128 KB Flash and 64K x 8 SRAM — firmware headroom for real-time control
The 128 KB Flash (128K x 8) and 64K x 8 SRAM give this MCU enough room for a moderate-sized application stack — think a CANopen node with USB firmware update capability, or a multi-axis stepper controller with a small RTOS. The 64 KB SRAM supports moderate data buffering; if your application needs larger frame buffers or extensive lookup tables, you will want to budget the RAM against your task list early in the design phase.
100-ball BGA — footprint and rework considerations
Housed in a 100-LFBGA (Low-profile Fine-pitch Ball Grid Array), this part is surface-mount only. The BGA package saves board area compared to an LQFP but requires X-ray inspection for solder-joint verification and a rework station with hot-air profile control. The 80 I/O count gives plenty of GPIO for parallel displays, external memory interfaces, or sensor arrays.
STMicroelectronics lists the STM32F105VBH6 as Active.