The STTH10R04G-TR is a 400 V, 10 A fast-recovery epitaxial diode from STMicroelectronics, housed in a TO-263 (D2PAK) surface-mount package. Its 40 ns reverse recovery time (trr) places it squarely in the boost-PFC and flyback secondary rectification sweet spot — fast enough to keep switching losses down in a 70–100 kHz continuous-conduction-mode PFC, but without the snap-off signature of an ultrafast diode that can ring up the EMI filter.
Ratings that drive the thermal and switching budget
At 10 A forward current the typical forward voltage is 1.7 V max — that is 17 W conduction loss at full rated current, so the D2PAK's tab area needs a decent copper pour or a heatsink if the average current stays above a few amps. The 175 °C maximum junction temperature gives headroom for high ambient or tight enclosures, but the leakage current at 400 V reverse is 10 µA at 25 °C and climbs exponentially with temperature — at 150 °C junction it will be orders higher, so the thermal design has to keep the junction well below the absolute limit during reverse bias.