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.     

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。     

世界钽粉生产工艺的发展

论述了国内外电容器级高压钽粉、中压钽粉、高比容钽粉的生产工艺发展过程。在钽粉生产工艺发展过程中,各种先进的装备被应用,各钽粉生产厂家围绕着钽粉比容的提高,杂质含量的降低,物理性能的优化等综合性能的改善,不断开发出新工艺、新技术,使钽粉适应并推动着钽电容器的发展。     

Structural capacitor materials made from carbon fibre epoxy composites

In this paper, an approach towards realising novel multifunctional polymer composites is presented. A series of structural capacitor materials made from carbon fibre reinforced polymers have been developed, manufactured and tested. The structural capacitor materials were made from carbon fibre epoxy pre-preg woven laminae separated by a paper or polymer film dielectric separator. The structural capacitor multifunctional performance was characterised measuring capacitance, dielectric strength and interlaminar shear strength. The developed structural CFRP capacitor designs employing polymer film dielectrics (PA, PC and PET) offer remarkable multifunctional potential.     

Elimination of the anomalous humidity effect in precisioncapacitance based transducers

An anomalous humidity effect has been observed in a precision capacitor-based displacement transducer. This effect displays a threshold, well below the dew point, above which the capacitance change exceeds by far the increase in moisture-caused dielectric constant of the air dielectric. This effect, common to air capacitors in general, results from water vapor adsorption on insulator surfaces. It can be eliminated by shielding the capacitor in a way which removes the humidity sensitive flux from the internal electric field of the capacitor     

化学法增大铝箔表面阳极氧化膜介电常数的研究与进展

目前通过电化学方法增大铝阳极箔的有效表面积已越来越困难,铝电解电容器的阳极箔正面临一场新的技术革新：形成高介电常数的复合氧化膜来提高铝氧化膜的比容。本文对形成复合氧化膜的化学方法,复合氧化膜的生长机理,当前研究热点及形成复合氧化膜技术的未来发展进行了综合评述。     

Numerical study of methods of linearization of the output characteristics of radio-frequency sensors of the level of dielectric media

Different constructions of the sensing elements of radio-frequency level sensors based on sections of long lines are numerically investigated by means of the Matlab program for the purpose of minimizing the measurement error caused by the nonlinearity of the output characteristic. It is shown that the nonlinearity is lowest for U-shaped designs. The nonlinearity factor KN may be regulated by varying the capacitance of a correcting capacitor connected to the input of the sensing element and (or) the length of one of the sections of the long line. In selecting an optimal capacitance of the correcting capacitor KN ≤ 0.15% for control media with dielectric permittivity in the range 2.2–30.     

Empirically-derived capacitor characteristic formulas from distributed modelling

Diffusion equation modelling is used to develop formulas for the normally fixed values of capacitance and resistance of the traditional capacitor equivalent circuit. The formulas define the dependence of the equivalent circuit values on metal film resistivity, capacitance per unit area, areal dimensions of the metallisation and on frequency. A multilayer capacitor topology, having both capacitor plates connected at the same end, is used for the derivation, but it is shown that the results are also representative for the more standard double-end connected topologies with some restrictions above the typical self-resonance frequency of these capacitors. The formulas allow accurate prediction of dissipation factor and input impedance according to the design parameters used in constructing the capacitor, thus providing powerful tools in capacitor design. The algorithms also facilitate the determination of internal voltages, currents and power distribution within the capacitor, thus exposing the effects, for example, of partial edge disconnection. The formulas may potentially provide a better capacitor equivalent circuit with dependent variables for circuit emulation. In the paper, the derivation process is described and the formulas tested against experimental results. A simple addition to the equivalent circuit is also included to model dielectric loss which dominantly determines the dissipation factor at low frequency     

Fabrication of large area hexagonal boron nitride thin films for bendable capacitors

Highly reliable and bendable dielectrics are desired in flexible or bendable electronic devices for future applications. Hexagonal boron nitride （h-BN） can be used as bendable dielectric due to its wide band gap. Here, we fabricate high quality h-BN films with controllable thickness by a low pressure chemical vapor deposition method. We demonstrate a parallel-plate capacitor using h-BN film as the dielectric. The h-BN capacitors are reliable with a high breakdown field strength of -9.0 MV/cm. Tunneling current across the h-BN film is inversely exponential to the thickness of dielectric, which makes the capacitance drop significantly. The h-BN capacitor shows a best specific capacitance of 6.8 F/cm^2, which is one order of magnitude higher than the calculated value.     

Polarization-switching D/A converter

This paper describes a novel digital-to-analog (D/A) conversion technique, which uses the analog quantity polarization as a D/A conversion medium. It can be implemented by CMOS capacitors or by ferroelectric capacitors, which exhibit strong nonlinearity in charge versus voltage behavior. Because a ferroelectric material inherently has spontaneous polarization and generally has a large dielectric constant, the effective capacitance of a ferroelectric capacitor is much larger than that of a CMOS capacitor of the same size. This ensures less influence of bottom-electrode parasitic capacitance on a ferroelectric capacitor. Furthermore, a data converter based on ferroelectric capacitors possesses the potential nonvolatile memory function owing to ferroelectric hysteresis. Along with the architecture proposed for polarization-switching digital-to-analog converter (PDAC), its circuit implementation is introduced. Described is implementation of two 9-bit bipolar PDACs: one is based on CMOS capacitors and the other on off-chip ferroelectric capacitors. Experimental results are presented for the performance of these two prototypes.     

改善有机片式固体钽电解电容器性能工艺研究

研究了在被膜过程中表面活性处理及掺杂对聚合物片式钽电容器容量、耐压、等效串联电阻(ESR)等特性的影响。研究结果表明表面活性处理后可以有效改善Ta2O5/PEDOT界面间的匹配,提高电容器容量引出效率;通过添加中间阻隔层(硅烷偶联剂)可以有效地阻挡杂质氧化性离子进入介质膜Ta2O5层,降低聚合物片式钽电容器的漏电流,提高耐压特性;实验结果表明在掺杂剂溶液的浓度为3%,补形成电压为赋能电压的70%时,能有效降低电容器ESR及漏电流。     

A solid-state relative humidity measurement system

The implementation of a solid-state capacitive relative humidity (RH) sensing system which employs a polymer as the moisture-sensitive material is discussed. The sensing mechanism is based on the fact that the dielectric permittivity of the insulating polymer, polyimide (PI), is linearly related to the ambient relative humidity. Therefore, the capacitance of a parallel-plate device using PI as the dielectric is a linear function of ambient RH (because PI does not swell during moisture absorption). Standard IC processing techniques are used to fabricate the PI-based integrated sensor capacitor. In order for such as sensor to be useful in the field, a voltage, current, or frequency output is desirable. A discrete capacitance-to-voltage converter circuit using this sensor capacitor has been constructed. The performance of this system is reported     

Aluminum oxynitride dielectrics for multilayer capacitors with higher energy density and wide temperature properties

Amorphous aluminum oxynitride (AlON) possesses unique properties of high dielectric strength, high resistivity, low loss, high decomposition temperature, chemical inertness, and high thermal conductivity. These properties make it a candidate for a next generation capacitor dielectric. DC pulsed magnetron reactive sputtering is used to produce amorphous AlON films on various substrates. Dielectric properties are optimized by adjusting DC power, pulse frequency, total pressure, substrate temperature, and gas ratio. Simple parallel plate structures are utilized to characterize the dielectric properties. Clearable electrodes are evaluated in device performance. Defects cleared without significant loss of capacitance. Temperature dependent dielectric properties were evaluated from − 200 °C to + 400 °C. Stacked multilayer capacitor device is developed for high energy density and wide temperature applications.     

The effect of spatial dispersion of the dielectric permittivity on the capacitance of thin insulating films: Non-linear dependence of the inverse capacitance on film thickness

An apparently non-linear relation between the inverse capacitance of thin insulating films and the film thickness is often observed in the thickness region up to a thousand ångströms and is commonly ascribed to film inhomogeneity, lattice imperfections or field penetration into the metal electrodes. This effect is considered in terms of the theory of non-local dielectrics for which the dielectric response to an electric field at different points is correlated over regions comparable with the local microstructure. The general theory is adapted to thin metal-film-metal junctions and the effective dielectric permittivity in the classical capacitance expression for a planar condenser is calculated as a function of the film thickness for various model systems. The resulting effects are predicted to be larger than those expected for field penetration. Comparison with experimental data for ionic oxide and sulphide films shows that the observed effects are most probablu too large to be ascribed solely to the non-local nature of the dielectric response, whereas the effects observed for films of organic acid salts have the order expected (corresponding to correlation lengths of one or two molecular layers).     

Influences of atomic hydrogen on porous low-k dielectric for 45-nm node

Atomic hydrogen generated by a heated tungsten catalyzer has been investigated in terms of the damage-less ash and restoration of damaged low-k dielectric. No difference of damaged thickness of low-k dielectric between before and after the ash by HF dip using patterned porous methyl silsesquioxane (MSQ) film was found. Moreover atomic hydrogen exposure slightly reduced capacitance of the micro-structured capacitor with the Cu wire and the CVD porous low-k dielectric.     

Fabrication of Al deposited sandwich capacitor structure with CdSe/PVA dielectric thin film by spin coating technique for high power applications: synthesis and characterizations

The capacitor structures were fabricated in the configuration of Al : CdSe/PVA : Al with CdSe/PVA as an insulating dielectric layer for high power applications. The sandwiched layer gave an excellent energy density and a better dielectric strength that was obtained from the amalgamation of CdSe and poly (vinyl alcohol). For the detailed analysis of the interaction between CdSe and PVA, transparent CdSe/PVA composites were synthesized by ultra-sonication technique with micrometer thicknesses at different wt% of CdSe. The UV absorption edge of PVA matrix corresponds to π→π* transition associated with ethylene unsaturation (C=C) was analysed and it was shifted towards higher wavelength with the CdSe incorporation. The sub-band states formation was evaluated, Urbach energy was increased up to ~835 meV, and an increase in structural defect was noticed by widening the tail state within the polymer matrix with the impurity addition. Optical parameters which include extinction coefficient (k) and index of refraction (n) have been determined. Three dielectric relaxations were pronounced as α, β and interfacial polarization and the high relative permittivity and the low values of dissipation factor indicated that the dielectric phenomenon was predominant in all membranes. Inspection of electrical conduction rate to temperatures was also investigated and the temperature coefficient of capacitance and temperature coefficient of permittivity were listed. Thermal stability could be enhanced with CdSe interaction and the variation in thermal parameters was discussed.     

高性能BaTiO_3/PVDF介电复合材料及其薄膜电容器应用

选用柔性高分子材料聚偏氟乙烯（PVDF）作为基体,纳米钛酸钡陶瓷（BaTiO3）作为填充相,采用简单的溶液共混以及流延工艺制备BaTiO3/PVDF薄膜。通过SEM观察了复合材料体系的微观结构,研究了BaTiO3/PVDF介电复合材料的介电性能。把所制备的BaTiO3/PVDF复合材料薄膜（70mm×30mm×25μm...     

Preparation,microstructural development and dielectric properties of Pb(Mg1/3Nb2/3)O3-Pb(TixZr1−x)O3 multilayer ceramic capacitors

Multilayer ceramic capacitors based on PMN-PZT solid solutions have been prepared using a 70 % Ag-30% Pd alloy as internal electrode. Some interaction of the electrode-dielectric with Ag⁺ diffusion into the dielectric was observed. The Ag⁺ diffusion influenced the normal microstructural development present in the PMN-PZT ceramics. In spite of this, the dielectric behaviour of a five active layers capacitor sintered at 1050 °C for 2 h in air showed a capacitance of 120 nF, an effective dielectric constant maximum of ~200 000 and dielectric losses of about 3% near room temperature and 1 kHz.     

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.     

Synthesis of copper-ferrous (CuFe) nanowires via electrochemical method and its investigations as a fluid sensor

The special behaviour of nanowires with respect to electrical conductivity makes them suitable for sensing application. In this paper, we present a copper-ferrous (CuFe) nanowires based sensor for detection of chemicals. CuFe nanowires were synthesized by template-assisted electrochemical method. By optimizing the deposition parameters, continuous nanowires on a copper substrate were synthesized. The morphological and structural studies of the synthesized CuFe nanowires were carried out using scanning electron microscope (SEM) and X-ray diffraction (XRD). Substrates containing CuFe nanowires were moulded to form a capacitor. Different chemicals were used as dielectric in the capacitor which showed that the capacitance was a nonlinear function of the dielectric constant of fluid unlike the linear relation shown by conventional capacitors. This unique property of the nanowires based capacitors may be utilized for developing fluid sensors with improved sensitivity.