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Date: | Sat, 17 Feb 96 13:52:23 EST |
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Good point! I agree on the linewidth tolerance issues. How about
layer counts higher than 10 layers? They get real fun to drill when
all internals are comprised of HTE copper. 1/2 oz is far more easier
to drill with all that accumulated copper. As circuit density
increases and linewidth decreases, the 1/2 oz copper will be vital
to hold required critical linewidth tolerances. Like .004".004"
(Trace/Space) on dual stripline trying to hit 50 Ohms.
(That ones fun! Especially when the material(s) tolerance window
gives you basically +/- 6 ohms)
Groovy
______________________________ Reply Separator _________________________________
Subject: FW: Half ounce internals
Author: [log in to unmask]
Date: 2/16/96 8:27 PM
One argument for using is 1/2 oz on internal layers is a reduction in line
width variation. There are very few PWB suppliers that can supply supply a
4 mil line +/-20% on 1oz copper. In addition, mixed copper thicknesses on a
layer pair [i.e. lyr 2 (top)and lyr 3 (bottom)] result in reduced yields. I
also don't believe there is anyone who can honestly quote a 3 mil line
+/-20% on 1oz copper and maintain the specification.
nwbluez
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From: TechNet-request
To: Technet
Subject: Half ounce internals
Date: Friday, February 16, 1996 4:40PM
A strong consideration for not using 1/2 ounce copper on internal
layers, is that you only half the width of copper to make a
connection at the barrel of plating. Possible problems. Be careful.
May not be reliable.
Norm Einarson
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