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Date:
May 10, 2006 12:13 PM
Author:
Steve Combs
Subject: Capacitor Shorts after Depaneling
We have a 6 up panel with a 1206 part .082" from the board scoreline. After depanelization when we run the board through ICT it fails for a short at that location. We have visually inspected at high magnification for any cracks in the body and at the terminations but none are visable. When you put a volt ohm meter on it it shows a dead short. We are using a CAB depaneler (http://www.cabtechn.com/separators.html) to separate the cards. (No hand breaking is allowed.) It is not a component issue since this part # is used across the board. Also, this is a leaded process and the V scores are to spec. We have seen this issue with other products but we added a rout to reduce stress at the trouble areas. This is not a option with this board and a respin will not happen. Has anyone else had issues like this? I was under the impression the the slicer type depaneler would put minimum stress on a board. Thanks in advance.
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=41461)
Date:
May 10, 2006 01:03 PM
Author:
PWH
Subject: Capacitor Shorts after Depaneling
It sounds like your depaneling method is good. The only thing left to look at is to see if the depaneler is hitting the part somehow from the cutter or the bottom plates. I've seen time and time again where an operator has a part in contact with the bottom plates on a cutter or nibbler and they don't realize they are damaging a part because they can't see the bottom side. If not an issue, then it's my opinion that stresses are induced in the PCB during reflow that are putting the surface in compression or tension. When you depanel, these stresses relieve and damage the solder joint. If you can't re-spin to a routed PCB, then you might have to skip this part SMT and place it hand-add to get you through the order.
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=41463)
Date:
May 10, 2006 01:21 PM
Author:
Steve Combs
Subject: Capacitor Shorts after Depaneling
Thanks for the reply. We have carefully inspected the part and solder joint after depaneling and all looks good. What is weird is if you remove the part from the board and check continuity with a meter you have a dead short. If you put on a new part on the board, voila, it passes. Like I said earlier, there are 2 other of the same part numbers located in the same area as the problem part but we have no issues with them.
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=41464)
Date:
May 11, 2006 05:28 PM
Author:
brad
Subject: Capacitor Shorts after Depaneling
Steve,
We have had the same problem at my company and unfortunately I do not have any good news for you. We are using a pizza slicer type depanalizer from FKN and if the MLCC caps are layed out too close to the edge they still break. We had to add the problem cap on by hand until we could get a re layout through where we moved the cap .25" away from the score line and reduced its size to an 0805 which solved the problem. Here is a link to the AVX website they have a ton of info on this subject. http://www.avxcorp.com/techinfo_doclisting.asp?Category=Ceramic+Capacitors
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=41493)
Date:
May 12, 2006 12:41 PM
Author:
Steve Combs
Subject: Capacitor Shorts after Depaneling
Thanks Brad. Good information.
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=41513)
Date:
May 17, 2006 05:36 PM
Author:
Stephen
Subject: Capacitor Shorts after Depaneling
Just curious.
Do you use a motorized one or a hand powered one.
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=41609)
Date:
May 18, 2006 10:14 AM
Author:
Steve Combs
Subject: Capacitor Shorts after Depaneling
Its motorized
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=41633)
Date:
May 25, 2006 11:38 AM
Author:
Renato Torres
Subject: Capacitor Shorts after Depaneling
Hi Steve
I had that problem before and what caused this it was the vibration of the depaneling process, without hitting any component, if the capacitor is too close to the depaneling edge chances are you are facing the same problem I had.
The way how we found this it was with the help of Massachusets University in a very precise study.
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=41788)
