Electrochemical Machining
A RepRap has the potential to make its own circuit boards by equipping it with an electrochemical printed circuit board head. With this ElectrochemicalMillingDrillingHead, it could mill a copper clad board. With this tool head, the tool head is the cathode, with a negative voltage, and the copper board is the positive anode. The workpiece is immersed in an electrolyte and the filtered electrolyte flows through or around the tool head. This is one of several Automated Circuitry Making ways for the RepRap project to produce its own circuit boards.
There is a thread on mentioning electrochemical board milling at:
http://blog.reprap.org/2006/11/universal-pcb-test.html
From that thread, Adrian mentioned that:
The Reprappers had an alternative idea: put a (bunch of) electrode(s) in a RepRap head and use electrochemical machining to make the PCB. Best electrolyte, according to my colleague Tony Mileham who's a world authority, would be sodium chlorate. Bit dodgy as it's
1. Horribly Poisonous, and
2. A fierce oxidsing agent...
Vik mentioned:
I'm,er, familiar with sodium chlorate. I've been accidentally poisoned by it and to be honest it wasn't a big deal. I wasn't even really sick after accidentally consuming a teaspoonful or so of the stuff. Wouldn't recommend it though, even if the LD50 is a few hundred grams (1200mg/kg in rabbits,apparently).
I must say, it's very easy to produce though. Fire 12V into salty water through a couple of old carbon battery rods and there she is.
The proximity of clorates and finely divided long-chain ketones would be a problem, however.
On a related note about etchants in general, Seagrol mentioned:
Might want to look at something even cheaper/more efficient as a PCB etchant. Might I suggest something self replenishing, hideously cheap, and readily available? Hydrochloric Acid and Copper Chlorate.
There is also a description of several methods of etching copper at:
http://chestofbooks.com/reference/Henley-s-20th-Century-Formulas-Recipes-Processes-Vol2/Etching-Fluids-for-Copper.html
There is an article on recovering copper from etching solutions at:
http://www.circuitree.com/Articles/Column/b4d49de37efe7010VgnVCM100000f932a8c0____
An explanation of copper electrowinning at:
http://electrochem.cwru.edu/ed/encycl/art-m02-metals.htm
-- Main.EnriquePerez - 04 Dec 2008
