Electrochemical Synthesis of Soft Magnetic Alloys and Laminates for High Frequency Field Application
Thin-film inductor cores are designed to minimize energy losses at high frequencies, particularly above 100 MHz. Such design improves the efficiency of power delivery in applications like voltage regulators, MEMS, and digital-to-analog devices. This study outlines the development and fabrication of multilayer laminate and bulk alloys. Using a combination of direct current (DC) and pulse current deposition methods, multilayered magnetic structures are produced from a single bath chemistry containing pyrrole monomer, phosphorus additive, or a combination of both. The resulting inductor cores consist of alternating high-moment magnetic alloy layers with a saturation moment of approximately 2.2 - 2.3 T and ultrathin, high-resistive phases. These resistive phases are formed either by polymerization of pyrrole or electro-reduction of phosphorus, with residual CoFe matrix and oxides. The lamination process ensures that the thickness of individual magnetic layers remains below their skin depth at a given frequency and serves as the resistive barriers mitigating eddy current flow between the magnetic layers. Compared to single-layer or bulk magnetic alloy counterparts, the synthesized laminates exhibit at least 50% higher resistivity. High-frequency characterization reveals that the lamination process significantly reduces permeability losses beyond the 100 MHz region, with most three laminate alloys experiencing less than 10% eddy-current-induced reduction in permeability between 50 MHz and 500 MHz. In contrast, non-laminated counterparts exhibit more than a 50% reduction in permeability within the same frequency range. Thus, the benefits of the laminate structure in suppressing eddy currents can be effectively leveraged in practical inductor designs to improve efficiency.
Multilayer laminates, Polypyrrole, Skin depth, Permeability, Electroreduction, Polymerization
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