Homebrew PCBs

"tda7000" <Tda7000@...> writes:
> So, I just have to keep adding a little hydrogen peroxide to
> reactivate each time I etch until I've etched enough boards to turn it
> dark, and then just bubbling will reactivate it?

Until you've converted it, you still have an HCl/H2O2 etchant.  The H2O2
breaks down over time, and the HCl evaporates, leaving you with just
water.  So, if you're doing this over time, the thing to do is mix only
enough HCl/H2O2 etchant for your board-du-jour, and keep adding it to
your etchant tank.  Over time, the CuCl builds up, and you need less
HCl/H2O2 for each board, and can start with the CuCl chemistry checks to
see what you need (HCl or H2O2) each time you etch.  Also you can keep a
chunk of copper in the etchant when you're not using it, so the excess
HCl/H2O2 doesn't go to waste.  A copper plumbing part will do, like an
elbow.  Just remember to take it out before adding the new etchant ;-)

Remember, the etch does Cu + Cl => CuCl, so you have to have free Cl in
the etchant also!  H2O2 alone is not enough.