I have found suitable replacements for the twin IRF350 in my max 20 plasma cutter. The old MOSFET did not have heat sink compound on them.

My question is, would putting the compound on the replacements interfere with the drain part of MOSFET as drain is "the case"? Thank you.

 

I have found suitable replacements for the twin IRF350 in my max 20 plasma cutter. The old MOSFET did not have heat sink compound on them.

My question is, would putting the compound on the replacements interfere with the drain part of MOSFET as drain is "the case"? Thank you.

Using a thin layer of heat sink compound between the case and heat sink is a good idea.
The compound should have no effect on the electrical connections.
Even if there is an electrical connection to the case through the heat sink, the mounting bolt will provide a good current path between case and heat sink.

 

Haven't seen your application, but soldering a mosfet can provide both good heat and electrical conduction. Of course, that is not possible when the mount is aluminum. Can you provide more information and maybe a picture?

John

 

Very good info, I will use the compound on my new MOSFET.