Homebrew PCBs

On Wed, 03 May 2006 20:48:38 +0200, Steve <alienrelics@...> wrote:

> and I think the
>
> oxidized copper comes out of solution and sinks.


It doesn't, for me. copper coming out i mean.

Something like that what you said is happening, yes. I'm not good at  
chemistry but the oxygen in the H2O2 or air combines with the hydrogen  
 from HCl and leaves Cl to make CuCl2 from Cu2Cl2 (or something like that,  
the green stuff from the brown stuff anyway).
Because you could also regenerate CuCl with chlorine gas (if you are keen  
on fatal accidents). So my thinking is the HCl and H2O2 is really only  
delivering chlorine atoms.

The growth of CuCl is very slow, if you only do a couple of boards every  
now and then almost not noticeable.
You could try to reduce growth by electroplating the copper out, i tried  
that a while ago with carbon electrodes and a wire to plate onto. It  
works, but it is difficult to avoid chlorine bubbles forming on the  
electrode (which is what is happening because you take the copper away  
 from CuCl i assume). The chlorine should not build a gas, it should grab  
hold of some copper from the brown stuff to form two green stuff, but  
that's not always happening apparently. maybe something like the apparatus  
used by fishkeepers to dissolve CO2 into water would help. basically a  
tube filled with marbles through which water is pumped, downwards. On the  
bottom a very small stream of CO2 bubbles is introduced. As they rise  
against the current and bump into the marbles the gas is dissolved. One  
should be able to set this up with a electrode at the bottom fairly  
easily, but since the growth is really so slow i never bothered to even  
try.

ST