Lantern PCB etching

Ryan and Pix have been having a crash course in backyard chemistry while etching the PCBs for the Peel Street Lantern control boards.

Other options would have been to mill or have the boards fabbed overseas, but because of the rapidly approaching deadline (Format Festival) we chose etching.

We’ve never been keen on chemical etching, but the acid cupric chloride process involves the least waste.

Pix & Ryan’s setup included:

  • Cereal storage containers
  • A woefully inadequate aquarium air pump (which was quickly replaced by…)
  • Industrial air compressor (which required…)
  • Foam block and rubber band based airflow regulator

The process involves:

  • Printing the circuit layout onto toner transfer paper
  • Ironing the toner onto the blank PCB material
  • Mixing up the hydrochloric acid & hydrogen peroxide solution
  • Accidentally sacrifice the copper from several boards to make acid cupric chloride 🙂
  • Regenerate the acid cupric chloride with copious quantities of bubbled oxygen
  • Etch as many PCBs as you can until the solution is saturated with copper
  • Clean the toner / etch resist off of the PCBs with acetone
  • Regenerate the solution, wash, rinse, repeat!

And of course, some happy snaps:

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3 Responses to Lantern PCB etching

  1. John says:

    How did you improve toner transfer? The pic looks like you lost alot of track but the final result looks perfect!

  2. pix says:

    Hi John,

    The selection of pictures is a little miss-leading. The picture shows an early test with store-bought blue toner transfer paper, but most of the boards were done using laser printing on to magazine paper (best seemed to be relatively thin shiny paper with mostly just black text).

    To be honest, the boards actually turned out pretty bad (mostly due to bad etching technique). As for the toner transfer, we got the best results when we just did all of the steps more slowly and more carefully.

    Some tips:

    – Clean the PCB with acetone to remove any surface oils.

    – Thoroughly heat the PCB before transferring (we did this using a clothes iron through waxy baking paper) but don’t over-do it as the copper can de-laminate from the fibreglass.

    – Thoroughly heat again when applying the printed page to the copper (you want the toner to re-melt on to the copper). Then let it completely cool, then soak it in water for a long time to soften the paper.

    – Instead of peeling off the paper, we rubbed the paper away. Soaked paper wadded-up works really well for rubbing the paper away gently without damaging the tracks.

    pix

  3. I thought you used the manual method of etching the pcb. That’s why it looks so great. You did a great job mate.

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