Ken,
        What type of oven do you have and how many zones do you have?
It may also be helpful to list the zome temperture settings for the rest
of us to comment.  Is this a panelized board with various routed areas
or does it have various cut-outs in it?

Wade Oberle
[log in to unmask]


        -----Original Message-----
        From:   Ken Nevius [SMTP:[log in to unmask]]
        Sent:   Tuesday, January 19, 1999 3:33 PM
        To:     [log in to unmask]
        Subject:        [TN] Bowed Boards

            We have been seeing boards come off our reflow oven with bow
and twist
            that exceeds IPC specs.  Our vendor insists that we are the
only
            customer that complains about this.  We had our reflow oven
calibrated
            and it looked fine.  The only thing about the profile that
may be
            suspect is the cooling rate may be a little too fast.
According to the
            vendor, they put all of their boards through a de-warping
process.
             The vendor has tweaked their de-warping process to cool
slower in an
            effort to make the problem go away.

            My question is:  This is our first bout with warping, what
should we be
            looking at for a cause?  Is it normal for a pc board vendor
to have to
            de-warp boards?


            Regards,

            Ken Nevius
            Veeder-Root
            Altoona,  Pennsylvania

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