WLCSP package — board assembly and rework implications
The STM32L4R5ZIY6TR: The 144-WLCSP package measures 5.24 x 5.24 mm with a fine-pitch ball array. This is not a hand-solderable QFP — it requires a solder-paste stencil, reflow oven, and x-ray inspection for void detection. The board layout must match the WLCSP footprint exactly; no pad fan-out is possible under the balls.
It is ROHS3 compliant. The base product number is STM32L4R5, and the series is STM32L4R — a current-generation ultra-low-power family with a roadmap. No successor has been announced, which is normal for an active flagship part.