Using a desktop vinyl/paper cutter to cut copper circuits

As part of my research with children, I have been working with paper as a substrate for circuits. Paper is an extremely versatile, cost-effective, craft-friendly, and expressive medium. Moreover, it is child-friendly and can tolerate mishaps that tend to occur while children are playing or learning. It is by no means as sturdy as a PCB, but paper circuits can be easily created and replaced. Needless to say, other researchers and makers have explored this space, and my work here is merely following their footsteps.

One method to create low profile electronic traces on paper is to use copper tape. This method is cheap and does not require anything other than a pair of scissors and a soldering iron. While this method works for tinkering and creating simple circuits with minimal components (e.g. light up LED, make a switch), it soon becomes very time consuming and error prone to create even slightly complicated circuits that employ SMD parts or microcontrollers. Part of my research, explores the use of intelligent paper circuit blocks that children can magnetically interface with to create a variety of craft visualizations. While I can create one or two paper circuit blocks with SMD traces by hand, it soon becomes tedious when you have to create enough for a classroom of children.

To solve this problem, researchers and makers have typically used desktop vinyl cutters to cut out copper circuits from adhesive backed copper foil. This requires an expensive vinyl cutter such as the Roland GX-24. This post details my efforts at replicating this process with a less expensive (~$200) desktop craft cutter, the Silhouette SD. This is a somewhat older craft cutter and has been superseded by the Silhouette Cameo. However, the methods detailed here should work with the newer Silhouette models as well. Rather than cut out each copper trace separately and transfer it by hand, I focused on cutting the entire circuit and transferring it as one piece to a cardstock substrate. This maintains pitch, or the relative distance between pins in electronic components.

The materials used in this process include:

A few notes on the materials: it is fairly important that a sticky cutting mat is used; without this, the copper sheet will bunch up. The default blades with the Silhouette SD do not perform well. The ratchet blade in my experience produced the best results. The copper sheets can be found on Ebay in packs of 4.

I used Eagle PCB Design to model a simple microcontroller circuit that actuates a RGB LED. This paper circuit block employs circular magnetic connectors to interface with other circuitry. I used a through-hole package for the microcontroller, 1206 SMD packages for the resistors, and 6x5mm SMD package for the RGB LED. These are slightly larger SMD package sizes and provide some distance between the copper traces. If the packages are too small, there is a tendency for the copper traces to lift up while being cut by the craft cutter. Additionally, a 1mm trace width was used for all the connections. The traces, pads and dimension layers were exported to an EPS file format using the CAM processor in Eagle. The EPS file was then converted to JPG using Photoshop. The resulting circuit image is shown below:

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The image can then be imported into the free version of Silhouette Studio. In order to cut the traces in copper, we need to trace the outline of the black connections. Fortunately, Silhouette Studio has a trace function (top right icon toolbar, also selected in the image below).

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To use this feature, we have to first click the button, “Select Trace Area,” then draw a selection bounding box around the image as shown in the screenshot below.

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With the bounding box drawn, we then set the high pass filter value to 12 and press the “Trace” function under the “Apply Trace Method” heading. This produces a red outline around the electronic traces.

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We then need to remove the original image by selecting and deleting it from the workspace. Once this is accomplished only the red outlines will remain as shown in the image below.

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Next, we firmly attach a piece or sheet of copper foil to the sticky cutting mat and load it into the machine (see image below). Make sure the copper sheet is secure on the cutting mat.

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Next under “Cut Settings,” we select “Printable Foil” as the material type. We also want to set the ratchet blade to 1. Please note that this does not automatically set the ratchet blade on the cutter to 1. That must be done manually while loading the blade into the cutter. If you find that your blade ceases to cut after cutting a few circuits then increase the blade and ratchet setting to 2 or 3. The relevant settings for cutting copper foil are shown below.

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Once we adjust the settings, we can then send it to the cutter. In the first image in the gallery below, we can see the resulting cuts for the circuit presented earlier. To transfer the copper from the sheet to the substrate, masking tape can be used to peel off the circuit (gallery below). If some of the traces are not lifting then push the masking tape back down and rub over the area. We can then cut the masking tape to the exact shape of the substrate and paste it on. In this case, the circuit is mounted on thick cardstock that is cut into the corresponding octagonal shape. When we peel off the masking tape, we are left with the full copper circuit on the substrate. All that remains is to remove the excess copper around the traces with a pair of tweezers.