Homebrew PCBs

On 5/05/2011 8:35 AM, tda7000 wrote:
>
> That's interesting... mine didn't actually go brown, but it didn't 
> seem to work after the initial use either.
>
> Maybe I have a different problem and that's why it won't regenerate?
>
> --- In Homebrew_PCBs@yahoogroups.com 
> <mailto:Homebrew_PCBs%40yahoogroups.com>, DJ Delorie <dj@...> wrote:
> >
> > It's not about dissolved oxygen, it's about converting the CuCl from the
> > brown form to the green form.
> >
>
That to me sounds like you don't have enough copper in the solution yet. 
cucl2 etching relies on an interesting reaction where one form of copper 
ion in solution will eat off the solid copper and create a different 
copper ion form. Then you use oxygen to convert the second (non 
reactive) form back into the first (reactive) form.
If you don't have enough copper in the solution (in second form) there 
won't be enough to convert into the reactive form, and you'll need to 
add h2o2 to do the reacting instead. Once you've re-used it enough and 
got plenty of copper ion in solution (brownish colour fluid) then bubble 
it to get clear green solution.

I personally didn't used h2o2 initially, I used a little bit of spent 
ammonium peroxide etchant that was saturated with copper from lots of 
use, and then added hcl to that. and added some copper wire to really 
saturate the brew with copper. Then bubble away!

Andrew


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