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Electro etching lead foil

May 2, 2008

We are trying to etch lead foil .006" to create defined line patterns. We are using a photo resist and sulfamic acid to etch out the patterns. We are using a low current in the process 6V 1.5 amps.

The problem is getting a defined edge to the pattern. The "electro polish" etching is leaking under the resist edges.

Any thoughts on how to fix this or is there a different process we can use to etch out patterns in lead foil?

Thomas Lachner
electro polish tech - Bonita Springs, Florida, USA

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May 2, 2008

Hi, Thomas. I'm not looking at it, of course, so I may be misunderstanding. But it sounds like what you are describing is not a failure of the resist, but natural undercutting. The thicker the lead foil, the worse the undercutting will be because the solution and electrochemistry doesn't know which lead you want it to dissolve; instead it dissolves any lead it can reach. The solution, but it isn't easy, is a jet of solution, because this gives directionality.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

Your analysis of our problem is correct. We could possibly use a thinner foil, but we are using a mild acid solution for the electrolyte so it would not be too difficult to add a small pump to provide a directional flow right at the part. I will give it a try.

Thomas Lachner
- Bonita Springs, Florida, USA
May 5, 2008