TECHNET Archives

August 2006

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Jerry Dengler <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Jerry Dengler <[log in to unmask]>
Date:
Thu, 31 Aug 2006 15:11:48 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (69 lines)
Steve,

This may sound strange but are you absolutely sure that the board is bad
before you "repair it".  In a previous life we had product that would
fail at test but actually had no defect.  The problem turned out to be
poor connections at test.  If you tested the boards they would fail at
an alarming rate.  When you disconnected and reconnected the boards they
may pass or may fail.  This finally lead us to the real problem.

Jerry Dengler 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Thursday, August 31, 2006 2:58 PM
To: [log in to unmask]
Subject: [TN] LLP (Leadless Leadframe Package) headaches...

Good Afternoon my fellow esteemed TechNet-ologists,
 
We're building a little double sided SMT board that has a National Semi
6-pin LLP (Leadless Leadframe Package) device on it.
We call this little board a "Leaf" board because of it's shape:
http://stevezeva.homestead.com/files/LLP.jpg
 
The problem on this board is the LLP device. We've gotten quite a few
boards back from test stating that the board failed test and that U4
needed to be re-reflowed. 
 
This is not the first time I've heard this prognosis from a test
department to correct a problem with a board. Almost every time I've
looked into this issue, I've not seen a problem with the solder joint,
or a problem with the reflow profile, or anything else that you would
naturally look at to try and explain why re-reflowing would correct the
problem. Not to mention the fact that the parts that are right next to
the questionable device are fine with no problems whatsoever. Yet when
you re-reflow the part it will usually pass test the second time around.
 
I've had this happen with QFP's, SOIC's, PLCC's, and now this LLP.
Obviously it must have something to do with the solder joint, but what
is it man?!?! I've scratched my head about this more than a few times. 
 
What does re-reflowing a perfectly good looking solder joint cause a
board to pass test where it didn't pass before?
 
-Steve Gregory-  

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

ATOM RSS1 RSS2