Chemical Milling & Etching

Process Definition & Working Principle

Chemical milling and etching (known in industry as chemical machining or Chemical Machining - CHM) is a non-traditional manufacturing process that removes excess material by controlled chemical dissolution (etching) from selective areas of a workpiece. These areas are defined by the selective application of acid- or alkali-resistant barrier coatings (polymeric maskants or photoresists). Unlike conventional machining methods, where material is removed via mechanical shearing and chip generation under the action of a cutting tool, chemical machining operates at the atomic level through oxidation-reduction chemical reactions.

The physicochemical principle of the process relies on mass transport and diffusion within the boundary layer located between the metal surface and the liquid etchant. This process is mathematically modeled using Fick's First Law of Diffusion:

$$J=-D\frac{\partial C}{\partial x}$$

Where: