50 MHz Cortex-M4 — what this core buys the design
The NXP MK12DX128VMC5 is a Kinetis K12 series microcontroller built around an ARM Cortex-M4 core clocked at 50 MHz.
The actual package is a MAPBGA (likely the 121-ball variant common to the K12 family), which means the part is a BGA. Rework requires a hot-air station with a fine nozzle and a preheat plate; the ball pitch is tight enough that a stencil and reflow profile matter more than hand-soldering skill.