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April 2003

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From:
Brian Ellis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 9 Apr 2003 08:59:54 +0300
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Adam

In a former life (c. 35 years ago), I used CuCl2 in a shop I directed.
My experience is that the oxygen addition could not come from O2 but had
to come from O. We had a system that measured the Redox and dosed in
dilute H2O2 and HCl (separate streams) in stoichiometric proportions. We
had a safety feature so that, if anything went wrong, no Cl2 was
generated. This was the only way we could get consistent results. The
etch time for a given weight of copper was constant for months on end.

We had an overflow, so that the excess quantity of solution was
collected for regeneration of the copper.

Brian

Adam Seychell wrote:
> 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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