Hey Etchers, mostly lurking, but i've been etching for over 30yrs.
Reguarding the Add-to-H2O discussion: normally, it's always
recommended to add the acid to the water. If exothermic (releasing
heat), the water absorbs the heat. In the cases of H2O2, like in
using sulfuric acid and H2O2 as an organic cleaner for silicon wafers,
i was instructed to add the H2O2 to the (96%) sulfuric. I've been
using FerricChloride etchant almost exclusivily in my long
etch-capade. I built a Kustom Spray Etcher a couple of years ago.
It uses a magnetic-drive pump. I mix my dry (anahydrous) FeCl first
with cold water, then I add hot water. I use large peanutbutter jars
as measuring/mixing containers. Probably not a good idea, since they
are NOT tempered glass....guess i've been "lucky" as I've been using
the same jars for over 20yrs!!! I'm wanting to try the HCL/H2O2
technique for quite some time, but haven't found the time. I have
several gallons of MuraticAcid, that I use to "rejuvenate" the FeCL.
It DOES work, but makes the solution thicker and harder to pump. I
burned up my older, adapted swamp-cooler pump. Now I run a magnetic
drive pump, but have never done any rejuvination. In addition to the
HCL/H2O2 etching, I want to try rejuvinating the FeCL using
electricity and a CurrentControlled powersupply...Hopefully, by the
end of this summer, I'll have some time for experiments....FeCl seems
to get more and more expensive, which is why i'm looking for an
alternative etching method. I used to get FeCl for $1 a pound. YES!
one dollar!! last time, cost about $8 a lb. If I buy 50lbs, I can
get it for about $5 a lb. Don't know if the HCL/H2O2 would work with
my spray etcher, but, for one-zee twos-zees, I think the HCL H2O2 will
be a nice quick alternative. Oh, BTW, I use the LaserToner technique
with the SuperFuser....well, enough rambling.....afn Tone
--- In Homebrew_PCBs@yahoogroups.com, "Les Kalmus" <lkalmus@...> wrote:
> 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
Show quoted textHide quoted text
> > > 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
> >
>