With the rapid development of information industry, laminated inductors, laminated porcelain beads and laminated LC composite components have become one of the most important laminated electronic components.
Traditional inductance element structure is the core of the wire winding coil, so as to obtain the required inductance and other parameters in miniaturization and electromagnetic interference resistance to further from deaf, adopts petrochemical alone can not only reduce the volume, but also has the very good magnetic shielding MLCI and MICB with small volume High reliable magnetic shielding, and is applicable to automatic assembly characteristics such as high density, has applied to computer video television camera auto electronic fax digital mobile communications in areas such as electromagnetic or radio frequency interference suppression.
1.Laminated inductive materials
MLCI and MLCB is one of the key technology of the preparation of high performance low temperature sintered ferrite magnetic powder (900), these magnetic powder should have the following features:
①to low temperature sintering: around 900 when sintering, can obtain dense microstructure and excellent electromagnetic properties.
② and Ag (Pd, Ag) plasma sinter: around 900 with Ag slurry when burning, does not react with Ag, not now Ag ion migration phenomenon.
③ satisfies the requirement of extending to printing process flow: magnetic powder granularity distribution of surface morphology characteristics for stretch film or printer art requirement.
④The soft magnetic ferrite suitable for MLCi and MLCB is spinel NiZn(Fe2O3 NiO ZnO) series, and flat hexagonal Co2Zn(Fe2O3 BaCO3 Co3O4) series.
Multilayer ceramic Inductance
（1）The preparation method of the material
The methods of preparing high performance low temperature sintered (about 900) ferrite magnetic powder mainly include solid reaction method and softening method.①solid reaction process
The sintering temperature of general NiZn ferrite is about 1200,to bring it down to around 900, take two steps:the first step is to replace the Ni+/Zn2+ with a fair number of Cu2+'s in the composition,and choose an iron deficiency formula.In the process, the specific surface area of magnetic powder is increased as much as possible, so as to reduce the sintering temperature to around 1050. The second step is to add flux or low melting point glass phase, and further reduce the sintering temperature to below 900. Thus, low temperature sintered NiCuZn ferrite magnetic powder is prepared.However, the performance of NiCuZn ferrite becomes very poor at 500MHz, and the sintering temperature of hexagonal Co2Zn series with good high frequency performance and general hexagonal ferrite is 1200~1300, which must be reduced to about 900.For example: first prepared with NiO MnO ZnO and MgO replacement part of Co3O4 burning block, ball grinding grinding.Then it was prepared according to the molar ratio of Fe2O3 BaCO3 Co3O4(burning piece) of 3:2:12, mixed by ball mill for 16h, and prefired in air for 2h at 950~1300.Then it is crushed by ball mill, in which CuO and/or Bi2O3 of borosilicate glass with mass fraction of 1%~5% are added as flux.The specific surface area of the powder is
10㎡/g,reduce the sintering temperature to 930.
Soft chemistry refers to the method of preparing materials by general chemical reaction at medium and low temperature or in solution. This method can make the initial reactants evenly mixed in molecular size, generate precursors or intermediates, and finally generate materials with specified composition structure and morphology. It has produced a series of new material preparation technologies mainly including; Sol-gel process, insertion reaction, ion exchange process, hydrothermal method, fluxing agent method, primary product method and some electrochemical processes.
NiCuZn ferrite powder is prepared by softening method, and its particle distribution is quite concentrated. Most of the particles are between 30~ 50nm. Under the condition of not adding any flux, spinel phase with compact microstructure and uniform grain can be obtained by sintering at a temperature below 900.
Hexagonal Co2Zn series ferrite powder was prepared by softening method. After pressed into green blank, it was sintered in 900 air, and the microstructure of uniform and compact grains was obtained. No giant crystals appeared.