Cross Section
IExternal 1 oz

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.

Copper Weight
1 oz/ft2 (35 μm)
Data Points
9 entries

Current vs. Trace Width

IPC-2152
Current (A)Min Width (mm)Min Width (mil)Notes
0.50.155.9Low current signals
1.00.4015.7Standard logic signals
2.01.0039.4Moderate power
3.01.7066.9Higher power traces
4.02.5098.4Power distribution
5.03.40133.9Main power feeds
6.04.30169.3High current
8.06.50255.9Very high current
10.09.00354.3Maximum 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)
Cross Section
Inner LayersInternal 1 oz

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.

Copper Weight
1 oz/ft2 (35 μm)
Data Points
9 entries

Current vs. Trace Width

IPC-2152
Current (A)Min Width (mm)Min Width (mil)Notes
0.50.3011.8Low current signals
1.00.7529.5Standard logic signals
2.01.9074.8Moderate power
3.03.20126.0Higher power traces
4.04.60181.1Power distribution
5.06.20244.1Main power feeds
6.07.90311.0High current
8.011.50452.8Very high current
10.015.50610.2Maximum 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
Cross Section
IExternal 2 oz

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.

Copper Weight
2 oz/ft2 (70 μm)
Data Points
9 entries

Current vs. Trace Width

IPC-2152
Current (A)Min Width (mm)Min Width (mil)Notes
1.00.207.9Low current signals
2.00.5019.7Standard logic signals
3.00.9035.4Moderate power
4.01.3553.1Higher power traces
5.01.8572.8Power distribution
6.02.4094.5Main power feeds
8.03.60141.7High current
10.05.00196.8Very high current
12.06.50255.9Maximum 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)
Cross Section
10 °C RiseΔT20 °C Rise

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.

Copper Weight
1 oz/ft2 (35 μm) External
Data Points
9 entries

Current vs. Trace Width

IPC-2152
Current (A)Min Width (mm)Min Width (mil)Notes
1.00.259.810 °C would need 0.40mm
2.00.6023.610 °C would need 1.00mm
3.01.0039.410 °C would need 1.70mm
4.01.5059.110 °C would need 2.50mm
5.02.0580.710 °C would need 3.40mm
6.02.65104.310 °C would need 4.30mm
8.04.00157.510 °C would need 6.50mm
10.05.50216.510 °C would need 9.00mm
12.07.20283.5Higher 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