Gil

I am dubious that this is a CAF failure. CAF failures have specific 
earmarks. They are cause by operating a board in a very high humidity 
environment at the board surface.
This is normally precluded because of the heat generated by the board which 
drives the local humidity to a low value even if the ambient humidity is 
high. The defect is by definition a growth that originates at the anode and 
eventually reaching a cathode.

I suspect that a conductive residue was present in or on the innerlayer that 
eventually caused a short to form between adjacent features. Some of the 
causes that I have seen for such a failure are: poor cleaning after etch, 
conductive residues such as human hair entrapped between layers and moisture 
in the innerlay and prepreg which eventually cause a short.

Best regards

Lee

J. Lee Parker, Ph.D.
JLP Consultants LLC
804 779 3389


----- Original Message ----- 
From: "Zilber Gil" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, September 04, 2007 1:25 PM
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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