hi Tim,

try baking the part and modifying the reflow profile, i.e longer pre-heat at
lower temp...that may help considerably

Marcelo

        -----Original Message-----
        From:   Stammely, Tim [SMTP:[log in to unmask]]
        Sent:   Saturday, October 31, 1998 7:29 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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