Metal 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.

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.

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.

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.

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

Moisture induced degradation of multilayer ceramic capacitors

When both precious metal electrode and base metal electrode (BME) capacitors were subjected to autoclave (121 °C/100% RH) testing for 500 h, it was found that the precious metal capacitors aged according to a well known aging mechanism (average capacitance degraded less than 3% from their starting values), but the BME capacitors degraded to below the −30% specification limit. One hypothesis for this new failure mechanism was that there could be oxidation or corrosion of the nickel plates. Another hypothesis was that the loss of capacitance was due to chemical changes in the barium titanate. This paper presents the evaluation of the two hypotheses and the physics of the degradation mechanism. It is concluded that there are chemical changes in the barium titanate resulting from the interaction of residual point defects from BME manufacturing and humidity in the field. The continuous reduction in capacitor size makes the newer base metal electrode capacitors more vulnerable to moisture degradation than the older generation precious metal capacitors. In addition, standard humidity life testing, such as JESD-22 THB and HAST, will likely not uncover this problem. Therefore, poor reliability due to degradation of base metal electrode multilayer ceramic capacitors may catch manufacturers and consumers by surprise.

電子材料 電子セラミック部品材料の開発

The aim of this paper is to focus on the development in the field of electronic ceramic materials, such as MnZn ferrites, multilayer ferrite chip components, and base metal electrode multilayer ceramic capacitors. There are many requirements for electronic ceramics, among which the reliability and low loss characteristics are of prime importance. New material technologies for ensuring high performance ferrites and highly reliable multilayer chip components are shown with special reference to the microstructure. For achieving high performance ferrite cores, adequate additives and control of nonstoichiometric oxygen content by firing conditions are quite important. Material technology for multilayer ferrite chip components are described with special reference to the behavior of silver during firing. Also, highly reliable multilayer ceramic capacitors with Ni electrodes have been developed by controlling chemical composition and grain boundary chemistry.