Common products include ornaments, electrical contacts, heat sinks, springs, RF shields, precision shims, lids, covers, fuel cell separator plates, seals and even hearing aid components. Photo etching can be an integral part of product design in printed circuit boards or in a process as simple as the application of a company logo. Options such as CAD and CAM support, design assistance and rapid prototyping extend the capabilities of this technique.
As with all chemical etching processes, there are several distinct steps involved in photofabrication. The desired design or shape is first printed, in either negative or positive form, on dimensionally stable mylar or photographic film. The metal, or in some cases glass, sheet to be etched is stripped of all oils and chemicals that may have accumulated during forging and fabrication using alkaline and acid cleaning solutions. The cleaned plate is coated with UV-sensitive photoresist which, when exposed, will act as a masking agent. The printed design is then applied to the plate and exposed to a UV light source. Some manufacturers forgo the printed versions and instead use a precisely patterned UV light to create the design. The end result of either process is that exposed photoresist will remain in place while unexposed portions will be easily removed leaving areas of the sheet unprotected. An array of machine powered spray nozzles will apply an etchant which will react with the isolated areas and create the design. The composition of this etchant chemical depends on the desired cut and specific type of metal in use. Ferric chloride dissolved in hydrochloric acid is the most common photochemical. After the acid has achieved its desired etch, both the reagent and the remaining masking are stripped. The metal is polished, any irregularities in the cut are burnished, and the machining is finished.
