Easy Exotic Substrate PCBs

In this instructable I am presenting a funny way of making 2-layer PCBs at home on a wide variety of substrate, here, a newspaper (so technically not a Printed Circuit Board, more like a Printed Circuit newspaper ?) but also on other types of substrate such as a tree leaf. I am using a process of copper foil gilding which is quite a bit older than I thought when I originally started this project. Egyptians used metal foils over 5 THOUSAND years ago ! At the time, they hammered pieces of gold into very thin sheets of gold, but I will be using off the shelf copper foils with gilding glue, the glue will be applied onto our substrate (the newspaper) in the desired design pattern through a screen-printing process. In this project, I am demonstrating the technique with a very simple circuit that you can replicate at home (all design files are available and listed thereafter) but you could apply this technique to other circuits. Note that you could also stack and connect multiple 2-layer PCBs to make multi-layer PCBs

This project is a revisiting of ancient processes with a twist !

1. Files: download the Kicad project and/or the completed screenprinting mask here
2. Materials for making a screen-printing screen (frame, screen, screen-printing emulsion, spatula)
3. Printer (laser or inkjet)
4. Gilding glue and gilding foil (I have use copper foil but you can use gold foil if you prefer)
5. PCB substrate: I am using newspaper but you can choose other materials (see below)
6. If you want to replicate the same circuit: 0805 1uF capacitor, 0805 1kOhm resistors (2x), 0805 470kOhm resistor, 6LR61 battery
7. Software: Kicad, Inkscape

The concept of this project is quite simple, as explained above, the circuit is designed in KiCAD using 2 copper layers. After this first step, I import the 2 layers in Inkscape and I mirror one of them and place same side by side in such a way that if I were to fold between them, they would be stacked exactly as designed in Kicad. I print this image on tracing paper (using a standard inkjet printer) and make myself a screen-printing screen following this previous Instructable of mine. I then deposit through the screen gilding glue and then the copper foil. I solder all the electronic components and then I fold the design. The finishing touch is to place the vias. In PCBs, vias are the conductive elements that connect the different layers together. I did not invent vias for paper PCBs as staples already are vias which I use both as the interlayer layers connectors as well as a way to keep the layers from moving.

In this Instructables, I am using a newspaper but you can choose whatever materials you want such as plastic, glass, wood, ceramics, cardboard, etc. I would not choose conductive materials as the gilding glue might not be insulating enough, If I needed to make a PCB on a piece of metal, I would deposit a thick layer of paint on the metallic substrate

The first step is to design a layout from a schematic, for illustrative purposes, I have chosen here the electronics equivalent of the “hello world”: a N555 based blinky. The schematic is fairly simple and works with a very small number of components (7 components total). I have used “large” SMDs as it makes the assembly easier. Drawing the schematic does not take into consideration or PCB manufacturing process, this arrives in the next step: circuit layout.

The layout is a bit different in that by using staples as vias, we have to make sure that we plan enough space to place the staples with some margin as working with a stapler is not the most precise way of laying out vias. In this design, I only have 4 vias the areas dedicated to accept the vias are highlighted on the picture above. In my case, as I am also soldering the through-hole N555 as a SMD, I also have to plan some space around the folded out pins of the N555.

Save the layout layers as separate SVGs files, we will make some modifications on them in the next step

In a tool such as Inkscape:

1. Import the 2 layers
2. Align them horizontally (I have used the vias area to align the 2 layers)
3. Horizontally mirror one entire layer (I chose to mirror the bottom layer)
4. Remove unwanted traces (in my case all inter-layer holes). This step is optional, it just makes the design clearer
5. Mark the fold line. At the end of the PCB making process, we will fold the entire design along this line transforming the 1 layer PCB into a 2 layer PCB. To mark the fold line, I have, once again used the vias areas. The fold line is in my case represented by 2 arrows. Those 2 arrows will be gilded in copper but not used in the electrical circuit
6. Add the connection point for the 6LR61 battery, the battery will be placed upside down onto the exposed copper connections and held in place by… gravity in this project

Print the mask either directly onto tracing paper or onto normal paper and then reproduce the design on tracing paper (which is what I ended up doing as I did not have any black ink in my printer and the other colors are just not masking enough). This design on tracing paper will be used to make the screen.

You can find how to make a screen-printing frame on the internet including in one of my Instructables, just follow the steps with the mask that we have just created

You can use this process on a lot of “exotic” types of PCB substrate, I am here using a newspaper so that I can open it, print both sides of the PCB in one go to later on fold the newspaper back to make my 2 layer PCB with the 2 layers mechanically perfectly aligned (if folded along the marked fold ligne).

You can use un-foldable substrate to, you will have to print the 2 layers separately (on a screen-printing frame you can just mask the unwanted layer with painter’s tape) and make sure the layers are aligned which is not necessarily trivial.

You can find here different trials on different materials (glass, plaster, wood and leaf), most were unsuccessful but the results are encouraging and the process can be dialed in in order to get working PCBs out of each of them. I did find making the PCB on glass to be a bit tricky because the surface is "too smooth" and the leaf is a bit hard to print on because of the leaf veins

The key of our process here is that the gilding glue I found has the same thickness as regular screen-printing paint making it compatible with the screen printing process. Use the screen to deposit the glue, and then the copper foil (check your gilding glue to know how much time you should wait for between glue deposition and applying the copper foil)

Before folding the PCB, solder the components, I first tried solder paste, but I got better result with regular solder wire. Be careful and take your time at this step as both the substrate and the copper traces are quite fragile.

Once the electrical components have been soldered on, fold the PCB, and staples the vias in place. Before working on you PCB, I recommend testing your stapling skills on a blank to make sure you can deposit the via exactly where you want. For me, most vias worked right out of the stapler but 1 did not, I chose to add soldering between the vias and the copper traces on all vias (and both sides) to insure good electrical connection.

1. As mentioned in the “CONCEPT” step, you can paint the substrate before building the copper traces but you can also paint the traces after they have been deposited to protect the copper from oxidation. This also allows you to build multiple layers on one side of the substrate.
2. In this Instructable, I have used copper foil but you can also use gold, silver, etc.
3. This process of making PCBs is actually quite ecologically clean, although the durability might be much lower.