In-situ fabrication of sacrificial layers in electrodeposited NiFe microstructures

This paper describes the development of a fabrication and etching process for the in-situ formation of sacrificial layers in electrodeposited NiFe magnetic alloys. Sacrificial layers consist of iron-rich material electrodeposited in a nickel-rich matrix. The iron-rich layers are formed using a pulsed electrolyte agitation scheme. The removal of sacrificial layers is investigated using a concentrated acid etching procedure as well as a potential-enhanced etching technique. The formation of sacrificial layers in electrodeposited microgears and planar films is demonstrated. We find that glacial acetic acid preferentially removes the sacrificial layers at a rate of 0.5 mu m hr(-1) while leaving the remaining nickel-rich structure unaffected. An applied potential is used to accelerate the etch rate of sacrificial material 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 affected during etching and retains its structural fidelity. NiFe sacrificial layers 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.