The STTH2002DI is a 200 V, 20 A fast recovery diode from STMicroelectronics, built for circuits where switching speed matters more than a standard rectifier. Its 40 ns reverse recovery time (trr) is the spec that decides fit: it keeps the diode from conducting backward during the turn-off transition, which directly cuts switching losses in PFC stages, output rectifiers in flyback converters, and snubber clamps. The 1.1 V forward drop at 20 A means 22 W of conduction loss at full load — the TO-220AC insulated package (with the tab electrically isolated) handles that heat, but the heatsink needs to be sized for the duty cycle.
Package and thermal: TO-220AC insulated
Through-hole TO-220AC with an insulated tab — the mounting hole is electrically isolated from the cathode, so no insulating washer or thermal pad is needed between the tab and the heatsink. Reverse leakage is 10 µA at 200 V, which stays low enough at elevated junction temperatures to avoid thermal runaway in typical 100 kHz SMPS designs.