Hi,
Actually these "unused" pads are replicates of the hole "rules" created for
the surface layers. Most routing packages, or routers, seem to do this by
default for each layer to save manual replication where traces, etc are to
be connected. (At least PADS, Alegro and Mentor do). On the grounds that
it's always easier to destroy than to build, it's easier to delete pad data
than to create it, so it's put in by default as there's a good chance it
will be needed.
I still say you should consider hole barrel strength/support issues before
just deleting them - e.g. they can constrain the "resin recession" and hole
wall pull-away that have been recent threads on this forum. Think of the
"unused" pads as 'wall ties' holding the copper at frequent intervals to
the hole wall. Copper bulging or pull-away in the event of recession or
whatever is reduced.
Peter Duncan
Hinners Hans M Civ
WRALC/LUGE To: [log in to unmask]
<Hans.Hinners@ROBI cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST
NS.AF.MIL> Aero/ST Group)
Sent by: TechNet Subject: Re: [TN] Remove unused "dead" pads on
<[log in to unmask]> internal layers
01/15/02 09:40 PM
Please respond to
"TechNet E-Mail
Forum."; Please
respond to Hinners
Hans M Civ
WRALC/LUGE
Hi Patrick,
As others have said, I don't think the class of board matters for "unused"
pads. It all depends on what your procurement documentation states, are
you
building to drawing or is there a clause that says process improvements
that
do not affect functionality are permissible.
"Are they really unused pads?"
They may be electrically nonfunctioning but they are there for a reason -
better lamination quality (avoiding low pressure areas or excessive prepreg
flow), better hole wall quality, better plating quality (esp. for any
isolated traces), reduced loading of your etch solution or better thermal
loading during assembly.
Hans
Integrity First - Service Before Self - Excellence in All We Do
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Hans M. Hinners
Electronics Engineer
Warner Robins - Air Logistics Center (WR-ALC/LUGE)
226 Cochran Street
Robins AFB GA 31098-1622
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-----Original Message-----
From: Patrick Lam [mailto:[log in to unmask]]
Sent: Friday, January 11, 2002 5:12 PM
To: [log in to unmask]
Subject: [TN] Remove unused "dead" pads on internal layers
Hi TechNetters,
For class 3 boards, is it acceptable to have unused pads removed on
interanal
layers.
Thanks,
Pat
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