Homebrew PCBs

I'm using 40 Vol, which I get at a Beauty Supply store. Best I can tell it's 12% H2O2, but that's very unclear. Anyway, using it 1:1 with muriatic acid (HCL) produces a very exothermic reaction that etches the board in just a few minutes, no heating and no bubbling.

Since I am NOT a chemistry major, and since the fumes seem caustic to my uneducated smell, I always do the etching outside.

Mark

-----Original Message-----
>From: Matthew Andrews <matt@...>
>Sent: Feb 28, 2011 7:01 PM
>To: Homebrew_PCBs@yahoogroups.com
>Subject: Re: [Homebrew_PCBs] Re: Question for the chemistry majors !!
>
> 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]
>> >
>> >
>> >
>> >------------------------------------
>> >
>> >Be sure to visit the group home and check for new Links, Files, and
>> Photos:
>> >http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>> >
>> >
>> >
>>
>> 
>
>
>
>[Non-text portions of this message have been removed]
>
>
>
>------------------------------------
>
>Be sure to visit the group home and check for new Links, Files, and Photos:
>http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>
>
>