kg7hf@comcast.net wrote:
> I would think that might be overkill, because when you bolt the spreader to
> the heat sink, the two pieces are going to conform to each other, in fact,
> they are going to expand and contract as the heat is applied and dissipated
> anyway.
I like the idea of trying as planer - although I shudder to think what
my wife would do to me if I sent metal through her big thicknesser :-)
Given the thickness of metal, I doubt there will be much movement in the
surfaces conforming. The issue is metal to metal contact at a much
smaller scale - undulations and high spots in the scale of 1" and
smaller, and also at a microscopic level.
The glass plate work shows how far from flat an extruded heatsink
surface is. If you take something that really is flat then centre punch
a hole, drill, tap and deburr it, go back to the glass plate and see
what a mound surrounds the new hole. Your heat spreader or transistor is
sitting on a small raised area and you've lost most of the thermal
contact area.
Air is a very poor heat conductor, and thermal grease is only marginally
better. Neither is a substitute for close fitting metal-metal contact.
Steve
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