Artiz--
Constantan is an alloy of Ni and Cu.
Dilute aqua regia etches both Ni and Cu, and can be patterned with
photoresist,
so you might try that. See the paper "Etch Rates for Micromachining
Processing II." PDFs are online.
    --Kirt Williams

> Does anyone know what kind of etchant is used in order to etch away PVD
> deposited constantan alloy films?