Always Add Acid means add the acid to whatever. This is a precaution
in case the mixture gets hot and splatters. The splatter will be the
liquid being added to, not the acid.
Les
--- In
Homebrew_PCBs@yahoogroups.com, "Jeffrey Jenkins"
<tesseract@...> wrote:
>
> --- 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
>