I feel your pain. I think the difference in paste deposit would be
significant and on fine pitch could lead in an increase in defects without a
new stencil or change in board design.  So, I talked to our parent (a board
shop) This is what they said: 

The bulging solder mask on the surface is a normal phenomenon that occurs
during via plugging of the holes.  If the hole size is to large to plug
during an initial coating of solder mask (usually larger than 7 mils), then
a secondary coating of mask is added which could add 2-5 mils in height
above the metal.  If the customer is concerned about additional height above
the metal and they want the holes plugged, epoxy filling is an option, but
an expensive one.

It sounds like your old vendor had a good process for your board design. Did
they close or were you bargain hunting?




*** We are Moving - March 20, 2007 ***
Guy Ramsey
R&D Assembly
1660 East Race Street
Allentown PA 18109-9580
(610) 264-1887
FAX (610) 264-1877

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Matt Kehoe
Sent: Friday, March 09, 2007 12:01 PM
To: [log in to unmask]
Subject: [TN] Paste Volume, off contact vs non off contact

We have been processing a family of boards for 3 years. No issues. New PCB
Vendor and the boards suddenly will not print very well. Sloppy printing
definition. Heavy heavy deposition.

Closer inspection reveals that the soldermask is built up .0012-.0019 over
the vias, preventing the stencil from gasketing. Vendor claims they are
built to print.. Opinions? 

Pictures at ;
http://www.sipad.com/ssiqa/3942vias.pdf
http://www.sipad.com/ViasBuildup.pdf

The question we are trying to answer is, if your boards came in with mask
this thick over the vias would you feel confident in running them without
modifing the stencil? Would you expect a significant increase in solder
volume?


mk

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0 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/contentpage.asp?Pageid=4.3.16 for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100
ext.2815
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------