Design, fabrication and characterization of thin power inductors with multilayered ferromagnetic-polymer composite structures

This paper presents the design, fabrication and characterization of ultra-thin inductors using a new class of multilayered ferromagnetic-polymer composite structures as magnetic cores. The multilayered composite structures comprise of high-permeability, high saturation magnetization (Ms > 0.5 T), low-coercivity magnetic layers stacked with ultrathin polymer adhesives. The adhesive acts as an insulating layer to reduce eddy current losses while also preventing degradation in permeabilities at higher operating frequencies. Toroid-based integrated inductors were designed with the composite structures to operate in the low MHz range for power conversion applications. The magnetic composite film synthesis and patterning was successfully combined with toroid coils in order to fabricate the inductors. The process of micro-patterning the composite structure and forming 3D coils around them to demonstrate ultra-thin inductors is described in detail. The fabricated inductors with the multilayered magnetic composite films showed stable inductance beyond 10 MHz and 10 × enhancement in inductance density over air-core inductors with the same designs.