Adam,

You are likely to get as many answers to this question as there are people
that have etched with cupric since the free acid parameters can be set from
zero Normal to as high as 5 Normal in every day running etchers.

Your regeneration system that you describe can work but simply pumping in
room oxygen would not be fast enough to regenerate the working solution
while average amounts of copper are being etched. The oxygen pumped would
have to be under very high pressure and that poses a whole new set of
problems.

The answers to your questions are not trade secrets but I am curious...What
is the end result of the project you are working on? Is this for scientific
curiousity or for a practical project?

You may contact me both on TechNet and offline to continue this discussion.

Best regards,

Phil Culpovich
[log in to unmask]
www.oxfordvue.com

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Adam Seychell
Sent: Tuesday, April 08, 2003 8:52 PM
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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