Nominal Package Dimensions For Courtyard Excess

In PCB design, courtyard excess refers to the specific clearance area between the combined physical boundary of a component (body and pads) and the outer boundary of its placement courtyard. This buffer zone ensures that components have sufficient space for manufacturing tolerances, mechanical assembly, and potential rework without interfering with neighboring parts.

Courtyards should not overlap in the part placement. Courtyards are used in a variety of ways in different CAD tools. The courtyard excess values are defined in the 3-Tier density levels for surface mount components.

In the Footprint Expert, the default courtyard outline maps to the pads and the Maximum package body dimensions. Mapping the courtyard outline to Maximum package body dimensions is affected by package tolerances. Package tolerances vary between component manufacturers affecting the resulting courtyard excess value. There is a Drafting Option switch in the Footprint Expert to change the courtyard outline to map to the Nominal package body. Using Nominal package body is not affected by package tolerances and provides a consistent courtyard excess for all footprints regardless of the package tolerance values. IPC-7352 only recommends mapping to the Maximum package dimensions, but industry consensus is leaning toward using Nominal package dimensions because component manufacturer tolerances are sometimes too robust and unrealistic.