External Layers (Outer)
10 °C Temperature Rise
Trace width requirements for outer layers with 10 °C temperature rise above ambient. Most conservative design for signal integrity and reliability. Based on IPC-2152 standard.
Current vs. Trace Width
IPC-2152| Current (A) | Min Width (mm) | Min Width (mil) | Notes |
|---|---|---|---|
| 0.5 | 0.15 | 5.9 | Low current signals |
| 1.0 | 0.40 | 15.7 | Standard logic signals |
| 2.0 | 1.00 | 39.4 | Moderate power |
| 3.0 | 1.70 | 66.9 | Higher power traces |
| 4.0 | 2.50 | 98.4 | Power distribution |
| 5.0 | 3.40 | 133.9 | Main power feeds |
| 6.0 | 4.30 | 169.3 | High current |
| 8.0 | 6.50 | 255.9 | Very high current |
| 10.0 | 9.00 | 354.3 | Maximum outer layer |
Design Guidelines
- • 1 oz copper: 35 μm thickness, most common for standard PCBs
- • 10 °C rise: Conservative design for reliability and signal integrity
- • External advantage: Better heat dissipation to air allows narrower traces
- • Solder mask: Covered traces carry 10-15% more current (better insulation)
Internal Layers (Inner)
10 °C Temperature Rise
Trace width for inner layers with 10 °C rise. Internal traces require wider widths due to reduced heat dissipation. Critical for multilayer board thermal management.
Current vs. Trace Width
IPC-2152| Current (A) | Min Width (mm) | Min Width (mil) | Notes |
|---|---|---|---|
| 0.5 | 0.30 | 11.8 | Low current signals |
| 1.0 | 0.75 | 29.5 | Standard logic signals |
| 2.0 | 1.90 | 74.8 | Moderate power |
| 3.0 | 3.20 | 126.0 | Higher power traces |
| 4.0 | 4.60 | 181.1 | Power distribution |
| 5.0 | 6.20 | 244.1 | Main power feeds |
| 6.0 | 7.90 | 311.0 | High current |
| 8.0 | 11.50 | 452.8 | Very high current |
| 10.0 | 15.50 | 610.2 | Maximum inner layer |
Design Guidelines
- • Thermal challenge: Inner layers dissipate heat through dielectric only
- • Width penalty: Need 1.5-2×¹ider traces vs. external for same current
- • Via stitching: Use thermal vias to help heat transfer to outer layers
- • Plane layers: Adjacent power planes significantly improve heat spreading
External Layers (2 oz)
10 °C Temperature Rise
Heavy copper (2 oz/ft2) outer layer traces carry significantly more current for same width, or same current with narrower traces. Used in high-power and automotive applications.
Current vs. Trace Width
IPC-2152| Current (A) | Min Width (mm) | Min Width (mil) | Notes |
|---|---|---|---|
| 1.0 | 0.20 | 7.9 | Low current signals |
| 2.0 | 0.50 | 19.7 | Standard logic signals |
| 3.0 | 0.90 | 35.4 | Moderate power |
| 4.0 | 1.35 | 53.1 | Higher power traces |
| 5.0 | 1.85 | 72.8 | Power distribution |
| 6.0 | 2.40 | 94.5 | Main power feeds |
| 8.0 | 3.60 | 141.7 | High current |
| 10.0 | 5.00 | 196.8 | Very high current |
| 12.0 | 6.50 | 255.9 | Maximum 2 oz outer |
Design Guidelines
- • 2 oz copper: 70 μm thickness, doubles current capacity approximately
- • Cost impact: Higher fabrication cost but reduces board size
- • Applications: Power electronics, automotive, high-current motor drives
- • Etching: Requires wider spacing between traces (etching factor)
Higher Temperature Rise
20 °C Temperature Rise
Acceptable for applications where higher temperature rise is tolerable. Allows narrower traces but increases board temperature. Use with caution in temperature-sensitive designs.
Current vs. Trace Width
IPC-2152| Current (A) | Min Width (mm) | Min Width (mil) | Notes |
|---|---|---|---|
| 1.0 | 0.25 | 9.8 | 10 °C would need 0.40mm |
| 2.0 | 0.60 | 23.6 | 10 °C would need 1.00mm |
| 3.0 | 1.00 | 39.4 | 10 °C would need 1.70mm |
| 4.0 | 1.50 | 59.1 | 10 °C would need 2.50mm |
| 5.0 | 2.05 | 80.7 | 10 °C would need 3.40mm |
| 6.0 | 2.65 | 104.3 | 10 °C would need 4.30mm |
| 8.0 | 4.00 | 157.5 | 10 °C would need 6.50mm |
| 10.0 | 5.50 | 216.5 | 10 °C would need 9.00mm |
| 12.0 | 7.20 | 283.5 | Higher temperature design |
Design Guidelines
- • Trade-off: Narrower traces acceptable with higher temperature rise
- • Total temp: Ensure Tambient + ΔT < max rating (typically 105-130 °C)
- • Derating: Reduce current in high ambient temperature environments
- • Reliability: Higher temperatures accelerate electromigration and aging