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Reply To: | TechNet E-Mail Forum. |
Date: | Thu, 21 Jan 1999 08:59:40 -0500 |
Content-Type: | text/plain |
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Ken,
You didn't say if the board is a multilayer, if so, you may need to
check lay-up construction for metal distribution. Uneven stackup can be
a major cause of warp. We are a pcb vendor and we do not regularly
'dewarp' boards.
Anne Ledger
EMDS, Inc.
> -----Original Message-----
> From: Ken Nevius [SMTP:[log in to unmask]]
> Sent: Tuesday, January 19, 1999 4:33 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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