Homebrew PCBs

Thanks Norm.

 

Yeah, I'm just reluctant about using actual HCl for the reasons you
mentioned.  I'm generally pretty careful but I'm also a bit accident prone
and I don't want to wreck something, or myself, messing around with that
kind of acid.  I've accidentally splashed this vinegar/salt/peroxide
solution on me and not even slight irritation.  I'm sure that wouldn't be
the case with HCl.

 

What I'm curious about though is that supposedly the reaction will still
work *without* salt.. just takes longer?

 

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com] 
Sent: Monday, July 17, 2017 10:46 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Salt/Vinegar/Peroxide

 

  

When you mix the salt (sodium chloride, NaCl) with vinegar (5% acetic acid,
HAc),  the result is  weak homemade hydrochloric acid (HCl) and some
leftovers.  It's slower because it's weaker, and needs replenishment as the
Cl ions are used up in the etching reaction (more salt = more Cl ions).
Might as well start with the pool muriatic acid (HCl), admittedly stronger
than the vinegar/salt, since that's what you wind up with anyway, just
weaker.  Beauty shop suppliers will have higher concentration peroxide in
quart bottles for reasonable prices. Their concentration is measured by
'volume'  -  typically,  40 volume = ~12%, IIRC, so use 1/4 as much as the
3%.  The overall solution will be stronger, since there is less water than
using the 3%. You just use less of the higher concentration peroxide.   Both
the pool acid and higher concentration peroxide are quite caustic/corrosive,
and need to be treated with real care and respect.  Rubber/plastic apron and
gloves, safety glasses!  Ventilation!  And don't use it (or ferric chloride,
for that matter) around your tools - the vapors from an exposed etch tank
will leave a nice rust patina on the iron surfaces!

If you can find it, Sechelle had written an excellent article on CuCl
etching, explaining the chemical process.  It seem to have disappeared from
it's old internet sites. 

Norm

 

On 7/17/2017 9:26 AM, 'Brad' unclefalter@...
<mailto:unclefalter@...>  [Homebrew_PCBs] wrote:

  

I'm trying to wrap my head around how this works, to better mix it.  I
actually like working with this method - the resulting etchant is way less
unpleasant than ferric or the HCl/peroxide stuff.  It is way slower,
although I've found adding peroxide/salt seems to speed things up a bit.

 

The only negative I've found is that peroxide typically is only available in
small 300-500ml bottles, which depending on which store you raid cost
anywhere from $1.99 to $3.99 CDN each.  And you kinda get weird 'is this guy
a terrorist?' looks when you check out six or eight of em at a time.  I've
looked around for 'bulk' peroxide but have only found industrial stuff that
is at 32% (vs 3%).. wondering how that would change things in the reaction?

 

I'm also wondering why it seems like I can keep the reaction going
indefinitely if I constantly intervene to stir, add a bit of salt, add
peroxide, etc.. but once I let it go it cannot be restarted again.  Also
curious why sometimes I get a blue coloured etchant at the end, whereas
other times I get this foamy, nasty green.

 

I'd love to figure this out more and refine it.  The real obstacle is the
cost and small quantities available of peroxide.  I'd love to find a way to
buy that that doesn't leave me feeling like a weirdo.  :)

 

Brad

 

 

 


 
<http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_cam
paign=sig-email&utm_content=emailclient> 

Virus-free.
<http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_cam
paign=sig-email&utm_content=emailclient> www.avg.com