Trace Width of a Printed Circuit Board

top layer PCB trace length (mil)

1000

minimum current (A)

3

minimum temperature (°C)

35

copper depth (mil)

1.4

FR-4 substrate depth (mil)

62

bottom layer copper area (

2

mil

)

ambient temperature (°C)

25

This Demonstration shows a plot with contours indicating the minimum required trace width for a range of allowable temperatures and currents in a printed circuit board (PCB). The trace width is specified for an external PCB trace of a particular length. Other parameters are the copper depth, the FR-4 substrate depth, the size of the copper plane (usually ground) on the reverse side of the PCB, and the ambient temperature. The calculation is done using basic heat transfer techniques and assumes uniform temperature for the PCB trace.