Electrode Multilayer Ceramic Capacitors Research Articles

Effect of A/B ratio on the dielectric properties and insulation resistance of barium titanate sintered in a reducing atmosphere

The effect of the A/B ratio on the dielectric properties and insulation resistance of barium titanate (BaTiO3) sintered in a reducing atmosphere was investigated in this study. The increased demand for high capacitance, miniaturized, and reliable base metal electrode multilayer ceramic capacitors (BME MLCCs) has emphasized improving insulation properties. This study added Y2O3, MgO, Mn2O3, and SiO2 to tailor the barium titanate properties. We investigated how changes in the A/B ratio affect the microstructure, defect chemistry, and Y3+ ion occupation in BaTiO3, affecting dielectric properties and insulation resistance. It was observed that the activation energies for grain and grain boundary conductivity are dominated by oxygen vacancy and (VBa″−VO··) defect pair, respectively. The Ti3+ and oxygen vacancy concentrations were directly proportional to the room and high-temperature resistivities, respectively. The sample with an A/B ratio of 1.002 had the lowest oxygen vacancy and Ti3+ ratio, resulting in a higher resistance and lower thermally stimulated depolarization current (TSDC).

Quality assessment and lifetime prediction of base metal electrode multilayer ceramic capacitors: Challenges and opportunities

Base metal electrode (BME) multilayer ceramic capacitors (MLCCs) are widely used in aerospace, medical, military, and communication applications, emphasizing the need for high reliability. The ongoing advancements in BaTiO3-based MLCC technology have facilitated further miniaturization and improved capacitive volumetric density for both low and high voltage devices. However, concerns persist regarding infant mortality failures and long-term reliability under higher fields and temperatures. To address these concerns, a comprehensive understanding of the mechanisms underlying insulation resistance degradation is crucial. Furthermore, there is a need to develop effective screening procedures during MLCC production and improve the accuracy of mean time to failure (MTTF) predictions. This article reviews our findings on the effect of the burn-in test, a common quality control process, on the dynamics of oxygen vacancies within BME MLCCs. These findings reveal the burn-in test has a negative impact on the lifetime and reliability of BME MLCCS. Moreover, the limitations of existing lifetime prediction models for BME MLCCs are discussed, emphasizing the need for improved MTTF predictions by employing a physics-based machine learning model to overcome the existing models’ limitations. The article also discusses the new physical-based machine learning model that has been developed. While data limitations remain a challenge, the physics-based machine learning approach offers promising results for MTTF prediction in MLCCs, contributing to improved lifetime predictions. Furthermore, the article acknowledges the limitations of relying solely on MTTF to predict MLCCs’ lifetime and emphasizes the importance of developing comprehensive prediction models that predict the entire distribution of failures.

Defect engineering boosts the reliability of ultra-thin MLCCs

Modern electronics highly demand base metal electrode multilayer ceramic capacitors (BME MLCCs) with ultra-thin dielectric layers and high capacitances owing to the trend for miniaturization. The reliability of MLCCs is crucial for practical applications and significantly affected by the lamination process and material defects. However, the detailed relationships between these factors and the reliability of ultra-thin MLCCs remain elusive. In this study, we investigated the influence of different lamination pressures (denoted as S1, S2 and S3) on the microstructure and reliability of BaTiO3 (BT) based protocol MLCCs with hundreds of layers. Microstructural observations reveal that among the devices, S2 has the highest roughness for both the Ni internal electrode and dielectric layers. Dielectric property investigations show that S1 and S3 meet the X5R standard and the designed capacity of 10 μF while S2 fails to meet the X5R standard at high temperatures. The electron energy loss spectra investigation reveal that oxygen vacancies are asymmetrically distributed on both sides of the Ni-BT interface in the individual dielectric layers, especially for S2, which indicates that one-side pressure lamination from the bar bulk induces sintering differences on the two sides of the dielectric layer. The results from this study indicate that applying an appropriate critical pressure between BT and Ni (S1) is preferable for decreasing the asymmetry and improving the reliability of MLCCs with ultra-thin layers.

Dielectric properties of BaTiO3 and Ba0.95Ca0.05TiO3 sintered in a reducing atmosphere

The dielectric materials utilized in high-performance barium titanate-based base-metal electrode multilayer ceramic capacitors (BME MLCCs) must satisfy stringent criteria such as high dielectric constant, low dielectric loss, high insulation resistivity, and reliability. In this investigation, the effects of raw materials, BaTiO3 (BT), and Ba0.95Ca0.05TiO3 (BCT) on densification, microstructure, and dielectric behavior were explored by introducing acceptor and rare earth elements. The findings revealed that BCT could attain densification at a lower sintering temperature of 1275 °C than BT. Moreover, BCT samples displayed relatively smaller grain sizes, resulting in a greater number of grain boundaries, which in turn increased the insulation resistivity. BCT had a lower oxygen vacancy concentration, thus resulting in lower leakage currents at high temperatures than BT. Substituting BCT for BT resulted in higher activation energies for conductivity in the core, shell, and grain boundary. This investigation demonstrates that BCT can enhance the dielectric properties, insulation resistance, and reliability of the BME MLCCs.

Effect of Ho‐Dy co‐doping on the electrical properties and reliability of BaTiO3‐based nanoceramics for Base Metal Electrode Multilayer Ceramic Capacitor

AbstractFine‐grained BaTiO3‐based ceramics with an average grain size of 120−140 nm were prepared by a chemical coating method. The effect of Ho‐Dy concentration on the microstructure, dielectric properties, and reliability of BaTiO3‐based nanoceramics was investigated. Results showed that appropriate doping contents of Ho and Dy provide the highest dielectric constant of 2323 at room temperature and the temperature stability satisfied EIA X7R specification. Higher doping concentration specimens exhibit lower dielectric constant but gentler temperature stability, indicating thicker grain shells. The failure time under the highly accelerated lifetime test increased along with the increase of Ho‐Dy and was consistent with the impedance analysis results. Doping elements are mainly distributed in grain shells, leading to an increase of resistance and activation energy. The compositions for the highest dielectric constant and best reliability were not the same, providing support for the composition design of dielectric layer material for different BME‐MLCC applications.

Oxygen vacancy region formation in BaTiO3 adjacent to the interface between the internal electrode and the dielectric layer in Ni–Sn internal electrode multilayer ceramic capacitor exhibiting leakage current suppression

This study underlines the ceramic BaTiO3 dielectric layer adjacent to the electrode of long-term reliability-improved Ni–Sn alloy internal electrode BaTiO3-based multilayer ceramic capacitor to clarify the cause of electric barrier formation. Electron energy loss spectroscopy measurements of the Ti L 3,2 near the edges and the O K near the edge structure changes to characterize the existence of an oxygen vacancy region, approximately 60 nm in width, and generated in BaTiO3 adjacent to the interface. Accordingly, the n-type semiconductor layer of BaTiO3 that originated from the oxygen vacancies, led to the formation of a rigid Schottky barrier at the interface.

Anti-reductive characteristics and dielectric loss mechanisms of Ba2ZnSi2O7 microwave dielectric ceramic

Abstract Ba2ZnSi2O7 ceramic was prepared by conventional solid-state method and sintering under four different atmospheres (air, O2, N2, and N2–1 vol% H2). The Ba2ZnSi2O7 ceramic exhibited a single phase under air, O2, and, N2, whereas two phases (including BaSiO3 impurity) were observed under the N2–1 vol% H2 atmosphere due to Zn2+ evaporation. Dielectric loss was proportional to oxygen partial pressure due to the conduction mechanism of dominant holes. The Ba2ZnSi2O7 ceramic exhibited good microwave dielectric properties (er = 8.3, Q × f = 27200 GHz, τf = −41.5 ppm/°C) under the N2–1 vol% H2 atmosphere, making it a novel candidate with good anti-reductive characteristics for base metal electrode–multilayer ceramic capacitor applications.

Effects of addition of Sc2O3 on microstructure and dielectric properties of BaTiO3-based X8R MLCCs

This study investigated the changes in dielectric properties of the disc capacitor and base metal electrode (BME) multilayer ceramic capacitor (MLCC) fabricated from the host material (BaTiO3 + 1.0 mol% MgO + 0.05 mol% MnCO3 + 1.37 mol% BaSiO3) with different amounts of Sc2O3 addition. The results of transmission electron microscope (TEM) analysis verified that the addition of 0.6 mol% Sc2O3 led to the formation of a grain core–shell structure. The formation of the grain core–shell structure can improve the temperature stability of the dielectric properties. The presence of Sc2O3 can increase the room-temperature insulation resistance and reduce dielectric loss (tanδ); however, an excessive addition of Sc2O3 resulted in the decline of the insulating property of MLCCs at a high temperature. This study revealed that the temperature coefficient of the capacitance (TCC) curves can be flattened by adding 0.3–0.6 mol% Sc2O3 into the host material so that the developed BME MLCCs can comply with the requirements of the Electronic Industries Alliance (EIA) X8R specification. In particular, the MLCC with 0.3 mol% Sc2O3 addition had satisfactory TCC stability and insulating properties; the dielectric constant was 2084, tanδ was 1.23%, the TCC at −55 °C and 150 °C was −2.8% and −5.8%, respectively, and the insulation resistance at −55 °C and 150 °C was 3.6 × 1010 Ω and 2.6 × 107 Ω, respectively.

Cu<sub>3</sub>TeO<sub>6 </sub>Dielectric Thick Films: Processing by Electrophoretic Deposition and Electrical Characterization

Te-based compounds are promising dielectric candidates for Base-Metal Electrode Multilayer Ceramic Capacitors (BME-MLCCs) and Low-Temperature Co-fired Ceramics (LTCCs) applications due to their low sintering temperature and good dielectric properties. In spite of the possible compatibility with Cu electrodes for microelectronics, data on compounds of the CuO-TeO2 system are scarce. Recently, we have reported the phase formation process of Cu3TeO6 and the first dielectric data for Cu3TeO6 ceramics. Due to the interest for some applications in thick films, in this work Cu3TeO6 thick films were fabricated by electrophoretic deposition (EPD) on platinized silicon substrates under different processing conditions. The relation between processing and film’s quality was established. ~ 50 μm Cu3TeO6 thick films sintered at 860 oC for 5 h exhibit a permittivity of ~2 and dielectric loss of 0.01 at room temperature and the temperature coefficient of the dielectric permittivity is 9.5×103 ppm°C-1 at 1 MHz from 40 °C to 120 °C. It is expected that this dielectric performance, when compared with the one of Cu3TeO6 ceramic counterparts, improves if the density of the films is increased.

Correlative Studies on Sintering of Ni/BaTiO3 Multilayers Using X‐ray Computed Nanotomography and FIB‐SEM Nanotomograhy

Synchrotron X‐ray computed nanotomography (nCT) and Focused Ion Beam–Scanning Electron Microscope nanotomography (FIB‐nT) were used to characterize baked‐out and sintered nickel (Ni) electrode–Multilayer Ceramic Capacitors. The three‐dimensional microstructures obtained by two different tomography techniques were quantified and correlated. X‐ray nCT is sufficient to reveal the pore characteristics, whereas the FIB‐nT enables the particles in the initial packings to be identified. In the dielectric ceramic layers, pores preferentially orient horizontally in the layer and the regions near the Ni/BT interface are denser than the inner regions. This anisotropy is possibly caused by compressive stress induced during the heating stage.

New Cu3TeO6 Ceramics: Phase Formation and Dielectric Properties

Targeting low temperature cofired ceramics (LTCC) applications and base-metal electrode multilayer ceramic capacitors (BME-MLCCs), ceramics of a new composition, tricopper tellurate (Cu3TeO6), are reported here. The crystal structure of Cu3TeO6 was determined to be cubic, Ia3, with the unit cell parameter a = 9.538 Å. The sequence of phase formation is proposed with the oxidation of tetravalent tellurium (Te(4+)) into hexavalent tellurium (Te(6+)) as a key step for the formation of Cu3TeO6. Ceramics sintered at 865 °C with densities of 94% exhibit two dielectric anomalies in the temperature dependence of the dielectric response, around -150 °C and +50 °C, respectively, accompanied by obvious frequency dispersion of the relative permittivity (ε(r)) and dielectric losses (tan δ), with an Arrhenius like behavior. A temperature stable dielectric region (near room temperature) formed between the two anomalies with ε(r) ∼ 12 and tan δ ∼ 0.01, and a very low positive temperature coefficient of the relative permittivity (TCε(r)), 2.07 × 10(-4) °C(-1), was obtained in the same region. The low temperature dielectric anomaly is associated with the possible mixed Cu(+)/Cu(2+) valence in Cu3TeO6 ceramics, while the high temperature anomaly is attributed to point defect ordering, including VO, CuCu2+(+)', which might be formed during sintering. Therefore, Cu3TeO6 ceramics are of interest in view of not only the possible applications in BME-MLCCs, LTCC, and related technologies, but also for their possible compatibility with low cost abundant Cu electrodes.

Uniform Coating of BaTiO3–Dy2O3–SiO2 Compound Nano Layer on Ni Particles for MLCC Electrode

Uniform coating of nanometer‐scale BaTiO3–Dy2O3–SiO2 layers on spherical Ni particles are achieved by controlled hydrolysis of tetrabutyl titanate (TBT), hydrothermal reaction with Ba(OH)2, and co‐precipitation of tetraethylorthosilicate (TEOS) and Dy(NO3)3. The composition of the coating layer is similar to rare earth oxide‐silica–doped BaTiO3, which is the main component of dielectric layer for base metal electrode (BME) multilayer ceramic capacitors (MLCCs). After coating, the shrinkage onset temperature of Ni particles is significantly increased. After sintered to pellets, the electrode has good electrical conductivity. This electrode material has good compatibility with rare earth oxide and silica‐doped BaTiO3 dielectric materials, and could serve as promising candidate for application in the next generation BME‐MLCCs.

Effect of Rare Earth Oxide Content on Nanograined Base Metal Electrode Multilayer Ceramic Capacitor Powder Prepared by Aqueous Chemical Coating Method

The aqueous chemical coating route is highly effective in preparing BaTiO3 nanoparticles uniformly coated with additives. Such nanoparticles can be used to produce nano-grained temperature stable BaTiO3 ceramics with core–shell structure, fulfilling the need of next-generation ultrathin layer base metal electrode (BME) multilayer ceramic capacitors (MLCCs). Rare earth oxides are an important class of additives owing to their ability to fulfill both donor and acceptor roles. In this paper, the effects of Y2O3 and Ho2O3 co-dopant content on dielectric and microstructural properties were investigated. By applying chemical coating, BaTiO3-based high performance temperature stabilized ceramics with the average grain size of about 130 nm, which met the requirement of next generation BME MLCCs, were obtained.

Preparation of BME MLCC Powders by Aqueous Chemical Coating Method

High and large capacitance base–metal–electrode multilayer ceramic capacitors (BME MLCCs) for future application require much thinner dielectric layers (<l μm) than ever before, which means that grain size uniformity of BME MLCC powder should be effectively controlled. In this paper, high-performance nanosized BME MLCC powder was developed by a novel and convenient aqueous chemical coating method. Various kinds of dispersants were used to disperse BaTiO3 particles in aqueous solutions. Poly(acrylic acid–comaleic acid) was found to be the best for dispersing. BaTiO3 particles were well coated by adding the doping elements into the uniform BaTiO3 slurry in the form of inorganic solutions and organic solutions under an appropriate pH value. Thermogravimetric analysis, transmission electron microscopy, and energy-dispersive spectroscopy were utilized in the study of calcining, microstructures, and element analysis. The dielectric constants of the ceramics at room temperature could reach 2100, with low dielectric loss <1.0% and high insulation resistivity ∼1012 Ω·cm. The average grain size is as low as about 130 nm.

Microstructure Evolution and Dielectric Properties of Ultrafine Grained BaTiO3-Based Ceramics by Two-Step Sintering

The base-metal electrode multilayer ceramic capacitors for future application require much thinner dielectric layers ( < 1 μm). Therefore, the grain size and uniformity of dielectric ceramics should be effectively controlled. In this paper, a two-step sintering (TSS) method has been utilized to prepare the ultrafine-grained X7R BaTiO 3 ceramics in reducing atmosphere with the average grain size below 200 nm. And the influence of TSS schedule on the microstructure (such as bulk density, grain size) and dielectric properties is discussed in detail. Furthermore, the development of core-shell structure and corresponding temperature coefficient of capacitance characteristics during the intermediate stage of TSS process has been systematically investigated.

Degradation behaviors and failure analysis of Ni–BaTiO 3 base-metal electrode multilayer ceramic capacitors under highly accelerated life test

The degradation in insulation resistance under highly accelerated test conditions was investigated in terms of micro-structural and micro-chemical changes in dielectric layer of multilayer ceramic capacitor. The ceramic capacitors were prepared by using BaTiO 3 powder with different size of 0.52 μm, 0.55 μm, and 0.58 μm. As the particle size of BaTiO 3 powder was increased, the capacitance and the dissipation factor were decreased. According to the result of highly accelerated test conducted at 150 °C, 75 V, and 20 h, failure in insulation resistance was increased with the particle size and the calculated FITs (failure in term) were 1.10 at 0.52 μm, 2.11 at 0.55 μm, and 6.69 at 0.58 μm, respectively. The failure was examined by X-ray photoelectron spectroscopy and transmission electron microscopy, which was attributed to the oxidation of Ni inner electrode that could create oxygen vacancies and increase electric conduction of the ceramic capacitors.

Effect of Heating Rates during Sintering on the Electrical Properties of Ultra‐Thin Ni–BaTiO3 Multilayer Ceramic Capacitors

Microstructural control in thin‐layer multilayer ceramic capacitors (MLCCs) is one of the present day challenges for increasing capacitive volumetric efficiency and high voltage dielectric properties. The present paper continues a series of investigations aimed at engineering the stability of ultra‐thin Ni layers in base‐metal electrode MLCCs. A kinetic approach based on the control of sintering profiles is found to not only prevent Ni electrode discontinuities, but also to significantly improve the interfacial electrical properties. Increasing sintering heating rates from 200 to 3000°C/h leads to a decrease in its temperature dependence of capacitance. Faster heating rates also reduce the BaTiO3 grain size, which is beneficial to the reliability of multilayer capacitors. A direct correlation between heating rates, the thickness of an interfacial (Ni, Ba, and Ti) alloy reaction layer and the interfacial contact resistance has been observed. The decrease in the alloy layer thickness at high heating rates leads to an increased effective Schottky barrier height between the dielectric and electrode toward its theoretical value of 1.25 eV for pure Ni–BaTiO3 interfaces.

Microstructure analysis of the Y5V multilayer ceramic capacitors based on BaTiO3

The Y5V-1206 base-metal electrode (BME) multilayer ceramic capacitor (MLCC) chips have been characterised for crystalline phases using X-ray diffractometry (XRD), and microstructure using optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The microstructure features found in the Ni electrode and the BaTiO3 dielectric layer are discussed in terms of the tensile backstresses induced upon firing due to constrained sintering heterogeneously. The chemical compositions containing BaO-excess and additives CaO and ZrO2, determined for BaTiO3 grains by energy-dispersive spectroscopy (EDS) equipped in the TEM are also reported. However, no rare-earth oxides were found in the grains. The representative microstructure of BaTiO3 grains containing dislocations is the “solid-solution” type distinctive from the “core-shell” of the X7R compositions. The fact that no ferroelectric domains were detected suggests that the BaTiO3 grains are pseudo-cubic with the c/a ratio ≈ 1.0.

Effects of Rare-Earth Oxides on Dielectric Properties of X7R Ceramics for Base Metal Internal Electrode Capacitors

The effect of rare earth oxides (Y2O3 and Dy2O3) on the microstructure and electrical properties of the X7R-type ceramics for base metal internal electrode multilayer ceramic capacitor (BME-MLCC) was investigated. As the amount of Y increased, the dielectric constants and the dielectric losses increased, while the temperature coefficient of capacitors (TCC) curve rotated in counterclockwise direction. On the contrary, the dielectric constants decreased with Dy, and the TCC curve remained the same. The grain growth can be inhibited by the Dy2O3, concluded from XRD analysis. The different influences on dielectric properties between Y2O3 and Dy2O3 were discussed by defect chemistry. Y3+ acted as acceptor, performing B-site substitution, while Dy3+ showed the amphoteric behavior. By optimizing appropriate qualities of Y2O3 and Dy2O3, the most-compatible composition for BME X7R ceramics can be obtained.

Termination of BME–MLCC Using Copper–Nickel Bimetallic Powder as Electrode Material

Microstructure of termination of a base metal electrode multilayer ceramic capacitor (BME-MLCC) using copper-nickel bimetallic powder as electrode material was investigated. Thick film paste containing nonagglomerated monodispersed copper-nickel bimetallic powder was applied in preparing the termination electrode of a BME-MLCC. Influence of an inorganic binder on the microstructure of the termination of BME-MLCC was studied. The distribution of metallic copper on the surface of glass bubbles in termination was investigated by energy dispersive X-ray. A scanning electron microscope and a polarized light microscope were applied to discuss the microstructure of thick film. The results show that suitable binder and firing temperature result in the excellent connection between internal and termination electrode, as well as one between termination electrode and green chip. The BME-MLCCs with a dense surface of end termination, high adhesion, and qualified electrical behavior were obtained. The rough interface from interfacial reaction between glass and chip gives high adhesion