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Selective copper etchant

I have the following question:

I have one microstructure which is composed of one layer of Ni(95%)/Fe(5%) (thickness: 350µm) and one layer of Cu (15µm). I would like to etch selectively the copper; the Ni/Fe should be not attacked. Do you know some etching solutions ding this ? What is the process ?

I'll read that the sample should be totally clean and that the parts should be wet (why)?

Thank you very much in advance.

Pascal MEYER
Electroplating and etching - Karlsruhe, Baden-Wurtemberg, Germany
2004

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You can use next solution:

210 gm natrium sulfide
15 gm sulfur
20 °C temp. (according to Praktische galvanotechnik,Saulgau 1997.)

Goran Budija
- Cerovski vrh Croatia
2004

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You may want to look at US Patent 5,304,284 (Jagannathan et al). A working formulation based on this patent is isopropanol or ethanol based, with added 2-butene-1,4- diol, triethylorthoformate, and copper tetrafluoroborate (I don't recall the exact ratios). I used it successfully on structures containing copper and NiFe alloys. Of course any non-R&D use probably requires licensing.

Emanuel I. Cooper
- Yorktown Heights, New York
2004