Homebrew PCBs

--- Stefan Trethan <stefan_trethan@...> wrote:

> On Mon, 26 Mar 2007 17:13:25 +0200, mycroft2152
> <mycroft2152y@...>  
> wrote:
> 
> >
> > The acid etching process does generate heat and
> bubbles. There can be
> > a mist of etchant that is almost invisible. You
> will notice the
> > effects, if not immediately, but in a very short
> period of time. Acid
> > burns cause intense pain and heal very slowly.
> Fabric distegrates.
> 
> 
> Those are generally symptoms of too much acid or
> H2O2 or both. It is a bit  
> tricky, maybe impossible, to avoid bubbles
> completely when working with  
> fresh HCl H2O2 etchants, but an excessive amount
> should be avoided. I have  
> once timed a board at eleven seconds, so i know what
> it means to use too  
> much (it was a tiny board and tiny container), do
> NOT try this with large  
> amounts. Anyway, reducing concentrations should
> reduce bubbling, and stop  
> the etchant heating too much (which will generate
> lotsa HCl fumes too). Of  
> course it'll slow things down and you might even
> have to replace or  
> replenish the etchant during the etch if you work
> with small amounts in a  
> small container, on a freshly made per board basis.
> 
> If you can at all get H2O2 in concentrated form, or
> if you are prepared to  
> go through the trouble of regeneration with air
> oxygen, it really pays to  
> feed it up to a proper CuCl etchant. I have my
> etcher (with a lid, but not  
> at all airtight), right next to the corner where i
> store round stock and  
> rods and stuff, some of it steel, and notice no
> corrosion. The etchant  
> does not produce any smell or fumes or bubbles, only
> during etching a  
> slight smell can be noticed from the air pumped
> through (agitation). Also,  
> CuCl only contains HCl in a relatively low
> concentration, so will not  
> cause burns (at least if washed off soon). It will
> only need tending with  
> additional HCl and H2O2 every few boards (depends on
> total volume) so the  
> risk can be reduced and proper gear can be worn at
> those times.
> 
> Having used both, permanent CuCl is much more
> comfortable, but you need  
> concentrated H2O2. Maybe electroplating regeneration
> would be an option  
> for those who can't get H2O2 easily. Maybe O2 gas in
> bottles (welding)  
> would work better than air, possibly using something
> like a downstream  
> dissolver, possibly an option if someone already
> keeps a oxy/acetylene  
> welder. Maybe it would even be reasonable to
> generate the oxygen by  
> electrolysis of water, but then it is probably
> easier to use  
> electroplating and feed the generated gas into a
> dissolver.
> 
> ST
> 
> 

Has anyone ever tried passing the air through one of
those ozonizer tubes found in water ozonizers? I
figure that the O3 might speed up regeneration.

- YD.



 
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