Copper etching is a selective removal process used to create images on a copper plate. Most etching processes require a plate covered in a nonreactive material that is then selectively removed. The plate is exposed to a corrosive that removes small amounts of copper while leaving the protected areas alone. In the past, this was done with wax and different acids. Modern copper etching generally uses less toxic materials such as ferric chloride instead of acid and sodium carbonate to remove it. Modern etching is used for everything from artistic expression to creating ink prints to laying pathways on circuit boards.
Historically, copper etching was a method of creating decorations on metal objects such as plates, guns or bells. The same person that made the item typically made these decorations. As time went on, etching become popular as a singular art form; the medium in this case was typically a sheet of copper with no purpose outside the art. Around this time, the first commercial uses of etching came into use, creating plates for the mass production of printed material.
All of these historical methods used the same process. The metal was covered in a layer of melted wax and allowed to set. The etcher would use a special knife to remove wax until the exposed copper formed the desired image or the image was the only part still covered. This prepared plate would be dipped in an acid bath or have acid poured over it. After an amount of time, the etcher took the plate from the acid and covered it in a neutralizing mixture.
Modern methods use the same basic process; they just change a few of the specifics. In commercial or industrial copper etching, the etcher may be computer-operated rather than run by a person. The acids and solvents used in the past have been replaced with non-toxic alternatives. In many cases, wax is still the preferred non-reactive substance, although some industrial processes use sheets of plastic instead. Lastly, the waste materials are often recaptured and recycled to use again.
The most common industrial use for copper etching is in the creation of circuit boards, such as the green boards common in everything from toasters to cellphones. To create a circuit board, the base material board is covered in a layer of extremely thin copper and then a layer of nonreactive plastic. A computer-aided etcher removes the unwanted plastic coating, and the entire board is sprayed with a dissolvent. This removes all the copper, except the still-covered pathways. The board is then stamped and drilled to make room for connected components.