Joe,
In answer to your 1st question as to why heatsinks would be isolated
from ground planes. In my experience this happens when you are making a
card as a 3rd party vendor to go in a conduction cooled rack and you
have no control over the ground quality of this rack. It would in this
situation unwise to prejudge the quality of the rack ground. VME board
manufactures adopt this policy for these reasons.
Best Regards,
Neil

>----------
>From:  Joe Reichert[SMTP:[log in to unmask]]
>Sent:  22 September 1997 16:57
>To:    [log in to unmask]
>Subject:       [DESIGNERCOUNCIL] Heatsinks to Ground Planes?
>
>Could anyone give me some insight as to why heatsinks would be isolated
>from ground planes?  My first thought would be to minimize emission or
>absorption of noise, but I've never had a problem with this...that I
>know of, anyway!
>
>Also, has anyone had any experience with using a copper layer to
>transfer heat from a heatsink to...(for instance an aluminum case).  The
>heatsink is applied directly to the copper layer and a few inches away
>the copper layer is attached to an aluminum case via a bracket.  (the
>aluminum case is sealed closed).  Any insight would be greatly
>appreciated!!!
>
>Thanks,
>Joe Reichert
>
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