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September 2002

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Subject:
From:
"McCall,Doug" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 17 Sep 2002 14:46:31 +0100
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Peter,

Have you considered the possibility of the solder resist being damaged
during
the solder wicking of the pads before placing the replacement package.  This

can make placing and getting good reflowed devices extremely anoying!

Also, might seem like a strange one, but I have seen what looks to be a
short on an x-ray which is actually intentional if you look at your gerber
files
where the two balls are for instance at ground etc ...

Regards,

Doug McCall
PCB Manufacturing Engineer - Eastbourne
BOC EDWARDS
Marshall Road,
Eastbourne,
East Sussex,
BN22 9BA UK
' +44 (0) 1323 501 147
7 +44 (0) 1323 509 824
*   [log in to unmask]

BOC Edwards is a part of BOC Limited
Registered Office: Chertsey Road, Windlesham, Surrey GU20 6HJ
Number 337663-English Register
Ultimate holding company: The BOC Group plc



        -----Original Message-----
        From:   Peter Lee [SMTP:[log in to unmask]]
        Sent:   09 September 2002 21:16
        To:     [log in to unmask]
        Subject:        [TN] BGA rework - excessive collapsing

        Technet,

        We are having problems replacing 35mm BGA, 1.27mm pitch on a OK
industry
        BGA rework station. The resulting X-ray revealed a solder bridge at
one
        corner.

        There was some warpage on the BGA but not significant. PCB was
        reasonably flat. Thermal profiling was done to ensure all temp. were
        optimum. I did notice the BGA balls collapsing quite a bit (at least
        half of the ball height) after rework.

        Anyone has suggestion on how to minimize the chance of bridging? Is
it
        common for BGA of this size? We don't have the capability to paste
the
        board for BGA rework.

        Rgds,
        Peter


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