Ed W1AAZ wrote:
> >The heatsink compound at RS says that it is highly conductive -- not
> >sure if they are speaking of electrical or heat only. It is a
> >silicon based product. Is this stuff ok?
>
> Many of the MOSFet's (and transistors) have their drain (or collector)
> electrically connected to the metal tab. When fastening the tab to the heat
> sink, the tab must be electrically insulated from the heat sink. This is
> typically done using a thin mica insulating washer. In addition metal
> hardware is typically used to fasten the device and a through the hole
> washer (teflon) must also be used.
I believe most heat sink compound is zinc oxide particles (which provide
the heat transfer) suspended in a high temperature grease (usually
silicone based). Both ZnO and silicone grease are dielectric, though
I can not cite a breakdown voltage spec or dielectric constant. I
know my jar of Wakefield heat sink compound claims to be electrically
non-conductive ;-).
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