Carrie,
From a high rel perspective in the Aerospace Industry, any part rated one
watt or greater had to be isolated from the PWB laminate surface.This could
be accomplished by a thermal plane on the suface, sleeving the part or
lifting it off the surface.
This goes back to the days when lower Tg FR4 materials were in use and may
have been more of a problem.In working with IPC, it was felt that the
compatibilities of the parts, materials used and the resultant exposures to
thermal excursions should be assessed prior to production.Any unique
requirements should be AABUS (as agreed between user and supplier) and
therefore is no longer part of the requirements definition.It it was to be
anywhere now, it should be in 6011 or 6012 as design related criteria.
Dewey


> -----Original Message-----
> From: Morse, Carrie [SMTP:[log in to unmask]]
> Sent: Thursday, March 11, 2004 7:27 AM
> To:   [log in to unmask]
> Subject:      [TN] Can't remember a darned thing!
>
> Since, for some reason, I can't remember a darned thing lately, I was
> wondering if someone could tell me WHERE within all of our IPC specs I
> can find where it specifies at what wattage we need to start raising
> resistors off the board (ex: 1W, 1.5W?)
>
> Thanks,
> Carrie
>
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