Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan"
<stefan_trethan@...> wrote:
 
> 
> I still think you are actually adding CuCl to your FeCl instead of  
> regenerating it?
> Or where is the iron coming from/the copper removed?
> 
> What peroxide concentration are you using for this?
> 
> ST
>

I've asked several people both in real life and online with better
chemistry skills than I have, and most of them think that it's
probably a little of both. Most generally agree that the excess oxygen
will recombine FeCl2 back to FeCl3, though I'm not sure of the
specifics of how that works. I used to get huge concentric rings of
copper crystals when I regenerated with muriatic acid alone (green,
not sure what kind of crystal they were... anhydrous copper chloride?)
that wouldn't dissolve in the FeCl3, but would instantly melt in
water, which I thought was odd since etchant usually has a pretty
large proportion of water in it. All rinse water goes to hazmat
disposal, which is free for small quantities.

I don't get any kind of solids out of the etchant anymore. I do get
some 'rust' fall-out now, but that could simply be because I
thoroughly regenerated my batch of etchant with anhydrous FeCl3 at one
point, thus doubling the concentration, and there may have been too
much to dissolve completely. It's not enough that the solution would
be mostly CuCl.

The peroxide I use is 12% strength. Each 10 volume = 3% (volume is the
ratio of hydrogen released into the air over a certain duration, or
something odd like that)