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October 2003

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Subject:
From:
robert Tarzwell <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 23 Oct 2003 18:49:22 -0500
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The methoed of layering dry film can be used up to about 20 oz of plated
copper, it is very accurate and fine featres, there is some concern to get
the surface flat, and plating bars help. THe most accurate I have produced
is 10 mil lines and spaces in 20 oz. I started with 1/2 oz and did not use
a tin etch resist , only a fast etch to keep things acurate.

You can buy copper up to 40 oz from many copper roof sheeting companies,
use full soft 110 and clean them well before laminating or dry film lots
of oil and crap . The best I got up to in etching only is about 12 -15 oz
and the accuracy was not good, 30 to 50 mil lines. most companies that
manufature heavy copper use a combination, start with 3 to 5 oz and plate
up 3 to 5 oz, cheeper , less time in the copper tank and good acuuracy
about 2-3 mils per oz line and spaces. The thicker copper in the vias
makes the board very strong and will not crack even with high theremal
cycling.
If you need help my e-mail is [log in to unmask]

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