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The Li–Al–Si glass-ceramics were prepared by conventional glass-ceramic fabrication method. The influences of Na2O content on the sintering property, microstructure, and coefficient of thermal expansion were investigated. The results show that the coefficient of thermal expansion of LAS glass-ceramics can be tailored to match that of silicon by the addition of Na2O content. Na2O has a remarkable influence on the crystallinity of Li–Al–Si glass-ceramic. The coefficient of thermal expansion of Li–Al–Si glass-ceramic is thus tunable between that of glass phase and crystal phase. The Si–O bond length change in stretch vibration modes introduced by Na2O also contributes to the variation of coefficient of thermal expansion of the Li–Al–Si glass-ceramics. The coefficient of thermal expansion of the Li–Al–Si glass-ceramic with 1.5 wt% Na2O addition is about +3.34 ppm/°C at 350 °C and shows a good compatibility to that of silicon in a wide temperature range, which makes it a promising candidate for anodic bondable low temperature co-fired ceramic substrate applications.

Li–Al–B–Si–O (LABS) glass-ceramics with a sintering temperature of 600 °C were studied for ultra-low temperature co-fired ceramics (ULTCC) applications. The crystal phase of LABS glass-ceramics is dendritic β-spodumene. The permittivity and dielectric loss of LABS glass-ceramics are e r = 5.8 and tg δ = 1.3 × 10 −3 at 10 MHz, respectively. The coefficient of thermal expansion (CTE) of LABS glass-ceramics is 3.23 ppm/°C, which is close to that of silicon. The dielectric and thermal properties of LABS glass-ceramics are closely correlated to the degree of its crystallization. The permittivity decreases continually while the dielectric loss decreases first and slightly increases with the increasing of crystallization of β-spodumene. The CTE of LABS glass-ceramics decreases as β-spodumene crystallized from LABS glass. The crystallization kinetic and mechanism of LABS glass-ceramics indicate that the β-spodumene crystallizes in a two-dimensional interfacial growth mechanism due to the migration of Li-ions. The diffusion coefficients derived from energy-dispersive X-ray spectroscopy (EDS) results indicated that both Al and Ag electrodes have good compatibilities with ULTCC tapes, which could reduce the cost of multilayer electro-ceramic devices dramatically by using the ULTCC and base metallization.

Two low temperature cofirable ceramic materials with thermal expansion coefficients (TEC) of 5.9 ppm/K and 6.6 ppm/K, respectively, were used in this work to introduce residual stress by the multilayer cofiring process. Theoretical calculation and finite element method (FEM) simulation were used to optimize the multilayered ceramic substrate composition design to obtain enhanced mechanical performance. Based on the failure condition of materials, the multilayered ceramic substrate has an optimal thickness ratio of the surface layers to the whole laminate (sandwich structure). Indentation method was used to measure the surface residual stresses and 3-point bending tests were used to measure the mechanical strength. Enhanced mechanical strength of 404 MPa can be obtained when the thickness ratio of surface layer to the whole laminate is 0.19.

Composites of Li-Al-B-Si-O (LABS) glass and β-Al 2 O 3 have been synthesized for low-temperature co-fired ceramics (LTCC) technology application. The main phase of sintered composites is Li 2 Al 2 Si 3 O 10 and β-Al 2 O 3 phase appears only when its content is higher than 35 wt%. The DC conductivities of sintered composites are all above 1 × 10 −8 S/cm at the temperature of 473 K. The activation energies of alkali ions of different composites are all between the conductivity measured perpendicular and parallel to the c-axis of Eucryptite, which proves the ionic conductance of composites is associated with the main phase of Li 2 Al 2 Si 3 O 10. The CTE of the composites increased with the increase of β-Al 2 O 3 . The CTE of 68 wt% LABS glass-32 wt% β-Al 2 O 3 is 3.15 ppm/°C (25300 °C), which matches that of silicon (3.2 ppm/°C, 25300 °C) well. The results indicate that the composites of Li-Al-B-Si-O glass and β-Al 2 O 3 can be a promising material for LTCC-silicon heterogeneous integration with anodic bonding technology. © 2018 Elsevier Ltd and Techna Group S.r.l.

This paper presents a kind of passive wireless pressure and temperature integrated inductor-capacitor (LC) resonant sensor based on low temperature co-fired ceramic (LTCC) technology. The pressure sensing part is dependent on a traditional cavity capacitor. The temperature sensing part is composed of an interdigital capacitor and a planar spiral inductor. The capacitance and the resistance of inductor coil would change as a response to temperature. The LTCC material with a low Young's modulus of ~65 GPa prepared by our laboratory was used to obtain high pressure sensitivity. The experimental results showed that the prepared sensor has a pressure sensitivity of 1.16 kHz/kPa, and a temperature sensitivity of 0.062% dB/°C within the range of 140–850 kPa, 50–500 °C, respectively.

In this study, undoped and Mn 2+ doped Ti 1-x Cu x/3 Nb 2x/3 O 2 (TCN, x = 0.2, 0.25, 0.3, 0.35) ceramics were prepared using a solid-state reaction method. The phase composition and microstructure of the TCN ceramics were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results indicated that the density and permittivity of the TCN ceramics increase with the increasing of the Cu and Nb content. However, Q × f value of the undoped TCN ceramics decreases with an increase in the sintering temperature. A small amount of Mn 2+ doping has no effect on the permittivity, but improves the Q × f value. X-ray photoelectron spectroscopy (XPS) analysis indicated that the transition of Cu 2+ to Cu + during the sintering process could be inhibited by Mn 2+ doping, which suppresses the formation of oxygen vacancies, as a result, the improvement of Q × f value. Excellent microwave dielectric properties with a permittivity of 95 and Q × f value of 20800 GHz (@3.50 GHz) were achieved from the 0.6 at% Mn 2+ doped TCN (x = 0.25) ceramics sintered at 1025 °C for 5 h.

CuO-B 2 O 3 -Li 2 O (CBL) glass-ceramic with a composition of 32 wt% CuO − 63 wt% B 2 O 3 − 5 wt% Li 2 O was prepared through conventional glass-ceramic route. The CBL glass-ceramic could be densified well by sintering at 625 °C for 30 min. The X-Ray diffraction (XRD) and transmission electron microscopy (TEM) analysis indicated that the CuB 2 O 4 phase was dominated in the sintered glass-ceramic, which showed excellent microwave dielectric properties with e r = 5.84, Q × f = 10120 GHz (at 13.44 GHz), and τ f = −33 ppm/°C. Furthermore, the CBL material is chemically compatible with both silver (Ag) and aluminum (Al) electrodes at their sintering temperatures. These properties indicate that the CBL glass-ceramic might be a promising ultra-low temperature co-fired ceramic (ULTCC) material for packaging substrate applications.

This work focuses on the temperature stability of resistance below the switching temperature of positive temperature coefficient resistor (PTCR) ceramics. The BaTiO 3 based PTCR powders were grinded by conventional ball milling and high-energy ball milling. Particle size distribution analysis showed that high-energy ball milling was much more efficient for particle size reduction. It was found that the PTCR ceramic with 3000 rpm for 1 h high-energy ball milling has uniform grain size distribution. The measurement results of the resistance–temperature characteristics of PTCR ceramics indicated that the temperature stability of resistance below the switching temperature of PTCR ceramics could be improved by high-energy ball milling, and the optimum temperature stability of resistance below the switching temperature existed in the sample of 3000 rpm-1 h. The capacitance–temperature characteristics of PTCR ceramics were also investigated.

A new type of low temperature co-fired ceramic (LTCC) composite, comprising beta-Si3N4 whiskers and calcium aluminosilicate (CAS) glass, is introduced in this paper. We show that the CAS-Si3N4 composite can be densified at 775-850 degrees C in air. The effect of beta-Si3N4 whiskers incorporation on the thermal conductivity of this relatively low-temperature sintered CAS-Si3N4 composite is investigated. The thermal conductivity of the CAS glass is increased from 1.6 to 7.9 W/mK after adding 35 vol% of beta-Si3N4 whiskers. Microstructure characterization and percolation model analysis indicate that the likely cause of increased thermal conductivity of the ceramic composites is the formation of thermal percolation networks. The crystallization of the CAS glass also contributes to the enhancement of thermal conductivity. The sample with the highest thermal conductivity shows a low relative dielectric constant of 7.1 and a dielectric loss of 0.006 at 1 MHz. Such a ceramic composite with excellent thermal and dielectric properties is a promising LTCC substrate material.