How many different ways are there to etch circuit board? Do they all need a laser printer?
Well, since a board has 2 faces and 4 edges, there are six ways it can be put in the etching tank.
I suspect you are more interested in the chemicals in the tank. There are many ways; all depend on oxidation of the copper. It is not"dissolved," as some may think.
Off the top of my head, common chemical methods are:
1) Ferric chloride
2) Cupric (II) chloride
3) Ammonium persulfate
4) Sodium persulfate
5) HCl + hydrogen peroxide
6) Electrochemical + chemical
7) Alkaline (mostly commercial), see:
http://www.chemcut.net/downloads/alkaline-etch-process.pdf
Ferric chloride is still the most common method. It is noted for having the least undercutting of the etched tracks. Notice, if you start with ferric chloride and replenish by re-oxidizing the bath and adding additional acid, you end up with a cupric chloride bath. The electrochemical method is interesting in that the copper is plated off the board until individual traces are separated. Then. the final removal is with conventional chemicals.
Chemcut is a good source for information on etching PCB's.
John