35 ns reverse recovery — what it buys you
The STTH302 is a 200 V, 3 A fast-recovery epitaxial diode from STMicroelectronics in a DO-201AD axial-lead package. Its 35 ns reverse recovery time (trr) puts it in the class of diode you pick for the boost stage of a PFC front-end or the output rectifier of a 100 kHz flyback converter — not for 50 Hz line rectification, where a standard 1N5408 would do. The 950 mV forward drop at 3 A is the trade-off for that speed; a Schottky at this voltage rating would drop less but lack the 175°C junction rating and the ruggedness against reverse-recovery snap-off that this part's epitaxial construction provides.
Package and thermal — the DO-201AD reality
The DO-201AD axial package is a through-hole format that needs the leads formed and inserted into the board. At 3 A continuous, the junction-to-ambient thermal resistance of this package means you will want adequate copper pad area or forced airflow if the ambient is above 50°C. For a rework or repair scenario, the axial leads make this a straightforward hand-solder swap — no hot-air profile needed.