Sahil Shah
4 min read

Rapid PCB Prototyping With Laser Engravers

  • pcb
  • laser engraving
  • electronics

In my electronics class, we made custom circuit boards by drawing with sharpie on copper-clad boards and etching the unprotected sections with Ferric Chloride acid. This process was very time-consuming and yielded large and imprecise boards. To streamline this process, I developed a method of creating PCBs in a similar method using the laser engraver.

A copper-clad board with circuit traces and pads hand-drawn in black marker.

The same board after etching, with the marker-drawn traces still covering the copper on bare fiberglass.

The finished hand-drawn board with the marker removed, showing uneven copper traces and a mounting hole.

This circuit board for a metal-detector uses the whole 1.5”x2” board and leaves a lot to be desisted in terms of accuracy as hand-drawn traces tend to be inaccurate.

My teacher and friends were unsure my idea would work, but I persevered.

These blank PCBs are made from a fiberglass-like material called FR4/G10 or Garolite, which is coated in a 1/1000” thick layer of copper. The process of making a circuit board involves removing most of the copper so that only circuit traces remain.

My first idea was to simply laser-etch away the copper layer but I soon learned that that would not work. The wavelengths of light produced by a CO2 or Diode Laser cutter reflect off copper and do not damage the material in any way. This both made my job harder and paved the way for my next idea.

Since I had to remove the copper using the acid, I would have to protect the areas of copper I wanted to keep with some coating; for this I chose spray-paint as it is cheap, plentiful, and easy to apply.

My first attempt used white spray-paint and only engraved a small outline around the traces I wanted to keep.

The touchscreen of an Epilog laser engraver running a 1200 DPI job at 100% speed and 50% power, with a thumbnail of the circuit layout.

A magnified view of thin engraved outlines around traces and pads on a white-painted board, with a distorted, scratchy section along one line.

Another magnified view of the white-painted board, where the engraved outlines look shallow and a section of the mask has torn.

The laser lines were from the start a little bit distorted and did not go through the mask layer fully

The next attempt, I used black paint and that seemed to improve the engrave depth but it still only burnt off the pigment and left a thin clear layer that would continue to shield the copper from the acid.

A board painted matte black with a compact circuit engraved into one corner, showing copper traces and pads through the paint.

At this point, I am already able to fit the original metal-detector circuit into half the space previously used.

I tested different speeds and powers but none of them were able to go through the clear coating.

After many tests, I tried sanding the board with scotch-brite before dipping it in the acid and that did scrape off the clear layer without damaging the mask. This worked but still took a long time to engrave.

With one pass of the laser, the paint was burning off and leaving residue, to counter this, initially, I had just slowed down the laser but that was wasting significant time so I tried running two passes of the same engrave job which did a much better job.

In parallel with fine-tuning the process, I was also starting to design my own PCBs that could be engraved. I used Fusion 360 eCAD (electronic CAD) to draw out circuit diagrams and design the final PCB.

A schematic in Fusion 360 with two chips, transistors, resistors, capacitors and a row of LEDs, drawn in orange on white.

The matching PCB layout in Fusion 360, with red traces on a dark board measuring 101.60 by 38.10 millimeters.

A 3D render of the assembled board with two chips, transistors, resistors, and seven red LEDs.

I used this design to make a PCB with all the knowledge I gained in the previous experiments.

*This video has been significantly sped up; total job was ~10 mins

Close-up of the etched board, with thin bright copper traces and round pads on a dark olive surface.

The full etched board on a gray surface, with copper traces running across its length.

The Final Process

Step 1: PCB Design

Design a circuit and the corresponding PCB in Fusion 360 using your components.

Step 2: Preparing the Blank PCB

First, clean off the oxidized copper layer with Scotch Brite, then paint over the PCB with matte black spray paint before giving it time to start oxidizing.

Step 3: Engraving

Engrave with two passes, 1200DPI on a laser engraver.

You will have to do some testing to find a speed and power combination that works well, and always prefer higher speed and power over lower speed and power. (some lasers might work better at almost max speed ~95%)

Step 4: Preparing for Acid

Sand off the clear coating to expose the unwanted copper. Then, drill a small hole in an unimportant part of the PCB to tie a string to. Finally, rinse the whole PCB in water and fully dry before putting in acid.

Step 5: Dip Into Acid

Leave in acid with heat and agitator on until all exposed copper has been dissolved.

Step 6: Remove Excess Mask

Use Steel wool to scrape off the excess mask covering the traces.

Step 7: Drill Holes

Use a Rotary Dremel and Dremel workstation/drill press with 0.7mm drill bits to drill holes into each pad.

Final Remarks

Developing this process was a journey that I am grateful I went on as it taught me a lot more than just how to make PCBs with the laser engraver.

Next year, I am going to refine this process to automatically drill the holes and make double-sided PCBs as well.

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