Homebrew PCBs

On 2/28/11 2:58 PM, Harvey White wrote:
>  
>
> On Mon, 28 Feb 2011 09:34:35 -0800 (PST), you wrote:
>
> >Was looking at the MSDS for the 30% h2o2 .. yikes ..
> >This etching boards can be dangerous stuff .. lol
>
> It won't be as dangerous as you think. Use 30 VOL (produces 30 times
> more oxygen) H202, That's 3% Hydrogen Peroxide. You get it at
> drugstores and the like. NOT 30%.
>
Are you sure that's correct? this
site(http://www.using-hydrogen-peroxide.com/hairdressing-peroxide.html)
indicates that 30Vol is 9% and that the 3% you find in drug stores is 10V.

Wikipedia also agrees with this, saying that 20-volume is equivalent to
1.667 mol/dm^3 or roughly 6%

-Matt Andrews


>
> Harvey
>
> >
> >Randy
> >
> >
> >
> >
> >________________________________
> >From: jurod81 <jurod81@... <mailto:jurod81%40hotmail.com>>
> >To: Homebrew_PCBs@yahoogroups.com
> <mailto:Homebrew_PCBs%40yahoogroups.com>
> >Sent: 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
> <mailto:Homebrew_PCBs%40yahoogroups.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 HCL LOL
> >> 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
> >>
> >
> >
> >
> >
> >
> >
> >
> >[Non-text portions of this message have been removed]
> >
> >
> >
> >------------------------------------
> >
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> >
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> >
>
> 



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