In-situ fabrication of sacrificial layers in electrodeposited NiFe microstructures

This paper describes the development of a fabrication and etching process f or the in-situ formation of sacrificial layers in electrodeposited NiFe mag netic alloys. Sacrificial layers consist of iron-rich material electrodepos ited in a nickel-rich matrix. The iron-rich layers are formed using a pulse d electrolyte agitation scheme. The removal of sacrificial layers is invest igated using a concentrated acid etching procedure as well as a potential-e nhanced etching technique. The formation of sacrificial layers in electrode posited microgears and planar films is demonstrated. We find that glacial a cetic acid preferentially removes the sacrificial layers at a rate of 0.5 m u m hr(-1) while leaving the remaining nickel-rich structure unaffected. An applied potential is used to accelerate the etch rate of sacrificial mater ial in dilute acetic acid as well as in a chloride-based etching solution. Under potential control, sacrificial layers are etched at rates approaching 80 mu m hr(-1). The remaining nickel-rich matrix is not significantly affe cted during etching and retains its structural fidelity. NiFe sacrificial l ayers of varying compositions are shown to etch at rates that depend on the iron content. The implications for using these techniques in conventional through-mold plating applications are discussed.