Electro-infiltration: A method to form nanocomposite soft magnetic cores for integrated magnetic devices

This article introduces a scalable, process-integrable manufacturing method for creating microstructured, nanocomposite soft magnetic cores on planar substrates such as silicon wafers or printed circuit boards. To demonstrate this electro-infiltration process, maghemite (γ-Fe₂O₃) nanoparticles less than 50 nm are first evaporatively consolidated from suspension into photoresist molds on a silicon substrate, forming dimensionally defined porous microstructures. Next, a high-saturation soft magnetic iron cobalt alloy (Fe-Co) is electroplated up from a conductive layer on the substrate to fill in the void spaces of the consolidated particles. The result is a dense, two-phase nanocomposite, where the maghemite nanoparticles form an inclusion phase in the electroplated metal matrix phase. Improved high-frequency permeability is observed in the 100 MHz-2 GHz range.