| With the continuous development of electronic industry, electronic equipment devices increasing more demands to the requirement of components. NiCuZn ferrite is known as the basic material of inductive electronic components which are needed to be further improved in the following aspects, such as the magnetic spectrum, the impulse field dependence of permeability, the DC-bias-superposition characteristics, and the temperature dependence of permeability. In this dissertation, the investigation was focused on these themes. The NiCuZn ferrite was prepared by traditional ceramic technology. The effects of formula, additive contents, and microstructure on the properties of material were analyzed, the research could be adopted to develop high performance low sintering NiCuZn ferrite components. The widespread application of smartphones and NFC technic has given rise to a new product electromagnetic (EM) shielding sheet. Beyond that, the preliminary research of industrial production process of electromagnetic shielding sheet has been carried on.Firstly, the magnetic spectrum was investigated based on the theory of critical size, the theory of component of permeability, as well as the NMGB (nonmagnetic grain boundary model) The results showed that, by controlling the average grain size under the critical size is favored to attain high cut off frequency on the premise of maintaining a certain permeability. It presented different effects of CO2O3applying on the two kinds of susceptibilities. Using Landau-Lifshitz equation to fit the magnetic spectra, the fitting curve could match the measure curve much better in the whole frequency band, when regarded the damping factor as a variable about frequency. It is putted forward the train of thought that the damping factor function could be used as a medium in analyzing the relationship between formula, process, microstructure and magnetic spectrum shape.Secondly, the impulse field dependence of permeability was investigated by using the NMGB model. The results showed that the glass phase addition can be used to form thicker grain boundary which is favorable to reduce the influence of impulse field on permeability. Samples with different grain size were analyzed using magnetic spectrum fitting method. The result showed that larger grain size was favorable to obtain better stability when sustaining impulse field, the variation range of domain wall motion susceptibility component was far less than the spin rotation susceptibility component because of the existence of domain wall, the variation of the spin rotation susceptibility reduced significantly.Thirdly, compound addition of low melting point glass and Bi2O3could obtain finer grain size and thicker grain boundary than each of two added alone, because of this compound addition was a feasible way to improve DC-bias-superposition characteristics. The research direction of ideal sintering aid was proposed, it could infiltrate with ferrite like Bi2O3, and could also hysteresis ion diffusion in the late sintering. By adjusting the content of sintering aid, the demagnetizing field could be changed which could adjust the temperature coefficient. And this method could be applicable to the whole spinel ferrite.Finally, industrial production process of electromagnetic shielding sheet was investigated. The results showed that, when mass production, the binary solvent slurry formula was designed. Due to fast volatile speed of binary solvent, the production efficiency was improved and the defect of raw sheet was reduced. Inspired by adhesive exist soften temperature, a pressure drying process was invented, the raw sheet was pressed and dried in the softening temperature of adhesive for a long time, discharge solvent as far as possible, it could make the raw sheet avoiding crimping in the evacuation process. Irregular cracking process was invented. Comparing with rules cracking process, irregular craking process improved the production efficiency and reduced the production cost. Contrasting the S11curve of the RFID antenna attach to nothing and with a ferrite sheet inserting between the antenna and metal sheet was a good method to the characterization of electromagnetic shielding sheet. The deviation value of the peak frequency of S11curves of the two situations which has been mentioned above has linear relationship with the deviation value of detectable distance of these two situations. Contrasting the S11curve could also be used to do the matching design of antenna and electromagnetic shielding sheet. |
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