3D-Printed PCB: Build a 12V Power Distribution Board

This Instructable shows you how to design and build a real, working printed circuit board without any chemical etching. Instead of the traditional subtractive process — which involves hazardous compounds like ferric chloride — this technique uses an FDM 3D printer to produce the mechanical substrate, with self-adhesive copper-clad strip applied to raised track extrusions to form the conductive paths.

The project, which is just an example for illustration, we'll build throughout this guide is a 12 V power distribution board that delivers three regulated DC outputs: a fixed 9 V via an LM7809, a fixed 5 V via an LM7805, and an adjustable output between approximately 1.25 V and 10.5 V via an LM317. All three regulators operate in parallel from the same 12 V input. This circuit is deliberately straightforward: the electrical behaviour is well understood, all parts are cheap and widely available, and the through-hole assembly is perfectly suited to the 3D-printed substrate.

This technique is best suited to low-power prototyping and educational contexts. PLA — the most common 3D printing filament — has a low softening temperature and is not flame-retardant, which rules it out for high-power or safety-critical applications. For everything else, it is a genuinely practical alternative that opens PCB fabrication to anyone with access to a desktop 3D printer.

All parts are standard through-hole components. The table below lists everything you need, with exact values and purchase links where the part number matters. Every connector uses the same 5 mm pitch terminal block, which simplifies wiring considerably.

Components :

U1 : 1 - LM7809 — fixed 9 V regulator - TO-220-3 - Datasheet ↗

U2 : 1 - LM7805 — fixed 5 V regulator - TO-220-3 - Datasheet ↗

U3: 1 - LM317L — adjustable regulator - TO-220-3 - Datasheet ↗

J1 : 1 - 12 V input terminal block (2-pin) - 5 mm pitch - MaiXu MX126 or equiv.

J2 : 1 - 9 V output terminal block (2-pin) - 5 mm pitch - MaiXu MX126 or equiv.

J3 : 1 - 5 V output terminal block (2-pin) - 5 mm pitch - MaiXu MX126 or equiv.

J4 : 1 - Variable output terminal block (2-pin) - 5 mm pitch - MaiXu MX126 or equiv.

D1, D2 : 2 - 1N4001 — general-purpose rectifier diode - DO-41 - Datasheet ↗

R1 : 1 - 200 Ω resistor (LM317 lower divider leg) - Axial, 15.24 mm pitch - Any ¼ W metal film

RV1 : 1 - 5 kΩ trimmer potentiometer - ACP CA9 horizontal- Sets V_out on LM317

C1 : 1 - 100 nF capacitor - Axial, 15 mm pitch- Input filter

C2 : 1 - 1 µF capacitor - Axial, 15 mm pitch - Output filter

MiniVoltemeter _ Banana connectors (5)

Tools and consumables

You will need a desktop FDM 3D printer loaded with PLA filament,, rosin flux paste or flux pen, solder (60/40 or 63/37, 0.8 mm diameter is easiest), self-adhesive copper-clad strip (the type sold for EMI shielding or stained-glass work, available in 6 mm or wider rolls), a sharp scalpel or hobby knife, a digital multimeter for continuity and resistance checks, and a heated sewing needle or fine-tip soldering iron bit for hole marking.

The first step is to design the schematic and PCB layout in KiCad, which is free and runs on Windows, macOS, and Linux. If you already have KiCad installed, create a new project and open the schematic editor. If you are new to KiCad, the official documentation at docs.kicad.org covers everything you need to get started.

The schematic

Place three voltage regulator symbols — LM7809, LM7805, and LM317 — side by side in the schematic editor.

Connect all three input pins to a common 12 V power rail and all three GND pins to the ground rail.

Add a 100 nF capacitor (C1) across the 12 V input rail and a 1 µF capacitor (C2) at the output of the adjustable section to improve stability.

For the LM317, wire a 200 Ω resistor (R1) between the output pin and the ADJ pin, then wire the 5 kΩ trimmer (RV1) from the ADJ pin to ground. This resistor divider sets the output voltage according to the relationship V_out = 1.25 × (1 + RV1/R1).

Place the four 2-pin terminal blocks for the 12 V input and the three outputs, and add two 1N4001 diodes (D1, D2) as reverse-voltage protection on the regulated rails.

Once your KiCad layout is finalised, export the board outline and copper tracks as an SVG file using File → Export → SVG.

Open the exported file in Inkscape, which is free at inkscape.org. KiCad SVG exports can contain redundant nodes, open path segments, or sub-pixel misalignments that are harmless for screen display but cause geometry errors when you try to import the file into a solid-modelling application. This cleanup step prevents those problems from propagating into your FreeCAD model.

In Inkscape, select all objects (Crlt A) and use Path → Break Apart to isolate individual path segments.

Then switch to the Node editor tool and examine each track path: close any open endpoints, delete duplicate overlapping nodes, and simplify any paths that have an unnecessary number of nodes for their shape.

When every path is clean, set a consistent document coordinate origin and verify the scale is correct — KiCad exports in millimetres, and Inkscape should preserve that unit.

Save the cleaned file as a plain SVG.

Open FreeCAD and import your cleaned SVG using File → Import. FreeCAD will convert the 2D vector paths into a set of Wire objects. Switch to the Part Design workbench. Select the board-outline path first and pad it (extrude it) to a thickness of between 1 and 2 mm — this is your base plate. Then select each track path in turn and pad it upward from the surface of the base plate to a height of 0.5 to 1 mm. These raised extrusions are the structures onto which the copper strip will be adhered in a later step.

Design constraints to respect

The extrusion height of the tracks is the most critical dimension. If the extrusions are less than 0.5 mm tall, the copper strip will not adhere reliably and may not be visible enough to trim accurately. If they exceed 1 mm, the legs of through-hole components will not protrude sufficiently below the board surface to be soldered properly. Stay within the 0.5–1 mm window for every track.

1. Track width : ≥ 1 mm (Below 1 mm, the copper strip cannot be trimmed cleanly)
2. Track extrusion height : 0.5 – 1 mm (Above 1 mm, component pins cannot protrude for soldering)
3. Base plate thickness : 1 – 2 mm (Balance Rigidity without excess print time or material)
4. Component pin holes : Ø 1.5 – 2 mm (Accommodates TO-220, axial and trimmer lead diameters)

After adding all track extrusions, create all component holes at the positions defined by your KiCad footprints. Use the Pocket tool to cut holes of 1.5 to 2 mm diameter through the full thickness of the base plate. Add mounting holes in the corners if you want to attach the board to an enclosure. Finally, export the completed model as an STL file for slicing.

Import the STL file into your slicer — Cura, PrusaSlicer, or equivalent. Because dimensional accuracy matters more than print speed here, choose settings that favour precision over throughput. A layer height of 0.2 mm gives a good balance between surface smoothness and print time. Set the infill to 20–30% for the base plate; the track extrusions should use a solid or perimeters-only infill to ensure the top surface is flat and will accept the adhesive copper strip without gaps.

Red is not a right colour. I recommend you to print in white or light-grey PLA. Light colours make it much easier to see where the copper strip has been applied, identify any misalignment during trimming, and read any text or markings embossed on the board surface. Avoid flexible or high-temperature filaments — PLA is chosen specifically because it is rigid and dimensionally stable at room temperature, which keeps the track geometry accurate.

Before doing anything with copper, go through every component hole in the printed board and verify that it is fully open. FDM printing frequently produces partial bridges across small holes — particularly at the transition between the first solid layer and the hole void — and these will cause problems during component insertion if not cleared now. Use a heated sewing needle or a hand drill of the appropriate diameter (1.5–2 mm) to clear each hole cleanly. Work slowly and check from both sides.

After clearing each hole, make a light mark on the top surface around it with the needle tip. This mark will serve as a reference point when you need to perforate the copper strip after it has been applied. It is far easier to locate the hole centres now, before the copper covers the surface, than to guess at their positions afterward.

Cut a strip of self-adhesive copper foil slightly longer than your longest track. Peel back a short section of the backing paper and align one end of the strip with the start of the first track extrusion. Press it down firmly along the entire length of the extrusion, peeling the backing as you go and maintaining alignment with the raised edge. The copper strip should sit flush on top of the extrusion with minimal overhang on either side.

Once the strip is adhered, use a sharp scalpel to trim the excess copper along both lateral edges of the extrusion. Hold the blade perpendicular to the surface and use the printed edge of the extrusion as a cutting guide. The goal is to leave copper only on the top and side faces of the extrusion — no copper should bridge across to the base plate or an adjacent track. Proceed track by track, working from the longest runs first and finishing with the shorter junction pieces and pads.

After all tracks are applied and trimmed, use the heated needle to re-open each component hole through the copper layer, using the marks you made in the previous step as guides. Press the needle tip straight down through the foil at each marked centre — do not drag it sideways, as that will tear the copper away from the surrounding pad area.

With all copper tracks in place and no components installed yet, carry out a complete electrical check using your multimeter. This step takes only a few minutes and can save you from the much more difficult task of diagnosing a fault after everything is soldered in.

Set the multimeter to continuity mode (or the lowest resistance range if your meter has no audible continuity function). Place one probe at one end of each track and the other probe at the far end, and confirm that the reading is close to zero ohms. A high or open-circuit reading means the strip has a gap — a piece of backing paper left under the foil, a section that was not pressed down properly, or a cut that went too deep. Lift and re-apply the affected section.

Next, check for short circuits between all pairs of adjacent tracks. Place one probe on one track and the other probe on each neighbouring track in turn. The reading should be open-circuit (infinite resistance) in every case. Any low-resistance reading between two tracks that are not electrically connected in the schematic indicates a short — usually a fragment of copper foil left between two adjacent extrusions during trimming. Remove it with the scalpel tip and re-test.

nsert all components into their holes and solder them to the copper tracks on the top surface of the board. The key challenge is keeping the iron contact time short enough that the PLA substrate does not soften. PLA begins to deform at temperatures above approximately 60 °C — well below the 300–320 °C of your iron tip — so every second of contact counts.

Apply a small amount of rosin flux to each joint before touching it with the iron. Flux removes the oxide layer from the copper surface, dramatically improving solder wetting and allowing the joint to form in one to two seconds rather than three to five. This shorter contact time is the single most effective way to protect the printed board. Touch the iron tip to the junction of the component lead and the copper track, feed a small amount of solder, and lift the iron as soon as the solder flows. Let the joint cool for at least ten seconds before soldering the next leg on the same component.

Solder the passive components — resistors, capacitors, diodes — first, then the terminal blocks, and finally the three TO-220 regulators. The regulators have the most thermal mass and are closest to the board surface, so they require the most care. Solder each of the three leads individually with adequate cooling between each joint.

Before connecting anything to the outputs, visually inspect every solder joint. Each joint should be shiny and smooth, with solder wetting both the component lead and the copper track surface. A dull, grainy, or balled joint indicates a cold solder joint — reheat it with a touch of fresh flux and a brief application of the iron. Check that no solder bridges have formed between adjacent tracks by looking across the surface at a low angle, which makes bridges visible as shiny connections between pads that should be isolated.

When you are satisfied with the visual inspection, connect a current-limited 12 V DC supply to J1 and measure each output with the multimeter before connecting any load. J2 should read 9 V (± 0.5 V), J3 should read 5 V (± 0.25 V), and J4 will read whatever voltage the LM317 divider is currently set to. To calibrate the variable output, insert a small flat-head screwdriver into RV1 and adjust it while monitoring the voltage at J4 until you reach your desired output level.

V_out = 1.25 × (1 + RV1 / R1) = 1.25 × (1 + 5000 / 200) ≈ 32.5 V max (limited to ~10.5 V by 12 V input)

Once all three outputs are confirmed, connect a small resistive test load to each output in turn — a 100 Ω 1 W resistor is suitable for a quick functional check — and verify that the output voltage remains stable under load. If any output drops significantly under load, check the solder joints on the corresponding regulator and its bypass capacitor.

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