On 02/27/2017 05:13 PM, Lee Hart via EV wrote:
Mark Hanson via EV wrote:
Heat sink grease should be NON conductive electrically but thermally
conductive white grease. You can also use thermosil less thermally
conductive but less messy or Kapton.
"Conductive" heat sink compounds usually aren't all that conductive
(i.e. they won't carry high currents). It just means you can't depend on
them as an insulator.
When you really do want high electrical conductivity, they solder the
chip to the heatsink. Note that "solder" can mean many different metal
alloys. Many of them melt at far lower temperatures, so you can solder
without damaging the semiconductor.
I'd prefer to be able to remove the components from the heatsync in the
future if I ever need to replace them, so I'm avoiding any adhesive or
solders.
All this may all be academic when attaching to an aluminum heatsink. The
aluminum is going to have an insulating oxide layer no matter how hard
you try. It takes *substantial* clamping force to break this oxide
layer; more that most semiconductors can stand.
My plan was to hit it with a bit of sand paper just before connecting.
It sounds like a lot of the electrical connectively may be coming from
the screw that holds the part to the heatsync (I imagine the threads
develop enough pressure to get through the oxide, even if the back of
the parts do not.)
Jay
_______________________________________________
UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
http://lists.evdl.org/listinfo.cgi/ev-evdl.org
Read EVAngel's EV News at http://evdl.org/evln/
Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
