[Elecraft] Thermal Interface, pads vs. grease question?

Mon Jan 6 17:38:01 2003

Hi Andrey,

We officially recommend that you use the thermal pads supplied with the
KPA100 kit instead of grease. They consist of a very efficient thermally
conductive compound coated on both sides a a very thin aluminum sheet. The
compound reflows when the transistors get hot the first time and fills all
of the small air gaps between the devices and the heatsink. It is very
effective and provides a better thermal bond in most cases than manual
application of thermal grease.

73, Eric  WA6HHQ
Elecraft
=========

Andrey Stoev wrote:
> 
> Hi,
> Soon I will be finishing up my KPA100, just waiting for some missing parts.
>  My question is about  the thermal pads used for the transistors in the final stage (Q1 and Q2).
> The kit comes with some thermal pads to serve as a thermal interface between the transistors and the heatsink. My question is: can i use a thermal grease, such as Arctic Silver III (http://www.arcticsilver.com/) instead of thermal pads. As far as i know Arctic Silver contains pure micronized silver and it has very low thermal resistance and very high thermal conductivity (>9.0 W/m-K - way better than the zinc oxide grease ("the white stuff") which is ~0.735 W/m-K)  I asume, it would be better thermal conductor than the supplied pads. The electric conductivity of the compound should  not be a problem, since the emiter ciruit is grounded anyway. Better thermal interface will improve the heat transffer and will provide the PA transistors with better cooling and more accurate temperature readings from Q3. Is there any potential problems or something that i am overlooking and is it safe to experiment with it?
> 
> Thanks and 73s
> 
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