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November 1998

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Subject:
From:
Rick Thompson <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 2 Nov 1998 08:20:08 -0800
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Tim,

In addition to the items mentioned by Mike, I'd stress that the preheat is
critical, at least in our expreience. We've found that in general, we've had
to increase preheat times over 'normal' oven profiles.  Also, the warping
down at the corners sounds like too much top heat.

Rick Thompson

> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Stammely, Tim
> Sent: Saturday, October 31, 1998 4:29 AM
> To: [log in to unmask]
> Subject: [TN] BGA rework question
>
>
> Hello all,
>
> We are trying to remove and replace two ORCA 432 pin BGA's on
> a big 14-layer
> board. We are getting alot of shorts after the rework(I'm
> x-ray inspecting).
> At first we tried solder pasting the pads with a mini stencil, but the
> amount of bridging we got caused me to try just fluxing the
> pads and letting
> the solder balls collapse, but we still got a lot of shorts. I am also
> noticing a lot of board warpage  during the rework heat cycle
> and it also
> appears that during reflow if I watch the component, the
> corners of the BGA
> collapse very early and the component almost appears to be
> bowing. Most of
> the shorts we are getting are in the corners where this last
> observation
> occurs making me think it is causing the shorts. Any
> suggestions on how to
> eliminate this problem?
>
> Thanks,
>
> Tim Stammely
> Manufacturing/Process Engineer
> MSI
> Manassas, VA
>
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