The STTH1R04 is a 400 V, 1 A fast-recovery rectifier from STMicroelectronics, built for the continuous-current side of a PFC boost stage or the secondary side of a flyback converter where reverse-recovery losses eat into efficiency. The 30 ns trr keeps the switching node from ringing into the MOSFET's body diode during hard commutation, which is the difference between a clean 100 kHz waveform and a hot, noisy one. Forward drop hits 1.5 V at the full 1 A rated current — typical for a fast-recovery part in this voltage class, and you budget that drop into the thermal calculation for the DO-41 axial leaded package. The 5 µA reverse leakage at 400 V is a room-temperature number; at the 175°C junction limit it rises substantially, so derate the reverse voltage if the ambient inside the enclosure runs hot.
ST lists the STTH1R04 as Obsolete. No last-time-buy window remains open through the franchised channel. Any stock you find today is independent-distribution inventory — pulled from overstock, allocation leftovers, or end-of-life buybacks. The DO-41 axial form factor is common enough that cross-shipping a reel from a broker is straightforward, but you want to qualify the date code and test a sample for trr and Vf before committing a production run.
Package and mounting — through-hole axial
The DO-204AL (DO-41) axial leaded package is a through-hole part. It wants a 0.025-inch diameter hole on 0.3-inch lead spacing. The tape-and-box packaging (TB) means the leads are formed for automatic insertion but the body is loose in a box, not taped on a reel — verify your pick-and-place or hand-loading workflow accepts that format.