Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "Herbert E. Plett"
<cachureos@...> wrote:
>
> --- William Kroyer <william.kroyer@...> wrote:
> 
> 
> > ... but I'm guessing it's "reguvinated" by simply adding 
> > more HCl or H2O2.
> 
> in other words: you are pouring more 'pure' etchant into the
weakened solution!
> 

Sort of... CuCl obviously has copper in it already. I think it's
CuCL2, stick copper in it and it pulls off copper to be come two CuCL.
Add HCl and the Clorine grabs onto the CuCl to become CuCl2 again. I
think the hydrogen just bubbles out.

You do end up with more CuCL2 etchant, so it does grow, but you are
not just adding more etchant, you are rejuvinating it.

I could be mistaken, but I think that if you add H202 or bubble air
through it, the oxygen grabs a copper away from CuCl, the extra
Chlorine grabs a nearby CuCl to become CuCl2 again, and I think the
oxidized copper comes out of solution and sinks. If you use a bubbler
to add oxygen, it shouldn't breed any new etchant. Same with H202,
except it probably becomes more watered down as no new CuCL2 is bred.
The H202 leaves H20 and no new CuCl2, just the old rejuvinated.

I think? Am I close, anyone?

Sounds like Sourdough bread.

Steve Greenfield