Relation between Permeability and Loss-Tangent beyond 10 MHz of Soft Magnetic Powder/Epoxy Composite Sheet

In this study, we focused on the development of a magnetic powder and epoxy resin composite sheet with high permeability and low loss beyond a 10-MHz frequency in order to meet the demands for higher performance, miniaturization, and low loss power inductor applications. Specifically, the characteristics of composite sheets using large-diameter magnetic powders primarily composed of amorphous Fe-Si-Cr-B-C and polycrystalline Fe-Ni and small-diameter magnetic powders composed of polycrystalline Fe-Si-Cr or spinel Mn-Zn ferrite were evaluated. According to the experimental results, the composite sheets using the polycrystalline Fe-Ni powders exhibited a high permeability and low loss-tangent (tanδ) at 20 MHz. Furthermore, in the development of magnetic powder/epoxy composite sheets with modified Cr-added Fe-Ni powders, we found that the composite sheets containing Fe-Ni-2Cr and Fe-Ni-3Cr achieved an enhanced balance of permeability and tanδ at 20 MHz. In addition, the trade-off relationship between the permeability and tanδ of the composite sheets was summarized, demonstrating that sheets containing Fe-Ni-2Cr and Fe-Ni-3Cr powders exhibited a superior balance of permeability and tanδ at 20 MHz.