In any Photochemical Machining process, the material should be coated with photo resist directly after cleaning. This reduces the chance of surface contamination and oxidation.The coating is photosensitive and resistant to the etchant used to cut the chosen metal. Dry film or liquid resist is applied to both sides of the work piece to allow etching for both sides simultaneously.
Using Photo Resists in the Photochemical Etching Process
Photo resist can be either a positive or negative masking. In positive masking the areas exposed to light during the imaging process wash away during the development stage. In the more commonly used negative masking the areas exposed to the UV light are bonded to the material and the non exposed areas are rinsed away during the development process.
Advances in resist technology combined with new and improved Computer Assisted Design (CAD) artwork have enabled photochemical milling companies to expose, develop and etch features not thought possible a few years ago.