Dry Film and Careful Cleaning Get a Working NFC Tag From a DLP 3D Printer
"The spacing and route width is not uniform but tolerable," maker Euclir explains. "Achieving 4.78 uH instead of calculated 5uH."
Pseudonymous maker "Euclir" has been experimenting with using a 3D printer to create homebrew near-field communication (NFC) tags — creating working PCB trace coils without the need for the "toner transfer" method.
"I use my DLP [Digital Light Processing] 3D printer with some dry film to make this PCB NFC coil," Euclir explains of the project. "The spacing and route width is not uniform but tolerable. Achieving 4.78uH instead of calculated 5uH. I think I found my new favorite method instead of using toner transfer."
The compact PCB created by Euclir is built around the STMicroelectronics M24LR04E Near-Field Communication (NFC) chip, connected to an off-board Arduino Nano-compatible microcontroller development board. Once the chip is programmed, the Arduino can be powered off and the circuit still operate — sending the stored data to a smartphone or other NFC-compatible device when scanned at close range.
The PCB is entirely home made, but without the usual approach of printing the traces on a laser printer then ironing the paper onto an unetched PCB to transfer the toner — an often-messy process. Instead, Euclir used dry film photoresist and a DLP 3D printer in an approach dubbed "maskless photolithography." "My previous problem with dry film is due to poor bonding between the film and the copper surface," the maker explains. "So I tried cleaning it with a bit of hydrogen peroxide and water. Then I use hot iron to bond both material. My next plan is to use thick Kapton tape with copper tape to make a flexible PCB with the same etching method."
More information is available in Euclir's Reddit post.