Paul- Good question. I'm not aware of any that don't attach through some
sort of interposer such as a standoff. The only time I've ever seen these
used were on wave soldering where the board had thru-holes in it, the
interposer (stand-offs) was actually part of the metal heat sink and a hefty
weight was used to keep the heatsink in contact with the IC (we used thermal
compound between the IC & heat sink). As I recall, Aavid made this heat sink
as a custom part for us; I believe it was made of a copper, but had a
coating on it to prevent premature oxidation (may have been solder or tin
dipped). I do remember it was very pricey; something like 10X what a
'normal' heat sink was. We eventually decided to move away from this because
of costs.

Quite honestly, it didn't work any better or worse than a heat sink held in
place by screw down standoffs.

Most heat sinks these days are made from aluminum just to keep costs down-
not sure if you want to try soldering these...

Hope this helps.

> Bill Davis, Ph.D.
> S3, Inc.
> Senior Scientist
> 408.325.7868
> [log in to unmask]
>
>


-----Original Message-----
From: PAUL BROWN [mailto:[log in to unmask]]
Sent: Thursday, October 07, 1999 8:49 AM
To: [log in to unmask]
Subject: [TN] hot topic


Hello all,

Does anyone out there know anything about surface mount heatsinks? This
would be a heatsink that is placed over top of a component before reflow
and attached directly to the board during the reflow process, or is
attached to some secondary features, which they themselves are attached
by surface mount.
Who makes them?  Were can I get them? How well do they work?
Any info would be much appreciated...........................Paul Brown

NPI Process Engineer
Newbridge Networks Corporation

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