Photochemical machining, also known as photochemical etching, is a specialized type of metal etching. During this process, enchants (corrosive materials used to remove materials) and photoresist (a light-sensitive material) join forces to machine (fabricate) sheet metal components. The process was first used for photo printing and engraving, and, as the technology evolved in the late 20th century, for circuit board printing. Today, photochemical machining stands alone as its own industry.
Photochemical etching is a very popular industrial process, preferred to punching, stamping, electrical discharge machining, laser and waterjet cutting and others. It has quite a few advantages that have contributed to its rise in prominence. First of all, this method offers highly complex parts with unparalleled detailing, made of any alloy or metal. Additionally, photo etching does not produce burrs or sharp edges. Finally, these high quality parts can be produced very inexpensively, in a matter of hours, instead of days or weeks. Photo etching does, however, have one drawback, which is that machined metal must be between 0.013 and 2.032 mm.
What are the applications of photochemical etching? The answer is: nearly everything! Photo etched parts are used in vastly diverse capacities, from semiconductor motors and fuel cell components, to battery grids, screens, fine filters and meshes.
How is photochemical etching put into action? The process first involves a modern spray-etching machine, which includes a conveyor belt upon which metal sheets and work pieces are transported. These parts enter a rigid polyvinylchloride chamber, where they are sprayed by hot etchant that exits from nozzles installed around the track. The perpendicular spray employed by these machines is designed to create a uniform, productive etch rate. The etchant most commonly used for this process is aqueous ferric chloride, except in the case of non-standard materials like silver and molybdenum, which use ferric nitrate. Ferric chloride is chosen because it is inexpensive and easily accessed, and effectively dissolves both alloys and metals. In addition, it is environmentally friendly. It has low toxicity and it is recyclable, filterable and replenishable.
It’s very important to observe and adjust the chemistry taking place during the etching process with on-site laboratory facilities. Do this, and expect great results.