Hi Adam,
I am running cupric chloride etching for almost 20 years .
Have in mind, that etching of copper is result of the following reaction:
Cu(0) + Cu(+2) = 2 CuCl .
Presence of univalent copper slow down the reaction dramatically due to
kinetics and also due to poor solubility of cuprous chloride.
"regeneration" is basically  re-oxidation of cuprous ion to cupric. In
alkaline condition ( as in ammoniacal etcher) it is working via atmospheric
oxygene. In acidic conditions this is not working and can be done only by
strong oxidizing agent such as hydrogen peroxide or chlorates. Control of
this can be done by redox or by photometer ( cuprous chloride is very dark
compared to pale green of cupric chloride ).
Free acid is required for both "regeneration" and dissolution of cuprous
chloride. Too high acid concentration will accelerate atack on Titanium
parts in the machine.
We are working at copper concentration at range of 140-150 gr/lt and free
acid arround 2.5 N. It is possible to push the copper higher without effects
on etching, but I need this "spare capacity" to get rid of acid rinse that
follows the etching section in the machine.
Edward


Edward Szpruch
Eltek Ltd
P.O.Box 159 ; 49101 Petah Tikva Israel
Tel  ++972 3 9395050 , Fax  ++972 3 9309581
e-mail   [log in to unmask]

> -----Original Message-----
> From: Adam Seychell [SMTP:[log in to unmask]]
> Sent: ã àôøéì 09 2003 5:52
> To:   [log in to unmask]
> Subject:      [TN] cupric chloride parameters
> 
> The CuCl2 +HCl is a new etchant I've been experimenting with in the lab. I
> am trying to develop a lab sized room temperature etching system that will
> be entirely regenerated with atmospheric oxygen and HCl/water additions.
> After many many hours of experimenting I have reached the conclusion that
> etching rate improves with increased dissolved copper(II), and around 160
> ~
> 180g/l showed to work nicely (specific gravity = 1.28). At 75g/l of copper
> the etch speed was 4 times slower. Surprisingly I also found the free HCl
> concentration has a relatively small effect on etch rate. It can etch
> happily  without acid ! ... BUT, the copper(I) produced during etching is
> the grand etching killer. If copper(I) is allowed to get too high it forms
> a
> white film over the copper and can stop etching dead in its tracks. So,
> copper(I) is kept very low by bubbling air through the acidic solution,
> HCl
> present 0.1 to 0.5N.
> 
>      HCl + CuCl + O -> CuCl2 + H2O
> 
> I have some questions on commercial CuCl2 etchers, such as operating
> parameters they use. What is the copper(II) concentration range, what is
> the
> specific gravity, and how much acid is in there ? What happens when copper
> gets too high, or when acid is too high ? Do my finding agree with those
> who
> have experience with CuCl2 etching ?
> 
> I'm especially interested finding information on the characteristics of
> cupric chloride etching and how each component effects etch rate and
> performance. Is all of this trade secrets ?
> 
> 
> Adam Seychell.
> 
> VIC, Australia.
> 
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