Effects of major process parameters on the permeability of sendust flake-based electromagnetic noise suppressors at high frequency bands (MHz or above)

The performance of electromagnetic noise suppressors manufactured using sendust flakes at megahertz and higher frequencies depends on permeability. Several factors, such as the magnetization, coercivity, and skin depth of the material, must be considered concurrently to improve permeability. To design a high-permeability noise suppressor, it is essential to understand the effects of the experimental variables of each process on the magnetic properties. In this study, the effects on permeability of the composition of sendust, the aspect ratio, and the experimental variables related to the phase and sendust were studied. The phase and microstructure changes were analyzed with respect to the annealing temperature using X-ray diffractometry and transmission electron microscopy. Moreover, the change in aspect ratio with respect to the milling time was analyzed using scanning electron microscopy and particle size analysis. In addition, composition analysis and vibrating sample magnetometer measurements were performed to confirm the effect of the sendust composition. A composite sheet was manufactured with consideration of all variables, and the permeability was measured using an impedance analyzer to confirm the effect of each process variable on the permeability.