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From [log in to unmask] Wed May 1 09: |
34:07 1996 |
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Question on annular ring and hole breakout. Why does IPC 276 permit
breakout on outers on multilayers with PTHs? I can understand
allowing it on inners, but not outers. Breakout on outers means that
the pad associated with the hole does not cover all of the plated
through hole. In outer layer processing the image of that pad
protects the hole copper during etch. If resist or resist plating does
not cover the holes during outer layer etch, won't the hole partially
etch out. I can understand inners, but not outers. Is the spec too
loose in this area? I have seen boards with outer layer breakout with
partially etched out holes.
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______________________________ Reply Separator _________________________________
Subject: Re: registration equipt
Author: [log in to unmask] at Dell_UNIX
Date: 4/25/96 12:14 AM
Paul Waldner (Multiline Technology),
Glad to hear from you again, Paul . Yes your equipment makes it more
possible to prevent breakouts. In fact we could not get even close without
some of it; however, we have designers pushing the 18 mil hole in the 25 mil
land for the 10 layer multilayer and people trying to build them on the 18 x
24 and the 24x 36 panel.and with a 1 or 2 mil annular ring. Good luck even
with the best equipment. Realistically, many people are building to the the
IPC-RB-276 class 2 specification which allows 90 degree breakout. There has
not been any problem that I am aware of except that the misregistration may
cause shorting to a nearby trace.
Phil Hinton
Hinton PWB Engineering
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