Current Carrying Capacity

What Is Current Carrying Capacity?

Current carrying capacity (also called ampacity) is the maximum amount of electrical current a PCB trace can carry without exceeding a specified temperature rise above ambient. When current flows through a copper trace, resistive losses generate heat proportional to I²R, where I is the current and R is the trace resistance. If the heat generated exceeds the trace's ability to dissipate it through the board and surrounding air, the trace temperature rises — potentially damaging the board material, degrading solder joints, or in extreme cases melting the copper trace entirely.

Current carrying capacity depends on trace width, copper thickness (weight), whether the trace is on an outer layer (better thermal dissipation to air) or an inner layer (heat trapped in dielectric), ambient temperature, and the acceptable temperature rise (typically 10°C to 20°C for most applications). IPC-2152 provides the industry-standard charts and formulas for calculating trace current capacity under various conditions. Power traces, motor drive connections, and battery charging circuits commonly require trace widths far wider than signal traces to safely carry their operating current without excessive heating.

Power-Aware Trace Sizing in AI Layout

Current carrying capacity is a physical constraint that intersects with routing density and board area — wider power traces consume more routing space and can create congestion around power components. Physics-driven AI layout tools can automatically size power traces based on their expected current loads, ensuring that each power net has adequate copper width while minimizing the impact on signal routing density. This automated power-aware sizing eliminates the common manual layout issue of power traces being undersized in congested areas or oversized in areas where space could be better utilized for signal routing.

Other glossary terms

Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.
There are no available glossary items matching the current filters.
Reset