Papers by Keyword: LTCC

Abstract: The performance of adding 0–3 wt% B₂O₃-CuO as a sintering aid to lower the sintering temperature of La_0.5Sr_0.5Co_0.96Ni_0.04O_3-δ (LSCN) was investigated through solid-state reaction method. Results of linear shrinkage curve, bulk density, and microstructure indicated that BCu addition could promote the sintering process and enhance the densification of LSCN ceramics. With the increase of BCu content, low absolute value of TCR could be achieved, while the conductivity was deteriorated obviously. For LSCN ceramics sintered at 950 °C, the bulk density, conductivity, and TCR were worse than those sintered at higher temperatures. Consequently, the BCu-doped LSCN ceramics might not suitable for the application in the field of LTCC.

Abstract: The effect of different amount of LMZBS glass on the sintering behavior, microstructure and microwave dielectric properties of the Li₂(Mg_0.96Ni_0.04)SiO₄ ceramics was investigated. The synthesis of materials was based on the solid-state reaction method. The micromorphology of the composite ceramics was confirmed using scanning electron microscopy. The microwave dielectric parameters were measured by the network analyzer. The mechanism of heat transfer coming from LMZBS glass lower the densification temperature of matrix ceramic from 1150°C down to 900°C. Excellent microwave dielectric properties were obtained with 1.2 wt% LMZBS glass sintered at 900°C for 4h (ε_r=5.77 and Q×f=29,558 GHz at 16 GHz, τ_f=-14.5 ppm/°C). There was a compatibility between the composite ceramic and Ag. Therefore, the aimed ceramic has great potential value of application in the field of low temperature co-fired ceramics of millimeter-wave devices.

Abstract: Sm₂O₃ additive significantly influenced the microstructure, mechanical, and electrical properties of BaO-Al₂O₃-B₂O₃-SiO₂ glass-ceramics. The calculation by the whole pattern fitting method based on XRD patterns revealed that Sm₂O₃ additive improved the crystallization process of this tetra-system and promoted the formation of major phase quartz. The sintering kinetics showed that Sm₂O₃ addition markedly reduced the sintering activation energy from 406.86 kJ/mol to 391.38 kJ/mol, which benefited the sintering densification and the grain growth, and thus enhanced mechanical properties. Doping 2% Sm₂O₃ reinforced the flexure strength from 136.3 to 171.6 MPa and the Young’s modulus from 49.4 to 79.7 GPa. It also exhibited low dielectric constant of 5.31, low dielectric loss of 5.30 × 10^-4, and high thermal expansion coefficient of 11.76 × 10^-6/°C.

Abstract: Multilayer low temperature co-fired ceramic (LTCC) is well known in usage as interconnect substrate, especially in high frequency application due to high electrical conductivity of the conductors and low loss of the LTCC dielectric. As substrate and packaging materials, there are many chips or devices placed on the multilayer LTCC board. In this paper, multilayer LTCC is implemented as the packaging at PIN photodiode (PD) module of the Radio over Fiber (RoF) system with the reason to increase thermal dissipation capacity of the PD module.

Abstract: The article deals with forming solid joints of Low Temperature Co-fired Ceramic with Alumina or Silicon Carbide chips. The aim of this study is to find material of standard thick film layer process, which would be useful for electronic chip packages designed for higher operating temperatures (from 150 up to 800 °C). Heraeus Hera Lock 2000 Low Temperature Co-fired Ceramics (LTCC) was chosen, because of its nearly zero shrinkage during firing. Also other LTCC types were used to comparison of results. Conductive and isolating thick film pastes are used for joining. Temperature cycling of samples was applied. Strength of cycled samples was investigated by mechanical shear tests. The structure of microsection of joints was analyzed using optical and scanning electron microscope. The results show that thick film pastes are usable for joining above mentioned materials in specific temperature range.

Abstract: The effect of subcritical crack growth is nowadays intensively studied mainly in relation to the strength of ceramic materials. The main aim of the contribution is to describe behavior of micro-crack propagating in the Low Temperature Co-fired Ceramics (LTCC) under subcritical crack growth (SCCG) conditions. The micro-crack behavior is significantly influenced by residual stresses developed in the LTCC due to different coefficients of thermal expansion of individual components. Two-dimensional numerical model was developed to simulate micro-crack propagation through the composite. The micro-crack propagation direction was determined using Sih’s criterion based on the strain energy density factor and the micro-crack path was obtained. The residual lifetime of the specific ceramic particulate composite (LTCC) was estimated on the basis of experimental data. The paper contributes to a better understanding of micro-crack propagation in particulate ceramic composites in the field of residual stresses.

Abstract: The contribution deals with the issue of mechanical response of the particulate ceramic composites used in microelectronic. Mechanical properties and behaviour of composites are highly influenced by residual stresses which are developed in material during cooling in manufacturing process due to the different coefficients of thermal expansions of individual constituents. The main aim of this paper is to estimate the elastic constants and strength of the selected particulate ceramic composites with considering the residual stresses. Three dimensional models and finite element method are used for numerical simulations. Results contribute to determination and better understanding of mechanical behaviour of the particulate ceramic composites.

Abstract: In this paper, the influences of sintering conditions on the phase transformation, microstructure, bulk density, bending strength, coefficient of thermal expansion, and dielectric properties of Li₂O-Al₂O₃-SiO₂ glass-ceramic were investigated. Conventional melt-quenching method was used to synthesize this glass-ceramic. Scanning electron microscopy, X-ray diffractometer and differential thermal analysis were employed to study this material. The XRD data show that Li₂OAl₂O₃7.5SiO₂ is the main crystalline phase of this glass-ceramic. ZrO₂ and CaMgSi₂O₆ are the two other phases in this glass-ceramic. The increasing sintering temperature and soaking time affect the phase composition obviously, which lead to the obvious variations of microstructure, mechanical, dielectric and thermal properties of this glass-ceramic. Sintering temperature and time play a key role in the sintering of Li₂O-Al₂O₃-SiO₂ glass-ceramic. The sample sintered at 800 °C for 30 min showed good microstructure, low sintering temperature of 800 °C, high density of ~2.6 g/cm³, excellent dielectric properties (εr: ~6.9, tan δ: ~2*10^-3), good bending strength of 143 MPa and adjustable CTE from 1.1 to 2.7 *10^-6 K^-1 close that of silicon. These results mean that the obtained LAS glass-ceramic can be used in the application of LTCC substrate, especially, the manufacture of the substrate of silicon.

Abstract: To lower the sintering temperature of ZnNb₂O₆ microwave dielectric ceramic, ZnNb₂O₆ doped with B₂O₃ were prepared by the traditional solid state reaction method. The effects of the amount of B₂O₃ (0.25-5.0wt.%) on the microstructure, density and electrical performances were investigated. The results show that a pure columbite ZnNb₂O₆ phase was obtained for all B₂O₃-doped ceramics. The microwave dielectric properties reached the maximum values of ε_r = 24.1, Q×f = 19502 GHz, τ_f = -52.19 ppm/°C for 1wt% B₂O₃-doped ZnNb₂O₆ ceramic sintered at 1050 °C for 4 h. All of evidences suggest that the enhancement of microwave dielectric properties is due to the enhanced ions-energy and ionic diffusion with the increase of sintering temperature. Furthermore, B₂O₃ doping can generate liquid phase and reduce the activation energy of diffusion to promote the materials sintering.

Abstract: An investigation of the several different techniques and method have been suggested in the design of compact microwave filters for the realization of high performance output micromachined microstrip low pass filters and highest attenuation loss is presented in this paper. It is shown that the basis for much fundamental microwave filter theory lies in the real of lumped-element filters, which lumped elements suffers for not suitable use in high frequency, because wavelength will decrease to short and the only distributed elements can practically well and the lumped elements circuit and work efficiently at low frequency or vice versa wavelength of distributed elements become too larger. In this paper, a review of numerous methods of design compact microstrip filters that have been offered over the last years is proposed, including a discussion of topologies and the structures used to make compactness size of microwave filters.