The 1st problem with pumping etchant is the metal parts in the system;
corrosion will rapidly become an issue.
I'm fabricating an etching bath myself. I'll post results as soon as my
finger heals, a little slip while fixing the clothes dryer. :) I'm staying
away from chemicals until the skin heals even if I wear gloves.
At 1st I thought that making air bubbles in the etchant was going to be a
breeze, yeah right. I quickly realized that air pressure, size and number
of holes, and adequate 'return' circulation had to be balanced; the stronger
the air bubbles going up, the more flow is generated upwards, so you need
more space for the flow to return to the bottom to complete the cycle. My
1st attempt using water resulted in a nice volcano effect and my wife
yelling at me for messing up the place. :D
I blocked the holes at both ends of the tubing grid and reduced the number
of holes along the middle area. I found a nice balance where I get decent
bubbles, limitted splashing (a cover will still be essential), and a good
return flow down both ends of the vertical bath. I have a plan for 2 large
PVC pipes to return the flow back to the bottom. This will maximize the use
of the chamber for PCBs, as it stands, 2-3 inches at both ends lack bubbles.
I have yet to fabricate the holder to dip the PCBs in the solution, that's
my last TO-DO item. I use a shop compressor, mated a quick release air
fixture onto the PVC piping, Gardena quick release garden hose fixtures
mated onto the PVC piping so I can easily remove the tubing grid from the
chamber for cleaning. I use an ordinary valve to limit the air flow into
the system, and I also bleed additionnal air leak at the compressor. I've
found that small pumps were just a tad weak, I prefer to use a stronger
source and limit the output.
As soon as I've burned some boards I'll post pics of the assembly.
Robert
:)
-----Message d'origine-----
De :
Homebrew_PCBs@yahoogroups.com [mailto:
Homebrew_PCBs@yahoogroups.com] De
la part de Stefan Trethan
Envoyé : mai 23 2005 11:39
À :
Homebrew_PCBs@yahoogroups.comObjet : Re: Re1: [Homebrew_PCBs] You guys have a look at this:
On Mon, 23 May 2005 12:32:05 -0400, microsoftwarecontrol
<
microsoftwarecontrol@...> wrote:
>
> I found well agitation is really esantial in etching. Uneven should be
> eliminated at all. I found a small cycling pump for chemistries, I
> only worry about flow
> rate
> of it. After
> I real test it, I will give result here.
> By the way, I think of glueing a narrow glass tank with bottom been
> heated.
> Is that kind of glue for home aquarium glass tank, OK? Can it take 70C?
I am not sure etchant pumping is the ideal agitation, there will always be
currents etc.
Small air bubbles work for me..
I dunno which glue you mean, probably silicone, and that should be fine at
70C.
But then, no etchant i know can be operated at 70C, what are you using?!?
ST
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