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Date: | Thu, 27 Feb 97 15:20:39 EST |
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Maximize total copper on all layers - this will minimize your etching
load (cost). Use solid copper borders with 0.125" vacuum channels.
Use 16ga. (0.060" thk.) separator plates, preferably hardened 420SS.
Ensure adequate resin volume to fill the non-functional space and
account for this reduced volume in the overall thickness prediction.
Depending on your chemistry, you can probably expect 6-8 mils of line
width reduction (i.e., blow the .024" track up to .030"-.032"). Can
your photoresist withstand the required etchant exposure time?
Keeping pH on the low end might buy you a little extra time. If this
is a high-volume program, do a mfg.cost reality check per pound of
etched copper. (Cupric chloride, incidentally, etches the same for
roughly half the cost depending, of course on a myriad of other
factors).
Good luck.
J.Felts
PC World, Toronto
______________________________ Reply Separator _________________________________
Subject: FAB: 3 layer board with 4 oz copper
Author: [log in to unmask] at INET
Date: 2/27/97 2:46 PM
I have 2 issues that I'd like to get some advise on.
1) Does anybody have advise on etching 4 oz copper? The traces are .024" and
we etch with ammoniacal etchant.
2) Is there any advise on laminating a 3 layer board with 4 oz base copper
on all layers? .062" finish thickness and the layup is at our discretion.
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