Definition

Trace width determines both current-carrying capacity and characteristic impedance. For current: 1oz copper at 10°C rise carries roughly 1A per 0.25mm width on outer layers, half that for inner layers. IPC-2152 provides detailed calculations. For impedance: wider traces have lower impedance - a 50Ω microstrip on FR-4 might be 0.2mm wide over a 0.1mm dielectric. Minimum trace width depends on manufacturing capability: 0.15mm standard, 0.1mm advanced, 0.075mm HDI. Trace width affects routing density, thermal performance, and signal integrity.