Editing Chemical Etchants

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Chemical etching is one step of some popular [[techniques | PCB fabrication techniques]].
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After masking off the parts of the copper-clad board you want to keep, you need to remove the parts you don't want to keep. This is usually done by chemically etching away the copper. There are a lot of different chemical techniques for doing this, each with its own advantages and drawbacks.
 
 
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.
 
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 ==
 
 
* [http://www.kobakant.at/DIY/?p=2575 How to get what you want: Salt and Vinegar Etching]
 
* [http://www.flickr.com/photos/jeanbaptisteparis/4831465916/ smt pcb with Salt and Vinegar]
 
* [http://www.instructables.com/id/The-Saltwater-etch-process/ The Saltwater etch process]
 
* [http://www.electro-tech-online.com/general-electronics-chat/33876-electro-etching-no-acid.html electro etching a PCB with vinegar, salt, and a 12 V power supply] (the copper etched off the PCB is plated on the anode?) -- however, other people claim that "You should not be using any acids (or basic 'acids') with your [electro] etcher at all. No FeCl no vinegar, etc ".[http://www.bladeforums.com/forums/showthread.php?t=671936]
 
  
 
== Ferric Chloride ==
 
== Ferric Chloride ==
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When the board is done etching, the etchant will probably look like green kool-aid, from the copper content in it. This stuff is highly corrosive and will burn skin, which is why you should wear gloves. But it is easy to handle, and fairly easy to dispose of. the etchant is easily deactivated with baking soda. Pour enough baking soda into it slowly (to keep it from boiling and overflowing... remember what happens with baking soda/vinegar? ya...) until it is a solid mass, then leave it in the sun to dry. You should contact your local authorities to find out what you should do with it next. Whatever you do, DO NOT dump the stuff down the drain, it will eat through your pipes just like any of the other etchants.
 
When the board is done etching, the etchant will probably look like green kool-aid, from the copper content in it. This stuff is highly corrosive and will burn skin, which is why you should wear gloves. But it is easy to handle, and fairly easy to dispose of. the etchant is easily deactivated with baking soda. Pour enough baking soda into it slowly (to keep it from boiling and overflowing... remember what happens with baking soda/vinegar? ya...) until it is a solid mass, then leave it in the sun to dry. You should contact your local authorities to find out what you should do with it next. Whatever you do, DO NOT dump the stuff down the drain, it will eat through your pipes just like any of the other etchants.
 
Alternatively, instead of disposing of the etchant, you can re-use it again and again. In fact, after etching a few boards with this solution, you will have successfully made [[Chemical Etchants#Acid Cupric Chloride|Acid Cupric Chloride]] (see below).
 
You can also find a detailed tutorial on etching at [http://robotplatform.com/howto/pcb%20etching/pcb_etching_1.html Muriatic Acid etching tutorial]
 
  
 
== Sodium Persulfate ==
 
== Sodium Persulfate ==
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== Acid Cupric Chloride ==
 
== Acid Cupric Chloride ==
Dead simple etchant made from ordinary, store-bought chemicals (hydrochloric acid and hydrogen peroxide). Has the advantage that it can be regenerated by bubbling oxygen/air through it, or by adding more H<sub>2</sub>O<sub>2</sub>. In addition, it doesn't get used up: the etchant bath simply grows with use (kind of like sourdough starter…)
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Dead simple etchant made from ordinary, store-bought chemicals (hydrochloric acid and hydrogen peroxide). Has the advantage that it can be regenerated by bubbling oxygen/air through it, or by adding more H<sub>2</sub>O<sub>2</sub>. In addition, it doesn't get used up: the etchant bath simply grows with use (kind of like sourdough starter…)
 
The used etchant also makes a great algecide/pH reducer for your pool (and a whole lot cheaper than that stuff they sell at the pool store).
 
The used etchant also makes a great algecide/pH reducer for your pool (and a whole lot cheaper than that stuff they sell at the pool store).
  
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== Disposal procedures ==
 
== Disposal procedures ==
Flushing used etchant down the drain is a bad idea (and usually illegal) because copper ion is toxic. The usual recommended way to dispose of hobbyist amounts of etchant is to convert it to a solid somehow and dispose of the solid in accordance with local laws.
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Flushing used etchant down the drain is a bad idea (and usually illegal) because copper ion is toxic. The usual recommended way to dispose of hobbyist amounts of etchant is to convert it to a solid somehow and dispose of the solid in the trash.
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* [http://www.kepro.com/fmc4.htm Kepro Circuit Systems] Removal of Copper and Persulfate from Spent Sodium Persulfate Etchant by Precipitation
  
 
== External Links ==  
 
== External Links ==  
 
* [http://www.instructables.com/id/Sponge-Ferric-Chloride-Method-Etch-Circuit-Bo/ "Sponge + Ferric Chloride Method -- Etch PCBs in One Minute!"]
 
 
* [http://www.k9spud.com/wiki/PCB:Etchants Ferric Chloride vs. Ammonium Persulfate] and other etching chemicals.
 
* [http://www.k9spud.com/wiki/PCB:Etchants Ferric Chloride vs. Ammonium Persulfate] and other etching chemicals.
* [http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/index.html Etching with Air Regenerated Acid Cupric Chloride] an excellent in-depth page on acid cupric chloride etching by Adam Seychell.
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* [http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/index.html Etching with Air Regenerated Acid Cupric Chloride] — an excellent in-depth page on acid cupric chloride etching by Adam Seychell.
* [http://www.esmonde-white.com/home/diversions/etching-a-copper-pcb Etching a Copper PCB with HCl and H2O2]
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* [http://esmonde-white.com/etching_pcb.html Etching a Copper PCB with HCl and H2O2]
 
*[http://www.mgchemicals.com/index.html MG Chemicals]A possible source?
 
*[http://www.mgchemicals.com/index.html MG Chemicals]A possible source?
* [http://reprap.org/wiki/MakePCBInstructions RepRap wiki: Make PCB instructions]
 
  
 
== Internal Links ==
 
== Internal Links ==

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