Steve, if you haven't already, ask your supplier why they want the
silkscreen between pads.  We've found that our vendors often have quirky
ways of handling things that support their own unique processes and that
anything we can do from a design standpoint to support that yields better
product, even if it doesn't make a lick of sense to us.  I've had the same
experience as Brad notes below, but I'd really love to know why they're
asking for such a thing and how successful they are doing it.

Bob
Robert A. Croslin
Manager, Engineering Services
Nielsen Media Research
375 Patricia Ave
Dunedin, FL 34698
727-738-7033
[log in to unmask]

 -----Original Message-----
From:   Vanderhoof, Brad [mailto:[log in to unmask]]
Sent:   Wednesday, July 31, 2002 4:27 PM
To:     [log in to unmask]
Subject:        Re: [TN] silkscreen as solder dam?

I have built boards with silkscreen between chip component pads and had
problems with glue adhesion.  The smt adhesive would peel the silkscreen off
the soldermask.  Now when I see this in design I ask to have it removed.

Brad Vanderhoof

-----Original Message-----
From: Steve Thomas [mailto:[log in to unmask]]
Sent: Wednesday, July 31, 2002 9:16 AM
To: [log in to unmask]
Subject: [TN] silkscreen as solder dam?


Greetings...

Our overseas assembler wants us to add a line of silkscreen between pads on
bottom-side 0603 R's and C's,
apparently as a solder dam to reduce bridging in wave solder.  There already
is mask between pads, so this seems
a bit out of the ordinary (we do very little two-sided assembly here but I
have never seen bridging on chips).

Has anyone ever seen this done?  Does this sound like a design band-aid to
fix a process problem (talk about the flip side of
a coin!)?  How do you attribute a bridge underneath a glued-on part to wave
solder?  I don't have the benefit of a thorough
knowledge of their process, but I'm speculating they may be printing their
glue with a squeegee contaminated with solder paste.

Your thoughts?

----------------------------------------------------------------------------
-----
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
ext.5315
----------------------------------------------------------------------------
-----

----------------------------------------------------------------------------
-----
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
ext.5315
----------------------------------------------------------------------------
-----

---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------