45 ns trr — the number that defines this part
The STMicroelectronics STTH1R06A is a standard fast-recovery rectifier diode rated for 600 V DC reverse voltage and 1 A average rectified current. Its 45 ns reverse recovery time (trr) places it squarely in the fast-recovery class, designed to handle the high-frequency switching in power supplies, PFC stages, and flyback converters where recovery losses directly affect efficiency and thermal budget. The 1.7 V forward voltage at 1 A is typical for a 600 V fast diode — expect conduction loss to be a factor in the heatsink calculation, not a surprise.
Package and reflow reality
It comes in a DO-214AC (SMA) surface-mount package. That is a standard footprint for automated pick-and-place, but the SMA body is small — check your solder-paste stencil aperture for adequate fillet height. No MSL rating is listed in the record, so treat it as MSL 1 by default (no bake required) unless the reel label says otherwise.