Homebrew PCBs

You say that the solution is brown because CuCl is present diluted in the etchant, and this can only happen when the chloride ion concentration is high, right?

And the way to get the etchant *right* is to bubble it a lot. Meaning I don't have to add more copper or water? (the etchant works as it is right now, btw)

About the look of the regenerated etchant: You mention deep green, I can see some green going on, at the sides of the tank where etchant has splashed, but the rest of the etchant is dark brown. Is it supposed to be clear in the end or not? If I pick up a drop of it in a piece of paper tissue it stains it green.

Thanks
Fp


  ----- Original Message ----- 
  From: Adam Seychell 
  To: Homebrew_PCBs@yahoogroups.com 
  Sent: Sunday, April 27, 2003 8:06 PM
  Subject: Re: [Homebrew_PCBs] Home made etchant


  I've seen what you have just described. What you are doing when 
  adding water to a dark solution of CuCl2 and some CuCl is the 
  CuCl precipitates out as what solid on dilution, thus leaving 
  only green CuCl2. The CuCl is only soluble (which makes the 
  solution dark brown) when the chloride ion concentration is high.
  Diluting will of course also reduce the concentration of CuCl2 
  and slow down etching rate.

  If you bubble enough air through the solution it *WILL* 
  eventually go deep green. Put a drop on a white piece of plastic 
  and come back in a few hours, if turns clear green then it means 
  the solution is not complete regenerated. Fine bubbles are many 
  times more efficient at regeneration than large bubbles. Aquarium 
  airstones are ideal. It can take an hour or more of vigorous 
  bubbling.

  Adam.

  frajopea wrote:
  > Hello,
  > 
  > I've been reading for a few weeks now, this is my first post.
  > 
  > There was a post about regenerating FeCl using HCl, I had a bunch of 
  > used up and very rusty etchant lying around so I did it. I poured HCl 
  > in the used etchant and the result was a very nice clear green/bluish 
  > solution that etched boards again. I was impressed.
  > 
  > Then there was the CuCl2 thread, where you just use copper, HCl and 
  > H2O...
  > 
  > With all this in mind, I kept using my regenerated etchant and 
  > pouring some HCl every now and then when it started to look brown. 
  > The thing is, now the etchant is brown, no matter how much HCl I put 
  > in it, I can't get it back to the clear transparent green I first had.
  > 
  > The other day, I was cleaning a board using water and: the clear 
  > green solution!... I made the experiment of adding water to a sample 
  > of the etchant and it did change color and turned clear green. The 
  > only problem is: it didn't etch, at least not fast enough for me to 
  > notice.
  > 
  > Now, I don't know enough about chemistry to figure this out, but is 
  > it possible that if I add copper and do the bubbling, that it'll turn 
  > clear green again? I mean, I think there's too much HCl and not 
  > enough of the other stuff!
  > 
  > Thanks,
  > Fp
  > www.tonepad.com
  > 
  > 
  > 
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