Received: |
by ipc.org (Smail3.1.28.1 #2)
id m0v6dJJ-0000RyC; Fri, 27 Sep 96 08:50 CDT |
Old-Return-Path: |
<simon.ipc.org!chaos!gray!bfgaero.com!larryc> |
Date: |
Fri, 27 Sep 96 9:49:12 EDT |
Precedence: |
list |
Resent-From: |
|
Resent-Sender: |
|
X-Status: |
|
From [log in to unmask] Fri Sep 27 08: |
57:23 1996 |
X-Mailing-List: |
|
TO: |
|
Return-Path: |
<DesignerCouncil-request> |
Status: |
O |
Resent-Message-ID: |
<"VuJIh3.0.Ck9.ekzIo"@ipc> |
X-Incognito-Format: |
VERSION=1.74 ENCRYPTED=NO |
From: |
|
X-Loop: |
|
Subject: |
|
Message-ID: |
|
X-Incognito-SN: |
632 |
Parts/Attachments: |
|
|
We have done our multilayer boards both ways, suppressing the internal pads
and including the pads. The end result, to us, it made no difference in the
attachment of the thru-hole component. The main difference is how the
vendorvenbor generates his board and if it makes a difference, real or
imagined, to them. We've heard that the internal pad helps to hold the
plating inside the hole since we're giving it an extra anchor, but you can
also increase other problems with desmear too. It may be only a function of
the thickness of your board. Generally, for us, .062. If you have a thicker
board, .093-.125, this may come in effect where an extra anchor or two will
help, but there has been no documentation that I have seen. One vendor
doesn't like to have them because he believes of the possibility of spinning
the internal pad since there is no track to hold it in place. This may or
may not be a valid point. He may be trying to extend the use of a marginal
drill bit too. What about it Pete? Don't you guys do this kind of testing
to right about in your magazine? I for one would like to know some
documented facts and get the matter settled. Until that time, as long as my
boards continue to work, I'll let the vendor do whichever way he considers
viable for his operation. I won't force him into possibly making a bad board
if I can't show him otherwise.
One other item. Plated and unplated drilled holes. We separate the two
files even though the finished hole size is the same. Our vendors tell us
that if we don't separate them then they have to manually find them to
oversize the plated holes somewhat. I don't like manual operations, to easy
for errors. Besides, it is very easy to set up your cad system to have
different drill types with the same drill size. The electronic drill
information file sent to the vendor has them broken down into drill sizes and
we specify plated or unplated.
Larry Campbell
BFGoodrich, Avionics Systems
[log in to unmask]
****************************************************************************
* The mail list is provided as a service by IPC using SmartList v3.05 *
****************************************************************************
* To unsubscribe from this list at any time, send a message to: *
* [log in to unmask] with <subject: unsubscribe> and no text. *
****************************************************************************
|
|
|