Chemical machining

Chemical machining is a process that enables metal parts to be machined chemically, i.e. by chemical attack or chemical dissolution using a suitable agent.

In most cases, the entire surface of the part is not machined, but rather localized: in this case, a spacer is used to locally protect the surface of the part wherever machining is not required. The process then boils down to two operations:

• deposit of a protective deposit according to the desired design;

• chemical etching of unprotected parts.

Chemical engraving dates back to the 1^st millennium, when the Arabs used the action of nitre salt (sodium nitrate) on metals. In the 15th century, the use of Judean bitumen, deposited and dried on a copper or steel plate, enabled the artist to draw with a dry point, thus freeing the metal, which was then etched with nitric acid: this was etching. This technique was used to produce decorative plates and printing clichés, for the reproduction of drawings.

The two main forms of current development in chemical machining are :

• chemical cutting 1 , which removes metal locally over the entire thickness of the part; this process has a wide range of applications, particularly in electronics (figure 1) and mechanical engineering; it is used to produce flat parts of various dimensions (from 1 mm ² to 1 m ²) from sheets or plates of relatively low thickness (10 µm to 3 mm);

• chemical milling 2 , creating hollows in surfaces; applications are in the printing...