Chemical Etchants

Sodium Persulfate

More environmentally friendly than ferric chloride. Can monitor the etching as initially clear new etchant solution turns blue from the copper ions.

Hydrochloric Acid and Hydrogen Peroxide

Dead simple etchant made from ordinary, store-bought chemicals. Has the advantage that it can be regenerated by bubbling oxygen/air through it, or by adding more H₂O₂. 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).

What you need:

• 38% Hydrochloric Acid, HCl (available at finer pool supply stores as Muriatic Acid)
• 3% Hydrogen Peroxide, H₂O₂ (available from any drug store)
• Plastic or Glass Pans, Jars, and tongs (no metal)

Directions:

1. Mix your HCl and H₂O₂ 1:1 in a non-metalic container, making sure to add the acid slowly to the H₂O₂. DO NOT ADD THE H₂O₂ TO THE ACID!!!
2. After you've masked your board, dip it in the solution and constantly agitate. You should notice a dark green cloud start to come from the board almost immedately which quickly dissapears or turns lighter as it gets further from the surface of the board.
3. Etching should take about 10min depending on the temperature and how well you agitated the etchant. When all of the copper is gone, dip in water to wash off any stray etchant and stop the reaction.
4. When done etching, save used etchant in a non-metalic container and mark clearly its contents.
5. If your etchant has become a dark, murky green color, add a little bit of H₂O₂ or bubble air/O₂ through the solution to regenerate it back to a light, transparent green color.

See links at bottom for more information on the chemistry and some pictures of the process.

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 the trash.

• Kepro Circuit Systems Removal of Copper and Persulfate from Spent Sodium Persulfate Etchant by Precipitation

External Links

• Ferric Chloride vs. Ammonium Persulfate and other etching chemicals.
• Etching with Air Regenerated Acid Cupric Chloride
• Etching a Copper PCB with HCl and H2O2