Obsolete — sourcing the STTH3R04Q for your BOM
The STTH3R04Q is listed as obsolete. That means STMicroelectronics has ended production; no further factory orders or last-time-buy windows remain.
A 35 ns trr places this diode in the fast-recovery class, suited for high-frequency switching in power supplies, PFC stages, and snubber circuits where a standard-recovery rectifier would cause excessive switching loss or ringing. The 400 V reverse voltage and 3 A average forward current cover common boost and flyback secondary-side rectification in the 50–150 W range. The 1.5 V forward drop at 3 A is typical for a fast-recovery device at this voltage class; expect higher conduction loss than an ultrafast or SiC Schottky, but the 35 ns recovery keeps the switching node clean.
DO-15 axial package — board-level fit
The STTH3R04Q comes in a DO-204AC (DO-15) axial-lead package, through-hole mount. This is a common 5 mm diameter, 7.6 mm body-length package with 0.81 mm diameter leads — a standard footprint for PTH rectifiers. The Tape & Box (TB) shipping format is typical for axial diodes; it feeds well into cut-tape or ammo-pack handling for hand-insertion or selective-solder processes. No MSL rating applies to hermetic axial diodes — no bake required before reflow, but the part is wave-solder or hand-solder only.
Junction temperature rating
Rated for a maximum junction temperature of 175 °C, which is the standard high-temperature limit for silicon fast-recovery diodes. This allows operation in elevated ambient environments such as enclosed power supplies, motor drives, or lighting ballasts where internal temperatures can exceed 100 °C. The 5 µA reverse leakage at 400 V is specified at 25 °C; leakage doubles roughly every 10 °C rise, so at 125 °C junction expect leakage in the tens of microamps — still manageable for most designs.