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When you start a new project in Pcbnew, the only trace width available is 0.25 mm (9.84 mils). If you need to create a trace with a different width, you will need to create a custom track width for that value.

For example, in the Trace Width Calculator recipe, I calculated that the minimum width for a power trace that can convey 1 A over 30 mm with a maximum of 10 degrees Celsius temperature rise is 0.30 mm. In Pcbnew, there is drop-down menu from where you can manually select the desired width of a track, titled “Track”.

Figure 26.1: The Track drop-down menu; there is only one width available by default. By default, this drop-down offer a single track width option: 0.250 mm. In this recipe, you will learn how to add '0.30 mm' as a track width option in the top toolbar drop-down menu. You can also use the exact same way to add custom Via sizes.

In Pcbnew, start by bringing up the Board Setup window. You can do this in three ways: 1. Click on File —> Board Setup 2. Click on the Track drop-down, and then “Edit pre-defined sizes…”. 3. Click on the Via drop-down, and then “Edit pre-defined sizes…”. In any case, you will see the same result (Figure 26.2) .

Figure 26.2: The Board Setup window with the Tracks & Vias pane selected. Select the Tracks & Vias pane, under Design Rules. There, you will see three columns: Tracks, Via and Differential Pairs. There’s a “+” button at the bottom of each column. Let’s add a few custom widths and Vias. To add each one, click on the “+” button and type in the numbers in the relevant row.

In Figure …, you can see my custom tracks and vias.

Figure 26.3: The Board Setup window with the Tracks & Vias pane selected; I have added several new custom track widths and vias.

Click 'Ok' to commit the changes, and confirm that the Track and Via drop-down menus show the new values (Figure 26.4).

Figure 26.4: The Track Width drop-down contains a custom value.

Let’s test that you can create a trace with the custom with. First, select the '0.30 mm' option from the track width drop-down menu. Then, use the 'X' shortcut or click on the Route Tracks button from the right toolbar to enter the track drawing mode. Draw a new track in the Page. Type 'Esc' to end the drawing, and choose the '0.25 mm' option from the track width menu. Draw another trace and compare its width to the first. I have also added a third trace, with 0.40 mm width. Notice that the traces have a different width?

Figure 26.5: Three traces with different widths.

You can change the width of a track at any time by using the trace’s properties window. Place your mouse on the trace, type the 'E' shortcut (for 'Edit') and select the desired width from the Width drop-down menu (see Figure 26.6).

Figure 26.6: How to change the width of a track via the Properties window. Click OK to make the change effective.