Gil,
Gil,
Some more things to think about in this analysis:
1. A few pictures are worth a thousand words. Do you have some photos
(global overview of ass'y and some local shots) that Steve can post?
2. Certainly, as has already been mentioned, random component failure
is high on the list, especially any parts that can be across the rails
such as big "H" bridge FETs, connectors, dc/dc modules, etc.
3. You said the board's been working for more than a year. That being
said, was it removed & reinstalled, pulled out of its chassis, swapped
into another slot, etc., prior to the incident?
4. A cross section in perpendicular axes to check registration and
verify stack-up is always a worthwhile effort.
5. What can you tell us about board assembly chemistry? No-clean, OA
w/wash, etc.? It may be informative to have some ion chromatography
done in a more remote, non-damaged area to see what the board's
cleanliness was like.
6. Is there any initial test & especially rework history on this board,
and if so, could this event be related to it?
7. When trying to pinpoint the location of the original failure, take
into account any airflows from fans that may have been running at the
time. Nothing like good steady airflow to get a honkin' 48 volt power
supply short to start melting its way through a board ... planes and
all.
8. If this occurred near the edge of the board, consider any possible
initial damage that could've been done to the laminate during
depanelization, especially if the board has buried capacitance (BC)
cores, with power and ground spaced 2-3 mils apart. In such a design,
fractured laminate can be a recipe for disaster, especially in high
humidity environments.
Bruce Tostevin
Benchmark Electronics
Hudson, NH
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Zilber Gil
Sent: Tuesday, September 04, 2007 1:26 PM
To: [log in to unmask]
Subject: [TN] Help needed on motherboard failure analysis
Hi,
Recently one of our motherboard failed. It reaches very high temperature
that melts the copper and explodes shooting (from the side of the board)
the melt copper to over 20 cm. the shooting hole cause delamination of
the board in the area. A lot of black smoke and was also seen. The max
voltage of the board is about 50V. The board worked fine for more then a
year. What could be the failure mechanism? Could it be due to conductive
filament formation (although the PCB should be free of that)?
Thanks
Gil Zilber
Elta Systems
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