偏平状センダスト粉末·ポリマー複合体の透磁率と伝導雑音抑制効果

抄録

In the past we fabricated and put to practical use novel noise suppressor sheets made of micro-forged Fe-Si-Al flakes and polymer. These composite sheets exhibit a peculiar dual dispersion in the frequency characteristics of the imaginary part of the permeability. For use as a noise countermeasure, a steeply rising profile accompanying wide dispersion is required for the frequency characteristic of μ”. In this work, the mechanism that brings about the dual dispersion and a method for controlling it are investigated with respect to the micro-forging process that changes the raw granules of Fe-Si-Al alloy into very thin flakes. In the initial stage of forging, the granules and the flakes coexist and the skin depth is estimated to be between the sizes of the granules and the flakes. Subsequently, the coexistence of eddy current loss in the granules and magnetic resonance loss in the flakes leads to a dual-peak profile of μ” in the frequency range from about 10 MHz to over 1 GHz. The improved performance of conduction noise suppression for these sheets was verified by setting them on a micro-strip line and measuring the variation of the transmission parameters S₁₁ and S₁₂ associated with the dual peak-loss.