120 V, 10 A Schottky pair — what you get
The STPS20L120CT is a dual common-cathode Schottky rectifier from STMicroelectronics, packing two 10 A diodes rated for 120 V reverse voltage into a single TO-220-3 through-hole package. Reverse leakage sits at 120 µA when blocking 120 V, a typical figure for a 120 V Schottky of this current class. The pair shares a common cathode, so it is wired for center-tapped or half-bridge topologies — the anode of each diode is independent.
ST officially lists the STPS20L120CT as obsolete. If this part is on your active BOM, you need to qualify a replacement or secure a lifetime buy from the open market now — the available inventory shrinks every quarter as existing stock gets consumed.
Package and mounting — the TO-220-3 footprint
The supplier device package is TO-220. For a rework or repair tech: the three leads are the two anodes and the common cathode tab — the tab is the cathode connection, so the heatsink pad is electrically live. Mount it with a mica insulator and thermal grease if the heatsink is grounded.
For volume production, plan on qualifying a pin-compatible replacement or securing a surplus lot that covers your remaining build requirements.