Boosting ultra-wide temperature dielectric stability of multilayer ceramic capacitor through tailoring the combination types of polar nanoregions

With the rapid development of space exploration and new energy vehicles,it is urgent to build ultra-wide temperature multilayer ceramic capacitors(UWT MLCCs)to match electronic circuits that can withstand harsh environmental conditions.Relaxor ferroelectrics with diffuse phase transition feature are potential dielectrics for the construction of UWT MLCCs.However,how to ensure high dielectric constant together with low dielectric loss in the wide temperature region is still a big challenge.Here,the above difficulties are addressed by tailoring the combination types of polar nanoregions(PNRs)in the(1-x)(0.8Na_(0.5)Bi_(0.5)TiO_(3)-0.2K_(0.5)Bi_(0.5)TiO_(3))-xNaTaO3(NBT-KBT-xNT)system.Compared with PNRS types of P4bm+R3c and P4bm+Pbnm,the combination type of P4bm+Pbnm+R3c PNRs in NBT-KBT-0.31NT is the most beneficial to obtain comprehensive excellent dielectric performance because it can balance the relationship between high dielectric constant and temperature stability over a wide temperature region.Further,by optimizing the laminating pressure and co-firing temperature to realize a tight interfacial structure between the dielectric layer and the Pt inner electrode,a record-high dielectric constant(er=(907%±15%))together with low dielectric loss(tan δ≤0.025)is achieved over an ultra-wide range from-61℃ to 306℃ for NBT-KBT-0.31 NT MLCC,demonstrating that tailoring the combination types of PNRs is a powerful strategy in designing UWT MLCC dielectrics.

Unusual local electric field concentration in multilayer ceramic capacitors

Local electric-field around multitype pores(dielectric pore,interface pore,electrode pore)in multilayer ceramic capacitors(MLCCs)was investigated using Kelvin probe force microscopy combined with the finite element simulation to understand the effect of pores on the electric reliability of MLCCs.Electricfield is found to be concentrated significantly in the vicinity of these pores and the strength of the local electric-field is 1.5e5.0 times of the nominal strength.Unexpectedly,the concentration degree of the pores in the inner electrode is much higher than that in the dielectrics and dielectric-electrode interfaces.Meanwhile,geometry orientations are found to have a remarkable influence on the local electric field strength.The pores act as an insulation degradation precursor via local electric,thermal center,and oxygen vacancies accumulation center.Such unusual local electric field concentration of multitype pores can provide new insights into the understanding of insulation degradation evolution,processing tailoring and design optimization for MLCCs.

Enhanced breakdown strength of BaTiO_(3)-based multilayer ceramic capacitor by structural optimization

0.5 wt%Nb_(2)O_(5)doped 0.12BiAlO_(3)-0.88BaTiO_(3)(12BA5N)multilayer ceramic capacitor(MLCC-1)was prepared,which satisfied EIA X7R specification(where X is the minimum temperature,R is the percentage of capacitance variation limit)at 1 kHZ.The distribution of internal electric field under breakdown voltage was simulated by finite element method(FEM),indicating that the electric field strength increased significantly at the terminal of internal electrode.These areas may become the headstream of breakdown for MLCC-1 due to the shape mutation.In order to improve the breakdown performance of MLCC-1,it was optimized by 12BA5N+2G green sheets(prepared by 12BA5N ceramic powder with 2 wt%B-Al-Si glass additive),then MLCC-2 was obtained which satisfied EIA X8R specification.Its BDS rose from 20 to29.4 kV·mm^(-1),and the electric field distribution of dielectric layer was also analyzed by FEM.Besides,it was also found that the grain size and the dielectric constants of"core"and"shell"parts for the 12BA5N+2G dielectric layer both contributed to the enhanced BDS of MLCC-2according to the simulation results from FEM.

Perspectives and challenges for lead-free energy-storage multilayer ceramic capacitors

The growing demand for high-power-density electric and electronic systems has encouraged the development of energy-storage capacitors with attributes such as high energy density,high capacitance density,high voltage and frequency,low weight,high-temperature operability,and environmental friendliness.Compared with their electrolytic and film counterparts,energy-storage multilayer ceramic capacitors(MLCCs)stand out for their extremely low equivalent series resistance and equivalent series inductance,high current handling capability,and high-temperature stability.These characteristics are important for applications including fast-switching third-generation wide-bandgap semiconductors in electric vehicles,5G base stations,clean energy generation,and smart grids.There have been numerous reports on state-of-the-art MLCC energy-storage solutions.However,lead-free capacitors generally have a low-energy density,and high-energy density capacitors frequently contain lead,which is a key issue that hinders their broad application.In this review,we present perspectives and challenges for lead-free energy-storage MLCCs.Initially,the energy-storage mechanism and device characterization are introduced;then,dielectric ceramics for energy-storage applications with aspects of composition and structural optimization are summarized.Progress on state-of-the-art energy-storage MLCCs is discussed after elaboration of the fabrication process and structural design of the electrode.Emerging applications of energy-storage MLCCs are then discussed in terms of advanced pulsed power sources and high-density power converters from a theoretical and technological point of view.Finally,the challenges and future prospects for industrialization of lab-scale lead-free energy-storage MLCCs are discussed.

Energy storage properties of 0.87BaTiO3-0.i3Bi(Zn2/3(Nb0.85Ta0.15)1/3)O3 multilayer ceramic capacitors with thin dielectric layers

Multilayer ceramic capacitors(MLCCs)for energy storage applications require a large discharge energy density and high discharge/charge efficiency under high electric fields.Here,0.87BaTiO3--0.13Bi(Zn23(Nbog8sTao.1s)u3)O3(BTBZNT)MLCCs with double active dielectric layers were fabricated,and the effects of inner electrode and sintering method on the energy storage properties of BTBZNT MLCCs were investigated.By using the pure Pt as inner electrode instead of Ago.6Pdo4 aloys,an alternating current(AC)breakdown strength(BDS)enhancement from 1047 to 1500 kV/cm was achieved.By investigating the leakage current behavior of BTBZNT MLCCs,the Pt inner electrode and two-step sintering method(TSS)were confirmed to enhance the Schottky barrier and minimize the leakage current density.With relatively high permitivity,dielectric sublinearity,and ultra-high BDS,the Pt TSS BTBZNT MLCCs exhibited a surprisingly discharge energy density(Udis)of 14.08 J/cm2.Moreover,under an operating electric field of 400 kV/cm,the MLCCs also exhibited thermal stability with Udis variation<±8%over a wide temperature (t) range from-50 to 175℃ and cycling reliability with Uais reduction<0.3%after 3000 charge-discharge cycles.These remarkable performances make Pt TSS BTBZNT MLCCs promising for energy storage applications.

Effect of SiO_2 addition on the dielectric properties and microstructure of BaTiO_3-based ceramics in reducing sintering

The effect of SiO2 doping on the sintering behavior, microstructure, and dielectric properties of BaTiO3-based ceramics has been investigated. Silica was added to the BaTiO3-based powder prepared by the solid state method with 0.075mol%, 0.15mol%, and 0.3mol%, respectively. The SiO2-doped BaTiO3-based ceramic with high density and uniform grain size were obtained, which were sintered in reducing atmosphere. A scanning electron microscope, X-ray diffraction, and LCR meter were used to determine the microstructure as well as the dielectric properties. SiO2 can form a liquid phase belonging to the ternary system of BaO-TiO2-SiO2, leading to the formation of BaTiO3 ceramics with high density at a lower sintering temperature. The SiO2-doped BaTiO3-based ceramics can be sintered to a theoretical density higher than 95% at 1220℃ with a soaking time of 2 h. The dielectric constants of the sample with 0.15mol% SiO2 addition sintered at 1220℃ is about 9000. Doping with a small amount of silica can improve the sintering and dielectric properties of BaTiO3-based ceramics.

Large electrocaloric effect in BaTiO_3 based multilayer ceramic capacitors

The electrocaloric effect(ECE) of multilayer ceramic capacitor(MLCC) of Y5 V type was directly measured via a differential scanning calorimetry(DSC) method and a reference resistor was used to calibrate the heat flow due to the heat dissipation. The results are compared with those calculated from Maxwell relations by using the polarization data obtained from the polarization–electric field hysteresis loops. The direct method shows a larger ECE temperature change, which is accounted for the situation approaches an ideal condition. For the indirect method using Maxwell relations, only the polarization projection along the electric field was taken into account, which will be less than the randomly distributed real polarizations that contribute to the ECE. The MLCCs exhibit a broad peak of ECE around 80 C, which will be favorite for the practical ECE cooling devices.

Energy storage properties of surface-modified BaTiO_(3)ceramic films for multilayer capacitors applications

Surface-modified BaTiO_(3)of 230 nm average grain size were synthesized by coating BaTiO_(3)particles with 3 wt.%Al2O_(3)and 1 wt.%SiO2.Ceramic films of different thicknesses were prepared via tape casting and laminating processes followed by two-steps sintering method.After sintering,the average grain size of Surface-modified BaTiO_(3)ceramic slightly increased to 275 nm,and great enhancement of AC breakdown strength(BDS)from 184 kV/cm to 665 kV/cm was obtained as the thickness of ceramic films decreased from 63μm to 12μm,resulting in improvement of discharge energy density from 1.14 J/cm3to 4.06 J/cm3.Because of their low-cost,easily fabrication,lead-free,improved AC BDS and discharge energy density,surface-modified BaTiO_(3)ceramic films appeared promising for applications in multilayer energy storage capacitors.

Series multilayer internal electrodes for high energy density glass-ceramic capacitors

The glass-ceramic dielectrics and internal electrode structures are investigated for improving the general energy storage density of capacitors. Calculation indicates that glass-ceramics acquired from glass matrix annealing at 850℃ for 3 hours can be approximately up to 17 J/cm3 in energy storage density. They are appropriately chosen as the dielectrics for preparing high energy storage density capacitors (HESDCs). A series multilayer structure of internal electrode is developed for the HESDCs, in which each layer is a combination of gold film and silver paste. This electrode structure promises the capacitor immune from the residual porosity defects inevitably brought by electrode paste sintering process, and specifically improves the electrical breakdown strength of the capacitor. Based on this new electrode structure, the energy storage densities of capacitors are increased by more than one order of magnitude compared with those traditional ones with only single layer of internal electrode. Thus, HESDCs based on the optimized glass-ceramic dielectrics can potentially achieve 7.5 J/cm3 in energy storage density, even taking into consideration the enlargement of total capacitor volumes while encapsulating practicable capacitors from dielectrics media.

BaTiO_(3)基超薄层BME MLCC的可靠性机理

多层陶瓷电容器(Multilayer ceramic capacitors,MLCC)作为市场占有率最高的无源电子元器件,是基础电子元件产业中需要突破关键技术的重点产品之一,在汽车电子、5G通讯、电网调频、航空航天等领域有广泛的应用。在小型化、薄层化发展趋势下,MLCC的介质层厚度不断降低,单层介质在相同电压下的电场显著增大,尤其是中高压超薄层MLCC。因此,MLCC的可靠性愈发成为一项关键的产品质量指标。本文结合加速老化测试、高温阻抗谱、漏电流测试,系统研究超薄层MLCC的劣化机理,揭示抑制氧空位的迁移与富集是保证超薄层MLCC可靠性的重中之重。为此,应减小介质层内部的氧空位浓度,增大其迁移所需的激活能,提高界面肖特基势垒,从而提升超薄层MLCC的可靠性。本文的研究成果为超薄层MLCC介质材料的设计提供了有力指导。

Ni–MgO核–壳纳米粉体的制备

采用包覆热分解烧结法,制备了多层陶瓷电容器内部电极用MgO包覆Ni纳米粉体,讨论了反应物浓度和分散剂含量对包覆纳米镍盐前驱体颗粒大小和均匀性的影响,分析了还原烧结温度对包覆纳米Ni粉球形度和分散性的影响,并利用X射线衍射仪、扫描电镜、透射电镜、热机械分析仪对MgO包覆纳米Ni粉进行了表征分析。结果表明:反应物浓度达到足以引起反应爆炸成核时,能够获得纳米镍盐颗粒;添加适量的分散剂,可以得到分散良好的纳米镍盐前驱体颗粒;还原烧结温度700℃时,可以获得球形度和分散性良好的MgO包覆纳米Ni粉;MgO包覆在纳米Ni粉表面,形成了核壳结构,该纳米Ni粉具有良好的收缩延迟效果。

基于机器学习的小容值MLCC容量模型的研究

小容值多层瓷介电容器(MLCC)容易出现容量命中率低的问题,本文通过机器学习算法建立小容值MLCC容量模型,采用MSE、R2、拟合精度和预测精度评估各模型的准确度。最后选择采用线性回归模型表达小容值MLCC的印刷层数和电容量之间的关系,并通过实际投产验证,证明该模型可以用于指导小容值MLCC的实际生产,提高小容值MLCC容量命中率。

MLCC手工焊接质量控制研究

针对多层瓷介电容器(MLCC)在手工焊接过程中可能引入的裂纹损伤从而降低其使用可靠性的问题开展了研究。探索了手工焊接过程中MLCC外形尺寸、印制电路板(PCB)是否预热、焊盘散热速率和焊接温度对MLCC裂纹的影响程度,摸索最优焊接工艺参数,尽可能消除MLCC应用过程中可能引入裂纹损伤的质量隐患,进一步确保MLCC的使用可靠性。

柔性端电极多层瓷介电容器失效模式分析与改进措施

柔性端电极多层陶瓷电容器(Flexible Termination Multilayer Ceramic Capacitors,FTMLCCs)在典型三层端电极基础上,引入由树脂和导电填充物构成的柔性电极层,在不增加电容尺寸或削减容量的前提下,降低瓷体开裂风险。但FTMLCC引入柔性层结构,降低瓷体开裂风险的同时也可能引入新的失效风险。选取两种1812尺寸FTMLCC产品为研究对象,利用扫描电子显微镜、聚焦离子束剖切与三维重构等技术进行了柔性层物理结构和结合界面特性的详细表征。通过装联、抗弯曲与环境试验评价的方法,对柔性电极结构、柔性层相关缺陷和失效模式进行了深入研究。研究表明,柔性端电极虽增强了MLCC抗弯性,但柔性层内空洞或弱层间结合力可能诱发电极内开裂或界面剥离等新失效模式,造成容量下降。因此,生产或使用FTMLCC产品时,需提升柔性层耐焊性,控制装联条件,并适当除湿,以保护瓷体,提升其装联可靠性。

制备工艺对多层陶瓷电容器容量的影响研究

多层陶瓷电容器在制备过程中,任何一个质量管控点的变化都会造成容量的变化。因此,在实际生产过程中,研究各工序制备过程对多层陶瓷电容器容量的影响因素,改善其容量命中率,提高产品合格率,具有重要的意义。

反铁电多层陶瓷电容器加速寿命试验与建模技术

本文研究了反铁电多层陶瓷电容器的温度、电压、电流多应力因子加速寿命试验方法与可靠性寿命建模技术,选取宏科电子公司的GCT41P-7680-X7Q-4000V-623M型号脉冲功率多层瓷介电容器样品,开展高温、高电压、大电流循环充放电寿命试验,获得了40个试样的加速寿命试验数据,基于试验数据分析结果,建立了反铁电多层陶瓷电容器PV+寿命预测模型以及相应的模型模型参数值。试验失效样品DPA分析发现,反铁电多层陶瓷电容器充放电循环工作失效模式为内电极界面分层失效,并就其失效机理进行了初步探讨分析。

基于MLCC电子陶瓷的片式电子元件高速智能切割机的设计和实现

电子产品的不断发展,对电子元件的尺寸、质量和生产效率提出了更高的要求。为了满足这些要求,设计了一种创新的高速智能切割机,旨在提高生产效率、降低制造成本和保证产品质量。从机体结构和框架设计、载台和真空吸盘系统及DD直驱伺服转动机构等方面探讨高速智能切割机的设计,然后结合高速智能切割机的特点,探讨切割机工作流程和控制系统的实现,进而推动电子元件制造业向智能化和高效化方向迈进。

Y_2O_3和ZnO共掺杂对BaTiO_3陶瓷的微观结构和介电性能的影响

研究了Y2O3和ZnO共掺杂对BaTiO3陶瓷的微观结构和介电性能的影响．XRD分析表明,Y2O3和ZnO促使BaTiO3的晶体结构由四方相转变为赝立方相;在此系统中Y2O3的固溶度低于1．5mol％,而ZnO的固溶度约3．0mol％．SEM显示Y2O3比ZnO更能有效地改善微观结构,其显著的晶粒抑制作用归因于分散于晶界的第二相Y2Ti2O7对晶粒生长的钉扎作用．适量Y2O3和ZnO的协同作用有助于形成壳-芯结构,并显著改善BaTiO3陶瓷的介电温度稳定性．在BaTiO3-Y2O3-ZnO新体系中获得符合XTR的高性能抗还原介质．

多层陶瓷电容器中的Ag─Pd系内电极浆料

从银钯化合物混合溶液中共沉淀中间体，再还原得到Ａｇ─Ｐｄ合金粉。其粒度随Ｐｄ量增加而降低。预氧化处理合金粉，得到表面为氧化钯和银而中心为Ａｇ─Ｐｄ合金的内电极粉。所配制的浆料可用于制备性能达到规定标准的多层陶瓷电容器。

多层陶瓷电容器废料中回收银、钯工艺的研究

研究了从多层陶瓷电容器（ＭＬＣＣ）废料中回收银、钯的方法，２００目的废料用４ｍｏｌ／ＬＨＮＯ３在８０℃下浸出２ｈ（液固比３），银、钯浸出率分别为９１％和９８％。用盐酸从浸出液中沉淀银，氯化银经熔炼得到９８％粗银锭，银回收率为８８％，用铁粉和丁基黄药分别从沉银母液和浸出渣洗水中置换、沉淀钯，用传统精炼钯的方法得到９９９５％Ｐｄ，钯回收率为９５％。