Mixed-signal MCU in a wafer-level package
The 51 GPIOs are brought out in a 66-bump WLCSP (3.8 x 4.2 mm), a fine-pitch wafer-level chip-scale package that saves board area but demands careful PCB layout and assembly capability.
1.8 V supply rail — plan the power tree accordingly
The internal POR and BOR circuits are calibrated for this low-voltage domain, so brown-out thresholds will be lower than what you see on a 3.3 V part — factor that into the system reset strategy. The WLCSP package has a 0.4 mm ball pitch typically, so the PCB requires via-in-pad or microvia capability for routing.
No end-of-life notification, no last-time-buy window. If dual-sourcing is a concern, the STM32F3 series includes pin-compatible siblings with different Flash/RAM or package options — ST's product-change notification (PCN) process applies if any variant shifts status.