The Basic Research Of LTCC Ferroelectric-Ferromagnetic Composite Materials

New electronic systems fo automotive/industrial/medical/aerospace will continue to challenge both packaging engineers and technology due to the increased performance requirements, higher densities, higher temperatives and limited space available. This challenge mandates the use of unique packaging techniques such as Low Temperature Co-fired Ceramic (LTCC) technology that must not only provide the increase circuit density but also the reliability, electrical and medical performance, thermal management, and hermeticity.Low Temperature Co-fired Ceramic (LTCC) technology is a new packaging technology for integrate circuit, which consists of buried passive devices such as transformer, conductors, resistors, and capacitors in the multilayer of module and can easily integrate with active devices such as power MOS, transistors, and IC module. Recently, this technology was widely focused and researched for its wonderful properties.Focused on the LTCC materials, we carried through some researches as follows:1. A low temperature sintering model was established based on the liquid sintering theories. The sintering temperature and sintering time dependence of relative density for the sintered ceramics were simulated.2. With the systemically analyses of the synthesis of ferroelectric-ferromagnetic composite materials, the low temperature sintered NiCuZn ferrites and perovskite BaTiO_k+X was chosen as the main components. A model was given by assuming the isolation of magnetic grains by surrounding non-magnetic layer to evaluate the internal field and the complex permeability of whole material as a function of the ratio of perovskite content to ferrite content.3. We researched the effects of preparation process on the microstructure and electromagnetic properties of ceramics. The pre-sintering temperature, milling time, firing rate, sintering temperature, and holding time are changed regularly to investigate the variation of the phase formation by X-ray diffraction studies, the micrographs of the sintered ceramics by SEM, and the bulk density by Archimedes method. The frequency dependence of complex permeability, quality factor, and dielectric constant are studied.4. The effects of sintering temperature and Mn ions contents on the microstructure and electromagnetic properties of NiZn ferrites are studied. To decreased the sintering temperature, CuO was introduced in NiZn ferrites first, and then the flux oxides such as Bi₂O₃, WO₃, and Nb₂O₅ are introduced in NiCuZn ferrites.The variation of microstructure and electromagnetic properties with these reducing-sintering-temperature oxides' content are investigated. Finally, we researched the influence of rare earth ions Ce⁴⁺ on low temperature sintered NiCuZn ferrites.5. A new ferroelectric-ferromagnetic composite material is synthesized by usual ceramic technology with NiCuZn ferrites and perovskite BaTiO_k+X as the main components. The microstructure and electromagnetic properties of the composite with different composition of NiCuZn ferrites and different perovskite contents are investigated. After that, the influences of flux oxide Bi₂O₃, WO₃, and Nb₂O₅ and the Ca²⁺, Ce⁴⁺ ions on this composite material are also studied.6. A LTCC band pass filter is designed with this composite material using the Ansoft HFSS software. This filter has insertion loss in the pass band < -2.8dB, the attenuation losses in the stopband were more than 40 dB, the centre frequency of the pass band is 1.9GHz and the 3 dB band width is more than 200MHz.