The Medusa Turns Your Gerbers Into Ready-to-Etch PCBs, Using a Mono LCD, UV LED, and Raspberry Pi
Pseudonymous maker "wolfy-j" has shown off a tool designed to make building custom printed circuit boards for prototypes quicker and easier: an ultraviolet lithography machine, dubbed Medusa, for transferring designs to treated blanks.
"I have a lot of blank PCBs with prepared UV resistant coating (photoresist)," wolfy-j explains. "I can upload [a] Gerber file (KiCad, DipTrace or EasyEDA, others should work too) to the Medusa and it will automatically convert it into positive or negative template. Then you put PCB into it and it will draw (50µm pixel) [the] template on PCB. Then you wash all uncured photoresist in soda and etch in any etchant you can find."
The device, which is housed in a 3D-printed chassis, is powered by a Raspberry Pi 4 Model B single-board computer connected to a monochrome 2k-resolution display panel originally designed for use in stereolithographic (SLA) 3D printers. There's a 5V step-down module, a 10W ultraviolet LED with driver, a 3W red LED, temperature sensor, and addressable RGB LEDs to provide a progress bar for feedback.
On the software side, Medusa runs the 64-bit build of Raspberry Pi OS Linux with the open-source tracespace Node.js toolchain for converting Gerber files into layers which can be displayed on the LCD panel as masks, plus Go-based hardware bindings and the Spiral framework for the web-based user interface.
"It takes around 20 minutes to make a single sided PCB with mask," wolfy-j explains. "Around 7 of these minutes are for etching. No hard chemicals. So far I have around 98 percent yield and [a] minimal trace width of 100µm."
More details on the project can be found on wolfy-j's Reddit thread.