Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "lcdpublishing"
<lcdpublishing@...> wrote:
>
> Jeff,
> 
> What is the ratio you use for that?  How long does it last? Which to 
> you add to which?  (Peroxide to acid or acid to peroxide)
> 
> Any other tips or info would be great.  When my current batch of 
> Ferric Chloride dies, I would like to use something else :-(

The ratio is 1 volume HCl to 2 volumes H2O2 and you Always Add Acid,
as they say (e.g. - 200mL h2o2 added to 100mL HCl). The solution heats
up maybe 10-15C when the peroxide is added but nothing spectacular.
Boards etch in 3-4 minutes with the usual agitation or "hand-rubbing"
- I wear nitrile (blue) gloves when using it because peroxyacids cause
hellacious skin burns, much worse than the pure acid does. That said,
the solution is very easy to work with and naturally decomposes back
to the acid and water (plus dissolved copper chloride) in a matter of
hours. I've been saving the used solution in a jug and will likely
precipitate out the copper with sodium bicarbonate (baking soda) or
hydroxide (lye) before dumping the rest down the drain (it'll then be
salt water - no harm there!).

All things considered I feel it is a much better etching process than
Ferric Chloride and less fussy than sodium or ammonium persulfate
(which are simply salts of peroxysulfuric acid, so they are
essentially a neutral pH (sodium salt) or slightly acidic (ammonia
salt) version of this process).

Obviously, I have some grasp of the chemistry here which is why I
didn't hesitate to give this etchant a try, but I wouldn't say it
requires any special knowledge to use it well or safely. I strongly
recommend that it only be used outside because the HCl fumes quite a
bit and that a garden hose be kept nearby to flood any spills.

-Jeff