Re: Magnetic Drive Etchant Pump

On Fri, 10 Aug 2007 08:40:53 +1200, Barry Lennox
<bt.l.barryl@xxxxxxxxxxxxxxx> wrote:
[snip]
I saw a very effective etching tank that used minimal etchant. It was
a *very* thin vertical tank made from two sheets of glass, but the
side "walls" were only strips of glass. 5 mm thick. The cunning part
was the bottom was 5 mm dia glass tube, with about 10 holes drilled
along it's length. One end was blocked off, and the other fed, via PVC
tubing, from an aquarium pump.

The drilling took some time and care with a special glass drill (Lee
Valley has them) but it was the only tricky part of the whole tank,
and the results were worth it.

It was all bogged together with RTV intended for aquarium tank
construction.

Heating of the tank and etchant was done by a *** of about 3mm alloy
held against one glass side with plastic clamps.The other side of the
alloy *** has about 10-12 WW power resistors epoxied to it, these
are connected to a variable DC supply set to provide whatever heat is
required.

The PCB is lifted out via a length of thin fishing line attached to a
tiny hole in one corner.

It was important to have a solid lid, otherwise the room filled with
etchant vapour.

Barry

I tried something similar except I made it out of polycarbonate and
sunk the thing in a bath of hot tap water.
The bubbler was a polyethylene tube at the bottom with holes punched
in it.

Etchant leaked out from around the tubing.
I tried to silicone seal around polyethylene tubing...Futile... :(
I might get it going again once I glueweld in some polycarbonate
tubing.

_______ __
/______/| _/ 6mm
| ||
|/\/\/\||
| * * ||
| * * ||<leak
|=============tube====<aquarium air pump>

The tube is the bubbler and also the tank bottom end piece.
D from BC
.

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