Fred <
        I have tried that on various occasions over the years and
actually use a thinning process to make 50u" nickel foil from 75u" foil.
In a word it is real tough. The hardest part is to get a uniform etch.
The cleanliness of the foil and the wettability of the surface by the
etchant solution are critical to success. A slow etch rate material will
give the best results. I did a lot of copper work in the 80's and found
that a solution of cupric or ferric chloride, (with a good surfactant ie
FLorad FC99) chilled to 40-50 0F gave the best results.( it etched very
slow , and the surfactant helped to uniformly wet the surface. Solution
movement was slow without direct sparging on the surface.  Even at that
it was difficult. The etch rate of the solution was constantly monitored
and used to control the process.
        A last thought is that unless the foil You are working with is a
precision rolled foil the thickness variation across the foil be too
great to allow precise control of the thickness.
If I can be of Further Assistance let me know

Russ Smith

E-mail russell.smith @ cibasc.com
 ----------
From: Fred Johnson
To: [log in to unmask]
Subject: [TN] copper etching
Date: Monday, March 23, 1998 9:02PM

Hello all;
I would be interested in hearing any comments about etching down 1oz.
copper foil to 1/4 oz or 3/8 oz.  It is our understanding that this
requires a
specific equipment set to control the uniformity of the thickness across
the panel surface; it is also our understanding that chemical control is
very important (although I am not sure what types of chemistry may used
for this process, i.e. cupric, sulfuric/peroxide, etc.).

Any suggestions for equipment and chemistries would be appreciated.

Regards,
Fred Johnson
JMSPI

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