High-performance laminated thin-film shield with conductors and magnetic material multilayer

This paper presents a laminated shield consisting of conductors and a magnetic material multilayer. The laminated shield provides a high shielding performance in an ultrahigh-frequency (UHF) band because the magnetic materials have high permeability and multi reflection occurs in the shield. Furthermore, the shielding performance is enhanced at the ferromagnetic resonance (FMR) frequency of the magnetic materials because the magnitude of complex permeability is maximized owing to the large imaginary part of permeability. We examined the shielding mechanisms of the laminated shield and a conductor shield by impedance calculation. The shielding performance obtained by impedance calculation coincides with that obtained by finite element method (FEM) simulation. The laminated shield is fabricated using a CoNbZr thin-film layer with a thickness of 0.2 μm and two Cu layers with a thickness of 0.4 μm. The measured shield effectiveness of the laminated thin-film shield is 27 dB higher than that of the conductor shield at a frequency of 470 MHz, which is similar to the results of impedance calculation and FEM simulation.