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How to Calculate the PCB Trace Impedance
2211 0 Mar 12.2014, 14:58:00

A Printed Circuit Board or PCB has a large number of traces. A trace is a thin copper conductor on a PCB that establishes low impedance electrical connection between its two points. The width and length of a trace are important considerations, especially in high frequency circuits. Such circuits may cause noise due to impedance mismatching and capacitive couplings. It is therefore sometimes desirable to calculate the impedance of a trace to create an efficient circuit layout.


1 Go to an online PCB trace impedance calculator, such as the one listed in the resource section at the close of this article.

2 Select the configuration of the PCB trace. PCB traces can be configured in essentially two different ways on a PCB. The first is on the surface and the second is embedded. The most common configuration is the surface microstrip, in which the trace is a strip of copper etched on the surface of the PCB. A stripline trace, on the other hand, is embedded inside the PCB. This can be either symmetric or asymmetric depending on whether it is in the middle of the PCB height or slightly off center. A microstrip trace is also sometimes embedded in the PCB, though this practice is uncommon.

3 Enter the dimensions of your trace in the calculator. The values you would need are the height, width and thickness of the trace. These values are entered into the PCB layout software while designing the layout. You would also need to enter the relative permittivity of the PCB board material.

4 Click on impedance calculation button, generally marked with "Z0." The impedance of your trace will be automatically calculated and displayed on the web page beside the calculator.

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