Electrochemical Machining (ECM) is an important method for removing metal by anodic dissolution in a conducting electrolyte. Metal removal is effected by a suitably shaped electrode (cathode tool).

ECM is a relatively fast method, with important advantages over more traditional machining methods (mechanical, laser, electrochemical discharge) since it can be applied to any electrically conductive material regardless of its hardness. Also there is no need to use a tool made of a harder material than the workpiece. Moreover, ECM is able to produce smooth, stress and crack free surfaces, which is of major importance for workpieces which have to function in extreme environments (temperature, pressure, etc.).

From a methodology point of view, a difference can be made between:

• ECM imaging processes, where the cathode tool shape moves with a certain feed rate (0.1 to 10 mm/min) towards the workpiece and its shape is reproduced in the workpiece (e.g. shave heads, airfoils)
• ECM processes producing internal structures in a workpiece (holes, cavities, tubes).

For ECM imaging processes, the major issue is controling the narrow electrolyte gap between cathode tool and workpiece, since dissolved metal ions, gas and heat have to be removed from this gap.

For internal ECM processes, a high forced electrolyte flow is still required for removal of metal ions, gas and heat, but in addition the shape of the produced structures depends strongly on the process conditions (electrolyte flow rate, DC/pulsed current or potential difference) and cell configuration (cathode tool shape, position and movement).

Electrochemical etching of metals is somehow related to ECM since it involves the selective removal of metal from an initial metal foil or predeposited metal layer. Typically, the metal is covered with a photoresist layer (photosensitive surface) and is selectively exposed to a UV light source. The photoresist on the exposed areas is removed by a chemical agent and subsequently the exposed areas are electrochemically etched. Most often, this processes are performed on a wafer carrier or some rectangular flat surface carrier. The applications are mainly in the micro-structure domain (e.g. MEMS).

Optimizing process conditions and cell configuration for ECM or electrochemical etching can easily be performed using Elsyca simulation tools: Elsyca ECM-Master (to be released soon) or Elsy2D.