Trace Resistance Input Panel
Enter physical trace data, copper properties, load current, and high frequency options.
Example Data Table
| Case | Length | Width | Copper | Current | Expected Use |
|---|---|---|---|---|---|
| Signal line | 75 mm | 8 mil | 1 oz | 0.1 A | Logic routing |
| Power branch | 120 mm | 30 mil | 1 oz | 2 A | Small supply rail |
| High current path | 60 mm | 100 mil | 2 oz | 8 A | Motor or LED driver |
Formula Used
Base resistance: R = ρ × L / A
Temperature adjusted resistance: RT = R × [1 + α × (T - Tref)]
Voltage drop: Vdrop = I × RT
Power loss: P = I² × RT
Cross sectional area: A = width × thickness × parallel traces
Skin depth estimate: δ = √(2ρ / ωμ)
The AC result is an engineering estimate. It uses skin depth and roughness factor to raise the resistance when frequency is high.
How to Use This Calculator
- Enter the total trace length from source to load.
- Enter trace width and select the correct unit.
- Choose copper thickness in ounces, micrometers, millimeters, or mils.
- Add parallel traces when several identical conductors share current.
- Set current, operating temperature, and copper properties.
- Enter frequency only when AC or fast switching behavior matters.
- Press calculate to view resistance, voltage drop, loss, and graph.
- Use CSV or PDF buttons to save the calculated report.
Trace Resistance Design Guide
Why Trace Resistance Matters
Trace resistance affects every printed circuit board. A copper path may look wide. Yet it can still waste power. It can also reduce voltage at the load. This matters in power supplies, LED boards, motor drivers, sensors, and chargers. Small resistance values become important when current rises.
Geometry Controls Resistance
Resistance depends on length, width, and copper thickness. Longer traces have more resistance. Wider traces have less resistance. Thicker copper also lowers resistance. Parallel traces share current and reduce the effective value. Extra bends and detours increase length. This calculator includes those allowances for practical board layouts.
Temperature Changes the Result
Copper resistance increases as temperature rises. A trace measured at room temperature will not behave the same inside a warm enclosure. The temperature coefficient adjusts the base value. This helps designers check worst case operation. It is useful for compact products where airflow is limited.
Voltage Drop and Heating
Voltage drop is current multiplied by resistance. Power loss is current squared multiplied by resistance. That means current has a strong effect on heating. A small resistance can still create noticeable heat at high current. Use the loss value to compare trace options. Lower loss usually improves reliability.
High Frequency Effects
At higher frequencies, current tends to crowd near conductor surfaces. This is called skin effect. Surface roughness can add more loss. The calculator gives an approximate AC resistance. It is not a field solver. It is a quick planning tool for early electrical decisions.
Better Board Decisions
Use this tool before routing final copper. Try wider traces, thicker copper, and shorter routes. Compare voltage drop with your circuit tolerance. Review current density for stress. Keep sensitive loads away from excessive drop. A simple resistance check can prevent many board problems.
FAQs
1. What is trace resistance?
Trace resistance is the electrical resistance of a copper path on a circuit board. It depends on length, width, thickness, copper material, and temperature.
2. Why does a PCB trace cause voltage drop?
Every copper trace has some resistance. When current flows through it, voltage is lost across that resistance. Higher current or longer traces increase the drop.
3. Does wider trace width reduce resistance?
Yes. A wider trace gives current more copper area. More area lowers resistance, voltage drop, and heating for the same current.
4. What does one ounce copper mean?
One ounce copper is a common board copper weight. It is approximately 34.8 micrometers thick before processing variations and plating changes.
5. Why is temperature included?
Copper resistance rises as temperature increases. Temperature adjustment helps estimate real operating resistance, especially inside hot or sealed enclosures.
6. What is current density?
Current density shows current per copper area. High values may indicate stress, heating risk, or the need for wider traces.
7. Is the AC resistance exact?
No. It is an estimate based on skin depth and roughness. Use field simulation or lab testing for critical high frequency layouts.
8. Can this calculator replace safety standards?
No. It supports early design checks. Always verify final layouts with board rules, thermal limits, standards, and real testing.