Ultra-low Temperature Co-fired Ceramic Research Articles

Microwave dielectric properties and bond characteristics of glass-free low permittivity LiVO3 ULTCC ceramics

The LiVO3 ultra-low temperature cofired ceramic (ULTCC) was synthesized by the solid-state chemical method and its crystal structure, sintering behavior, and microwave dielectric performances were systematically studied by X-ray diffractometer (XRD) and Scanning electron microscope (SEM). XRD showed that LiVO3 were pure monoclinic single phase with a space group of C2/c. Furthermore, the best microwave dielectric properties Q × f = 16,900 ± 720 GHz, εr = 8.78 ± 0.06, and τf = − 117 ± 2.3 ppm/°C could be obtained when LiVO3 sintered at optimal sintering condition 520 °C/8 h affirmed by SEM. The microwave dielectric properties were also deeply investigated utilizing the P–V–L chemical bond theory. The microwave dielectric performances of LiVO3 had a great closer relationship with the V(1)–O bonds explained by analysis data. The low permittivity LiVO3 with attractive features highlighted it to be a good candidate for ULTCC applications.

Bulk glass-ceramic composites and ULTCC substrates for microwave and millimetre-wave applications

In this study, a new ultra-low-temperature co-fired ceramic (ULTCC) glass-ZnO-SiO2-B2O3CeO2−MgO-Al2O3 composite was developed and its applicability as a dielectric substrate in emerging high-performance communication technologies in the microwave and millimetre-wave frequency ranges was investigated. The novel material composition enables achieving good sinterability at a low fabrication temperature of 470 °C. Extensive studies have been conducted on the microstructure, porosity, water absorption, surface roughness, and thermal expansion coefficient. Following this analysis, the dielectric properties of the bulk glass-ceramic composites and the final ULTCC substrates were characterised. These measurements were conducted within a broad frequency range of 5 GHz–1.1 THz using split-post dielectric resonators, a Fabry-Perot open resonator, and a time-domain spectrometer, resulting in quasi-continuous frequency characteristics of the complex permittivity. Furthermore, the fabricated ULTCC substrates were subjected to surface-wise measurements, which provided 2D maps of the dielectric properties as qualitative and quantitative measures of the uniformity and quality of the material.

Low permittivity MgF2-LiF ceramics with ultra-low dielectric loss for ULTCC applications

In this work, MgF2–xwt%LiF (x = 0.5, 1.0, 2.5, 4.0, 5.0) ceramics have been prepared through the standard solid-state reaction method. X-ray diffraction patterns and scanning electron micrographs revealed the successful preparation of dense MgF2–LiF composite ceramics at an exceptionally low sintering temperature range of 525–600°C. The optimal microwave dielectric properties (εr = 5.09 ± 0.03, Qf = 100,733 ± 1646 GHz, τf = −67.4 ± 3.3 ppm/°C) were achieved in MgF2–0.5 wt%LiF ceramics after sintering at 550 °C for 3 h. The present ceramics exhibited an outstanding combination of low-εr, high Qf, and an ultra-low sintering temperature, surpassing the performance of most low-temperature-fired dielectric materials. Moreover, the theoretical Qf value, extrapolated from the fitting of infrared reflectivity spectra, was calculated to be 326,583 GHz, indicating significant potential for further Qf improvement. Additionally, the chemical compatibility with Al electrodes was confirmed, suggesting promising potential for ultra-low temperature co-fired ceramic (ULTCC) applications.

MgF2-based microwave dielectric ceramics with ultra-low sintering temperature and high thermal expansion coefficient

Ultralow-temperature co-fired ceramic (ULTCC) materials with low permittivity and dielectric loss are considered promising materials for 5 G communication applications. Herein, a novel multiphase xMgF2-(1x)LiF (x = 0.20, 0.35, 0.50, 0.65) microwave dielectric ceramic was prepared via a conventional solid-state method for ULTCC applications. The ceramic achieves densification at a sintering temperature of 625 °C. The xMgF2-(1-x)LiF ceramics exhibit tunable permittivity ranging from 5.21 to 7.30, Q×f from 39400 to 52800 GHz, and τf from − 61 to − 98 ppm °C−1. Analysis of the crystal structure and microstructure revealed that the volatilisation of fluoride ions in the ceramics led to an increase in defect concentration, contributing to an unfavourable decrease in dielectric loss. The 0.35MgF2-0.65LiF ceramic shows comprehensive properties with the highest Q×f value (52800 GHz) and low permittivity (6.40). Furthermore, the thermal expansion coefficient is an important performance parameter in ceramic packaging with the 0.35 MgF2-0.65 LiF ceramic exhibiting a colossal thermal expansion coefficient of 28.69 ppm °C−1, thus enabling excellent compatibility with printed circuit board (PCB) substrates. Moreover, these high thermal expansion coefficient ceramics are excellent candidates for packaging.

Structure, composition, microwave dielectric properties and improved ultra-low temperature sintering characteristics of Lyonsite structural Li2Mg2Mo3O12 ceramic

(1-x)Li2Mg2Mo3O12-xTiO2 (x = 0.1–0.5) composite ceramics are prepared by solid-state sintering process. And the structure, composition, microwave dielectric properties and ultra-low temperature sintering characteristics are studied. The result of two-phase (Li2Mg2Mo3O12 and TiO2) coexistence is definitely identified through XRD, mapping and Raman analysis along different regions. Furthermore, as the sintering temperature increases, the enhanced degree of densification plays a positive role in determining microwave dielectric properties. Sintering additives are used to lower sintering temperature of 0.6Li2Mg2Mo3O12-0.4TiO2 composite ceramics, where 1 wt% H3BO3 is applied to reduce the temperature from 750 °C to 700 °C and maintain excellent microwave dielectric characteristics. The cooling mechanism of sintering aids are also thoroughly studied. In all, 0.6Li2Mg2Mo3O12-0.4TiO2 composite ceramic with 1 wt% H3BO3 sintered at 700 °C displays excellent microwave dielectric properties (εr∼11.27, Q × f ∼43056 GHz, τf ∼ -3 ppm/°C). It can be served as a pioneering candidate in applications of ULTCC (ultra-low temperature co-fired ceramic).

Microwave dielectric properties of a novel Li2O–Al2O3–B2O3 glass-ceramic for ULTCC application

The 50 Li2O - x Al2O3 - (50 - x) B2O3 (x = 3–7 mol%) glass-ceramics were prepared by solid-state reaction method. Homogeneous glasses were obtained by water quenching, and the glass-ceramics with the LiBO2 and Li3AlB2O6 as main crystalline phases were prepared after the subsequent sintering process. The appropriate content of Al2O3 can significantly improve the densification and crystallization of Li2O - Al2O3 – B2O3 (LAB) glasses. The fully densified glass-ceramics with 4 mol% Al2O3 exhibit uniform and fine microstructure and large volume density. This glass-ceramic sintered at 650 °C for 7 h displays excellent microwave dielectric properties with εr = 5.47, Q × f = 21814 GHz (at 13.6 GHz), and τf = - 61.3 ppm/°C. Additionally, the LAB glass-ceramics are chemically compatible with aluminum (Al) and silver (Ag) electrodes at their sintering temperatures, which shows significant potential in ultralow temperature co-fired ceramic (ULTCC) for packaging substrate applications based on their good microwave dielectric performance and good chemical compatibility.

Low-loss and ultra-low temperature sintering microwave dielectrics of pure and Ag-modified K2Mg2(MoO4)3 ceramics

Novel K2–2xAg2xMg2(MoO4)3 (x = 0–0.09) ceramics were synthesized by conventional solid-state sintering method. Based on the X-ray diffraction (XRD) patterns, all samples were identified to belong to an orthorhombic structure with a space group of P212121(19). The pure phase K2Mg2(MoO4)3 specimen when sintered at 590 °C revealed the favorable microwave dielectric properties: εr of 6.91, Q×f of 21,900 GHz and τf of −164 ppm/°C. The substitution of Ag+ for K+ in K2–2xAg2xMg2(MoO4)3 (x = 0.01–0.09) ceramics led to the more stable structure and dramatically enhanced the Q×f to a value of 54,900 GHz at 500 °C. The microwave dielectric properties were related to the relative density, microstructure, ionic polarization, lattice energy, packing fraction, and bond valence of the ceramics. It was suggested that for ultra-low temperature co-fired ceramic (ULTCC) applications, K1.86Ag0.14Mg2(MoO4)3 ceramic could be sintered at 500 °C, which revealed an excellent combination of microwave dielectric properties (εr =7.34, Q×f =54,900 GHz and τf =–156 ppm/°C) and good chemical compatibility with aluminum electrodes.

Sintering behavior, structure and dielectric properties of CuO-ZnO-MgO-B2O3 glass-ceramics for ULTCC applications

High performance ultra-low temperature co-fired ceramic (ULTCC) materials were prepared from CuO- MgO- ZnO- Al2O3- B2O3- Li2O glass-ceramics. The sintering behaviors, crystalline phase evolution, microstructure and dielectric properties, as well as their compatibility with Ag and Al electrodes, were investigated. With the suitable substitution of MgO for ZnO, the dielectric properties of glass-ceramics were improved. It is mainly associated with the fine microstructure, highly crystallinity, and decrease in tetrahedral distortion in the crystal lattice. All the glasses completed the densification at 575–600 °C, and ZnB4O7 is the only crystalline phase precipitated from the glasses. Moreover, the glass-ceramic with 1 wt% MgO sintered at 575 °C for 5 h, exhibited low relative permittivity ~ 7.1 and low dielectric loss ~ 6.40 × 10−4. And the glass-ceramic with 4 wt% MgO sintered at 600 °C for 5 h, also displayed low relative permittivity ~ 7.1 and low dielectric loss ~ 5.77 × 10−4. Both two glasses have good sintering compatibility with silver and aluminum electrodes, which provided high potential for ULTCC application.

Sintering behavior, structure, and microwave properties of novel Li2xCu1-xMoO4 ceramics

In this study, we prepared a novel series of Li2xCu1-xMoO4 (x = 0.02, 0.04, 0.06, 0.08, and 0.10) microwave ceramics. The dynamic sintering behavior, crystal phases, micro-morphologies, and dielectric properties of the samples were studied. The substitution of Li+ contributed to refining the crystal grain size, promoting the densification of microstructure, and enhancing the quality factor. Due to different valence substitutions, Cu+ ions were created, which were verified by X-ray photoelectron spectroscopy (XPS) and Raman experiments. In addition, the Raman shift, full width at half maximum (FWHM) value of the A1g peak, and crystal microstrains were analyzed to gain a mechanistic understanding of the influence of structure on the dielectric properties. When x = 0.08, the Li2xCu1-xMoO4 ceramic sintered at 675 °C exhibited optimal comprehensive properties with εr = 8.17, Qf = 68 476 GHz, and τf = −25 ppm/°C, and good chemical stability between the ceramic and Al electrode was also achieved. These promising properties make Li2xCu1-xMoO4 (x = 0.08) more suitable for ultra-low temperature co-fired ceramic (ULTCC) applications.

Microwave dielectric polymer-ceramics sintered at near room-temperature with moisture-proof ability

(1-x)H3BO3-xPE (x = 0.0–0.5) microwave dielectric polymer-ceramics (composite ceramics) with ultra-low sintering temperatures (60–110 °C) were prepared via the traditional solid-state method to improve the moisture-proof ability of H3BO3 matrix ceramics. X-ray diffraction (XRD), back-scattered scanning electron microscopy (EDS-SEM), and Raman spectroscopy confirmed that H3BO3 and PE could coexist without intermediate phases. As the x value increased, the dielectric Q value and resonant frequency (Q × ƒ) decreased from 116,000 GHz (at 15.0 GHz) to 37,000 GHz (at 16.3 GHz), the relative permittivity (εr) varied between 2.83 and 2.14, and the temperature coefficient of the resonant frequency (τƒ) shifted from −147 ppm/°C to +27 ppm/°C in the (1-x)H3BO3-xPE (0.0 ≤ x ≤ 0.5) microwave ceramics at their optimal sintering temperatures. A near-zero τƒ value (+9 ppm/°C) was obtained in the 0.7H3BO3-0.3 PE composite, which simultaneously exhibited an εr value of ~2.38 and a Q × ƒ value of ~46,000 GHz (at 15.7 GHz) after sintering at 100 °C for 1 h. Interestingly, through the hydrolysis experiment (24–384 h), the Q × ƒ values of the 0.7H3BO3-0.3 PE and/or 0.6H3BO3-0.4 PE polymer-ceramics were basically maintained at approximately 35,000–40,000 GHz. These results showed that the novel (1-x)H3BO3-xPE polymer-ceramics should be the potential candidates for ultra-low temperature co-fired ceramic (ULTCC) technology.

Novel scheelite‐type [Ca0.55(Nd1‐xBix)0.3]MoO4 (0.2 ≤ x ≤ 0.95) microwave dielectric ceramics with low sintering temperature

AbstractNovel scheelite‐type [Ca0.55(Nd1‐xBix)0.3]MoO4 (0.2 ≤ x ≤ 0.95) ceramics were prepared using the solid‐state reaction method. According to the X‐ray diffraction data, a solid solution was formed in 0.2 ≤ x ≤ 0.95 and all the samples belong to pure scheelite phase with the tetragonal structure. As revealed by Raman spectroscopy, the number of vibrational modes decreased with the increase in x value, which further indicated that Bi3+ ions occupied A‐site of scheelite structure. As the x value increased, the sintering temperature decreased from 740°C to 660°C; the permittivity increased from 12.6 to 20.3; the Qf value first decreased slightly and gradually remained stable. Based on the infrared reflectivity spectrum analysis, the calculated permittivity derived from the fitted data shared the same trend with the measured value. The [Ca0.55(Nd0.05Bi0.95)0.3]MoO4 ceramic sintered at 660 °C attained a near‐zero value temperature coefficient ~τf (−7.1 ppm/°C) and showed excellent microwave dielectric properties with a ɛr ~ 20.3 and a Qf ~ 33 860 GHz, making this system a promising candidate in the ultralow temperature cofired ceramic (ULTCC) technology.

High relative permittivity Bi4B2+xO9+3x/2 (x = 1.5, 2, 2.5, 3) microwave ceramics for ULTCC technology

Bi4B2+xO9+3x/2 (x = 1.5, 2, 2.5, 3) compounds with high relative permittivity and ultra-low sintering temperature were prepared using the conventional solid-state method. Due to the volatilisation of B2O3 during sintering, a Bi4B2O9 single phase was obtained in excess addition of boric acid for x = 2.5. The densest structure of the Bi4B2+xO9+3x/2 (x = 2.5) ceramic, sintered at 585 °C, exhibited good microwave dielectric properties of a relative permittivity (εr) = 42.5, quality factor (Q × f) = 3240 GHz, and temperature coefficient of resonance frequency (τƒ) = −59 ppm/°C. As the value of x changed, the second phases of Bi2O3 and Bi3B5O12 appeared, and the (εr) and (τƒ) values decreased. The Bi4B2+xO9+3x/2 (x = 2.5) ceramics did not react with either Ag or Al, indicating that they are good candidate materials for ultra-low temperature co-fired ceramic (ULTCC) applications.

Synthesis, microstructure and characterization of ultra-low permittivity CuO–ZnO–B2O3–Li2O glass/Al2O3 composites for ULTCC application

In view of lead-free low-softening CuO–ZnO–B2O3–Li2O glass, novel glass/Al2O3 ceramic composites were prepared by solid-state reaction route for ultra-low temperature co-fired ceramic (ULTCC) applications. The phase evolution and compositions, microstructure and microwave dielectric properties of the composites were studied by XRD, SEM and dielectric property measurement. Four phases including Cu2Al6B4O17, Li2CuB4O8, CuB2O4 and Al2O3 coexist in the glass/Al2O3 ceramic composites sintered in the range of 640–660 °C. However, the contents and types of the phases depend on the composition of the composites and firing temperature. The optimum properties with a permittivity εr = 3.79, a quality factor Q × f = 38557 GHz (at 16.64 GHz) and a temperature coefficient of resonance frequency τf≈0 ppm/oC as well as a heat conductivity λ = 1.46W(mK)−1can be achieved for the glass/ceramic composite containing 10 wt% Al2O3 sintered at 640 °C. Moreover, the composite can be co-fired compatible with Ag and Al electrodes.The as-prepared glass/Al2O3ceramic composites are promising candidate for ULTCC application.

Structural and dielectric studies of MBi2B2O7(M = Sr&Ba) glass- Bi24B2O39 microcrystal composites

20MO.55Bi2O3.25B2O3 (M = Sr, Ba) glasses have been prepared by conventional melt quenching method and the Bi24B2O39 (boron sillenite) crystalline phase by solid state reaction technique. The effect of variation in wt% of Bi24B2O39 crystalline phase on 20SrO.55Bi2O3.25B2O3 (SBB) and 20BaO.55Bi2O3.25B2O3 (BBB) glasses has been investigated. The sintered density of the glass samples were characterized by Archimedes' method. The X-ray Diffraction method, Fourier Transform-Infrared (FT-IR) spectra and FT- Raman spectra are used for structural investigations, whereas Scanning Electron Microscope (SEM) analysis is used for the microstructural study. The effect of the Bi24B2O39 crystalline phase as filler in the glass network is confirmed from the FT-IR and FT-Raman spectra. The dielectric properties of the selected samples, analyzed using an Impedance analyzer, show that the dielectric constant slightly increases with increase in the wt% of Bi24B2O39 crystalline phase on glasses and the BBB glasses show higher dielectric values than the SBB glasses. The glass ceramic composites show low sintering temperature (<650 °C), dielectric constant in the range 10–16 and dielectric loss of ~0.0069, suggesting that they can be used as promising candidates for Ultra Low Temperature Cofired Ceramic Applications(ULTCC).

Sintering behavior and dielectric properties of ultra-low temperature glass/ceramic composites

Na2O-K2O-SiO2-B2O3-Al2O3-P2O5 (NKAP) glasses with low melting temperatures were obtained by melting. NKAP glass/ceramic composite ULTCC (ultralow temperature co-fired ceramic) materials were prepared at sintering temperature (<700 °C) by mixing traditional ceramic materials (alumina, quartz and zirconia) and low melting NKAP glasses. Quartz and monolithic zirconia can form stable composites with low melting NKAP glasses. Thus, we prepared ULTCC composite materials containing high amounts of quartz and zirconia. However, alumina and NKAP glasses partially reacted during sintering. Sintering temperature of NKAP glass/ceramic ULTCC composite was lower than 680 °C with the minimum sintering temperature of ˜ 550 °C. All samples containing NKAP glass/quartz ULTCC composites demonstrated excellent dielectric permittivity (equal to 6.51 with loss ˜8 × 10−3) and mechanical bending strength equal to 82 MPa. Our results can be used for fabrication of multilayer ULTCC packaging structures with tailored physical properties.

ULTCC Glass Composites Based on Rutile and Anatase with Cofiring at 400 °C for High Frequency Applications.

The article presents the very first materials to the ultralow temperature cofired ceramic (ULTCC) technology with the sintering temperature of 400 °C. The dielectric composites are based on a rutile and anatase with commercial GO17 sealing glass. In addition to the bulk samples, the tape casting procedure is also introduced to show its feasibility to cofiring with commercial Ag electrodes at 400 °C. The structural, microstructural, thermal, and microwave dielectric properties in the green and sintered samples were investigated. The optimum amount of glass to fabricate substrates was found to be 30 vol %. The ULTCC substrates with the anatase TiO2A-30GO17 and rutile TiO2R-30GO17 that were sintered at 400 °C showed a relative permittivity of 9.9 and 15 and a dielectric loss of 0.006 and 0.003, respectively, at the measurement frequency of 9.9 GHz. The temperature dependences of the relative permittivity were +70 and −400 ppm/°C, respectively. Moreover, the coefficients of the thermal expansion of the substrates were 7.4 and 8.3 ppm/°C in the measured temperature range of 50–300 °C. A preliminary test to study the feasibility of the anatase TiO2A-30GO17 for a dual band antenna was performed due its relatively stable temperature behavior.

Temperature stable K0.5(Nd1−xBix)0.5MoO4 microwave dielectrics ceramics with ultra‐low sintering temperature

AbstractK0.5(Nd1−xBix)0.5MoO4 (0.2 ≤ x ≤ 0.7) ceramics were prepared via the solid‐state reaction method. All ceramics densified below 720°C with a uniform microstructure. As x increased from 0.2 to 0.7, relative permittivity (ɛr) increased from 13.6 to 26.2 commensurate with an increase in temperature coefficient of resonant frequency (TCF) from – 31 ppm/°C to + 60 ppm/°C and a decrease in Qf value (Q = quality factor; f = resonant frequency) from 23 400 to 8620 GHz. Optimum TCF was obtained for x = 0.3 (−15 ppm/°C) and 0.4 (+4 ppm/°C) sintered at 660 and 620°C with ɛr ~15.4, Qf ~19 650 GHz, and ɛr ~17.3, Qf ~13 050 GHz, respectively. Ceramics in this novel solid solution are a candidate for ultra low temperature co‐fired ceramic (ULTCC) technology.

Fabrication and microwave dielectric properties of CuO-B 2 O 3 -Li 2 O glass-ceramic with ultra-low sintering temperature

Abstract 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.

Tape casting system for ULTCCs to fabricate multilayer and multimaterial 3D electronic packages with embedded electrodes

A 3D multilayer structure built by two ultra-low temperature co-fired ceramic (ULTCC) compositions with silver embedded electrodes are co-fired at a temperature of 450°C. The 3D multilayer module is prepared by laminating the ULTCC green tapes with a new binder system, which organics can be completely burned out at temperature of 250°C before the sintering of the ULTCC 3D modulus. High-density microstructures are achieved for the sintered module. In this study, the ULTCC feasible binder system is introduced. Also, ULTCC multilayers and multimaterial structures with surface and embedded silver electrodes are fabricated. This research opens up a new horizon for fabrication of electroceramic devices with embedded electrodes in multimaterial devices.

Evaluation of a Lead-Free Ultra Low Temperature Co-Fire Ceramic (ULTCC) Tape Designed for Lamination on Aluminum Substrates and a Compatible Co-Fireable Silver Conductor

Abstract Light-emitting diodes (LEDs) are the product of choice for many commercial and industrial lighting applications. Due to increasing power densities, alternative mounting solutions are being evaluated in order to achieve the lowest junction temperatures and lowest thermal resistances. Previous papers have explored the benefits of using a thick film system as opposed to a traditional Metal Core Printed Circuit Board (MCPCB). The advantage of being able to directly insulate a heat sink eliminates additional MCPCB layers and mechanical attachment that can decrease the thermal conductivity of the module and increase cost. Lower thermal resistance results in higher performing LED modules at a lower cost and a longer lifetime. A process has been developed and evaluated where an ultra-low temperature co-fired ceramic (ULTCC) tape will be laminsated directly on to an aluminum heat sink in order to electrically isolate the substrate. The green tape will then have a silver conductor applied to it and fired in one step. Using a tape system as opposed to an ink system creates many advantages. The tape system allows for processing in cavities, which is beneficial for recessed lighting and three-dimensional substrates. The co-firing silver conductor reduces the number of firing steps, leading to less dimensional variation of the heat sink and lower processing costs. This paper will discuss the material solutions, processing requirements, and reliability data for a completely co-fired ULTCC system on aluminum.