Electronic Circuits and Projects Forum

http://en.wikipedia.org/wiki/Electro_chemical_machining

It has limited usefulness in PCB etching, chemical methods aren't really that bad and the electro-chemical method stops working if electrical contact is broken and can etch underneath the masking media more readily than a pure chemical reaction can so it becomes impractical for fine traces. If appropriate agitation is used in a chemical bath the copper removal rate on a PCB is almost completely uniform, the electrochemical method depends highly on the cathode to anode surface area ratio and distance of the applied electric fields. Current density variations occur from these difference and from the variations in the copper thickness and how that thickness effects the current density over time as the board etches at different points. I think it's most common industrial usage is as a final polish and surface finishing process on complex geometries, like turbine blades made out of exotic metals, because the pieces are relatively large so their electrical coupling is very strong, something as thin as the copper trace on a PCB is tenuous at best.. The surface area and current density calculations are so far past nightmarish that it would be applicable at best as an art, one however which I would respect, but art non-the-less. As you scale up the process chemical etching a board becomes more viable not less, otherwise this kind of thing would be used for mass production of PC boards, and it's not.

Originally Posted by Rolf

Than I added a little vinegar and a very small amount of table salt, don't ask me how much! Shortly thereafter bubbles started to form at the copper anode.

Rather a misleading title? - 'no acid' - you then proceed to add acetic acid to the mix

Do that outside. Those bubbles are hydrogen.

Originally Posted by Rolf

Yes, his is similar but he uses Old Sulphuric Battery Acid (diluted) but I use Vinegar and Salt. Quite a difference in chemistry, I would think but then I am no chemist.

I am not sure what you mean by quite a difference in chemistry. The advantage of using sulfuric acid in electrolysis versus NaCl as your primary electrolyte is there is no chance to produce chlorine gas.

Although an explosion is probably unlikely if the process is well ventilated, hydrogen and chlorine form a classic, photochemically calatyzed, explosive mixture. John

Edit: Of course, chlorine by itself is a poisonous gas and has been used in warfare for that purpose.