Controller heat sink - thermal paste?

I want to put thermal paste on the controller mosfet heat sink. But when I opened it up there is a plastic material between the mosfets and the conductive metal of the heat sink which connects to the case. Should I put ceramic thermal paste (it’s the only thing I have, shouldn’t be conductive) between the plastic and the mosfets and between the plastic and the metal bar?

PS: I just blew up my multimeter and almost my finger. I tried to use voltmeter mode while a probe was connected to the 10A unfused amp measuring thing. BOOM!

The tape is there to protect against internal shorts of a chip so all others don't get shorted.

I re pasted mine too leaving the tape where it is, and it did lower the temps by about 8C. I put the thermal paste between the metal bar and the side of the controller. No unscrewing of the mosfets needed from the tape and the metal bar.

Remember, the paste is not there to conduct heat. It's actually not all that conductive of heat, compared to a direct metal-to-metal connection.

It is there to fill the tiny air gaps and scratches in a properly fitting heatsink-to-component connection, and *only* those gaps, to keep the air that otherwise fills them from blocking the heat flow.


The kapton tape by itself is probably better than paste on top of kapton.

If you want to really improve cooling, make the back of the FET mounting bar, the part that connects to the case, as flat and smooth as possible, and do the same to the inside of the case itself where the bar mates with it. Look up "lapping" as used in CPU cooling/overclocking; this is what you would do.

If it is done right you wont' actually need paste, and will ahve a much better thermal path just because much more metal is actually now in contact. (and no paste in the way of the heat path).