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I made a PCB (printed circuit board) for the first time, and the process included covering the board with the shape we want, exposing the board to UV light and then putting it in a developer which removes the part of the resin that was exposed to the UV radiation.

My question is, what is this developer? I think it has the commercial name of CIF (http://uk.farnell.com/cif/ar46/developer-ready-for-use-1l/dp/1783557), but what is it really? What does it do to the board and why only to the UV-exposed part?

Thanks!

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Developers are usually solutions of $\ce{NaOH}$ or $\ce{KOH}$ (perhaps with some additives). Negative photoresists uses organic developers/solvents. From your description, I assume, that you use a positive photoresist. Positive photoresists are more soluble after exposition to the UV light - polymer bonds are disturbed and therefore more soluble (in areas where exposed). Please see illustration. For more detailed information look for Photoresists and Photolithography.

wiki

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    $\begingroup$ Yup, NaOH. For future reference, they have to include these things on the MSDS sheet, so you can often look there to see what the major components of these sorts of things are. $\endgroup$ – Michael DM Dryden Jun 22 '15 at 16:28
  • $\begingroup$ Why is it soluble in a base such as NaOH? $\endgroup$ – Whyka Jun 25 '15 at 9:03
  • $\begingroup$ The reaction is based on alkaline hydrolysis. But I suggest to ask another question. $\endgroup$ – Jaroslav Kotowski Jun 26 '15 at 6:21

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