Heat Sink Question

[Keith]

I just purchased a few Heat Sink mounting kits that come with the hardware and an insulator to support a TO-220 mount. My question is do I need to purchase and apply a heat sink compound to this assembly or is the mounting kit and insulator sufficient? Thanks.....

[Kiriakos-GR]

Usually I add thermal compound in the back plate of the transistor and at the heat sing.
The existence of the insulator plate does not change anything.

 

[alm]

Depends on the type of insulation. Hard stuff like mica needs thermal grease to fill all voids, the soft silpads can be deformed and will do most of the work themselves, although I guess a tiny amount of thermal grease wouldn't hurt. Thermal grease is necessary to displace any air that's inevitably present between two hard surfaces that are not perfectly flat, but copper or aluminum conduct much better, so always use thermal compound sparingly.