Thanks JRod ..
Well for not being a chemistry major.
Looks like the most detailed answer thus far.
Where do I purchase 30% H2O2 ?
If the main ingredient in the HCL / H2O2 Solution is the H2O2, then what
is the purpose of the HCL ? Or is the H2O2 causing the HCL to etch in some way?
Understood about the hazmat,will proceed accordingly..
I also thought I read somewhere about someone etching with ferric chloride and
recharging it
with either HCL or H2O2 .. ?? thoughts?
∗∗ You end up with a solution containing copper chloride and sodium chloride in
solution.∗∗
Still cant dump this down the sink in this form?
Thanks for the great detailed answer ..
Oh .. heating made big difference ..
I have both ferric chloride and the HCL / H2O2 mix .. but used the ferric
chloride cool
and it took hours to do one board .. heated it up and the time was greatly
reduced..
I assume the temp / time is not linear ???
Randy
________________________________
From: jurod81 <
jurod81@...>
To:
Homebrew_PCBs@yahoogroups.comSent: Mon, February 28, 2011 11:03:38 AM
Subject: [Homebrew_PCBs] Re: Question for the chemistry majors !!
Hey Randy-
I will preface this with - I am not a chemistry major, but I do know a bit of
chemistry (more organic than inorganic).
To answer the original question: what the bubbles are that come off of the board
from peroxide + HCl etch, it is actually brings up an interesting bit of
chemistry. If you look at a oxidation-reduction table you will see that hydrogen
is below copper, so as a rule of thumb most Brønsted-Lowry acids such as HCl
cannot oxidize copper by themselves (nitric acid not included). Peroxides are a
little special; they are very unhappy molecules and easily decompose into
hydroxyl radicals on their way to becoming water. These hydroxyl radicals have
an oxidation potential close to fluorine and can easily attack copper metal
which has a full outer electron shell. The bottom line is that the gas given off
on the copper clad is oxygen (O2) and hydrogen (the final electron receptor in
the reaction), and I am sure that a bit of HCl off gassing since this is an
exothermic reaction. You end up with copper chloride as a final product. If you
want to practically speed up the reaction electrolysis is not going to help you
by very much, I would suggest either starting with a higher % of peroxide,
agitate your solution (with air bubbles or shaking) or warm you solution up a
bit.
For those that are interested, Iron choride acts as a Lewis acid since Fe(III)
has a higher reduction potential then copper with will act as an electron
acceptor. The iron is reduce to Fe(II) and you end up with copper in solution.
Ammonium persulfate works on a similar free radical principle as the peroxide +
HCl principle, the only downsides are that it tends to be slower, you end up
with ammonia gas given off, and the persulfate decomposes rather quickly after
you add it to water meaning it is not very reusable (a day or two at the most
depending on how contaminated your starting water was).
You can reuse your etchant many times before tossing it (I recharge mine by
adding a bit more 30% peroxide). When you do toss it you can easily reclaim your
copper before dumping it down the sink since copper ions do very terrible things
to the environment (and your septic system's bacteria). You can neutralize the
acid by throwing some baking soda (Sodium bicarbonate) into the solution and the
peroxide by dumping some bread yeast which contains an enzyme called peroxidase
into the solution. You end up with a solution containing copper chloride and
sodium chloride in solution. Then you can run an electrolytic cell with copper
as the cathode (hooked up to the (-) terminal) and an inert carbon anode.
Chlorine will be given off at your anode and your cathode will grow some more
copper until the solution becomes depleted (then hydrogen bubbles will start
forming on it). Otherwise you may want to consider disposing of it as hazmat
when your county does one of those household hazardous material drop-off days.
My township does one every 6 months or so – good for dropping off unused paint
etc.
-JRod
BTW - Hydrogen and oxygen are a bad combination. All they need is a little heat
or a catalyst to get over the activation energy and you have fire.
--- In Homebrew_PCBs@yahoogroups.com, "Randy S." <rj3819@...> wrote:
>
> I'm not talking about Chemistry.com here either ..lol
>
> Ok .. using muriatic acid .. with the hydrochloric acid in it mixed with
> peroxide.
>
> I looked a chemelec's website where he uses sulfuric acid and electrodes
> to remove over 90% of the copper, then finishes the board off in ferric
> chloride.
>
> So .. I thought if should work with other acids ..
> I put a electrode in on the negative lead and a scrape piece of board on the
> positive lead, started cranking up the voltage .. and it did indeed start
> drawing
> current and bubbling .. no ventilation so I shut it off right away ..
>
> The questions are :
> He mentioned gases from the electro-etch process, which makes sense as
> there are bubbles .. which are toxic .. I assume the gases from his acid would
> be different then the gases from mine. Chemistry majors ?? What is the gas
> being released from my H2O2 and HCLLOL
> Some kind of a hydrogen chloride gas ?? sounds toxic and flammable .. lol
>
> I was thinking I would make a setup to use my solution, aearate the tank and
> use some electro-etching, if that what it is , to help the process along ...
>
> Sound ok ? Would there be problems with that ?
>
> thanks all
>
> Randy - N2CUA
>
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