PCB trace

From HwB

According to recommendations in IPC-2221 (formerly IPC-D-275, MIL-STD-275) on how to calculate minimum PCB (printer circuit board) trace width.

Below table is valid for:

  • PCB material FR-4
    • Board thickness=1.6mm (0.063")
    • Trace thickness=35μm (1 oz)
  • Allowed temperature rise=10 °C

Contents

Table

Current Width (inner) Width (outer)
A mils mils
0.010.3080.118
0.051.540.591
0.13.081.18
0.26.152.37
0.412.34.73
0.412.34.73
0.515.45.91
0.618.57.1
0.721.58.28
0.824.69.46
0.927.710.6
1.030.811.8

Note: 1 mil = 1/1000" = 0.0254 mm

Graph

Outer traces (0-1 A)

Gnuplot Plot

Outer traces (1-10 A)

Gnuplot Plot

Inner traces (0-1 A)

Gnuplot Plot

Inner traces (1-10 A)

Gnuplot Plot

Formula

Given:

  • I [A] (Current)
  • T [°C] (Temperature rise)
  • m [oz] (Mass of PCB trace)

Constants:

  • y = 1.378 [mils/oz] for copper
  • b = 0.44
  • c = 0.725
  • k = 0.048 (for outer layers)
  • k = 0.024 (for inner layers)

Formulas:

  • A [mils2] = <math>{(\frac {I}Template:KT^b)}^{\frac {1}{c}}</math> (PCB trace area)
  • l [mils] = <math>\frac {A}{m y}</math> (PCB trace width)

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