Magnetic Properties of Soft Magnetic Powder/Epoxy Composite Sheet

This paper describes the development of a composite resin magnetic sheet of soft magnetic powder and epoxy resin used in the beyond 10MHz band magnetic devices. Magnetic powder and epoxy resin were mixed, dispersed and formed into a sheet shape by the bar coating method. Fe-Si based polycrystalline powder, Fe-Si-Cr based amorphous powder and Fe-Si-Nb-Cu-B based nanocrystalline powder with an average particle size of 3 μm were used as the soft magnetic powder. In addition, submicron Fe-Si-Cr based powder was used to further increase the packing density of the magnetic powder. As the evaluation of the magnetic sheet, saturation magnetization, coercivity, relative magnetic permeability and loss-tangent in 10MHz – hundreds MHz were measured. A magnetic sheet using the nanocrystalline powder and submicron powder showed high relative permeability of 13 and low loss-tangent of 0.05 at 100MHz.