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September 2007

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Subject:
From:
John Burke <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, John Burke <[log in to unmask]>
Date:
Wed, 5 Sep 2007 06:57:39 -0700
Content-Type:
text/plain
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text/plain (126 lines)
To get that bad it must have been forming for some time> I have had boards
do exactly that from CAF formation. Basically the filament grows, shorts,
fuses, over and over again all the while degrading the materials around it
until eventually it has enough current capacity to go into melt down.

Gil - What is the board material, and what is the minimum drilled hole to
internal copper feature clearance?

This will be a factor along with the voltage - which by the way is perfect
for CAF formation, and the humidity, which generally needs to be over 80%.

John

 
 
John Burke
 
(408) 515 4992

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Reid
Sent: Wednesday, September 05, 2007 4:33 AM
To: [log in to unmask]
Subject: Re: [TN] Help needed on motherboard failure analysis

Hi Gil,

I have seen this sort of failure a few time, although not that dramatic, and
they were attributed to CAF. The product passed burn-in and testing after
assembly, then failed months later in the field. A cross section from a
similar hole, near the failure site, one that is not damaged, may
demonstrate a laminate crack, delamination or crazing. If there is a pathway
(crazing, dielectric cracks), a CAF type failure mode may develop in humid,
thermal cycling environment.


Sincerely,

Paul Reid

Program Coordinator

PWB Interconnect Solutions Inc.
235 Stafford Rd., West, Unit 103
Nepean, Ontario
Canada, K2H 9C1

613 596 4244 ext. 229
[log in to unmask] <mailto:[log in to unmask]> 


-----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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