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Build your own circuit boards

The Blog has two posts of interest today. One takes note of the hazmat problem that results if you use ferric chloride to etch circuit boards – the resulting copper chloride should not go down the drain. The other is a list of the 10 Best Electronics Suppliers. Both posts refer to Instructables.

The board etching chemistry alternative is based on hydrochloric or muriatic acid, which is commonly used for sanitizing swimming pool water. Hydrogen peroxide (3% for mouthwash) is also used in a 2:1 by volume ratio with 10M HCL. Over time, the dissolved copper creates a cupric chloride solution which can be used indefinitely by refreshing the acid (re Etching with Air Regenerated Acid Cupric Chloride).

Before there’s much copper dissolved in the solution, Cu + 2 HCl + H2O2 -> CuCl2+ 2H2O is the dominant net reaction. That is, the extra oxygen in solution from the peroxide is oxidizing the copper metal, in presence of the acid, to make copper (II) chloride. That’s our starter etchant. The resulting CuCl2 shoud be a nice emerald green color.

After you’ve dissolved a lot of copper into the solution, and used up all the peroxide, the copper chloride does most of the etching for you: CuCl2 + Cu -> 2 CuCl. That’s the end etchant.

Eventually you etch so much that you convert all the CuCl2 into CuCl, which doesn’t dissolve copper (and is a yucky brown color). As long as you’ve got enough acid in the solution, you can simply add more oxygen to re-oxidize the copper(I), making more copper(II) chloride and water: 2 CuCl + 2 HCl + O -> 2 CuCl2 + H2O. And then you can etch again.

That will get you the circuit board. To populate it, you need parts. 10 Best Electronics Suppliers provides a list of sources for those. It cites the big ones like DigiKey, Jameco, Radioshack, and Mouser and provides a comment about focus and selection.

After this, it’s soldering and debugging and packaging …

Open Circuits has a rundown on chemicals usable as etchants, including the one suggested by Instructables.

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