Hi Daan,

If the same solder paste is used on other boards and there is no problem, I
do not see how the solder paste could be the cause of the voids problem on
this specific board.
I agree with the e-mail that recommends taking cross sections.
I had a similar "BIG" problem on boards that were built using sequential
lamination. By taking cross sections of the problem solder joints I found
out that the copper plating on top of the epoxy that filled the blind via
was partially missing. Further analysis proved that the electroless copper
did not cover the epoxy that filled the blind vias properly, hence the
electro plated copper was missing from these spots. It seems to me that the
pure resin, filling the blind via holes and going all the way to the
surface, needed special treatment different from the standard permanganate
that is normally used to prepare the inside of the holes for plating. AOI
was not able to detect the missing copper. If your vias in pads board is
built using sequential lamination, this could be the problem.

Regards,

Sherif Refaat, Eng.
Technology Roadmap Consultants Inc.
Montreal, Quebec, Canada
E-mail: [log in to unmask]
Tel. (514) 624 9842
Fax (514) 624 0091




----- Original Message -----
From: "d. terstegge" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, May 28, 2002 6:37 AM
Subject: [TN] Anti-voiding solder paste


Dear Technetters,

I'm having some problems with really big voids (up to 50% of the diameter)
in the solderjoints of BGA's. The problems occur on our only board that has
via's in the BGA-pads. The via's are filled and plated, so from the outside
you don't see they're there.
I'm quite sure that it's the board that's causing the problems, but the
boardvendor does not agree and thinks our solderpaste is causing it.
To prove that I'm right  (or to solve the problem if the boardvendor is
right !) I'd like to do some tests with a solderpaste that's known to cause
a minimal amount of voiding. From earlier discussions I learned that such
solderpastes exist.
Does anyone have a recommendation for such a solderpaste ?

Daan Terstegge
SMT Centre
Thales Communications
Unclassified mail
Personal Website: http://www.smtinfo.net

----------------------------------------------------------------------------
-----
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
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 delivery of Technet send e-mail to [log in to unmask]: SET
Technet NOMAIL
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 1.8d
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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL
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
---------------------------------------------------------------------------------