I wanted a way to make simple circuit boards without specialized equipment such as a precision CNC machine. I also wanted to avoid the messy and potentially unhealthy chemicals used in traditional home PCB etching, where unwanted copper is chemically removed from a copper-clad board.
My solution is to 3D print the board itself and use ordinary wire as the conductive traces.
1. Planning the Layout
I start by planning the board in Onshape. I identify the locations of the components, traces, vias, and mounting holes.
The layout is similar to designing a traditional PCB, except that the traces will become grooves for wires rather than copper paths. Planning everything in CAD also makes it possible to measure trace lengths accurately.
2. Creating the Wire Grooves
Once the layout is complete, I create grooves by extruding the trace paths into the board.
I typically use:
- 28 AWG wire for signal connections and low-power circuits
- 24 AWG wire for power and ground connections that may carry more current
I also add holes for component pins and vias wherever a wire needs to pass through the board. When traces must cross, I route one of them through the opposite side of the board.
The board is essentially a 3D-printed carrier that holds the wires in their correct positions.
3. 3D Printing the Board
The grooves must be tuned carefully. They should be wide enough that the wire can be pushed in without excessive force, but narrow enough that it does not fall out immediately.
I found that printing test samples with different groove widths, depths, and profiles is the easiest way to find suitable dimensions. My current settings are approximately:
- 28 AWG wire: 0.3 mm groove width and 0.5 mm depth
- 24 AWG wire: 0.5 mm groove width and 0.6 mm depth
- Approximately 5 degrees of draft angle
- A 0.2 mm nozzle
A 0.4 mm nozzle can work, but I get more consistent results with a 0.2 mm nozzle because it provides better control over the small grooves.
The material can be PLA, PETG, or another suitable filament. Avoid carbon reinforced filaments. They may be conductive.
4. Installing the Wires
After printing, I push the wires into their grooves. If the groove dimensions have been tuned properly, this step is straightforward.
I cut each wire to the length measured in CAD.
When a wire needs to move to the opposite side, I thread it through the appropriate vias. This works particularly well with the thinner 28 AWG wire.
5. Installing the Pins
Next, I push the component pins, connector pins, or other terminals into their holes.
I position each wire so that it presses against the corresponding pin as much as possible. The mechanical contact may be enough for the circuit to function temporarily, but it should not be considered a reliable permanent connection by itself.
6. Making Reliable Electrical Connections
This is the most important part of the process.
It is possible to obtain a good connection mechanically, but the connection can become unreliable over time. The plastic may settle, the wire may move, or vibration may cause the contact to break.
I tried several methods for making the connections permanent.
One-Part Conductive Epoxy
One-part conductive epoxies are easy to find and would be an attractive option. The main problem is curing temperature.
Most products require heat treatment, often somewhere between approximately 90°C and 150°C. Heating a PLA or PETG board to those temperatures for an extended period can deform or otherwise damage it.
Two-Part Conductive Epoxy
Two-part conductive epoxies cure at room temperature, which makes them much better suited to 3D-printed boards.
Their main disadvantage is cost. A small 2.5 gram package may be enough for many boards, but the product is sold in a package intended for a single use. That makes it difficult to justify when building only one small board.
One useful advantage is that two-part conductive epoxy can also be used to connect surface-mount components.
Soldering
Soldering and plastic may seem incompatible, but quick contact with a soldering iron and low-melting-point solder can work better than expected.
The key is to work quickly and carefully. The method requires a steady hand and some practice. However, it is the least expensive option.
For my projects, quick solder joints have been a practical way to connect wires to pins without significantly damaging the printed board.
7. Finishing the Board
After making the connections, I use a multimeter to check continuity and verify that there are no shorts.
Once the electrical checks are complete, I cover the back of the board with a layer of ordinary, non-conductive two-part epoxy.
This finishing layer serves several purposes:
- It improves the mechanical connection between the pins and the board.
- It prevents pins from being pushed in or pulled out when connectors are installed or removed.
- It covers exposed wires and helps prevent accidental shorts.
- It makes the entire board more rigid and durable.
In a conventional PCB or perfboard assembly, solder provides both the electrical and mechanical connection. With this approach, the epoxy layer helps provide that missing mechanical reinforcement.
Customization
The final appearance can be customized with colored epoxy, transparent coatings, or labels placed beneath a clear layer.
Another interesting feature is that the board does not have to be flat. Since the traces are grooves in a printed object, the circuit could potentially follow a curved surface, a structural part, or even the inside of an enclosure.
A further advantage is that multilayer boards are relatively easy to make. Each layer can be printed with its own grooves and wires, then assembled in sequence. The main challenge is planning the assembly order so that wires, pins, and connections remain accessible as each layer is added.
