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Calculate Trace Width

In this tutorial, we'll calculate the trace width and secondary parameters of a single microstrip transmission line with a solder mask. This line is located on the first layer of a sample 6-layer PCB stackup shown below. The required PCB thickness is 1.5 mm. The reference layer is located on the second layer of the PCB. The target characteristic impedance is 50 Ohm.

6-layer printed circuit board

  1. In the Calculation settings groupbox:

    • Set Target to Transmission line
    • Set Target type to Single-ended

    Then select the Coated microstrip (CM-1B) structure.

    tut-calculate-trace-width-select-structure

  2. Set calculation mode to Lossless.

    tut-calculate-trace-width-set-lossless

  3. Enter the known transmission line parameters:

  4. Set H1, Dielectric height to 0.125 mm

  5. Set T1, Trace thickness to 0.018 mm

  6. To calculate the trace width, check the radio button next to the W1, Trace width parameter.

  7. Set the target impedance (Zo) to 50 Ohm.

!!! Note 

   To calculate the trace width without lateral undercut, set identical values for the **W1** and **W2** parameters before running the calculation.

![tut-calculate-trace-width-set-trace-parameters](../images/tut-calculate-trace-width-set-trace-parameters.png)

  1. Click Calculate to run the calculation.

    The results will be displayed in a table at the bottom of the window.

    tut-calculate-trace-width-results

The first two columns display the calculated trace width (W1) and the upper trace width (W2). Both values are identical. The subsequent columns show the precise calculated characteristic impedance and the secondary parameters of the transmission line.

The trace width (W1) required to achieve a characteristic impedance of 50 Ohm is 0.2132 mm.