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June 2000

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Subject:
From:
Gerry Savard <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 26 Jun 2000 11:21:02 -0400
Content-Type:
text/plain
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text/plain (70 lines)
I've seen shorting between center balls on BGA's caused by popcorning of
the device.  When it delaminates the laminate buldges downward, causing
pressure to be applied to the solder balls and causing bridging.  This
might not be your problem, but it's a possibility especially since it's
occurring on a particular device. Wave solder is another avenue to
investigate, particularly if there are open vias next to the BGA pads.

 Good luck.

Gerry Savard

----------
> From: Brad L. Matthies <[log in to unmask]>
> To: [log in to unmask]
> Subject: [TN] Reflow Oven Causing Bridging???
> Date: Monday, June 26, 2000 9:20 AM
>
> TN,
>
> I have been asked to take a look at our convection reflow ovens to
> verify that they are not causing bridging on an array packages?!?  The
> ovens have recently been relocated and the CFM is slightly less than
> what the previous set-up had, but is still above what the equipment
> manufacturer requires.  The array package has recently begun to show
> bridging between pins (not always the same two pins) on the center
> grouping of balls on only one of the three array packages.  There are
> two other array packages on this same board, and they show no bridging.
> We are using a x-ray to view these three compontents post reflow.  Our
> analysis indicates that the stencil is showing signs of wear and needs
> to be replaced, but I have been asked to look at the reflow profile as
> well.  I have no idea if a reflow oven (convection) can cause the type
> of bridging we are seeing.  If if could, wouldn't the bridging present
> globally or randomly rather than in the same location on the same
> component ID?  I am also wondering if a Wave profile can cause
> re-reflowed joints that would result in bridging on array packages.  Any
> thoughts would be greatly appreciated.
>
> Regards,
> blm
>
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