A piece of natural or synthetic mica cut to match the footprint of a power transistor or voltage regulator. It sits between the component's metal backing and a grounded aluminum heatsink. Mica boasts excellent electrical insulation properties while remaining highly thermally conductive, preventing short circuits without trapping destructive heat inside the semiconductor package.
Don't forget to put a mica insulator and a dab of thermal paste behind that TO-220 transistor before you bolt it down, or you'll short the collector straight to the chassis.
Rookies often forget the thermal grease; a dry mica insulator leaves microscopic air gaps that ruin the thermal transfer.
Related terms
TIM
A time interval meter, an instrument used to measure the precise time elapsed between two events.
Thermal design power
The maximum amount of heat a cooling system must be able to dissipate from a chip under typical heavy workloads.
MOSFET
A metal-oxide-semiconductor field-effect transistor is a voltage-controlled switch used to amplify or switch electronic signals.
Hot chassis
A piece of equipment where the metal frame is electrically connected directly to the mains power line.