Difference between revisions of "Chemical Etchants"
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== vinegar and salt == | == vinegar and salt == | ||
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| + | * [http://www.kobakant.at/DIY/?p=2575 How to get what you want: Salt and Vinegar Etching] | ||
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| + | == Ferric Chloride == | ||
| + | This is the most common hobbyist etchant. Ferric chloride, FeCl<sub>3</sub>, is a brownish substance. It's usually sold in a bottle (dissolved in water, perhaps with a little acid or peroxide) or as a powder (which you have to dissolve in water). | ||
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| + | When in solution, ferric chloride is a ferric ion (Fe<sup>3+</sup>) and a chloride ion (Cl<sup>-</sup>). The ferric ion reacts with the metallic copper on the circuit board in a redox reaction, producing a ferrous ion (Fe<sup>2+</sup>) and cuprous or cupric (Cu<sup>1+</sup> or Cu<sup>2+</sup>) copper. The chlorine is just along for the ride. The copper ion, unlike the metallic copper, is soluble, so it leaves the circuit board and goes into solution. The reaction products form a black sludge which settles to the bottom of the etching tank. After etching enough copper, all your Fe<sup>3+</sup> is used up and your solution is full of Cu<sup>1+</sup>, and you need to get more etchant. | ||
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| + | == Ammonium Persulfate == | ||
| + | Expensive & hard to control and optimize the process parameters (such as specific gravity & pH value). | ||
Revision as of 18:16, 21 July 2022
removed spam, working to restore page revert to 26 June 2013
This article is a stub. You can help Open Circuits by expanding it.Chemical etching is one step of some popular PCB fabrication techniques.
In this technique,
- one starts with a copper-clad board.
- one puts a mask over all the copper he want to keep. There are a variety of ways to do this -- see Toner Transfer and Photoetching.
- one removes the parts he don't want to keep, by chemically etching away the copper.
- cleanup: wash off the board in the sink; carefully store or dispose of the acid.
There are a lot of different chemical techniques for doing this, each with its own advantages and drawbacks.
None of these chemicals is incredibly dangerous, but they can all be toxic or caustic, and should be treated with care. Eye protection and gloves are a very good idea. Before you start, make sure you know how dangerous each chemical is, and figure out what you will need to do if you spill it or get it on yourself. Washing with plenty of water is usually a good start. For some chemicals you may want to keep a neutralizing agent handy. An MSDS (Materials Safety Data Sheet) for the chemical will give you some basic information.
vinegar and salt
Ferric Chloride
This is the most common hobbyist etchant. Ferric chloride, FeCl3, is a brownish substance. It's usually sold in a bottle (dissolved in water, perhaps with a little acid or peroxide) or as a powder (which you have to dissolve in water).
When in solution, ferric chloride is a ferric ion (Fe3+) and a chloride ion (Cl-). The ferric ion reacts with the metallic copper on the circuit board in a redox reaction, producing a ferrous ion (Fe2+) and cuprous or cupric (Cu1+ or Cu2+) copper. The chlorine is just along for the ride. The copper ion, unlike the metallic copper, is soluble, so it leaves the circuit board and goes into solution. The reaction products form a black sludge which settles to the bottom of the etching tank. After etching enough copper, all your Fe3+ is used up and your solution is full of Cu1+, and you need to get more etchant.
Ammonium Persulfate
Expensive & hard to control and optimize the process parameters (such as specific gravity & pH value).
