What is the problem? Your design seems to be rather conventional. Are
the boards exposed to extreme vibration or acceleration, like certain
MIL products? For me, 12x13mm caps are not large. I would say that your
copper pad adhesion on the substrate isn't good. 5.7x1.6 = 9.12mm2.
Typical copper to FR-4 adhesion is 20N/mm2, so your case is equal to
20x9.12= approx. 180 N. And your caps do not weigh much.
/Inge

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Carl Proescholdt
Sent: den 7 februari 2008 23:51
To: [log in to unmask]
Subject: [TN] Retention for Larger SMT Electrolytic Capacitors

We are seeing many more larger (12.5mm Dia and 13 mm tall) SMT
electrolytic capacitors being designed into the boards we are building.
With this style part, the body is relatively large compared to the pads
(Which are 5.7mm long X 1.6mm Wide in this case).  This has led to
increased handling damage where the pads get ripped off the boards even
when operators are trying to handle them with care.  

Has anyone developed an effective method to increase the attachment
strength of these types of parts?  The only idea I have had other than
glue, is to greatly increase the pad size while using solder mask to
define the opening to match the recommended pad size for the part, but I
don't want to go off chasing a bad idea for no good reason.

As a secondary question on these types of parts, I have seen the
manufacturers selling leadfree versions that are not designed to be
reflowed at higher temps that a true Rohs compliant part should be.  Any
good ideas around that one?

Thanks!

Carl Proescholdt
dca manufacturing    

---------------------------------------------------
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
-----------------------------------------------------