I'm will you. CAF is more fuse like. If aboard failure caused this, it would
have done so by causing a component to fail. Even a shorted polarized cap
not likely to have a low enough resistance to cause the power drop to be in
the copper like that. I like the transient theory, failed SCR, shorted FET .
. I have seen that turn board copper into a puddle at only 25 volts.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar
Sent: Wednesday, September 05, 2007 3:03 AM
To: [log in to unmask]
Subject: Re: [TN] Help needed on motherboard failure analysis
Gil,
Is this a howitzer of some kind?
What motherboard? Computer or servo system or medical apparatus or what?
We may get a clue if you could describe the board a little. How many layers?
Power supply capability? Fuses? Connector size? Capacitor size?
Is this an office box, outdoor working, in a vehicle or what? Sounds to me
as not being an office machine. 50 Volts is a lot. You may get some 100
amperes of current during milliseconds, which means maybe a 5,000 Watt
spike, enough to cause severe damage. My first idea is an incoming
transient. Have you checked the status of the components on the board.
That should be first step. Finally , I don't think the cause is the board.
Start checking the components. Blown power tyristors, FETs, transistors?
Look for cooling problems, number one today. Check inductors, DCDCs,
tranformers, if there are any on the board. Look for overheated components
that can have melted solder in PTHs. Wished I had that board on my desk,
very delicate case!
Inge
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Zilber Gil
Sent: den 4 september 2007 19:26
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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