Definition

Current capacity (ampacity) is the maximum current a trace can carry within acceptable temperature rise - typically 10°C, 20°C, or 30°C above ambient. Depends on: trace width, copper thickness, layer location (external vs internal), and acceptable heating. IPC-2152 provides charts and formulas. Rule of thumb for 1oz external: 1A per 0.25mm width at 10°C rise. Internal traces carry ~50% less due to poor heat dissipation. For high current, use multiple vias in parallel, thicker copper (2-4oz), or copper pours. Thermal simulation validates high-power designs.