35 ns reverse recovery — the switching-loss ceiling
The STTH3R06S is a 600 V, 3 A fast-recovery epitaxial diode from STMicroelectronics, housed in a DO-214AB (SMC) surface-mount package. Its 35 ns reverse recovery time places it in the ultrafast class for a 600 V part — fast enough to keep switching losses low in a continuous-conduction-mode PFC boost stage running at 100 kHz or so. The 1.7 V forward drop at 3 A is the conduction-loss trade-off for the speed. At 175°C maximum junction temperature, the die can handle the thermal stack from both conduction and switching losses in a compact layout.
SMC package — rework and board-fit realities
DO-214AB (SMC) is a standard footprint — the same as many 3 A to 5 A rectifiers. The cathode tab is the backside of the package; the copper pad area under it sets the thermal resistance to the board. A 600 mil² pad with a via array to an inner-layer copper pour keeps the junction below 125°C at 3 A continuous. It reworks cleanly under hot air at 290°C with a 3–5 second dwell. The package body is large enough to grip with tweezers, and the polarity band on the cathode end is moulded into the body — no ink mark that can rub off.