50 ns reverse recovery — what it buys the switching stage
Its 50 ns reverse recovery time places it in the ultrafast class — the stored charge clears quickly enough to keep the switching losses low in a 50–100 kHz PFC boost stage or a center-tapped output rectifier on a flyback converter.
Obsolete — sourcing and replacement strategy
ST lists the STTH15AC06CFP as obsolete.
TO-220 Full Pack — no insulator needed
The TO-220-3 Full Pack (ST calls it TO-220FPAB) is a fully isolated plastic package. The back tab is electrically isolated from the die, so the part can be bolted directly to a heatsink without a mica washer or thermal pad — one fewer assembly step and a lower thermal resistance junction-to-case. The 175 °C junction rating lets it run hot in a cramped PSU or an engine-bay converter without derating the 7.5 A average current per diode.
Common-cathode pair — one part replaces two discretes
The 1-pair common-cathode configuration means the two anodes are independent and the cathodes are tied internally. That matches the topology of a center-tapped secondary rectifier or a two-diode boost PFC where the cathodes share the output rail. Using the STTH15AC06CFP saves the board space of two separate TO-220 diodes and cuts the pick-and-place count in half.