The STM32F405VGT6J is an STMicroelectronics ARM Cortex-M4 MCU running at 168 MHz, with 1 MB of Flash and 192 KB of SRAM. This is the part you pick when you need DSP-class number crunching and enough memory to run a real-time OS with a moderate application stack, all in a 100-pin LQFP that reflows cleanly with a standard hot-air station.
Obsolete — sourcing plan needed
STMicroelectronics lists the STM32F405VGT6J as Obsolete. For production or repair, you are looking at the independent surplus and broker channel.
Package and rework — 100-LQFP
The 100-LQFP (14x14 mm) is a garden-variety quad flat pack with 0.5 mm pitch. It reworks well under hot air — the exposed pad is absent, so no risk of cooking the board from underneath.