Graphite vs. Grease TIM

Petio_Natzkin

Hi,

what are the advantages and disadvantages of a graphite sheet versus grease TIM for power modules like the Wolfpack CAB016M12FM3?

BrettSparkman

Hello Petio_Natzkin,

Graphite sheets typically rely on high compression to achieve their claimed good thermal performance.

Good is relative; it has lower performance than many grease TIMs in application from our experience.

It doesn’t tend to fill gaps as well, even under high compression. 

We do understand it could perhaps help lifetime due to no pump-out/drying mechanism, but there are also TIMs formulated to reduce pump-out/drying.

We use graphite sheets on some of our test benches for ease of application and cleanup, but ONLY for modules with baseplates.

We still recommend a grease TIM, regardless. 

The thermal interface is very important for WolfPACK.

Especially for WolfPACK products, performance may suffer, as the compression is only provided by the spring tabs (and not direct bolts into a large rigid baseplate).

The offset of the compressible layer could also increase spring relaxation, further reducing potential compression.

Our WolfPACK datasheet values are based on the grease TIM we use, and may vary depending on coldplate and TIM utilized in the end application.

Some more information about this here: https://forum.wolfspeed.com/discussion/385/wolfpack-thermal-resistance

Thanks,

Brett

Petio_Natzkin

Thanks for the educational answer, Brett!