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Author Topic: Home PCB Etching Solution from Vinegar  (Read 36378 times)
KB4QAA
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Posts: 3257




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« on: December 20, 2013, 12:44:10 PM »

Split from PCB topic:
---------------------------------------------------
updated with chemical formula corrections and safety notes.  

There are many home etchant alternatives to Ferric acid:  hydrochloric acid/muriatic acid; Drano derived solutions; Copper chloride; search the internet.

One I just tried this morning is White Vinegar (Acetic Acid typically 5%), Hydrogen Peroxide antiseptic, (H2O2,typically 3%) and Table Salt (NaCl2 Sodium Chloride)all from the grocery or pharmacy.  Worked like a charm.  I warmed the Vinegar (only) in the microwave before adding the Peroxide and Salt and set it on the drip coffee burner to keep it warm.  It ate up some copper foil to look like lace in about 20 minutes.  

The Solution:
Equal parts vinegar and peroxide worked fine, dump in plenty of salt (to the point of having undissolved salt in the bottom of jar) since it is consumed in the reaction. You should see a vigorous fizzing at the copper surface. Add more salt as the reaction slows.  

The solution will turn green as the copper is converted to Copper Acetate and/or Copper (II) Chloride.  If the reaction stops before etching is  complete, replace the solution, or you can fiddle by adding more solution.

Tips:
Stirring or swirling the solution will speed it up, as will brushing the copper surface with a sponge, cotton swab or non-reactive brush.  Again, keeping the solution warm accelerates the reaction tremendously.


Hazards:
-Copper Acetate is somewhat toxic to humans and very toxic to plants and algae, even when diluted tremendously with water (EPA limit 5ppm).   Minimize contact with your skin and don't ingest it.   Copper Chloride is a component of the green Verdigris Corrosion found on old copper and brass.

 -When mixing chemicals be careful of sudden vigorous reactions that may splash or burn you.   Normally solids, like the salt are not added to hot acids.  In this case things should be fairly tame, but be careful.  

Disposal methods:
-Neutralize by absorbing with Baking Soda (Sodium BiCarbonate) or Laundry/Wash Soda (Sodium Carbonate), put wet solid in plastic bag and put in trash.
-Add scrap Aluminum, watch brown copper precipitate (yes you can strain thru coffee filter and sell to scrap yard!) and solution turns back to clear.  Solution is converted to Aluminum Acetate (Burows solution) which is non toxic and is used to treat Poison Ivy and skin rashes (but buy yours at the pharmacy).  Flush with plenty of water or to be ultra safe, use the Baking Soda method.


Tips:
-Heat accelerates chemical reactions. 10C (or roughly 18F) increase in temp doubles speed.
-The gas evolved is Hydrogen or Oxygen (I couldn't find a match to confirm).   Don't let the kids smoke near your lab.  Use a little ventilation.
-Avoid touching the green copper solution.  Rinse hands and equipment well.
-This same solution works just as well with aluminum metal.  
-Sharpie Marker does not hold up with this solution!  I have not tried it with dry transfer or laser printer resists.
-The application for artistic uses or etching Homebrew panels (and then applying paint into etched areas or Reverse Etching) are many.
-A warming plate can be obtained by purchasing a coffee mug warmer (about $10), or chopping the top off an old drip coffee maker and removing the plumbing.  This same plate can later be used to warm the PCB when doing Surface Mount or regular soldering.

Of course, Vinegar alone, will do the job; or Vinegar and Salt, or Vinegar and Hydrogen Peroxide if that is all you have.  But it will just take longer by hours.

Caveat

My university chemistry is about thirty years old.  Corrections gratefully accepted.

Why this wasn't thought of years ago is surprising. I couldn't believe how quick and simple it is.
« Last Edit: December 20, 2013, 01:42:09 PM by KB4QAA » Logged
KB4QAA
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« Reply #1 on: December 20, 2013, 01:48:47 PM »

Numerous corrections and additions made over the course of about an hour or so, particularly for chemistry and safety.  Bill.
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W5FYI
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« Reply #2 on: December 21, 2013, 12:47:25 AM »

Two more for you; I think you meant "ferric chloride solution" instead of "Ferric acid," and table salt is NaCl, not NaCl2.

Actually, I learned of this method about a year ago. I think I first saw it in Make magazine or on YouTube. Its major drawback it that it is so much slower than the ferric chloride or hydrochloric acid and peroxide methods, and its major benefit is that most people already have the "chemicals" on hand.

Thanks for bringing it to this forum.
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K8AXW
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« Reply #3 on: December 21, 2013, 08:45:39 AM »

I've always used Ferric Chloride.  Three major things I learned about using this etchant.

1 - It is slow.  That spells disaster on many PCBs with narrow/thin traces because the longer the PCB is in the etchant the more undercutting you will have, which in some cases will eat through narrow/thin traces.

2 - Heating Ferric Chloride to 100-110°F speeds things up quite a bit....like from 20 minutes to 10 minutes.

3 - Etching time is reduced dramatically if the etchant is agitated, especially using aeration. 

I've used a fish tank pump with two outlets for years, feeding plastic tubing glued to the bottom of my homebrew tank.  The tubing has many holes made with a red hot needle and the result is thousands of bubbles agitating the etchant.  With the heated etchant and aeration, you can say it almost washes the copper off.

Al - K8AXW
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KB4QAA
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« Reply #4 on: December 21, 2013, 10:34:02 AM »

-Chemistries noted.  Unfortunately I can't modify the original post.  I'll keep the spare Cl atom; never know when it may come in handy.  Smiley

-Air hose piercing!  That is one detail I've never seen mentioned.  Thanks.  bill
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WD4HXG
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Posts: 297




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« Reply #5 on: December 21, 2013, 06:58:18 PM »

Check out the last third of the page at this web site
on using Ferric Chloride with a sponge wipe. Author
claims you can etch a board in just a couple of minutes
using his technique. You use a sponge, an ounce or
two of ferric chloride solution and a zip lock bag.

http://www.pcbfx.com/main_site/pages/tech_support/no_etching_tank.html

Also the etching speed is reported to be increased in
another website by adding citric acid to the Ferric
Chloride. Google Edinburg method. This is more of
an arts and craft site but it provides interesting
reading.

http://www.polymetaal.nl/beguin/mape/edinburgh_etch.htm

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K8AXW
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Posts: 6360




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« Reply #6 on: December 21, 2013, 08:22:04 PM »

QAA:  To elaborate on the pin holes in the plastic hose......

I have a dual output fish tank aerator.  I use a length of 1/4" clear plastic tubing from each output and glued to the bottom of my etching tank.  The two lengths of tubing are separated by about 2" and each end of the tubing is pinched and glued shut. 

Each length of the tubing has a pin hole spaced about every inch or inch and a half.  I used a red hot needle held with pliers to make the holes. 

The result is that when the tank is filled with etchant and the pump is turned on the tank is filled with air bubbles which not only adds oxygen to the etchant but also provides a "washing" action which reduces the etching time considerably.

Al - K8AXW
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