Study Of NiCuZn Ferrites As A Substrate Material For Multilayer Chip Inductors

With the rapid development of electronic products,the demand for multilayer chip inductors（MLCIs）in electronic components is increasing day by day.In order to ensure that MLCIs has good stability under operating conditions,there is an urgent need to improve the DC-bias superposition characteristics of the MLCIs base material.In this paper,we investigated the effects of Ni Cu Zn ferrites,the substrate material of MLCIs,on the bulk density,microstructure,magnetic properties and DC-bias superposition characteristics by investigating the composition and preparation process of NiCuZn ferrite materials.The obtained contents and the results of the study are as follows:（1）When the mixed oxide is held at 850℃for 2 h,the spinel structured ferrite without impurity phase can be obtained;the density of the ferrite material increases and then decreases with the increase of the addition of the sintering aid Bi₂O₃,and when the addition of Bi₂O₃is 0.4 wt%,the ferrite material has the best comprehensive performance with the bulk density of 5.15 g·cm^-3,the saturation magnetic induction B_sof 238.3 m T,and the coercivity H_cof 178.8 A·m^-1.（2）With the increase of Ni²⁺content,the saturation magnetization M_s of the NiCuZn ferrite powders gradually decreases,the coercivity H_cincreases continuously,and the magnetocrystalline anisotropy constant K₁first increases and then decreases,when the Ni²⁺is 0.43,the comprehensive performance of the powders is the best,and the corresponding magnetic properties values of 63.62 emu·g^-1,27.36 Oe and 1813.17Oe·emu·g^-1,respectively.When the DC-bias magnetic field is<400 A·m^-1,the incremental permeability of the material decreases rapidly,mainly due to the displacement of the domain walls,and the rate of decrease is influenced by the two parameters M_sand K₁of the material.When the magnetic field strength is≥400 A·m^-1,the incremental permeability of the material decreases slowly,mainly because the number of rotatable domains decreases significantly until it disappears and the material became a single-domain structure,the decrease of incremental permeability is caused by the rotation of the magnetic moment in the domains and the rate of decrease is influenced by the material K₁.（3）The water quenching temperature of the pre-synthesized ferrite powders has a significant effect on its particle size and sintering properties,when the water quenching temperature is 500℃,the particle size of powders is the smallest（D50=2.675μm）,corresponding to the best overall performance of the ferrite material,the bulk density of 5.24 g·cm^-3,B_sof 268.1 m T,and H_70%of 28 A·m^-1.（4）The addition of non-magnetic layer SiO₂has a great influence on the properties of ferrite materials.When powders addition is used,the grain size of the corresponding specimen（Si-P-1.00）decreases from 6.91μm to 1.13μm when the addition amount was 1.00 wt%;when sol-gel addition is used,the average grain size of the corresponding specimen（Si-S-1.00）is 0.96μm when the Si O₂sol is added at1.00 wt%,at which the bulk density of the material is 4.83 g·cm^-3,B_sis 195.3 m T,corresponding incremental permeability of H_70%is 85.4,which is 38 A·m^-1higher than that of the sample（Si-P-1.00）H_70%.