多层陶瓷电容器材料的发展与动向

近十年来,随着电子信息技术的发展,多层陶瓷电容器(MLC)的研制也在突飞猛进。本文详述了MLC材料三大门类的研究与发展概况。高、中温烧结体系技术成熟,门类齐全,仍是当前MLC工业化生产的主体;低温烧结体系和抗还原性体系也已崭露头角,且前景可观。但是,各种新体系的开发完善和实用化还是一项长期的工作。     

新型多纤维陶瓷电容器的设计

提出了一种新型多纤维陶瓷电容器(MFC)。MFC由众多纤维电容器并联而成，而每根纤维电容器由内电极(导电纤维)、介电层和外电极构成。理论分析表明，当纤维直径与介电层厚度相匹配时，MFC的电容比多层电容器(MLC)的电容大，而且MFC也具有更优异的抗击穿性能。     

创见声明全系列SD闪存卡绝无质量不稳定

针对中国某网站对于闪存卡控制芯片支持MLC内存状况之不当解读，与指出创见SD闪存卡质量不稳定之错误评论，创见资讯特此郑重声明予以澄清，创见全系列SD闪存卡技术领先，产品性能稳定，     

MLC叶片位置PID控制器设计与仿真研究

针对肿瘤治疗病灶靶区的要求,描述适形放射治疗装置中多叶准直器(MLC)的结构和工作原理,设计一种针对MLC叶片位置精度的PID控制器,并进行仿真模拟,结果表明该方法能较好地满足多叶准直器叶片位置控制的精度。     

中国先进陶瓷研究及其展望

本文综述了中国在先进陶瓷，包括结构陶闪必功能陶瓷的研究概况及其展望。从本世纪五十年代以来，我国即开展先进陶瓷的基础研究和应用研究。在此基础上，逐步形成了在这一领域听研究趋向，即多相复合陶瓷，纳米陶瓷和陶瓷材料的剪裁与设计。     

从发明专利看无铅压电陶瓷的研究与发展——无铅压电陶瓷20年发明专利分析之一

无铅压电陶瓷的研究与开发已引起世界各国的高度重视。本文综合分析了近20年无铅压电陶瓷发明专利约140篇。从发明专利角度评述了无铅压电陶瓷的研究与发展现状，简要介绍了目前受到广泛研究的BaTiO3(BT)基无铅压电陶瓷、Bi1/2Na1/2TiO3(BNT)基无铅压电陶瓷、铋层状结构无铅压电陶瓷及铌酸盐系无铅压电陶瓷，并侧重介绍这些无铅压电陶瓷的组分、性能和制备方法。从无铅压电陶瓷发明专利的进展可以看出，在过去20年中，为促进人类社会的可持续发展，无铅压电陶瓷得到了广泛的研究和开发，并取得重要进展。     

陶瓷超塑性的研究进展

本文综述了氧化锆及其复相陶瓷超塑性的研究现状，论述了陶瓷超塑性的变形机理，微观特征和断裂特性。同时，分析和对比了陶瓷超塑性与金属超塑性的特点。目前，对于正确理解超塑性陶瓷的变形机理，还需进行大量工作。     

陶瓷超塑性的研究进展

本文综述了氧化锆及其复相陶瓷超塑性的研究现状，论述了陶瓷超塑性的变形机理，微观特征和断裂特性。同时，分析和对比了陶瓷超塑性与金属超塑性的特点。目前，对于正确理解超塑性陶瓷的变形机理，还需进行大量工作。     

浅谈陶瓷工艺对古代陶瓷山水装饰风格的影响

从艺术自身发展而言，陶瓷山水装饰从萌芽、发展到成熟与前朝有着一脉相承地关系。古代陶瓷山水装饰风格的形成和转变有诸多因素，其中陶瓷工艺是对陶瓷山水装饰的风格形成有着重大的影响。陶瓷艺术是工艺美术，离不开必要的技术这一先决条件，工艺的发展也推动着陶瓷山水装饰不断进步。     

泡沫碳化硅陶瓷的导电性能

采用高分子热解和反应烧结方法制备出泡沫碳化硅陶瓷，研究了泡沫碳化硅陶瓷的体积分数变化和钛的掺杂对泡沫碳化硅陶瓷骨架导电性能的影响．结果表明：随着泡沫碳化硅陶瓷的体积分数提高，泡沫碳化硅陶瓷的电阻率降低，这是泡沫碳化硅陶瓷筋中部碳化硅的面积增加所引起的；掺杂的钛转变成TiSi2导电相改善了泡沫碳化硅陶瓷的导电性能．TiSi2呈现离散和团聚两种形态分布，以不规则的形状位于碳化硅晶界之间，在碳化硅中作为施主杂质．泡沫碳化硅陶瓷表现出的正或负温度系数取决与掺杂的钛量的多少．     

Apparent coefficient of thermal expansion and residual stresses in multilayer capacitors

The thermal expansion behavior and residual stresses in multilayer capacitor (MLC) systems are analyzed in the present study. An MLC consists of a laminate of multiple alternating electrode layers and dielectric layers sandwiched between two ceramic cover layers. An analytical model is developed to derive simple closed-form solutions for the apparent coefficients of thermal expansion (CTEs) of the laminate. Plasticity of electrodes is included in the analysis. The predicted apparent CTEs are compared with measurements of some laminated ceramic composites. The effects of plasticity on apparent CTEs and residual stresses in MLC systems are discussed.     

Multilayer ceramic capacitor electrdes: powder technology and fired properties

The properties of Pd/Ag thick-film multilayer ceramic capacitor (MLC) electrode pastes are directly related to the characteristics of the metal powders. Better performance is obtained when deagglomerated powders are used. Improvements in precious metal powder technology has produced electrodes that permit a 30% reduction in precious metal consumption with superior functional and cosmetic properties. Use of deagglomerated powders also enables manufacture of MLC electrode pastes which print smooth enough so as to be compatible with wet stack process, where the surface roughness of the dried electrode is a primary concern.     

Multifiber ceramic capacitor

A new type of capacitor, multifiber capacitor (MFC) is proposed. It is made up of fiber capacitors (elements) connected in parallel and bonded together with a binder. Each element consists of fiber core (inner electrode), dielectric coating and outer electrode. Analysis indicates that MFC has the optimum capacitance in comparison with multilayer capacitor (MLC) when the diameter of fiber core is carefully matched by the thickness of dielectric coating. Since dielectric layer of a wide range of thickness can be produced more easily as fiber coating than as flat tape, MFC can cover a wider range of capacitance than MLC. Apart from as a possible substitute or supplement to MLC, MFC is potentially useful to bridge the gap between ceramic MLC and thin film capacitor used in integrated circuits. MFC also has better resistance to dielectric breakdown. The possible techniques for the preparation of MFC are also described.     

Two-dimensional array transducers using thick film connection technology

A connection technique for two-dimensional array ultrasound transducers developed by combining a conductive lambda/4 mismatching layer with a multi-layer ceramic (MLC) connector using thick-film microelectronic technology is described. The connector consists of 20 thick films of alumina and screen printed metallization with customized interconnections between the layers called vias. Ten ground layers are interleaved between ten signal layers to reduce elecrical crosstalk. A lambda/4 mismatching layer of conductive epoxy is bonded between each PZT element and the silver metal pad of the MLC connector to provide an effective low impedance backing. In the current configuration, a 16x16 transducer array, 0.6 mm element spacing, is expanded to a 16x16 grid of connector pins at a standard spacing of 2.5 mm. Vector impedance, sensitivity, bandwidth, interelement uniformity, and crosstalk are all in good agreement with arrays of conventional fabrication. However, an array with MLC connector can be fabricated more quickly independent of the number of elements.     

Refinement on the theoretical analysis of multifiber ceramic capacitor

In a previous paper, a new type of ceramic capacitor, multifiber ceramic capacitor (MFC), was designed and analyzed to compare the properties with multilayer ceramic capacitors (MLC). Refinement on the theoretical analysis of the MFC is presented in this paper for the capacitors made from dielectric film less than 2 m thick. A critical _c exists above which the specific capacitance of an MFC is higher than an MLC, where is the ratio of the dielectric thickness of the MLC and the MFC. Such a _c value is readily attainable because a high-quality dielectric coating on fiber substrates can be easily produced by modern thin-film technology. In other words, MFC has the potential to surpass MLC in term of the specific capacitance. Core fibers (inner electrodes) with a small diameter should be selected, whenever possible, for improved specific capacitance. The choice of possible materials for the MFC is also discussed.     

Multilayer piezoelectric ceramics for two-dimensional array transducers

In medical ultrasound imaging, 2-D array transducers have become essential to implement dynamic focusing and phase-correction in the elevation dimension as well as real-time volumetric scanning. Unfortunately, the small size of a 2-D array element results in a small clamped capacitance and a large electrical impedance near resonance. These elements have poor sensitivity because their impedance is much higher than the electrical impedance of the transmit and receive circuitry. Sensitivity can be improved by using an N layer structure of PZT ceramic with the layers connected acoustically in series and electrically in parallel. For the multilayer ceramic (MLC), the damped capacitance is multiplied by a factor of N(2) and the electrical impedance by 1/N(2) compared to a single layer element of the same dimensions. A 3x43 phased-array transducer has been fabricated using 3 layer PZT-5H material. Each element had a thickness of 0.66 mm and an area of 0.37x3.5 mm. The MLC was manufactured using thick film technology with plated-through vias to electrically interconnect the electrode layers. The completed transducer was compared to a single layer control array of similar dimensions. With a light epoxy backing and a lambda/4 matching layer, the MLC array elements had an impedance of 100 Omega at series resonance of 2.25 MHz, compared to 800 Omega for the control elements. The lower impedance of the MLC elements resulted in a minimum round-trip insertion loss of 24.0 dB, compared to an 34.1 dB for the control array elements. These results were consistent with KLM modeling. B-scan images were made of cysts in a tissue-mimicking phantom and of the left kidney in vivo. The images clearly showed a higher signal-to-noise ratio for the MLC array compared to the control. As a result, 2-D arrays made of multilayer ceramics can be used to form images at a higher frequency and greater range than single layer arrays.     

Non-Newtonian fluid flow model for ceramic tape casting

The current device of miniaturisation and higher device counts in integrated circuit (IC) packages has significantly increased the use of both multilayer ceramic packages (MLCP) and multilayer capacitors (MLC). Currently, one of the main methods used for the manufacture of flat ceramic packages with precise thickness control and consistency is the tape casting technique. Since these tapes can be cast with thickness of about 100 μm, it is crucial that the control of green tape thickness is precise, and that these thickness values are reproducible consistently. The flow of the slurry onto the casting surface can be modelled as a two dimensional fluid flow through a parallel channel. By choosing a suitable constitutive model, the predictions of the proposed model and existing models were compared with experimental results. The proposed model accurately described the fluid flow characteristics of the process, and had good agreement with experimental results.     

Thermal shock resistance of miniaturized multilayer ceramic capacitors

The thermal shock resistance of miniaturized multilayer ceramic capacitors (MLCs), of sizes 0402, 0603, 0805 and 1206, was investigated by comparing the leakage currents before and after thermal shock. It was generally found that smaller capacitors have a higher thermal shock resistance than larger ones. The 0402 MLC possesses a thermal shock resistance in excess of 420 C. The linear interdependence of thermal shock resistance and reciprocal of half thickness, as predicted by conventional thermal shock analysis, was not observed. Instead, the thermal shock resistance of an MLC was found to be inversely proportional to the total area of its ceramic surface. This confirms that pre-existing flaws on the ceramic surface dominate the crack initiation process and are therefore primarily responsible for determining the thermal shock resistance of an MLC.     

铅系弛豫体基与钛酸钡基独石电容器介电特性的比较

对比研究了典型铅系钙钛矿型弛豫铁电陶瓷独石电容器及钛酸钡基独石电容器的介电特性随温度、电场等条件下的变化规律。结果表明,尽管在弱电场下弛豫体陶瓷与钛酸钡陶瓷的介电行为存在较大的差别,但在强电场下这种差别会减小。从应用的角度看,两种电容器的介电性能在强电场下的相似性是弛豫体电容器取代传统钛酸钡电容器进入大规模应用的重要保证。同时,弛豫铁电陶瓷具有较高的介电常数,这一优势可为电容器设计中提高元件综合性