Development of an EMI shielding ferrite: a case study

Ni-Zn EMI shielding spinel ferrite of the composition Ni/sub 0.30/Zn/sub 0.60/M/sub 0.10/Fe/sub 2/O/sub 4/, where M=Cu, have been synthesized by the conventional ceramic route and the properties were tailored for its use in ribbon flat cables of digital equipments in the operating frequency range of 30-200 MHz. These highly dense soft ferrites were obtained by the incorporation of sintering aids such as Cu. The microstructure of the ferrite showed angular grains of size /spl sim/20 /spl mu/m and inter/intragranular porosity. The spinel ferrite was lossy in nature and had a Curie temperature of /spl sim/170/spl deg/C and possessed impedance of 23.3, 59.6 and 121.5 Ohms at 30, 100 and 200 MHz respectively.