Why sleeves over Mosfet and Transistor?

MrChips

Joined Oct 2, 2009
20,368
They are thermal insulating pads. They are required to conduct the heat away from the transistor tab and still provide full electrical insulation from the mounting hardware. I have never seen one like that before.

Google thermal transistor insulating pads.
Also Keratherm transistor insulators.
 

MrChips

Joined Oct 2, 2009
20,368
The weird thermal paper stuff is most likely mica insulators. You apply silicone thermal paste on these.

Another option is to choose transistors with the insulated tab option. It is a good idea to check all the different package styles of the same transistor designation. Often times there is an insulated version.
 
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