Bill, I fall into the same camp as Peter, I like the non-functional pads for
additional hole wall support. If however you have a high layer count board
with heavy (>1oz) Cu then hole quality can (probably will) be affected to
some degree by the retention of the NFP's. Para 9.1.4 in IPC 2222 refers
Regards
Ian Fox
Goodrich Engine Control Systems
-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: 27 March 2003 05:43
To: [log in to unmask]
Subject: Re: [TN] non functional pad removal
No specs, Bill, but some experience that may help.
"Non-functional pads", as you probably know tend to be generated as an
inherent feature of routing packages - you specify through-holes and
associated pads for the outer layer of a PCB, and that information gets
copied throughout the layer stack to save the router having to re-specify
them for every layer that needs connection to the barrel.
Thus there are plenty of internal pads that have no traces attached to them
on certain layers, and these are the 'non-functional' ones. Some fab houses
like to remove these pads, especially in fine line boards, to reduce any
risk of short circuits occurring between them and neighbouring traces or
other electrically powered features. I wonder how good the etching processes
are whenever I get a removal request from a fab house. There are usually
options in Gerber readers used by fab houses to remove these pads at the
press of a button, but the customer should be given the option of retaining
or removing the pads if there is not other instruction one way or the other.
I specify not to remove N-F pads on my PCB drawings.
Keeping or removing N-F pads is subjective. Me, I prefer to keep them, as I
believe that they help to support the barrel plating against resin recession
and hole pull-away effects, should there be any, but others I respect are
quite happy to get rid of them. I disagree with them naturally, but it makes
for healthy debate.
Peter
Bill Decray <[log in to unmask]> 27/03/2003 04:33 AM
Sent by: TechNet <[log in to unmask]>
Please respond to "TechNet E-Mail Forum."; Please respond to Bill Decray
To: [log in to unmask]
cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
Subject: [TN] non functional pad removal
Hello fellow TechNet Guru
Does anyone have or know off any specifications that talk about removal of
non functional pads and what effects it has on a finished circuit boards if
any
Highest Regards,
William W. DeCray III
Waytec Electronics Corp
Engineering Services Manager
PHONE:(434) 237-6391 ext 115
CELL: (434) 851-6115
FAX: (434) 237-1324
E-mail:<[log in to unmask]>
Web http://www.waytec.com
FTP ftp://ftp.waytec.com
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