Ceramic Substrate Research Articles

Low Parasitic-Inductance Packaging of a 650 V/150 A Half-Bridge Module Using Enhancement-Mode Gallium-Nitride High Electron Mobility Transistors

Because of their fast-switching speed and small die size, gallium-nitride high electron mobility transistors are challenging to package for low parasitic inductance and high heat dissipation in power electronics applications. In this article, a packaging technique was developed for making half-bridge modules of a 650 V, 150 A enhancement-mode gallium-nitride power transistor. The package consists of the device chips interconnected between a printed circuit board and an aluminum-nitride direct-bonded copper substrate. The dice are bonded on the insulated ceramic substrate by silver-sintering to ensure high thermal performance and joint reliability. The source, drain, and gate pads are connected by silver-sintering gold-plated pins or silver rods, which are aligned by holes or grooves in the circuit board. For electrical insulation and mechanical robustness, the space surrounding the device is filled by injecting and curing an underfill polymer. Electrical and thermal simulations of the package show that the half-bridge module has a 1.122 nH power-loop inductance, and 0.099 °C/W junction-to-case thermal resistance. Packages of the half-bridge module were fabricated, and their static and dynamic performances were characterized.

Defect detection of low-resolution ceramic substrate image based on knowledge distillation

Defect detection of low-resolution ceramic substrate image based on knowledge distillation

Effects of microalgal concentration and pH with flocculant on microfiltration

To make algal biomass a suitable feedstock for fuel and bioproducts, a practical way of dewatering and concentrating algal cells must be devised. In this study, a system comprising microfiltration membranes combined with a flocculant was developed on a low-cost ceramic substrate to harvest Tetradesmus obliquus efficiently. The effects of tannin-based flocculant concentration, microalgal concentration, and pH on microfiltration were studied. Permeate flux was evaluated for 5400 s through experiments to analyze the total resistance and the fouling mechanism. Results show that the cake filtration model best represented the data. The experiments at pH 4 and 0.06 kg/m3 of microalgae (with flocculant) showed improved results with a reduction in the J/J0 (permeate flux/initial flux) ratio of 39%. In addition, the effects of critical flux, transmembrane pressure, and fouling mechanism on microfiltration were investigated under the best conditions studied. Applying the stepping method to the critical flux yielded a permeate flux of 2.2 ? 10-5 m3m?2s?1. The 70 kPa condition showed the highest permeate flux (3.0 ? 10?5 m3m?2s?1) and a low cake pore blocking coefficient (k) obtained by the modified Hermia model. This study showed that Tanfloc at low pH could maximize microalgal separation in membrane processes.

ITO Thin Films for Low-Resistance Gas Sensors.

Indium tin oxide thin films were deposited by magnetron sputtering on ceramic aluminum nitride substrates and were annealed at temperatures of 500 °C and 600 °C. The structural, optical, electrically conductive and gas-sensitive properties of indium tin oxide thin films were studied. The possibility of developing sensors with low nominal resistance and relatively high sensitivity to gases was shown. The resistance of indium tin oxide thin films annealed at 500 °C in pure dry air did not exceed 350 Ohms and dropped by about 2 times when increasing the annealing temperature to 100 °C. Indium tin oxide thin films annealed at 500 °C were characterized by high sensitivity to gases. The maximum responses to 2000 ppm hydrogen, 1000 ppm ammonia and 100 ppm nitrogen dioxide for these films were 2.21 arbitrary units, 2.39 arbitrary units and 2.14 arbitrary units at operating temperatures of 400 °C, 350 °C and 350 °C, respectively. These films were characterized by short response and recovery times. The drift of indium tin oxide thin-film gas-sensitive characteristics during cyclic exposure to reducing gases did not exceed 1%. A qualitative model of the sensory effect is proposed.

Preliminary Study on the Fabrication of Multi-Layer Screen-Printed Electrode for Biosensor Application

ytical device that combines certain biological and physical elements. Several types of transducers are used for physical elements, such as optical, electrochemical, thermic, or gravimetric. Nowadays, electrochemical transducers have become widely used for the application of biomedical sensors. Electrochemical measurement devices called screen-printed electrodes (SPEs) are created by printing several types of ink on a ceramic or plastic substrate. SPEs enable speedy in-situ examination with high repeatability, sensitivity, and accuracy. In this study, SPEs were fabricated using a personalized CNC machine

Degree of conversion and bond strength of resin cements through different thicknesses of lithium disilicate ceramic using different curing modes

Objectives: The aim of this in vitro study was to assess the physical and mechanical properties of resin cements to ceramic substrate using different curing modes by evaluating the degree of conversion and bond strength of these cements. 
 Methods: Hundred twenty square lithium disilicate ceramic discs specimens of three thicknesses (0.5, 1 and 1.5 mm) and 10x10mm diameter were bonded to 120 bovine teeth using two resin cements (one light cure and one dual cure) and using two curing modes (ramp and continuous). As a result, 12 experimental groups were established for bond strength testing. degree of conversion of luting cements was evaluated using Fourier transform infrared spectroscopy (FTIR).
 Results: using the continuous mode compared to the ramp after controlling the type of resin and material thickness showed no significant difference(P>0.001) in SBS and DC. the effect of changing the material thickness between 0.5mm, 1mm and 1.5mm after controlling the resin type and mode of light curing, showed significant difference (p<0.001) from 1mm to 1.5mm using light-cured resin and continuous curing mode for SBS. while for the DC these correlations between different material thicknesses and both light cure type of resin and continuous light-curing mode was significant (p<0.001), it was also significant with dual cure cement. This study also evaluated the effect of using dual-cured resin cement compared to the light-cured resin cement on the SBS and DC, for the SBS the effect was significant with higher thicknesses (p<0.001 for the thickness of 1.5 mm) but not significant with thicknesses less than this such as 0.5mm and 1mm (P>0.05).
 Conclusion: There is no change on the effect of changing light curing mode on the DC and SBS increasing the thickness decrease SBS and DC, dual-cured resin performed better when used for thickness of 1.5mm.

Polyamide nanofiltration membrane with MoS2 interlayer on tubular ceramic substrate for desalination

The tubular ceramic substrate has great potential in membrane separation because of its excellent solvent and temperature resistance, pressure stability, and long service life. However, it is still a challenge to prepare an ultrathin intact selective layer by interfacial polymerization (IP) on a porous tubular ceramic substrate, due to its large pore size and defects on the surface. In this study, a molybdenum sulfide (MoS2) interlayer with a loose structure was formed on the tubular ceramic substrate via hydrothermal, which provided a large surface area and fast transport channels. Subsequently, a polyamide (PA) skin layer was formed on the MoS2 interlayer through the IP procedure to obtain a composite membrane for desalination. The prepared PA/MoS2/ceramic composite membrane showed excellent water permeance of 17.7 L·m−2·h−1·bar−1 with a 96.8 % rejection of Na2SO4. Moreover, the prepared membranes showed good pressure resistance and long-term stability under cross-flow filtration within 30 days.

Design and performance evaluation of an all-ceramic high-temperature test sensor

To meet the test requirements for the surface temperature parameters of next-generation ceramic matrix composite equipment components, this study designed and fabricated an all-ceramic material high-temperature test sensor, including a substrate, sensitive layer, and protective layer. The sensor was prepared using the thick-thin film integration process. The ITO-In2O3 thick film thermocouple was prepared on ceramic substrate using screen printing technology, and the Al2O3 thin film protective layer was prepared by pulsed laser ablation and the sol-gel method. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to study the microstructure, phase, surface element composition and chemical transition state of the prepared thermocouple. The results show that the sintered thermocouple has a compact structure and good electrical conductivity. Static and dynamic test platforms were built to test the performance of thermocouple, and test results show that the prepared thermocouple has good repeatability and stability in the temperature range of 25–1300 °C. The average Seebeck coefficient reached 129.80 μV/°C. In the thermoelectric stability evaluation experiment (1300 °C for 8 h), the peak output voltage was 153.2 mV. The limit test temperature of the thermocouple reached 1500 °C. When the temperature difference was 1382 °C, the peak output voltage was 169.974 mV. The dynamic properties of the sensor were studied using pulsed laser heating, and the results showed that the dynamic response time constant of the thermocouple was 3.52 ms.

Fabrication and Calibration of Pt-Rh10/Pt Thin-Film Thermocouple.

Aiming at the dynamic testing of the ignition temperature of micro-initiating explosives, a novel Pt-Rh10/Pt thin-film thermocouple was designed in this paper. The author carried out the preparation of the thermocouple by using a screen printing process on an Al2O3 ceramic substrate. The formed thermocouple was made of Pt-Rh10 wire and Pt wire as compensation wires, with a size of ≤ 1 mm and a thickness of about 6 μm. In the testing process, the static calibration of the thermocouple at 50~600 °C and 650~1500 °C was completed by a portable temperature verification furnace and a horizontal high temperature verification furnace, and the results showed that the Seebeck coefficient of the thermocouple was about 10.70 μV/°C, and its output voltage-temperature curve was similar to that of a standard S-type thermocouple, which achieved the effective temperature measurement up to 1500 °C. The dynamic response of Pt-Rh10/Pt thin-film thermocouple was then tested and studied using the pulsed laser method, and the results show that the time constant of the thermocouple prepared in this paper is about 535 μs, which has the characteristics of fast response and high precision high-temperature testing. Compared with the traditional thin-film thermocouple, the thermocouple has excellent electrical conductivity, more oxidation resistance, the surface layer is not easy to peel off and other advantages.

Ceramic tiles coated with Zr‐Ag co‐doped TiO2 thin film for indoor air purifying and antimicrobial applications

AbstractIn this study, Zr‐Ag co‐doped TiO2 (ZAT) photocatalyst films having varied numbers of layers (1, 2, 3, and 4) have been developed to coat on ceramic tile substrates by sol‐gel spin coating technique. The specimens were tested to determine antibacterial activity against Escherichia coli and the capability to degrade gaseous formaldehyde under visible light. X‐ray diffraction, ultraviolet and visible absorption spectroscopy, water contact angle, and scanning electron microscopy were applied to characterize the structural and morphological properties of the samples. The photocatalytic reactivity of the nanocomposite films was investigated by the decolorization of methylene blue (MB) dye under visible light irradiation. The results showed that the two‐layer ZAT photocatalyst film on ceramic tile exhibited the highest photocatalytic decolorization of MB, with 60.36% efficiency. The ZAT tile had formaldehyde degradation efficiency up to 32.74% within only 6 h under visible light irradiation, higher than that of the bare ceramic tile (4.90%). Additionally, the ZAT thin films could enhance anti‐E. coli activity and could be capable of degrading air pollution.

Preparation and performance of CaO-MgO-SiO2-Al2O3-CaF2 glass/Al2O3 ceramic with high flexural strength

A high flexural strength low temperature co-fired ceramic material was obtained by mixing the CaO-MgO-SiO2-Al2O3-CaF2 glass and Al2O3 by the weight percentage of xAl2O3+(1-x)CaO-MgO-SiO2-Al2O3-CaF2 (x = 30, 35, 40 and 45 wt.%). The sintering behavior, crystalline component, mechanical, electrical and thermal properties were investigated in depth. The X-ray diffraction data demonstrated that Al2O3, CaMgSi2O6, and Mg2SiO4 were formed during the sintering process. The glass/ceramic composites with 35 wt.% Al2O3 sintered at 910 °C for 2 h exhibited excellent mechanical properties, with a flexural strength of 310±14 MPa. The excellent mechanical properties are mainly attributed to the following three aspects: grain refinement, improved fracture energy, and the synergistic effect of the relative contents of Al2O3 and the CaO-MgO-SiO2-Al2O3-CaF2 glass. The results suggest that the CaO-MgO-SiO2-Al2O3-CaF2 glass/Al2O3 composites can be regarded as promising candidates for low temperature co-fired ceramic substrate applications.

Core-Shell Structured Carbon@Al2O3 Membrane with Enhanced Acid Resistance for Acid Solution Treatment.

Ceramic membrane has an important application prospect in industrial acid solution treatment. Enhancement of the acid resistance is the key strategy to optimize the membrane treatment effect. This work reports a core-shell structured membrane fabricated on alumina ceramic substrates via a one-step in situ hydrothermal method. The acid resistance of the modified membrane was significantly improved due to the protection provided by a chemically stable carbon layer. After modification, the masses lost by the membrane in the hydrochloric acid solution and the acetic acid solution were sharply reduced by 90.91% and 76.92%, respectively. Kinetic models and isotherm models of adsorption were employed to describe acid adsorption occurring during the membrane process and indicated that the modified membrane exhibited pseudo-second-order kinetics and Langmuir model adsorption. Compared to the pristine membrane, the faster adsorption speed and the lower adsorption capacity were exhibited by the modified membrane, which further had a good performance with treating various kinds of acid solutions. Moreover, the modified membrane could be recycled without obvious flux decay. This modification method provides a facile and efficient strategy for the fabrication of acid-resistant membranes for use in extreme conditions.

Synthesis and Characterization of Single-Phase α-Cordierite Glass-Ceramics for LTCC Substrates from Tuff.

Single-phase α-cordierite glass-ceramics for a low-temperature co-fired ceramic (LTCC) substrate were fabricated from tuff as the main raw material, using the non-stoichiometric formula of α-cordierite with excess MgO without adding any sintering additives. The sintering/crystallization behavior and the various performances of dielectric properties, thermal expansion, and flexural strength of the glass-ceramics were detected. The results indicated that only single-phase α-cordierite crystal was precipitated from the basic glass sintered at the range 875-950 °C, and μ-cordierite crystal was not observed during the whole sintering-crystallization process. The properties of glass-ceramics were first improved and then deteriorated with the increase in tuff content and sintering temperature. Fortunately, the glass-ceramics sintered at 900 °C with 45 wt.% tuff content possessed excellent properties: high densify (2.62 g∙cm-3), applicable flexural strength (136 MPa), low dielectric loss (0.010, at 10 MHz), low dielectric constant (5.12, at 10 MHz, close to α-cordierite), and suitable coefficients of thermal expansion (CTE, 3.89 × 10-6 K-1).

Development of evaporation technique for concentrating lead acid wastewater from the battery recycling plant, by nanocomposite ceramic substrates and solar/wind energy

Wastewater from car battery recycling plants contains lead ions. This acidic wastewater was treated by the solar steam generation method. In this research, a light porous ceramic substrate (PCS) was made based on clay, human hair, and nano-hydroxyapatite. The physical and chemical characteristics of this PCS were identified by SEM, XRD, FTIR, BET, and TGA. The high porosity in PCSs was created due to the removal of human hair in the calcination process inside the furnace. Microchannels with capillarity and hydrophilicity of nano-hydroxyapatite quickly pump water molecules to the surface of PCSs. The wastewater treatment process was carried out on two laboratory and semi-industrial scales. The temperature of the surface of the PCSs reached 70 °C in less than 60 min with the radiant heat transfer mechanism, and the water molecules were evaporated with an evaporation rate and thermal conversion efficiency were 9.22 Kgm−2h−2 and 90%, respectively. The wind blew the vapor away from the system and the rate of evaporation increased. PCSs had the ability to regenerate after several consecutive cycles.

Study of Internal Stress in Conductive and Dielectric Thick Films

This paper is focused on the study of internal stress in thick films used in hybrid microelectronics. Internal stress in thick films arises after firing and during cooling due to the differing coefficients of thermal expansion in fired film and ceramic substrates. Different thermal expansions cause deflection of the substrate and in extreme cases, the deflection can lead to damage of the substrate. Two silver pastes and two dielectric pastes, as well as their combinations, were used for the experiments, and the internal stress in the thick films was investigated using the cantilever method. Further experiments were also focused on internal stress changes during the experiment and on the influence of heat treatment (annealing) on internal stress. The results were correlated with the morphology of the fired thick films. The internal stress in the thick films was in the range of 8 to 21 MPa for metallic films and in the range from 12 to 16 MPa for dielectric films. It was verified that the cantilever method can be successfully used for the evaluation of internal stress in thick films. It was also found that the values of deflection and internal stress are not stable after firing, and they can change over time, mainly for metallic thick films.

Tailor‐made FAU zeolite composite membrane for wastewater treatment

In this work, a novel multipurpose Faujasite (FAU) zeolite composite membrane was fabricated by in-situ hydrothermal method to separate different solute molecules such as vanillic acid, phenol, and brilliant green from the aqueous solution. The coal fly ash based ceramic substrate was synthesized and used as substrate for preparing the zeolite composite membrane. The X-ray diffraction (XRD) pattern confirmed the crystalline nature of membranes and the presence of Quartz and hematite in the composite membrane. The presence of Si-O and Al-O in zeolite coated composite membrane was confirmed by Fourier Transform infrared spectroscopy (FTIR) analysis. Scanning electron microscope (SEM) analysis showed the porous structure and 8.34 μm thickness of zeolite coating on membrane. The isoelectric point of composite membrane was observed at pH 2.07 through zeta potential analysis. Brunauer-Emmett-Teller (BET) surface area, average pore volume and pore diameter of zeolite composite membrane were estimated as 6.406 m2/gm, 0.0070 cm3/gm, and 4.371 nm, respectively. The hydraulic pore radius and porosity of composite membranes were 27.7 nm and 20.1%. The maximum separation efficiency of FAU zeolite composite membrane towards vanillic acid, phenol and brilliant green was estimated as 78.67%, 89.13%, and 94.28%, respectively, for 200 mg/L feed concentration at 276 kPa applied pressure. The results obtained in this study reveals that the multipurpose FAU zeolite composite membrane fabricated in this study can be effectively used for separation of various solutes molecules present in the wastewater.

Highly flexible all-inorganic nanofiber networks with stress-accommodating microstructure for light-activated wearable chemiresistive sensor

Inorganic semiconductor chemiresistors have been the mainstream of well-explored gas sensing technology. However, the intrinsic fragile and rigid nature seriously impedes their future application in the thriving wearable sensing devices. Herein, we demonstrate a flexible all-inorganic semiconductor-based chemiresistive sensor through in-situ anchoring nanosheets-assembled SnO2/SnS2 sensing layer on flexible yttria-stabilized zirconia (YSZ) ceramic nanofiber networks. It is revealed that the flexible YSZ ceramic substrate possesses low section modulus in bending and good toughness that is mainly derived from its unique nanofiber structure (300 nm in diameter) and ultrafine grain size (16 nm). It is first demonstrated that nanosheets-assembled sensing layer characterized by abundant void spaces plays a pivotal role in affecting the flexibility of inorganic nanofiber networks. The void spaces between SnO2/SnS2 nanosheets, acting as stress-accommodating microstructures, could effectively releasing stress concentration, enabling abnormal mechanical flexibility of inorganic YSZ/SnO2/SnS2 network. In addition, to achieve more compatibility with wearable application and realize room-temperature gas sensing function, visible light rather than traditional high heat is employed as excitation source to activate the flexible YSZ/SnO2/SnS2 chemiresistor. This work shows the possibility of inorganic semiconductor chemiresistor for application in wearable sensing device and offers a valuable guidance for constructing flexible room-temperature inorganic chemiresistor.

Cyclic fatigue vs static loading for shear bond strength test of lithium disilicate and dentin substrates: A comparison of resin cement viscosities.

To explore the effect of resin cement viscosities on the shear bond strength under static and fatigue load of lithium disilicate and dentin substrates. Bonded tri-layer samples (lithium disilicate ceramic cylinder, resin cement, and substrate - ceramic or dentin) was performed considering 2 factors (n=15): "resin cement viscosity" (high, HV; or low, LV) and "loading mode" (static, s-SBS; or fatigue shear bond strength, f-SBS). The specimens were subjected to s-SBS (1mm/min, 1kN load cell) and f-SBS (cyclic fatigue, initial load: 10N; step-size: 5N; 10,000 cycles/step; underwater). Failure mode, topography, and finite element analysis (FEA) were performed. The resin cement viscosity did not influence the s-SBS and f-SBS of lithium disilicate substrate; however, it affected the bond strength to dentin, with HV presenting the worst fatigue behavior (f-SBS=6.89MPa). Cyclic loading in shear testing induced a notorious detrimental effect with a relevant decrease (16-56%) in bond strength and survival rates, except for dentin substrate and LV. Most failures were adhesive. A distinct pattern comparing the disilicate and dentin was identified and FEA demonstrated that there was a stress concentration on the top of the cement layer. Cyclic fatigue loading in shear testing has detrimental effects on the adhesive behavior and survival probabilities of bonded lithium disilicate sets, regardless of resin cement viscosity. In contrast, resin cement viscosity affects the bond strength and the survival rates of dentin substrate submitted to cyclic loading mode, in which a low viscosity results in better performance.

Microstructure evolution and fracture mechanism of the interfacial region between MAO ceramic film and Al-Mg-Sc alloy substrate

Surface ceramics on Al-Mg-Sc alloy with micro-arc oxidation (MAO) was attracting increased attention in industrial field. The mechanisms concerning high bonding strength between MAO ceramic film and metal substrate were not yet clear. In this study, MAO ceramic films were constructed on Al-Mg-Sc alloy surface to reveal the microstructure evolution and fracture mechanism of the metal/ceramic interfacial region. The results indicated that the interfacial region exhibited an Al-Mg-Sc/Al 2 O 3 composite laminated structure mainly composed of Al 2 O 3 . The Al substrate near the interface presented fine grained structure, only a few grains grow along <001> and <101> plane, while almost all the grains were oriented along <111> plane. The fracture mechanism of the interfacial region in the tensile process was a mixed mode of ductile and brittle fracture.

An Integrated Structure–Material Optimization Strategy for the Packaging of High-Voltage Insulated Gate Bipolar Transistors

High-voltage insulated gate bipolar transistors (IGBTs), such as silicon carbide (SiC)-based ones, are promising as wide bandgap (WBG) power modules. However, current IGBT packaging methods are unsuitable for high-voltage applications due to excessive electric field stress, which increases the risk of partial discharge or electrical breakdown, compromising their insulating property; a new packaging solution is, therefore, needed. In this study, an integrated structure–material optimization strategy through the combination of the finite-element method (FEM) and materials optimization is proposed to reduce the maximum electric field stress ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {max}}$ </tex-math></inline-formula> ) at the triple junction, i.e., the interface of the ceramic substrate, the metal electrode, and the polymer-based encapsulation, of an IGBT. In epoxy resin encapsulation, it was determined that a symmetrical and chamfered electrode structure with a smooth transition at the triple junction reduces <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {max}}$ </tex-math></inline-formula> from near 280 to 40 kV/mm at an operating voltage of 27.5 kV. Furthermore, when the permittivities of the substrate (AlN) and encapsulation materials (BaTiO3–resin composites) satisfy an optimal ratio, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {max}}$ </tex-math></inline-formula> can be further reduced to 34 kV/mm (a 15% decrease). These results indicate that the integrated structure–material optimization strategy effectively enhances the insulating property of the high-voltage IGBTs.