I use a Starrett Grade AA 12x18" granite surface plate I found at an
equipment auction decades ago. Close to 100# if I remember and it hasnt
moved from its perch since I got it home.
Carl
KM1H
----- Original Message -----
From: "Steve Thompson" <g8gsq72@gmail.com>
To: <amps@contesting.com>
Sent: Thursday, December 12, 2013 3:35 AM
Subject: Re: [Amps] Arctic Silver
I'll echo other's comments about Arctic Silver, which I've used on
numerous high power transistor amps.
Taking for granted that the copper heatspreader and main heatsink are
milled truly flat, the crucial thing is to get the transistor flange flat
as well. The majority I've handled are not anywhere near flat, and always
bowed upwards in the centre (something that hasn't improved since the
package style first appeared ~30 years ago). I use the method mentioned by
others - fine emery face up on glass. Mirror glass is good, as it tends to
be made better and any imperfections in the surface show up.
If the copper spreader is thick enough, the heat is spread over a large
enough area whereby the heat sink compound is less significant and the
regular white stuff can be used - but even that varies in quality. I stick
to Dow Corning or Emerson.
Don't assume your copper spreader is flat just because it was machined so
in the workshop. Most of it is rolled and it's quite normal for it to
change a bit after the hard outer layer is skimmed off (just like timber).
Steve
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