Photo chemical machining is also known as photo chemical milling, photo etching, and PCM. Photo etching is the process of fabricating sheet metal components through the use of special etchants like ferric chloride. By corrosively machining away certain areas within a piece of sheet metal, PCM is able to produce accurate and detailed metal components that are necessary for a wide range of different applications.
A wide range of different materials are suitable for photo etching work, including aluminium, brass, copper, inconel, manganese, nickel, silver, steel, stainless steel, zinc and titanium. However, despite the large scope in terms of materials, PCM work is restricted in terms of the sizes that can be used. Photo etching is limited to materials that are between 0.00005 and 0.080 inches thick, which makes the process a popular one with circuit board design and related applications. Along with electronics, photo etching is also widely used in a number of other industries that require access to accurate and detailed metal components.

Photo etching is often used as an alternative to other processes such as stamping, punching, laser cutting, and water jet cutting. There are a number of advantages to using photo etching rather than these other techniques, especially with regard to the production of accurate and detailed components. Photo etching is also capable of maintaining dimensional tolerances and not creating burring or sharp edges that were not included in the design. The process of photo etching starts with the initial design and printing of this design onto an optically clear piece of photographic film. Two sheets of this photographic film are then made into a phototool, which is then used to optically and mechanically register the design onto the sheet metal part.

The actual process of transferring the design from the film onto the metal components takes place with the help of an etchant, which is typically in the form of a aqueous solution like ferric chloride. This solution is heated and directed under pressure on both sides of the metal plate, with the design controlling how the metal corrodes and forms the final product. Photo etching is widely used across the world, and has become an integral part of the circuit board design and electronics industry. There are a number of companies who specialise in the process of photo etching and create custom components for a range of applications.