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From someone coming from electronic engineering not skilled in chemistry,

There are transparent electric conductors in form of ITO ( Indium tin oxide ) coated glass or transparent PET films ( Polyethylene terephthalate ). By etching the ITO coating we can create transparent circuit boards and with the case of ITO coated PET also flexible transparent circuit boards.

There seems to be very little info on what can be used for etching ITO PET sheets. For ITO coated glass, people use HCL with no issue, but will HCL also work to etch ITO but leave the transparent PET film intact, or do PET and HCL react?

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    $\begingroup$ It is prohibited to store hydrochloric acid (or any other acid for that matter) in PET as that PET will eventually break up. The process, however, isn't all that fast, so you might get it good if you are very careful with timing. ITO-coated polypropylene or (better) polyethylene, however, would be fine $\endgroup$ – permeakra Dec 30 '17 at 14:39
  • $\begingroup$ I see, but how long are we talking about? Etching shouldn't take more than 30 minutes and ideally no more than 5 minutes. Is that long enough exposure to cause degrading, or are we talking about much longer? $\endgroup$ – Mark Legault Dec 30 '17 at 15:49
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You can etch ITO on PTE by mean of conc. HCl solution without problems. The treatment duration depends on the ITO thickness but is limited to minutes.

Just make few samples (residuals from cutting etc will suffice to make this test) to find out how long it takes to fully remove ITO.

No reference need it as I do etching of ITO coated PTE electrodes since years.

For sake of completeness let me add that I never investigated PTE itself prior and after the etching so I do not know if there are changes which, for instance, may interfere with long (very long) stability etc.

In my case it suffices that PTE maintains its transparency and still behave as a robust but flexible substrate. It seems it could be your case, too.

Just to be pedantic. Obviously after etching the foil must be washed thoroughly.

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  • $\begingroup$ Thank you. What can be used for the photoresist? This is out of the scope of the question so I'm posting as a comment. Also, what concentration are you using? $\endgroup$ – Mark Legault Dec 30 '17 at 21:28
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    $\begingroup$ Conc HCl is ok. Is what is generally used. Its dilutions will still work but I do not any practical reason to use them. More handling more hazard more time etc. As masking materials in a pioneristic stage we used nail varnish. Then I introduced 3M magic tape and similar drawing adhesive tapes. But our structure are at millimetres scale or more, and easy to draw. Often I do just define the structure by means of the top electrode. If you need more precision than photo resist tecnology or so will be necessary $\endgroup$ – Alchimista Dec 30 '17 at 21:44
  • $\begingroup$ adhesive tape is ok, so is 1mm precision, but how can you create a mask out of it without cutting by hand? $\endgroup$ – Mark Legault Dec 30 '17 at 21:52
  • $\begingroup$ That is the point. If you need a circuit is getting tricky. In my case I just define basic geom. shape so it is easy to cut the tape with a cutter and the help of preprinted drawing that I use as background. For complicated and or finer patterns again you will have to look for technologies used in semiconductors and optics labs. $\endgroup$ – Alchimista Dec 30 '17 at 22:11

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