Datasheet

STM32F103x8, STM32F103xB Package characteristics
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Figure 36. Recommended PCB design rules (0.80/0.75 mm pitch BGA)
Dpad
Dsm
Dpad 0.37 mm
Dsm
0.52 mm typ. (depends on solder
mask registration tolerance
Solder paste 0.37 mm aperture diameter
– Non solder mask defined pads are recommended
– 4 to 6 mils screen print