Printed Circuit Boards -- The Third Way
How To Expose Printed Circuit Boards With a 3D Resin Printer
M.A. Haidekker, April 2026
MOTIVATION
Prototyping any electronic device, especially when the device needs to be durable and rugged, requires printed circuit boards (PCBs). In addition, many modern components, such as MOSFETs, ADCs, DACs, or power management ICs, are available only in surface mount packages, which are simply impractical for solderless breadboards.
Without doubt, professionally made PCBs are the ideal solution, but costs and the wait time may play a role. The company I usually contract with -- Silver Circuits -- requires a minimum of four panels, which ship for around $80. Turnaround time with shipping is between one and two weeks. What if we need only one PCB, and fast? CENGR has a PCB mill, in which areas between copper traces is removed mechanically. In my experience, the LPKF PCB mill has frequent downtimes, requires critical adjustment of PCB flatness, sometimes does not fully carve out the path between traces, and -- most importantly -- is limited to structures larger than about 20 mils (0.5 mm).
A long time ago, I used photo-sensitized boards: PCBs that are coated with a photosensitive polymer (photoresist). When the photoresist is exposed to violet or UV light, it gets activated and can be washed off with a diluted sodium hydroxide (NaOH) solution. Unexposed photoresist is unaffected by NaOH and remains in place. In a subsequent chemical etching step, exposed copper is removed, but copper that is still covered by photoresist remains in place and forms the traces. At that early time, I used an X-Y plotter and a darkroom. I was able to plot the PCB at 2:1 scale, then photographically reduce its scale to 1:1 and create a lithography film "pouch" into which the PCB slides for two-sided exposure. But who has a darkroom nowadays? And where to get the critical lithography film? At some point, I built a device that illuminates the board with a tightly focused laser. The laser was scanned across the board, line by line, and modulated on/off to create the exposure pattern. The exposure pattern was, in fact, a black-and-white image of the PCB, and I modified the open-source gerbv to export images at precisely 1000dpi. This solution worked, but the mechanical scanning required many hours for exposing merely a single side of a PCB.
RESIN PRINTERS
When I purchased a resin 3D printer, I immediately recognized that the printer's screen can project an image onto the build plate much like the pattern I generated with the laser, but without mechanical scanning. The roughly 600 dpi resolution was acceptable, and the wavelength seemed to be in the right range, too. At first, I tried to "bake" resin onto copper-clad PCBs and use the resin as photoresist. Apparently, I am not the first one with this idea (example here). I tried that method with partial success, but ultimately did not reach the resolution I was aiming for. Moreover, I found the process of converting the Gerber files to a flat, prismatic 3D model unwieldy. My modified version of gerbv produces pixels. The printer's screen casts pixels onto the buid plate. Do I really need to make a 3D model from the Gerbers and go through an STL file and slice it just to arrive back at pixels? Once I discovered the UVTools software, I knew the answer is no.
WHAT YOU WILL NEED
In this article, I will explain how to get from a PCB layout to Gerber files, then to the Creality Halot cxdlp file and finally how to expose a photoresist PCB. This article is based on the Halot-One Plus, which I reversibly modified for PCB exposure, but which is now my dedicated PCB printer as it is out of production and spare parts are no longer available. The Halot-One Plus has a bed of 172 x 102 mm with 4320 x 2560 pixels, which gives a pixel size of 40 x 40 microns (1.57 mils). PCBs would have to be converted into a raster format (image) at 635 dpi.
What you will need:
- Software to create a PCB layout. I use the gEDA project's PCB software, but alternatives, such as KiCAD exist. Familiarity with creating custom footprints is a plus.
- A 3D resin printer and the print bed information (size, DPI). Most printers will deviate from the Halot-One Plus, in which case you need to modify the instructions accordingly.
- Software to read Gerber files and convert them into raster images at your printer's resolution. gEDA's gerbv has this capability.
- Software to manipulate images, such as GIMP, the GNU Image Manipulation Program.
- UVTools
- CAD software (e.g., FreeCAD) to create tools, such as the PCB adapter frame.
- Copper-clad PCBs with photoresist coating, single- or double-sided.
- Developer and etchant -- more about those later. Plus: personal protection gear (protective eyewear, latex or nitrile gloves)
Proceed to Part 2 of this article for the step-by-step instructions.
Copyright notice: All information, images, and downloadable files are licensed under the Creative Commons License CC-BY-SA.