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'[OT] Etching fluids'
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
Also Ferric Chloride.
Are there any other etching liquids you can recommend?
Thanks in advance
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.
Robert A. LaBudde
|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: lcfltd.comral
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"
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.
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.
For many years I use cupric chloride as etchant,
This etchant can be regenerated by adding hydrogen peroxide and hydrochloric
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.
I heard of a sign etching company that uses ferric chloride for many etch
but for zinc, they use nitric acid because of a neat
recycling path they found. They bubble ammonia gas through the spent
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
company found for stannous fluoride in the sixties! (gulp...)
> -----Original Message-----
> 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.)
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.
At 18:59 12/10/99 -0500, you wrote:
Any URL or other such reference you can give, Dennis? Sounds
Dennis Plunkett wrote:
Do you have more information on these boards? Can I use them for prototypes or
is there special equipment involved?
Dennis Plunkett wrote:
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
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.
Nathan S. Shirey
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
"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
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.
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