Dittos to all what Dwight said. . Seal bagging will prevent oxidation only. If warpage occurs  during  assembly, it can be corrected.  Many boards are mounted in such a way that will make them flat. As long as warpage is within limits, it's fine.  On the other hand, boards that need to slide into a card cage have to be straight or very little warpage, much less than the limits.
        Regards,
        Ramon.


> -----Original Message-----
> From: Dwight Mattix [SMTP:[log in to unmask]]
> Sent: Wednesday, May 05, 2004 1:54 PM
> To:   [log in to unmask]
> Subject:      Re: [TN] Raw Card warpage
>
> At 12:09 PM 5/5/2004 -0500, Victor G. Hernandez wrote:
> >Fellow TechNetters,
> >
> >    At a PWB factory setting is a final baking process permissible to
> >correct any warpage prior to customer shipment.
>
> Some customers allow it or do not specify either way.  Some customers
> specify against it.  If not specified either way then tacit approval for
> "flat baking" is generally assumed to be given.
>
> >Once the sealed bag is
> >open and product not used for an extended period of time will the
> >warpage return.
>
> Not necessarily. It will only rewarp if the pwb design is unbalanced
> (either in dielectric stackup or in metal pattern distribution).  An
> unbalanced design will (re)warp to some degree when heated during solder
> assembly.
>
> Dwight Mattix
> Sr Staff QE, Corp Eng
>
> >Victor G. Hernandez
> >
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