What the 125 ns trr means for your switching stage
The STTH6012W is a 1200 V, 60 A fast-recovery rectifier from STMicroelectronics, built for high-voltage, high-current power conversion. Its 125 ns reverse recovery time (trr) is the headline number — fast enough to keep switching losses manageable in continuous-conduction-mode PFC stages and hard-switched SMPS output rectifiers running at 50–100 kHz. At 60 A average forward current and a 2.25 V forward drop at that current, the junction temperature rating of 175°C gives thermal headroom, but you will still need a proper heatsink — the DO-247 tab is designed for one.
Mounting and field-service angle
Through-hole DO-247 with straight leads — no hot-air station needed, just a soldering iron and a desoldering pump. If you are swapping this in a power supply on site, the orientation is obvious: the metal tab is the anode, the cathode is the centre lead. The package is standard enough that a replacement from the field kit will fit without bending leads. Just watch the heatsink — the mounting hole pattern is the same as TO-247, so the thermal interface is straightforward.
Lifecycle — still an active line
The base product number STTH6012 covers the whole family, so if you need a different package variant later, the design can migrate within the same silicon.