I am happy to say that I can now see unmistakeable signs of progress
with my etchant. I now have about 17 litres of it, in a 34 litre
Coleman cooler, gugrgling away on the floor next to my laundry tubs.
The air bubbler I made is the type described at Think & Tinker:
http://www.thinktink.com/stack/volumes/voliii/equipmnt/bubltank/bubltank.htmI am using air from the exhaust output of a small vacuum pump.
Sometime recently, the bubbler started putting out more air, so almost
all the surface of the etchant is constantly bubbling vigorously. I
don't know whether the sparger moved, or the pump, which has carbon
vanes, suddenly decided to put more air out. The pump has been running
continuously for several days with only slight heat to the touch for
the motor case. The pump casing seems even less warm than the motor
casing.
Anyway, I can see two changes tonight (in addition to the more
vigorous air bubbling).
The etchant is an even deeper brown color than it has been for a few
days. It is so dark I can hardly see the wire under the etchant
surface. And all the remaining wire is clearly decreasing in diameter.
(I hung one piece of copper wire over the edge of the tank about 4
days ago. The etched part is 1/2 the diameter or less than the
unetched end). Also, at the start, the whole mass of copper wire was a
large jumble, with some wire under etchant and some above it. Clearly
the etchant is working, because the level of wire above the surface
has substantially decreased.
It is great to see this working, after the slow start I had, and all
my worrying and wondering. I hope I will be able to start etching
boards within a week or so. Yahoo!
I do like this process because:
1) it is non-polluting
2) replenishing HCl is cheap and easy to do
3) a Coleman cooler, 8 litres of HCl, and 5 pounds of copper wire,
along with a bubbler are all it took me to get started, (along with a
hell of a lot of advice)
4) this list is a great source of information and encouragement
(thanks Adam, and everyone else who helped!)
5) cheap and dirty chemical analysis is possible - see:
http://www.pacificsun.ca/~robert/pcb/pcb.htmfor related work by Donald Aitken and Robert Grauman
Grant