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PICList Thread
'[OT] Etching fluids'
1999\10\11@173634 by Kev Howard

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Firstly,  thanks to all for help with PICS!

I don't wish to add to the "noise" level but thought this would be an
interesting question for all the geniuses!

Can anybody help with information regarding "reforming" etching fluids so the
copper can be removed and the fluid re- used?
Good for the enviroment!
I normally use SodiumPersulphate, which is supplied to me in a white powder
form.

Also Ferric Chloride.

Are there any other etching liquids you can recommend?

Thanks in advance

Kev

1999\10\11@184710 by Tony Nixon

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I've been using Ferric Chloride for years now and it serves my purposes
well. If you look at the method I use at
http://www.picnpoke.com/projects/pcb.html, you will find that the
solution lasts a long time with excellent results. I've been using the
same batch for years. I don't know if it's recylable, but all I know is,
when it turns green, it's dead.

--
Best regards

Tony

http://www.picnpoke.com
Email spam_OUTsalesTakeThisOuTspampicnpoke.com

1999\10\11@233556 by Robert A. LaBudde

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At 08:44 AM 10/12/99 +1000, Tony wrote:
>I've been using Ferric Chloride for years now and it serves my purposes
>well. If you look at the method I use at
>http://www.picnpoke.com/projects/pcb.html, you will find that the
>solution lasts a long time with excellent results. I've been using the
>same batch for years. I don't know if it's recylable, but all I know is,
>when it turns green, it's dead.

You should be able to regenerate the solution electrolytically by using
iron and a copper electrodes. Iron will oxidize from one electrode and
copper will plate out on the other. So the copper electrode is the cathode
and the iron one is the anode.

You could calculate the necessary voltage from the half-cell potentials,
but I don't have a table handy. So I would suggest connecting a ammeter in
series and increasing the driving voltage up from zero until current starts
flowing, then stop. The necessary voltage should only be ~ 1 V.

Too high a voltage and you'll electrolyze the water or hydrochloric acid
present. So stop quick if you see any bubbles on the electrodes, and don't
breathe any funny colored fumes!

================================================================
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS  e-mail: .....ralKILLspamspam@spam@lcfltd.com
Least Cost Formulations, Ltd.                   URL: http://lcfltd.com/
824 Timberlake Drive                            Tel: 757-467-0954
Virginia Beach, VA 23464-3239                   Fax: 757-467-2947

"Vere scire est per causae scire"
================================================================

1999\10\12@105403 by Randy A.

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Ferric Chloride is probably the least expensive and most environmentally
friendly etching solution that you can use and yes, it does last a long time
if properly stored.

Granted, it might take a bit longer to etch than some of the more exotic
etchants but overall it can't be beat for doing small runs and prototyping.

Just my thoughts on the matter.

Randy A.

1999\10\12@143611 by Mark Willis

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My brother used to run a small 1-day PCB shop, with a partner.  They
were using Sulphuric acid with H2O2, IIRC (And I may recall incorrectly
- it's been ~17-18 years!  I'll check tomorrow when my dad, the chemical
engineer, is back in town; don't act on this post alone, PLEASE!), they
neutralized the acid I think, then precipitating that Cu2S3 out by
boiling the water off slowly, and taking the resulting nice dry
(pretty!) Green-Blue crystals off to the local disposal site.  (They
concentrated it because disposal was paid on a per-pound basis.  And
they generated a fair amount of liquid, easier to concentrate it.)

For hobbyist/prototype use, Ferric Chloride's just fine.  Use what works
for you.  I stay with Ferric Chloride, myself, right now.

 Mark

1999\10\12@170854 by sbb.simpeltron

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For many years I use cupric chloride as etchant,
This etchant can be regenerated by adding hydrogen peroxide and hydrochloric
acid.
It is a very clean bath and the only waste is pure copper oxide (when the
surplus of the bath is neutralised).
Whenever you have used this bath you never use ferric chloride again or
sodium persulphate again. You get a mess with ferric chloride and  holes in
you cloths wit sodium persulphate.

Mail me private if you want a recipe.

{Quote hidden}

1999\10\12@200020 by john_g

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I heard of a sign etching company that uses ferric chloride for many etch
baths,
but for zinc, they use nitric acid because of a neat
environmental/economical
recycling path they found.  They bubble ammonia gas through the spent
etching solution
to get ammonium nitrate with zinc bound in it.  They SELL that as special
corn fertilizer instead of having to pay to get it removed!

I would like to hear what Mark's dad thinks of for copper?  Is there a
set of low heat, low mist wet chemistry pathways that yields
layers of copper plated onto stainless
steel collector plates, plus a weak solution that
can be turned into soybean fertilizer?

What regions have farmland low in trace copper?

What other metals are acceptable for prototype PCB's?

Tin via wet chemistry?

Aluminum via vacuum deposition over polymer insulators/semiconductors on
biodegradable celluloid substrates?  Etch it quick in caustic and dry it off
in a hurry like a photo print so it doesn't curl?

Lot's of paths would be way better than the recycle pathway the Crest
toothpaste
company found for stannous fluoride in the sixties!  (gulp...)

John G

> -----Original Message-----
they
> neutralized the acid I think, then precipitating that Cu2S3 out by
> boiling the water off slowly, and taking the resulting nice dry
> (pretty!) Green-Blue crystals off to the local disposal site.  (They
> concentrated it because disposal was paid on a per-pound basis.  And
> they generated a fair amount of liquid, easier to concentrate it.)

1999\10\12@211406 by Dennis Plunkett

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Etching as we know it is becoming a thing of the past. Sinate-Esta PCBs are
the way to fly, and they are here now! The good thing is that these boards
are/will be cheaper than equivalent mulit layer FR4, have direct bonding to
form interconnections, great for RF etc.. (I love this stuff and can rant
and rave more!) Talk to your manufacturer about these. Some are not doing
them as yet. Hewlet-Packard have only recently started on them.

Dennis







At 18:59 12/10/99 -0500, you wrote:
{Quote hidden}

1999\10\12@212920 by Mark Willis

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Any URL or other such reference you can give, Dennis?  Sounds
interesting.

 Mark

Dennis Plunkett wrote:
{Quote hidden}

1999\10\13@120139 by Brian Kraut

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Do you have more information on these boards?  Can I use them for prototypes or
is there special equipment involved?

Dennis Plunkett wrote:

{Quote hidden}

1999\10\13@120148 by Randy A.

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Dennis:

The new PCB technology you speak of is very interesting. However, how much
does it presently cost, taking into account the equipment required and the
cost of the rest of the supplies etc.  Please keep in mind that most of the
people on here are hobbyists or like myself only doing a few boards a month
and the lower the cost the better as long as it turns out a satisfactory
product.

If these new type PCBs are in fact inexpensive to make, please let us know
more details about them.  I myself am always looking for easier and cleaner
ways to do the job.

Regards,
Randy A.

1999\10\13@122258 by Nathan S. Shirey

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what should I use to coat my boards after I etch them? I'm using just the
cheap copper kit form radio shack, they recommend that I coat them with
something so they don't tarnish
nate

1999\10\13@185216 by Tony Nixon

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"Nathan S. Shirey" wrote:
>
> what should I use to coat my boards after I etch them? I'm using just the
> cheap copper kit form radio shack, they recommend that I coat them with
> something so they don't tarnish
> nate

Electrolube make a clear protective laquer that you spray onto finished
boards. You can solder through it after it dries. I should be easy to
get hold of.

--
Best regards

Tony

http://www.picnpoke.com
Email EraseMEsalesspam_OUTspamTakeThisOuTpicnpoke.com

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