Electrostatic force acting on conductive ball between electrodes

To advance electrostatic applications such as novel printing technologies and solder ball control for LSI bumping, the electrostatic force acting on a conductive ball between two electrodes is calculated. The electrostatic force increases as the ratio of the ball diameter to the electrode separation increases. The electrostatic force is also calculated for the case when a charge pattern is formed on the insulating layer on the upper electrode. In this case, the electrostatic force initially varies as the square of the charge pattern area but eventually plateaus to a constant value as the area increases. Experiments investigating the force acting on the ball are performed. The force estimated from these experiments agrees with the value obtained by electric field analysis.     

Simulating percolating behavior of conductive particles in anisotropically conductive composite films

A numerical scheme is developed to simulate the percolating behavior of conductive particles within a non-conductive matrix film with a preferential alignment of particles achieved via externally imposed deterministic driving forces. The sharp transition from non-conducting to conducting of the composite film is successfully revealed with the model. The percolation behavior is studied in terms of four percolation parameters, including the percolation probability, the normalized shortest percolation path, normalized gyration radius and density of the percolation cluster, subject to variation in five important system parameters. These include particle concentration, relative importance of the externally applied force, film thickness, film width and particle size. The threshold particle concentration can be reduced by increasing the strength of the deterministic driving force, decreasing film thickness, increasing film width or using smaller size particles. Our study suggests that using stronger applied force for wider and thinner films containing smaller particles may be a good practice to obtain anisotropically conductive films with a light particle loading that possess good conduction capability in the thickness direction and good insulation in the planar direction. Received: 19 February 2001 / Accepted: 30 May 2001 / Published online: 30 August 2001     

Enhanced dielectric constant resolution of thin insulating films by electrostatic force microscopy

Electrostatic force microscopy has been shown to be a useful tool to determine the dielectric constant of insulating films of nanometer thicknesses that play a key role in many electrical, optical and biological phenomena. Previous approaches have made use of simple analytical formulas to analyze the experimental data for thin insulating films deposited directly on a metallic substrate. Here we show that the sensitivity of the EFM signal to changes in the dielectric constant of the thin film can be enhanced by using dielectric substrates with low dielectric constants. We present detailed numerical calculations of the tip-sample electrostatic interaction in the following setup: an insulating thin film, a dielectric substrate (or spacing layer) of known low dielectric constant and a metallic electrode. The EFM sensitivity to the dielectric constant increases with the thickness of the spacing layer and saturates for thicknesses above 100-300 nm, when it is close to that of an infinite medium.     

Actuation behavior of waterborne polyurethane/conductive filler nanocomposite electrode

This study dealt with the Maxwell stress effect of waterborne polyurethane (WPU)/conductive filler nanocomposite, which was a promising candidate for a material to be used in a dielectric elastomer actuator electrode. Conductive nanocomposites were produced by using three types of conductive filler: carbon black (CB), vapor grown carbon fiber (VGCF), and silver powder (Ag). Among them, conductive nanocomposite containing VGCF exhibited the lowest threshold concentration; and the mixture of CB and VGCF (CB/VGCF) filler had a synergistic effect to electrical conductivity. Actuation test revealed that CB/VGCF nanocomposite electrode had the largest displacement. Then it could be stated that the improvement of the displacement in CB/VGCF nanocomposite electrode originated from the increase in relative dielectric constant. In addition, a unique feature for the hysteresis of bending deformation was observed. This feature is that the prior application of an electric field significantly improves the bending speed in the successive application. Also, the effect of electrode thickness on the displacement and breakdown strength was examined.     

非聚焦电子束照射SiO2薄膜带电效应

采用考虑电子散射、俘获、输运和自洽场的三维数值模型, 模拟了低能非聚焦电子束照射接地SiO₂薄膜的带电效应. 结果表明, 由于电子的迁移和扩散, 电子会渡越散射区域产生负空间电荷分布. 空间电荷呈现在散射区域内为正, 区域外为负的交替分布特性. 对于薄膜负带电, 电子会输运至导电衬底形成泄漏电流, 其暂态过程随泄漏电流的增加趋于平衡. 而正带电暂态过程随返回二次电子的增多而趋于平衡. 在平衡态时, 负带电表面电位随薄膜厚度、陷阱密度的增大而降低, 随电子迁移率、薄膜介电常数的增大而升高;而正带电表面电位受它们影响较小.     

Electric charge of a lightning ball

The electric charge of a lightning ball is found by comparing the electrohydrodynamic stabilities of a charged drop in an electrostatic suspension and a lightning ball floating in a superposition of the gravitational field and the surface electric field. It has been assumed that the electric field strength at the surface is limited by a breakdown value. For a lightning ball radius of 15 cm, its charge is estimated as several microcoulombs. Accordingly, the density of electrostatic energy accumulated in the lightning ball is on the order of one-hundredth of a joule per square centimeter. The density of the material that constitutes the lightning ball has been estimated for the case when the electric field strength at the site of its origination is several times higher than that in fine weather. The density of the lightning ball turns out to differ from that of air by only a few percents.     

Nonlinear optical properties of composites based on conductive metal-alkanoate liquid crystals

The dynamic holography in new composite materials based on a novel class of metal-alkanoate ionic liquid crystals (ILCs) is studied experimentally and theoretically. The composites are formed as a dielectric dye film covered by lyotropic metal-alkanoate ILC and ionic smectic glasses with doped dye molecules. The dynamic gratings are created by nanosecond pulses of double frequency Nd:YAP laser, the recording demonstrates fast erasure time of residual thermal gratings. The nonlinear optical properties are determined by the resonance nonlinearity in photosensitive centres of ILC. Note, that permanent relief gratings will be formed on a dielectric dye film only as well as in composite cells either with nematic LC or with polymers under action of pulsed laser radiation. Lyotropic ILC layer applied over the dye film provides the dynamic regime of grating recording in composite cells. We found a secondary thermal grating is much smaller, the conductive ILC matrix provides effective heat dissipation and erasure of this thermal grating. A theory of Raman-Nath self-diffraction holography on thin films followed from the wave equation and the nonlinear mechanism of absorption saturation is developed to explain experimental results.     

静电场模拟描迹实验的误差分析和仪器改进

静电场模拟描迹实验是大学物理实验中非常典型的一个实验,在该实验中,误差的主要来源有探针的不同步,导电介质的导电性,电压表内阻等。本文通过描绘同轴圆柱电极板的等势线分布图,定量的研究了以上几种误差来源对实验结果的影响,找出了最佳的实验条件,并对实验仪器进行了改进,大大降低了实验的误差。     

The interfacial effects on the conductive performance of the composite films based on materials with electron and ionic conductors

Laminated and blending composites are designed to study the interfacial effects on the overall conductivity based on materials with different conductive mechanisms. The blends exhibit porous morphology because of the phase separation among the components, providing lager contacting areas between polymer chains and ions, and also more moving spaces for them, and hence their conductivity increases with the addition of polyaniline (PAN) to a maximum value of 0.075?S?cm^?1 at 75% PAN of polyvinyl butyral (PVB) (wt.%). The laminated films also show conductivity improvement, but inferior to that of blends from room temperature to 60?°C. The element parameters of the interfaces have great effects on their conductive performances as tested by the electrode/solid polymer electrolytes (SPE)/electrode model. The values of the electrode/SPEs interface are in the same magnification, while the value between PAN and PVB/polyethylene glycol₄₀₀/LiClO₄ layers is much bigger than those of the electrode/SPEs, providing the fact that the interface effect between different materials (metal/polymer, polymer/polymer) plays a vital role in determining their overall conductive performances.     

球透镜的衍射焦斑强度分布研究

根据国内外光通信耦合器件发展的趋势,研制了一种新型玻璃,依靠液体表面张力的作用,首次采用槽沉法来制备球透镜,得到了理想的效果。通过对直径为0.8mm的球透镜的焦斑强度分布进行研究,结果表明:当通光孔径分别为0.2mm,0.4mm和0.8mm时,球透镜的衍射焦斑强度的分布分别为0.2μm,0.4μm和1.0μm。因此,伴随着通光孔径的增加,球透镜的衍射焦斑强度分布增大,衍射的强度减小。     

Electrostatic precipitation in wire-to-cylinder configuration: Effect of the high-voltage power supply waveform

The purpose of this paper is to study the effect of the high-voltage power supply waveform and the presence of a dielectric barrier on the collection of submicron particles in a wire-to-cylinder electrostatic precipitator. The experiments are carried out on two reactors (with or without dielectric barrier on the surface of the cylindrical collector electrode) with the same active section and volume. The results show that the highest collection efficiency is obtained with the negative dc corona. At equivalent electric power consumption, the Dielectric Barrier Discharge (DBD) is as effective as the positive dc corona and the ac corona. The efficiency can reach 99% with both studied reactors, if the necessary power is provided.     

Measurements of air discharges from insulating,electrostatic dissipative and conductive materials with different ESD probes

In this work, we have compared the performance of three different kinds of passive resistor-transmission line ESD probes: an unshielded ball probe, a shielded ball probe with the ESD current collected on a coaxial wire tip, and a needle-like probe. We have measured discharges from ESD sources having different surface resistivities including charged insulator surfaces, electrostatic dissipative materials and metal plates. In compliance with the results, there is no single probe type that is ideal for all kinds of situations—there are significant differences between the probe responses comprising sensitivity, charge transferred and peak ESD current. As expected, the initiation of air discharges was suppressed in accordance with increasing surface resistivity of the ESD source.     

Numerical simulation of conductive particle behaviour at the surface of a plate electrode affected by a DC corona field

The electric field in certain electrostatic devices can be modeled by a grounded plate electrode affected by a corona discharge generated by a series of parallel wires connected to a DC high-voltage supply. The system of differential equations that describe the behaviour (i.e., charging and motion) of the conductive particle in such an electric field has been numerically solved, using several simplifying assumptions. Thus, it was possible to investigate the effect of various electrical and mechanical factors on the trajectories of conductive particles. This model has been employed to study the behaviour of coal particles in fly-ash corona separators.     

The Casimir effect in a solid ball when εμ = 1

The Casimir surface force density on a solid ball is calculated assuming that the medium satisfies the relationship εμ = 1, ε being the permittivity and μ the permeability. Remarkably enough, the cutoff problems which otherwise plague calculations of the Casimir stress on dielectric nonmagnetic balls disappear, and one arrives at a cutoff independent, finite, and repulsive result for the force. When μ → 0 or μ → ∞ one finds exactly the same result as in the case of a perfectly conducting shell. Another virtue of the theory is that one may avoid the subtraction of contact terms, as the contact terms are simply vanishing. Finally, the theory is immediately applicable to a gluonic (nonquark) bag in QCD, assuming no gluonic interaction. The surface force in QCD becomes repulsive, just as in QED.     

Redesign of a soft conductive rubber strip electrode for measurement of surface resistance according to IEC 60079-32-2 within the context of the PTB Ex Proficiency Testing Scheme

To ensure worldwide quality and homogeneity in the field of explosion protection, not only uniform rules in the form of IEC standards but also the active participation in interlaboratory comparisons are necessary. The “PTB Ex Proficiency Testing Scheme” is the first global proficiency testing program of its kind in the field of explosion protection. It serves as proof of competence and provides laboratories with a complete system for their own performance evaluation.In 2015, the program “Electrostatic Charge - Test Round 2015” was launched within the PTB Testing Scheme. The participants of the program performed surface resistance and transferred charge tests according to IEC 60079-0 and IEC 60079-32-2 on various types of test samples. The new standard IEC 60079-32-2 proposes different kinds of electrodes for the user, such as conductive silver paint electrodes, soft conductive rubber strip electrodes on spring-mounted metal tongues or conductive foam strips mounted on an insulating support, depending on the geometry of the sample. These different types of electrodes as well as the construction latitude for each electrode could lead to deviations between the results of different test laboratories due to better or worse electrode contact with the test sample.Therefore, the proficiency team and electrostatic experts at PTB decided to design an accurate and user-friendly electrode which meets the requirements of IEC 60079-32-2. This paper provides information about the electrodes' design as well as the results of comparable measurements.     

Synthesis and conductive properties of nanoisland Sn,Al, and Cu films

Nanoisland Sn, Al, and Cu films were synthesized on dielectric substrates and their morphology and conductive properties were investigated. It is shown that the initial effective film thickness significantly affects the morphological parameters of nanoislands. Study of the surface conductivity of the films at the condensation stage revealed the conductivity drop after termination of the deposition, which is related to the nanostructuring processes. It was found that the temperature dependences of the film conductivity include three portions: the low-temperature portion of the activation growth, the decrease upon nanostructuring, and the high-temperature portion of the activation growth.     

光电反馈式静电悬浮的机制研究

本文主要讨论光电反馈式静电悬浮的理论问题。研究在静电场作用下导电悬浮体的静电感应机制和绝缘悬浮体的静电极化机理,推导出悬浮体表面的感应电荷或极化电荷的计算公式,以及作用于悬浮体上的静电悬浮力的计算公式,在理论上揭示了静电力与电极电压、电极面积、悬浮间距及悬浮体电学特性等因素之间的关系。结果表明,导电悬浮体表面的感应电荷量比绝缘悬浮体表面的极化电荷量多,因此前者所受的静电悬浮力比后者大,但两者均可实现静电悬浮,这些结论与实验结果完全符合。本文工作为实现静电悬浮的光电反馈控制提供了理论依据。     

Forces and charges on a slightly deformed droplet in the DC field of a plate condenser

A conducting drop in partial wetting on the lower electrode of a plate condenser and surrounded by a dielectric fluid is considered. When a DC field is applied the drop, acquiring electric charges, is subjected to an electrostatic force normal to the electrode. The force exerted on undeformable drops was previously calculated. In this paper, the distortion from a spherical shape is asymptotically calculated at low electric Bond numbers to generalize previous developments. A mechanism is proposed to explain the drop detachment, leading to an electrical field strength threshold. Some experiments were performed confirming the mechanism.     

不同电极结构下介质阻挡放电电离特征的试验研究

由于具有工作气压高、放电均匀等特点,大气压介质阻挡放电成为近年来非平衡等离子体领域研究的主要技术。电极结构是电离特性的主要影响因素之一,因此,通过电极结构优化来改善电离特性,对等离子体放电设备的应用领域拓展及性能优化至关重要。为改善大气压介质阻挡放电的电离特性,产生高活性、高均匀性的低温等离子体,基于自主设计的同轴介质阻挡放电装置进行了不同电极结构的电离试验及参数诊断;在一个标准大气压、放电频率11.4 kHz、放电峰值电压5.4～13.4 kV条件下进行了氩气电离试验;采用原子发射光谱法（AES）对氩等离子体谱线的激发、分光进行了检测分析;研究了螺纹电极、齿状电极、圆柱电极放电的特征光谱参数及外施电压对介质阻挡放电特征参数的影响。结果表明,齿状电极放电所形成等离子体的放电强度更大且放电效果显著,电子平均能量利用率低,电子激励温度弱于圆柱电极;圆柱电极放电强度较弱,但易形成大面积均匀性等离子体;大气压环境下电子激励温度不因外源电压的升高而单调递加,这表明通道内微放电的主要特征并不依赖于外施电压的供给,而是取决于电极结构、气体组份、气体压强;增大外施电压仅能增加单位时间内微放电的数量,经整合电子激励温度可达3 500 K,符合典型的低温等离子体特征。     

Self-consistent calculation of electrostatic force for two kinds of mesoscopic surface structures

The scanning electrostatic force microscopy (SEFM) can acquire information of surface structures in a non-contact way. We calculate the electrostatic force between the charged tip and polarized surface structure in SEFM in the framework of self-consistent integral equation formalism (SCIEF), incorporating the image method to treat the electrostatic coupling of substrate and tip. We consider two kinds of surface structures, one is the topographic structure on the surface, the other is the dielectric structure embedded in the substrate. The force pattern of the topographic structure shows a protrusion around the surface structure. However, the force pattern displays a hollow around an embedded structure with a dielectric constant less than that of substrate medium. For an embedded structure with a larger dielectric constant, the force pattern exhibits a protrusion, and the force signal is much weaker than that of the topographic structure. Therefore, it is expected that one may identify these surface structures from the pure electrostatic force information in SEFM. The force signal of the densely arranged dielectric pads is simply the superposition of force signal of each pad individually, the interference effect of electric field is not remarkable. Received: 26 March 1998 / Accepted: 9 June 1998