Research On DC-Bias-Superposition Characteristics And Application Of Low Temperature Sintered NiCuZn Ferrites

Multilayer chip inductors with small size,excellent high frequency characteristics and suitable for surface mounting are increasingly replacing traditional inductors in recent years.It is widely used in various electronic products.However,there is always a certain DC leakage current in the actual circuit of this kind of electronic products.Therefore,it is required that the laminated chip inductors have better resistance to DC-bias to ensure the normal operation of the products.As a key material for chip inductors,NiCuZn ferrite material directly affects the DC bias superposition of the device.Therefore,in this paper,DC-bias superposition characteristics of low-temperature-fired ferrites have been investigated for the stability of multilayer chip high-power inductors.Then we designed and produced multilayer chip high-power inductors based on the ferrite which we had prepared.The specific research contents are as follows:First of all,in the material research,the relationship between the microstructure of the doped ferrite material and the DC-bias superposition is studied.Preliminary doping experiments of doping low-melting Bi₂O₃-ZnO-B₂O₃?BZB?glass and composite binary oxide Bi₂O₃-CuO in NiCuZn ferrite materials have found that the formation of fine grain structure is beneficial to enhance the DC bias of the material.However,samples with fine grain structure are often accompanied by lower sintering density,which leads to deterioration of magnetic properties such as saturated magnetic induction strength.In order to obtain samples with both fine grain structure and high density,a multi-melting aid system with a certain melting temperature gradient was designed in this paper.By ingeniously utilizing the difference between the effect of additives on the densification process and grain growth process of NiCuZn ferrite.Finally,dense multiple microstructures with fine grains were obtained.The results of the doping of low melting point BZB glass and higher melting point oxide Bi₂O₃ or Bi₂O₃-CuO show that the introduction of multi-fusing system significantly improves the DC bias characteristics of the material due to the formation of a special dense microstructure.Improved material density and magnetic properties.Considering three important parameters of DC bias characteristics,density and saturation magnetic induction,it is found that when the CuO doping amount is 0.02wt%and the sintering temperature is 890°C,the material has the best comprehensive performance(saturation magnetic induction intensity is 312mT,density is 4.82g/cm³,H_70%=625A/m).Finally,using the self-developed NiCuZn ferrite material,the application research of the device was carried out.First,the 0805 laminated chip inductor was designed using Ansoft HFSS software.Then,the DC bias characteristics were simulated using Maxwell software.The results show that the saturation current Isat is 1.8A when the inductance is0.97?H.The designed laminated chip inductor fully meets the project's index requirements.