: Moving away from fixed 3-tier systems to scale annular rings proportionally with hole diameters.
The IPC-7351C PDF provides the formulas to calculate all three. It is the designer's responsibility to choose the correct tier based on the product requirements, not just copy a generic footprint from a CAD library. ipc-7351c pdf
Today, the IPC-7351C standard is deeply integrated into PCB design software. : Moving away from fixed 3-tier systems to
The most interesting story is what the PDF doesn't shout. IPC-7351C was the result of a battle between two tribes: ipc-7351c pdf
(relocated to the beginning of the name in the "C" revision) Refined Courtyard Guidelines : Shifts from rectangular courtyards to contour courtyards