John,

My short answer is the board thickness requirements do not need to be
referenced in 6012.  The board print controls the total thickness,
dielectric and tolerance.

Of course, it never hurts to have a default value if there is no print so I
would not be opposed to such an addition.

Mike

> -----Original Message-----
> From: John Perry [SMTP:[log in to unmask]]
> Sent: Wednesday, September 20, 2000 5:37 PM
> To:   [log in to unmask]
> Subject:      [IPC-600-6012] End Product Requirements for Board Thickness
> Tolerances
>
> Hello Everyone,
>
> IPCWorks 2000 has come and gone.  Ready for Expo in Anaheim?  Sheez, are
> you kidding?
>
> As participants in the IPC-6012 and IPC-A-600 groups, many of you have
> also been involved with the IPC-2220 design series, and many of you may
> recall the ancient IPC-D-300G Printed Board Dimensions and Tolerances
> document.  This old dinosaur was recently replaced by the IPC-2615,
> thankfully without the outdated end-product requirements such as bow and
> twist and annular ring, all of which have been updated through the years
> where they belong - in the design and performance specs.
>
> One, however, hasn't been transferred to the appropriate requirements
> documents, and I wanted to make sure that it was an intentional exclusion.
> IPC-D-300G used to provide tolerances for board thicknesses.  We don't
> have any applicable tolerances for this in any of the other spec.  Sure,
> IPC-4101 does provide tolerances for laminate materials (Table 7) , and
> IPC-6012 and IPC-A-600 provide thicknesses for foil plus plating (under
> review now as we speak!), but did we intentional avoid the transfer of
> nominal thickness tolerances for finished rigid boards to the design and
> performance series of documents that we currently use for boards?  Should
> we point people to the use of IPC-4101 in conjunction with the IPC-6012?
> As always, your input is much appreciated.
>
> Best Regards,
>
>
>
> John Perry
> Technical Project Manager
> IPC
> 2215 Sanders Road
> Northbrook, Il 60062
> 1-847-790-5318 (P)
> 1-847-509-9798 (F)
> [log in to unmask]