Effect of annealing treatment on electromagnetic shielding effectiveness of double-layer FeSiBCuNb/Cu composite strips

Double-layer Fe73.5Si15.5B7Cu1Nb3/Cu composite strips were prepared by depositing copper films on the surface of Fe73.5Si15.5B7Cu1Nb3 amorphous strips using magnetron sputtering. The structure of Fe73.5Si15.5B7Cu1Nb3 amorphous strips and the double-layer composite strips before and after annealing was performed by X-ray diffraction. The electrical and magnetic properties of the composite strips were tested by Hall effect tester and impedance analyzer, respectively. Furthermore, the shielding effectiveness (SE) of the composite strips before and after annealing against electromagnetic waves in the range of 1-9 GHz was measured by vector network analyzer. The results show that the SE of amorphous strips annealed at 320 degrees C is better than that of 380 degrees C and 440 degrees C. The composite strip depositing copper film for 20 min and then annealed at 320 degrees C for 30 min has the highest SE of about 110.1 dB at 6.7 GHz, which is 28 dB higher than that of Fe73.5Si15.5B7Cu1Nb3 amorphous strips. Due to the addition of the conductivity (sigma) of the strips sputtered copper film, the ability of this strip to reflect electromagnetic waves is improved. After annealing, the effective permeability of FeSiBCuNb/Cu composite strips increases, so the magnetic loss also increases.