Definition

A footprint (or land pattern) defines the copper pads, solder mask openings, and silkscreen markings needed to mount a specific component package on a PCB. Footprints must match the component's lead pitch, pad dimensions, and overall package size. IPC-7351 provides standardized footprint dimensions for common packages. Footprints include three density levels: most (largest pads, easiest assembly), nominal, and least (smallest pads, highest density). For new components, obtain recommended footprints from manufacturer datasheets or use IPC calculators. Incorrect footprints cause assembly defects: too small leads to weak joints, too large causes bridges.