Trace Resistance

Trace Resistance

Every copper trace on a PCB has electrical resistance. Understanding this is crucial for power delivery: too much resistance drops voltage across the trace, causing components to receive less power than expected.

The resistance formula is:

R = ρ × L / (W × T)

Where:

• ρ = resistivity of copper = 1.72 × 10⁻⁸ Ω·m
• L = trace length (meters)
• W = trace width (meters)
• T = trace thickness (meters)

Common copper weights:

Example: A 100 mm long, 0.5 mm wide, 1 oz (35 μm) trace: R = 1.72×10⁻⁸ × 0.1 / (0.0005 × 0.000035) = 98.3 mΩ

Your Task

Implement traceResistance(lengthMm, widthMm, thicknessMm) that returns resistance in milliohms (mΩ).