28 December 2008

Electrolytic Saltwater Etching of Copper

Results from electrolytic saltwater etching of copper



In my days at a semiconductor capital equipment company I made a lifelong friend. When we first met, she was a "process" engineer who etched the dielectric material on silicon wafers; then she etched conductive materials; then she was a product support engineer, et cetera.

A month ago I showed her the Art Jewelry magazine article on etching copper, nickel silver, brass and other materials in a salt water solution using a D cell battery. As an etcher, she was very interested. She'd never etched at home. Her current company (where they have a chemical that etches metal in only 20 seconds) is on holiday break, so this week she's free to come out and play.

Play we did - in our nerdy way. The local Radio Shack had only one single D cell battery holder, prompting an etching experiment. I purchased the single D holder, and also holders for a single C and two Cs.

We placed
two sets of copper anodes and cathodes in almost identical etch setups at the same time. The main differences between the two was the number of C batteries and the resist designs on the copper.



Loooooook at the difference in the water color after a few minutes. The double C setup skipped the blue-green water phase and headed right to the orange water phase of the process. After five minutes the copper had significantly etched. After an hour, the copper was more than ready to be taken out. The single C battery tub etched much slower; after 2 hours the depth of the etch was still shallower than the 1 hour double C etch.

We etched both sides of the anode and purposely ignored recommendations to duct tape the edges - as you can see on Ben's piece at the far left.



Next time the process will be tweaked a little. Some rubber cement on the lead to the anode. Alligator clips instead of twisted and wrapped wires. Perhaps try a new type of metal. Duct tape on the edges. And, we'll measure the voltage and current from the single and double C setups and compare to the recommended single D setup.

By the way, we were shocked not to find a molecular orbital diagram of the process on wikipedia! ;-)

2 comments:

  1. i'm doing the same thing right now, but with one of those battery chargers you can carry in your glove compartment. For resist, I ironed on the laser toner from a design that was printed onto ink jet photo paper using a Laser printer.

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  2. please tell me what is the battery charger that you can carry in the glove compartment, and where do you find it???/ and how long did it take to etch............

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