Role of Length Scale on Pressure Increase and Yield of Poly(vinyl butyral)–Barium Titanate–Platinum Multilayer Ceramic Capacitors during Binder Burnout

The binder-burnout kinetics of poly(vinyl) butyral from BaTiO₃ multilayer ceramic capacitors with platinum metal electrodes were analyzed by combining thermogravimetric analysis with infrared spectroscopy. The rate of weight loss was accelerated when both BaTiO₃ and platinum metal were present, and the presence of both metal and ceramic enhanced the production of CO₂. The activation energy and pre-exponential factor were determined by analysis of the weight-loss data with a first-order kinetics model. Then, the decomposition kinetics were incorporated into a coupled heat- and mass-transport model to predict pressure increases as a function of the heating cycle. The heating cycles determined in this manner then were used to evaluate the yield of capacitors 1.3–3.8 cm long and 0.3–1.3 cm high. The optimum yield was realized at an aspect ratio (height:length) of 1:3.     

Finite-Element Analysis of Ceramic Multilayer Capacitors: Modeling and Electrical Impedance Spectroscopy for a Nondestructive Failure Test

The opportunities are introduced to calculate the electrical, mechanical, and thermal couplings of ceramic multilayer capacitors (MLCs) with the finite-element method. The results may lead to improvements in the production, integration, and operation of MLCs. In this paper, a comparison is given of calculations and measurements of electromechanical resonances in the impedance spectra of MLCs. The simulation of defective capacitors with three different types of assumed faults reveals the changes in the impedance spectra due to these defects. This allows the prediction of flaws in MLCs based on measurement of the impedance spectra.     

Theoretical Models for Binder Burnout

The kinetics of binder burnout, from a ceramic green body, are considered for the case of an "unzipping" binder which decomposes to produce a volatile monomer. The process is considered to fail if the concentration of monomer in the green body exceeds that in equilibrium with vapor at 1 atm (≅10⁵ Pa), when an internal bubble would be expected to form. Steady-state diffusional calculations and computer simulations explore the size and temperature dependence of the process and are in agreement. The model suggests that it is not feasible to burn out a large flat piece greater than about 3 mm thick, without going to very long times of burnout. The kinetics are significantly improved if porosity develops in the piece during the early stages of decomposition, as opposed to the retreat of the binder into the piece on a uniform front.     

Hot-Stage Study of Bubble Formation During Binder Burnout

A technique for observing bubble formation during binder burnout in ceramics processing has been developed using the hot-stage microscope. Four sets of samples were designed to meet different objectives of the study. Bubble nucleation, growth, and shrinkage were observed. Influencing factors, such as initially trapped gas bubbles, amount of residual solvent, ceramic powder surface, and heating rate were studied.     

Electrode-Based Causes of Delaminations in Multilayer Ceramic Capacitors

Delaminations are a principal quality problem in the manufacture of multilayer ceramic capacitors (MLC's). They are defined as a separation of the electrode and dielectric layers and can result in electrical shorts and/or life failures. Delaminations originate from many sources in MLC manufacture, but we have identified four which are caused by the electrode. High levels of organic resin in the electrode paste lead to high resin content in dried electrode prints, requiring removal of large amounts of organic residues during burnout, causing delaminations. Catalysis of these organics by the precious metals also causes delaminations from rapid evolution of gas and heat release during burnout. Poor adhesion of the dielectric tape layers to dried electrode prints during MLC buildup can cause "green-state" delaminations which remain through firing. Sintering shrinkage mismatch between the electrode and dielectric layers leads to internal stresses in MLC's, resulting in delaminations. We discuss these electrode-based mechanisms of delamination and the design of electrode pastes which solve these problems.     

Degradation of Multilayer Ceramic Capacitors with Nickel Electrodes

The mechanism of degradation, or IR drop, of BaTiO₃-based Ni-electrode chip capacitors has been studied, with special attention to the microstructure. Degradation occurred mainly at the center of the capacitors. Longer-life capacitors were obtained under conditions of low oxygen partial pressure, 10⁻¹² atm, during sintering, and had larger grain sizes and smaller quantities of grain boundary phase. The existence of oxygen vacancies in the grain boundary phase was confirmed by cathode luminescence measurement. Double layers along the surfaces of the Ni electrodes were also related to the life of the capacitors.     

Statistical Determination of Plating Process Variables for Multilayer Ceramic Chip Capacitors

The effects of the following barrier layer plating process variables on reliability of multilayer ceramic chip capacitors are discussed: media type, nickel plating thickness, lead concentration, pH, tin plating current density, number of capacitors, and percent loading of the plating barrel. The dielectric was formulated from a lead magnesium niobate material. Evaluations were done with respect to capacitance, dissipation factor, conductance, dry life (temperature bias) test, solderability (with and without steam aging), and voltage surge test. Several of the in-process variables studied were found to have a statistically significant effect on some of these response variables. The data indicate that the most significant inprocess parameters in the barrier layer process, of those included in this study, are media type and percentage loading of the barrel. Variables of marginal significance are number of capacitors, lead in the bath, and tin plating current density. The other variables had no discernible effect on the response variables studied. The presence of such a large experimental error in life test was a significant outcome of the study and indicates a need for further study on means of obtaining reproducible life-test results after plating.     

Rapid Thermal Processing of Pb(Mg0.7Zn0.3)1/3Nb2/3O3 Multilayer Ceramic Capacitors

Fast firing, with total sintering times of between 3 and 15 min, was utilized to process multilayer ceramic capacitors of dielectric composition Pb(Mg_0.7Zn_0.3)_1/3Nb_2/3O₃. This dielectric composition has been studied extensively because of its diffuse phase transition, which is intrinsic to relaxors, and also its high dielectric constant. The fast-firing procedure, which did not utilize any prevention for PbO volatilization, has been shown to be a feasible method for the processing of these components. Sintering times in the range of 12 to 15 min at 1100°C resulted in components with weak field dielectric constants in excess of 12 000 and grain sizes in the range of 1 μm or less. The development of a pyrochlore phase at the component surfaces was less influential on the dielectric performance of the components because of the internal nature of the electrodes.     

陶瓷电容器的制备工艺概述

简介了新型陶瓷电容器的优点、功能、类型和发展现状及表面层陶瓷电容器、表面层型陶瓷电容器和晶界型陶瓷电容器的产生机理和区别，和影响陶瓷电容器性能的诸多因素，如显微结构、掺杂元素和包覆改性等；回顾了国内外陶瓷电容器的烧成工艺发展历史，如高温一次烧成、低温一次烧成、独石法和激光辐射法等；展望了陶瓷电容器在21世纪的研究和应用前景。     

高压陶瓷电容器发展概况及其应用

介绍了高压陶瓷电容器用介质材料的组成、生产工艺 ,以及提高其耐压性的各种方法。     

Finite-Element Analysis of Ceramic Multilayer Capacitors: Failure Probability Caused by Wave Soldering and Bending Loads

A two-dimensional numerical model that predicts the reliability of multilayer capacitors (MLCs) during soldering and bending is presented. The Weibull parameters used in the model are based on measurements of soldered MLC devices. The preheating and soldering temperatures have a dominant impact on the failure probability, in comparison to the thickness of the nickel layer, the soft solder geometry, and the number of inner electrodes. Comparison of calculated and measured reliability of three MLC sizes leads to the assumption that residual stresses due to the manufacturing process or size-related microstructure are important.     

Infant Mortality, Freaks, and Wear-Out: Application of Modern Semiconductor Reliability Methods to Ceramic Multilayer Capacitors

An overview of the methods of modern semiconductor reliability and accelerated life testing based on the lognormal distribution is given, Bimodal distributions due to the presence of freak failure populations are also discussed, along with the Fowlkes test for a bimodal lognormal distribution. A novel analysis of recent published results on capacitor reliability is given, based on the known properties of the lognormal and Weibull distributions as well as recent experience in their application to semiconductor device reliability. For test periods of 168 and 1000 h, estimates of the required voltages and temperature stresses as well as sample sizes are made to ensure a hazard rate of less than 100 FIT (failures per unit time) per capacitor after 40 yr of operation. The results show that the customary accelerated test at twice the rated voltage and 125°C for 1000 h, is insufficient. Comparison with data from a recent highly accelerated life test (HALT) indicates that the HALT procedures may be useful as an effective screen. Bimodal failure distributions are shown to be due to the presence of freak (early failure) populations of about 10%.     

Mechanical Failure Characteristics of Ceramic Multilayer Capacitors

The results of both uniaxial and biaxial flexure as well as toughness testing on actual commercial ceramic capacitor samples are reported. Necessary procedural adjustments are outlined for miniaturizing the applied-moment double-cantilever-beam test to accommodate these small samples. Strength and toughness testing showed that the metal electrodes lowered the fracture toughness and that the metal-ceramic interface was a preferred fracture path for crack propagation parallel to the electrodes. However, toughness did not clearly depend on crack propagation parallel or perpendicular to the electrodes, nor with flexural strengths. Flexural strengths were 0 to 40% lower, with the electrodes perpendicular to the tensile surface vs. parallel to the tensile surface. Fractures initiated from machining (or impact) flaws, or voids of various sizes, shapes, and locations, thus explaining the poor correlation between strength and toughness. Biaxial flexure tests of dielectric specimens of various sizes indicate that such a test could be scaled down and "calibrated" for actual testing of capacitors; e.g., a decrease in strength with increasing specimen thickness to support diameter ratio is indicated.     

Influence of Electroless Nickel Plating on Multilayer Ceramic Capacitors and the Implications for Reliability in Multilayer Ceramic Capacitors

The influence of electroless nickel plating on lead-based relaxor ferroelectric multilayer ceramic capacitors (MLCs) was studied by a comparison experiment. It was found that the influence is related to reactions in the electroless plating. It is proposed that adsorbed hydrogen atoms generated in electroless plating can diffuse into the ceramic bodies of MLCs and undergo some reduction reaction with them, resulting in the failure of electroless nickel plating. The implications for the negative influence of electroplating on MLCs and for the degradation in MLCs are also included, in which much attention is paid to the reduction reaction of hydrogen atoms generated by electrolysis of water.     

Binder Distribution in Ceramic Greenware During Thermolysis

Capillary forces were shown to influence the distribution of polymer-plasicizer mixtures within ceramic green bodies during binder thermolysis. Isothermal thermogravimetric analysis was performed on tape-cast sheets of an aluminapoly(vinyl butyrall-dibutyl phthalate composite and direct observations were made of the binder distribution and pore growth after partial pyrolysis. This led to the investigation of a model system, an alumina-eicosane composite, by similar experimental techniques. The early stage of binder removal was found to be similar to the drying of particle beds in which capillary forces draw liquid into the smaller pores at the surface. The morphology of the binder distribution produced by these processes dictates which mass-transfer resistances may be controlling in binder burnout. A model is described that determines the length scale over which capillarity acts based on measurable physical parameters of the binder system and the packing of the ceramic particles.     

日本中高压陶瓷电容器发展概况及动向

本文概要介绍日本中高压陶瓷电容器用介质材料组成,提高耐压的各种结构设计、电极制作、包封工艺、应用及动向。     

Electrodeposition Method for Terminals of Multilayer Ceramic Capacitors

A method using a combination of electroless and electrolytic plating was developed to provide an alternative method for forming the end terminals of multilayer ceramic capacitors. Electrodeposited terminals were formed by using electroless copper followed by electrolytic nickel plating. The electrical characteristics of the electrodeposited terminal capacitors were compared with standard capacitors and found to be identical.     

Defect Formation during Supercritical Extraction of Binder from Green Ceramic Components

Supercritical extraction in carbon dioxide has been used to remove binder consisting of 60 wt% poly(vinyl butyral) and 40 wt% dioctyl phthalate from multilayer ceramic capacitors containing barium titanate as the dielectric. The amount of binder removed increases as both the temperature and pressure of the supercritical fluid increases; a maximum of ∼50% of the binder can be removed using carbon dioxide in 3 h at 75°C and 40 MPa. During depressurization from the supercritical state, defects such as fracture and delamination were occasionally observed in the green body. The occurrence of defects is related to the rate of depressurization, the permeability of the body, and the green strength of the body. The origin of the defects is discussed, and ways to mitigate them are presented.     

Effect of Activated Carbon Bed on Binder Removal from Ceramic Injection Moldings

Weight losses during the binder removal from ceramic injection moldings that have been placed in beds of activated carbon powder and two types of alumina powder were compared. The effect of the specimen size and shape on debinding in a bed of activated carbon was investigated. Because of the structure of its particles, activated carbon powder allowed binder losses in ceramic moldings that consisted of submicrometer-sized particles to increase at a temperature of 130°C. The binder loss in a bed of activated carbon was dependent on the ratio of surface area to volume of the body that was extracted. Renewal of the sorption abilities of the bed of activated carbon after saturation with binder increased the rate of binder removal.     

YSZ/Al2O3/YSZ多层陶瓷叠层制备方法的研究

本文分别采用三种叠层方式制备YSZ/Al2O3/YSZ多层陶瓷,通过实验得出:由于YSZ与Al2O3陶瓷烧结性能的差异,导致YSZ与Al2O3陶瓷叠层共烧时容易分层翘曲,YSZ与Al2O3主要依靠层间的物理啮合作用而结合。通过在流延YSZ层与丝网印刷Al2O3层之间增加印刷YSZ过渡层的叠层方法,可以改善YSZ流延层与Al2O3丝网印刷层之间的结合,而得到结合良好的YSZ/Al2O3/YSZ多层陶瓷共烧结合界面。