pcb-pool etch bath


  • Flower vase
  • 50W aquarium heater
  • Aquarium air bubble thingy with pump
  • 3D-printed top and PCB holder

Note: the PCB holder doesn't have much grip. The 3D-printed screws are also a bit difficult to tighten/loosen.


PCB Holder

The PCB holder already has some grooves to better hold the board. However, these weren't wide and deep enough to really hold on to the board so we've simply used a saw and widened them a bit.


The heater is a simple aquarium heater. By design the peak temperature is 37C controlled by a bimetal switch. This temperature is not high enough for sodium persulfate (Natriumpersulfat) etching.

The mod overrides the bimetal switch and puts the heating element into an always-on mode. A temperature sensor element was also fitted inside the heater just above the heating element to measure the approximate temperature of the heating element. There's a conversion table for sensor resistance to temperature.

Tests showed that controlling the temperature is not necessary, since the heating element peaks at around 55C and begins to slowly (read: several minutes) oscillate between around 45C and 55C. The modified heater was able to raise the temperature of the etch batch to around 47C which is a nominal increase of around 10 Kelvin over the unmodified off-the-shelf model.

dsc_4197.jpg Soldering in the bimetal override.

dsc_4199.jpg Fitting a temperature sensor inside the heater.

dsc_4200.jpg Fixating the sensor using hot glue.

dsc_4201.jpg No more temperature dial, just the cables for override and temperature sensor.

dsc_4202.jpg Test-driving the modified heater.

friedhof/beta-layout/etchbath.txt · Zuletzt geändert: 2020-07-20 10:08 von neos