Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

My chemicals finally arrived today so I made up a batch of cupric
chloride etchant. The ingredients I used were:

250g copper oxide
790 ml 35% hydrochloric acid. This is probably not as accurate as going
by weight but there is no way I am letting that stuff near the kitchen
scales :-)
enough water to make up 2.5 litres

I added the acid to about 1 litre of water a little at a time, stirring
all the time. Once all the acid was in the solution reached 30 deg
centigrade, from 13 deg C when I started. I then added the copper oxide
and stirred well. I dumped the whole lot into a 2.5 litre container and
topped it up with water.

The end result was a fairly deep green solution. In my etch tank at 35
deg C it took 20 minutes to etch a board which seems slightly slower
than new ferric but a lot quicker then the manky old ferric I was using
:-) It does not seem to be as agressive as ferric. The board I used was
an old board that was over exposed and has been lying around for about a
year. Some areas took a while to start etching due to accumulated
oxides, fingerprints etc. A piece of the same board dunked in ferric
seemed to etch more evenly.

35% HCl is pretty nasty stuff. I mixed up the solution outdoors in
fairly damp conditions and there were clouds of fumes coming from the
container of acid.

All I need to do is get the new light box sorted out and I will be able
to try the etchant properly.

Les