Chemistry of metal etching

Businesses which require intricately designed metal parts manufactured in small quantities are often told that chemical etching is the most effective way of manufacturing the metal parts. Hence they would like to know the etching definition chemistry so that they can take the right decision, to find out if it will provide the levels of accuracy they require. Understanding the etching process will also help decide whether the manufacturer will be able to deliver the metal parts in the specified design of the promised quality according to the delivery schedule required.
Etching is traditionally defined as the process of using an acid or other corrosive chemical for cutting into a metal, alloy or other material to create a design or pattern according to the requirement of the customer. Typically in many appliances, machines and gadgets, there are some metal components which have intricate designs. Manufacturing these components using conventional methods like machining, laser cutting, wire erosion can be expensive and time consuming. Etching can be used for a wide range of metals like aluminum, stainless steel, mild steel, spring steel, nickel, copper, brass, beryllium,silver and bronze.
The metal part which is being etched is first cleaned to remove any dirt and impurities. Then based on the pattern which is being etched, a UV photo resist is applied to both sides of the metal using special rollers. Any excess material which is applied is then removed. Special care is taken to ensure that the pattern applied on both the sides are aligned perfectly using a photo tool which acts on both sides of the sheet. The metal sheet on which the artwork has been applied is then exposed to UV light, to harden the pattern on the metal before it is subjected to chemical washing.
The metal sheets are then passed through a ferric chloride solution. The chemistry of etching, involves the ferric chloride reacting with the metal surface which is not coated, to form a liquid, which is then washed away. The ferric chloride does not act on the surface which is coated with the photo resist, so a pattern is formed in the uncoated metal area. A large number of sheets can be placed on the conveyor which is subjected to etching using ferric chloride, for large scale production. One of the major advantage of using this method for metal part production is that force is not required, and burrs are not formed.
The etched metal parts are then placed on a wire tray and passed through a stripping chamber where the photo resist is then removed. The etched parts are then checked for quality using the latest optical inspection equipment, ensuring that the dimensions and design meet the customer specifications. One of the advantages of using this method of production of sheet metal parts is the high level of accuracy since the tolerance is 0.010 mm. The manufacturing facility conforms to the Aerospace standards and is approved by Rolls Royce. After the metal parts conform to quality checks they are then processed further or packed and sent to the customer.