Break the Rectangle: How to Design and Create Custom-Shaped PCBs

For too long, our electronic projects have been confined to boring squares. But your project has a personality, and its circuit board should too! Imagine a PCB shaped like your logo, an animal, or a unique form that fits perfectly inside a custom 3D-printed case.

This guide will show you the professional technique for designing PCBs of virtually any shape, complete with intricate internal cutouts. We'll use the powerful (and free) combination of Inkscape for vector design and KiCad for the electronics, focusing on a key feature that makes complex designs possible: the Path Difference command.

Step 1: Create Your Main Board Outline in Inkscape

First, we need to design the primary, external shape of your board. Inkscape is a vector graphics editor, which is perfect for creating the precise lines a PCB manufacturer needs.

1. Set Up Your Workspace: Open Inkscape and immediately go to File > Document Properties. Change the "Display units" and "Units" to mm. This is the standard for PCB manufacturing.

2. Draw and Combine: Use Inkscape’s shape tools (circles, squares, etc.) and the Bezier tool (for custom curves) to draw the parts of your outline. If you use multiple shapes to create your outline, you must combine them into a single object. Select all the parts of your main outline and go to Path > Union. This merges them into one solid shape.

Step 2: The Magic Step – Creating Cutouts with Path Difference

This is where you create holes, slots, or any other internal cutout in your board. This is perfect for mounting holes, display windows, or simply for artistic effect.

1. Draw Your Cutout Shapes: On top of your main board outline, draw the shapes you want to cut out. These can be circles for screw holes, rectangles for USB port openings, or any custom shape you need.

2. Perform the Subtraction: The order of selection here is critical.

   • First, click to select your main board outline (the larger shape).

   • Next, while holding the Shift key, select all the shapes you want to use as cutouts.

   • With everything selected in the correct order, go to the menu and click Path > Difference.

The smaller shapes will vanish, leaving perfectly clean cutouts in your main board shape. You now have a single, complex path that represents your final board, complete with holes.

Step 3: Exporting Your Design for KiCad

While the design work is done in Inkscape, KiCad needs it in a specific format. We'll use the DXF (Drawing Exchange Format).

1. Select Your Path: Click on your final, complex board shape to select it.

2. Save As DXF: Go to File > Save As.... In the format dropdown, choose "AutoCAD DXF R14 (*.dxf)".

3. Confirm Export Settings: A popup will appear. Ensure your "Base unit" is set to mm and, most importantly, check the box for "Use LWPOLYLINE type for all paths." This format works best with KiCad.

Step 4: Importing the Blueprint into KiCad

Now, let's bring your custom design into the electronics environment.

1. Open the PCB Editor: In your KiCad project, open the Pcbnew editor.

2. Select the Edge.Cuts Layer: On the right-hand "Layers" panel, click on Edge.Cuts. This layer defines the physical boundary of the board, including all outlines and cutouts.

3. Import Your DXF: Go to File > Import > Graphics. Select the DXF file you just saved. In the import window, confirm that the "Graphic Layer" is set to Edge.Cuts and click OK.

Your custom shape, complete with all its internal cutouts, will now appear on the KiCad canvas, ready for you to add components, route traces, and pour copper fills. The design process is the same as for a rectangular board, but now you're working within the creative canvas you designed yourself.