IEC 60097: Grid Systems for Printed Circuits — The Coordinate System of PCB Design

2.54 mm: The Invisible Grid That Governs Every PCB Design

IEC 60097 defines the printed circuit grid system. The fundamental grid pitch = 2.54 mm (0.1 inch) — a legacy of the DIP-packaging era that remains the default Grid setting origin in every PCB EDA tool.

Why 2.54 mm? Because early DIP ICs had 0.1-inch pin spacing — the finest pitch that human hands could reliably handle. Subsequent SMD packages (SOIC, QFP, BGA) subdivide 2.54 mm: 1.27 mm (0.05″), 0.635 mm (0.025″), 0.5 mm, 0.4 mm — every one a binary fraction of 2.54 mm.

Design rule: All pad centers must land on the standard grid — SMT pick-and-place machine vision systems rely on this. A design that deviates from the grid requires either a higher-precision placement machine (more expensive, slower) or manual soldering (less reliable).

TN Lab — Every pad position on every PCB is determined by binary subdivisions of a 2.54 mm grid.