Forget The UV Resist Mask: Expose Custom PCBs Directly On Your SLA Printer

Art of 3D printer in the middle of printing a Hackaday Jolly Wrencher logo

For the enterprising hobbyist and prototyping hardware developer, creating custom PCBs remains somewhat of a struggle. Although there are a number of approaches to go about this, they usually involve printing or drawing a mask that is used to expose the photoresist layer on the to-be-etched PCB. Here [Andrew Dickinson]’s Photonic Etcher project provides an intriguing shortcut, by using the UV source of an MSLA 3D printer directly after converting the project’s Gerber files into a format the MSLA printer can work with.

The concept is as simple as can be: since MSLA printers essentially function by creating a dynamically updated UV mask (either via an LCD panel or DLP system), this means that an MSLA printer can be used to expose the PCB’s UV-sensitive photoresistive coating, effectively making the mask there insoluble during the etching step. This can be done with negative as well as positive photoresistive coatings, depending on the use case.

The obvious advantage of this approach is that you don’t need an additional UV source or any kind of separate mask, only an MSLA printer with a large enough work area to fit the PCB you wish to expose. One limitation of [Andrew]’s project at this point is that it can only convert Gerbers to PWMS (Photon Mono) files, but this can presumably be fairly easily extended to support more MSLA printers.

22 thoughts on “Forget The UV Resist Mask: Expose Custom PCBs Directly On Your SLA Printer

  1. It takes a lot of dedication to make your own 2 layer boards, when there are quite a few board houses who will make your board for less than the cost of raw materials. Especially when you consider that many devices are only available in fine pitch surface mount.

    1. Surface mount is the only reason why this is appealing at all – drilling the damn holes for through hole parts is a nightmare and best left to the fab, but single sided smt breakout boards with no holes would be super convenient this way.

      1. Yes, for simple designs. But on more complex boards, the vias are going to be a nightmare, especially if you want them underneath low profile chips. Another problem is the lack of solder mask which makes soldering fine pitch more difficult, and also presents the risk of corrosion when flux is wicked under flat parts.

  2. Am I missing something? You load a Gerber into this Photonic Etcher online app and it converts it to a .pwms file (only one format, no choice) which is Anycubic’s Photon Workshop Slicer app’s output for Anycubic SLA printers.

    It seems you don’t need [Andrew Dickinson]’s Photonic Etcher app to do this, there are other programs that can convert all sorts of file types. For example see [Jan Mrázek]’s comment in this post for a free alternative cross-platform app called UVtools.

    What I was expecting with Photonic Etcher was actual instructions on exactly how to handle, load, expose, and develop the UV presensitized board with the SLA printer. But there doesn’t seem to be anything about that.

    1. @Leo said: “I wonder what’s the minimum trace pitch that you can get with this. And the minimum footprint size. Didn’t find any info on that unfortunately.”

      Good question. Let me take a stab at answering it with respect to 2D only printing, which applies to exposing a flat presensitized UV PCB…

      The actual print resolution depends on the number of LCD pixels and the size of the LCD. A “2K” resolution is typically found on low-cost resin printers. And of course the maximum print size is limited by the LCD size. Digging around for a minute I found this example:

      * ELEGOO 6.08 Inches (diagonal) Monochrome 2K LCD Compatible with ELEGOO Mars 2 and ELEGOO Mars 2 Pro Resin 3D Printers with 1620×2560 Resolution, Active Area 3.25 x 5.14 inches 4.5 out of 5 stars 222 ratings $34.99 each:×2560-Resolution/dp/B08LGGH62X

      So the 3.25 x 5.14 inch LCD has 1620 x 2560 pixel resolution. Therefore the long side can make 5.14 / 2560 = 0.00201 inch wide lines minimum, and the short side can also make 3.24 / 1620 = 0.00201 inch wide lines minimum.

      If you pay more you can buy printers with higher resolution and/or larger LCD screens. In reality though the viscous property of the resin and the minimum step size of the Z (vertical) axis limits the minimum resolution attainable in 3D prints. However there should be no resolution limits like that if you are exposing a flat (2D) presensitized UV PCB in near direct contact with the LCD.

      See [1] and [2] for more in-depth discussions regarding the size and resolution of 3D prints.

      * References:

      1. Easily Calculating Resolution for 3D Printers

      2. The Resolution, Printing Size and Accuracy in Resin 3D Printers

    1. The point of copper clad prototyping has become less about cost and more about speed. Cost used to be an issue but now if you got two weeks then you can get PCBs cheaply. As such, copper clad prototyping has become about the speed at which it can be done.

  3. It would seem to me, that since the MSLA printers use an LCD or DLP, you would need to convert your gerber into- effectively- a monochrome bitmap. But I am under the impression that there is no way to send said bitmap to the printer directly? You have to convert it into a different vector format such as gcode? Only to be rasterized by the printer back into a bitmap again for the LCD/DLP? Seems needlessly complicated, am I missing something?

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