400 V, 30 A fast recovery — the switching rectifier for PFC and output stages
The STTH30R04W is a 400 V, 30 A fast recovery epitaxial diode from STMicroelectronics, built for hard-switched power conversion where reverse recovery losses matter. Its 100 ns trr at 30 A forward current puts it in the fast-recovery class — fast enough for continuous-current-mode PFC boost stages and secondary-side output rectification in 400 V bus supplies, without the cost and gate-drive complexity of a SiC Schottky.
DO-247 through-hole — package and mounting realities
The STTH30R04W comes in a DO-247-2 package with straight leads, a through-hole package that handles the 30 A current and the associated thermal load better than a surface-mount D²PAK at this power level. The two-lead form — anode and cathode on the body, with the metal tab as the cathode contact — is the standard for bolted mounting to a heatsink. The through-hole leads take solder or a press-fit socket; the tab is typically greased and screwed down with an M3 or #6 hardware, with an insulating washer if the heatsink is at chassis potential. For a rework technician: the DO-247 is one of the friendlier packages to extract. The leads are thick enough to survive a desoldering iron or a hot-air preheat from the board side without lifting the pad. Orientation is unambiguous: the tab is the cathode, same as the TO-247 but with a narrower body.
The reverse leakage is 15 µA at 400 V reverse voltage, a typical figure for a fast-recovery epitaxial diode at this voltage class. Leakage doubles roughly every 10 °C above 25 °C junction, so at 125 °C Tj expect leakage in the low-milliamp range — budget for it in the bias supply or snubber design.