Why? It’s a basic part on JLC PCB which we’ll use to order your PCB

Datasheet:

https://www.lcsc.com/datasheet/lcsc_datasheet_2302211130_STMicroelectronics-STM32F103C8T6_C8734.pdf

Make sure to use the LQFP48 pinout

Some good sections to read:

• Pinouts and pin description(LQFP48): Pg. 26