Electrical Equivalent Circuit Analysis Research Articles

Corrosion assessment of passivation film generated on solder surface in artificial sweat solution

As the electric joint, the reliability of solder alloy is very important for the circuit card. Since the corrosion might lead to the failure of solder, various characterization methods have been used to assess the corrosion property of Sn-0.7Cu solder alloy in artificial sweat such as the potentiodynamic (PD) polarization, the potentiostatic (PS) polarization, the electrochemical impedance spectroscopy (EIS) and Motty-Schottky (MS) measurement. The EIS results showed that the passivation film owns better barrier properties in alkaline artificial sweat solution. The analysis of electrical equivalent circuit suggested that the passivation film resistance in alkaline solution is two orders of magnitude higher than that in acid solution, which were also supported by MS measurement. The better barrier properties of intact passivation surface contributed to corrosion resistance in alkaline artificial sweat solution. After a typical PD polarization process, the scanning electron microscope (SEM) with energy dispersive spectrometer (EDS) has been employed to characterize surface morphology and chemical composition of passivation surfaces. This work can provide some suggestions for the personalized design of wearable devices by considering the sweat corrosion effect.

Mechanistic analysis of anodic dissolution of cobalt in alkaline glycine solution

The kinetics of dissolution of Co in alkaline glycine solution under anodic conditions was investigated. Potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) data of Co dissolving in 0.1 M glycine solution at pH 10 were acquired. At low overpotentials, in the active region, the polarization current increases with potential, whereas at high overpotentials, in the passive region, it decreases with potential. Co surface exposed to the alkaline glycine solution was characterized using scanning electron microscopy and x-ray photoelectron spectroscopy, and based on the binding energies of the deconvoluted peaks, oxides, hydroxides, and Co-glycine complexes were identified as the likely species present on the surface. Impedance data was subjected to electrical equivalent circuit analysis, and a circuit with three Maxwell elements was found to model the faradaic impedance. Polarization and EIS data were also analyzed in the framework of mechanistic analysis, and a mechanism with four adsorbed intermediates is proposed. The proposed model captures the salient features of the polarization and EIS results.

Applicability of Electrical Equivalent Circuit Analysis Based on Voigt Model to Electrochemical Degradation Diagnosis of Heavy-duty Coating on Inner Surface of Oil-strage Tank and its Validation Using Depth Profile Analysis by IR and Raman Spectroscopy

Applicability of Electrical Equivalent Circuit Analysis Based on Voigt Model to Electrochemical Degradation Diagnosis of Heavy-duty Coating on Inner Surface of Oil-strage Tank and its Validation Using Depth Profile Analysis by IR and Raman Spectroscopy

Influence of Water on the Interface between Hydrophilic Ionic Liquid and Single Crystal Bismuth Electrodes

Ionic liquids (ILs) as solvent-free electrolytes are new favorites for interfacial chemistry as well as for many other potential applications in electrochemical systems, such as supercapacitors, solar cells, fuel cells and secondary ion batteries. One of the main advantages of ILs is the good electrochemical stability. Differently from the hygroscopic, bulky ILs, many ILs are completely miscible with water, conventionally defined as hydrophilic. As an inevitable impurity, water has a strong effect on the surface of ILs within the electrochemical stability region where condensation of water molecules is dependent on applied potential [1-2]. The electrochemical faradic processes at the interface affect both charge transfer and energy storage processes. Those prompt us to focus on the interaction of ILs and water at electrified electrode interface, and the formation kinetics of the electrical double layer (EDL). Adsorption of particles, such as molecules or ions, contributes to the variety of EDL structure at ionic liquid│electrode interface. Halide ions, namely chloride, bromide and iodide, have been studied as part of a group of strongly adsorbing anions to form a dense layer at Bi(hkl) electrodes [3-4]. Electrosorption of water on electrode surface depends not only on the water-ion interaction, but also on the water-eletrode interaction [2]. To further explore the interaction mechanism of water molecules at electrified electrode interface, classical electrochemical methods (cyclic voltammetry and electrochemical impedance spectroscopy) as well as in situ scanning tunneling microscopy (STM) method have been applied to study the effect of water on the interfacial structure of ionic liquid 1-ethyl-3-methylimidazolium trifluoromethylsulfonate (EMImOTf)│Bi(hkl) interface. Single crystal bismuth electrodes as working electrodes have variable electronic properties and surface structure. Electrical equivalent circuit analysis derived from impedance data has been applied to characterize the interfacial processes [3]. The fitted data double layer capacitance (Cdl ) has a good agreement with the series capacitance (Cs ) at lower frequency, suggesting relative sluggishness of dried IL system. Compared with dry EMImOTf, systems with up to 0.1wt% water additive have a pronounced peak in Cdl vs. potential curves, observed within less negative potential region, showing that water has a much stronger interaction with IL anions than with the cations. OTf⁻ anions combined with aliphatic imidazolium cations are generally thought specifically adsorb at metallic electrodes due to the presence of sulfonyl groups. The different metallic properties of bismuth single crystal planes also show a difference in capacitive behavior. Other parameter, such as charge transfer resistance (Rct ) reveals how water adsorption process varies with applied electrode potential. The in situ STM results show that there are no surface reconstruction processes at Bi(111) surface within the studied polarization range. It should be noted, however, that for other single crystal planes surface reconstruction process are observed by varying the applied potential value, being affected by both anion adsorption and water content. Acknowledgements This work was supported by the Estonian Ministry of Education and Research (projects no. IUT 20-13, PUT1033, PUT1107 and PSG 249) and Estonian Centres of Excellence project TK141.

Application and Simplification of Cell-Based Equivalent Circuit Model Analysis of Electrical Impedance for Assessment of Drop Shock Bruising in Japanese Pear Tissues

This study was conducted with the objective of applying cell-based electrical equivalent circuit analysis for the assessment of bruising of tissues in Japanese pears after drop tests, as well as to simplify the analysis. The equivalent circuit analysis of electrical impedance values was conducted on the bruised regions of the pear tissues. The analysis showed that the resistance of the protoplasm of the injured tissues slightly increases, and the capacitance of cell membranes and the resistance of apoplastic fluids significantly decrease. Thus, it was theorized that these parameters are influenced by cell membrane destruction. Further, it was found that Cole-Cole plot parameter obtained from the frequency characteristics of the impedance of the tissues can express changes in the apoplastic fluid resistance. These results show that equivalent circuit analysis can be used to assess bruising of pear cells caused by drop shock, and the analysis can be simplified using Cole-Cole plots. We expect these results to aid in the development of physical damage assessment methods for distributed fruits.

Micro Electrical Impedance Spectroscopy (μEIS) Fabricated on the Curved Surface of a Fine Needle for Biotissue Discrimination

AbstractThis work presents a novel micro electrical impedance spectroscopy (μEIS) technique that can measure and discriminate the electrical signal responses of biotissues in real time. An EoN (EIS‐on‐a‐needle), EIS on the surface of a fine needle (400 μm in diameter), was fabricated using a newly developed flexible photomask film. The base material of the photomask is parylene‐C, which allows uniform contact on the curved surface of the needle; thus, the designed electrode patterns of the photomask can be transferred onto the needle surface with a high resolution (2.95 % or less in dimensional error). To validate the developed EoN as an electrical sensor, ex vivo experiments with various biotissues—butchered pork (skin, fat, and muscle) and human breast tissues (normal and cancerous)—were conducted by measuring real‐time electrical impedance during a frequency sweep. The conductivities (relative permittivity) of the pork tissues were evaluated by electrical equivalent circuit analysis: 56.6 mS/m (37,800), 68.0 mS/m (74,755), and 74.9 mS/m (26,145) for the skin, fat, and muscle, respectively. Moreover, the normal and cancerous tissues were well distinguished by electrical resistance at 4.04 kHz for various cancer grades (Elston grades 1, 2, and 3). Analysis of the electrical impedance suggests that the EoN can be utilized to diagnose the physiological states of biotissues in clinical use.

Constant-Phase Element Characteristics Caused By Resistivity Distribution in High Performance Anti-Corrosion Organic Coating Applied to Oil Storage Tank

The internal bottom plates of oil storage tanks are exposed to a corrosive neutral electrolyte solution containing chloride ions and oxygen that are enough to cause severe corrosion. For this reason, the steel plates are generally coated with a heavy-duty coating aims to isolate the steel substrate from the corrosive electrolyte. Since the coating has exceptional durability, the visual defects of the coatings in many oil storage tanks are almost undetected in spite of a long period of use (i.e. over twenty years). On the other hands, it is supposed that the barrier properties of the coatings decrease due to the electrolyte solution uptake. For appropriately maintaining the coatings, an evaluation method for the visually non-defective coatings are required. Since impedance measurements [1][2] are suitable for the evaluation of visually non-defective coatings, they have attracted much attention as a method for the quantitative evaluation of the coatings applied to oil storage tanks. However, the clarification of the degradation process of the coating, which is needed for the electrical equivalent circuit analysis, has not been achieved. It is important to interpret the electrical property of the coating sufficiently for the sensitive evaluation of extracting time-constant components. According to Van Westing et al. [3], the impedance characteristics of a high performance anti-corrosion organic coating are interpreted by CPE (constant-phase element). Therefore, it is suggested that the CPE is a useful circuit element to evaluate the impedance of the coatings on the internal bottom plates of oil storage tanks. However, there is possibility that the analysis of an impedance spectrum by using the CPE causes the ambiguity of the physical interpretation in an experimental object. Thus, it is necessary to evaluate the anti-corrosion performance of the coating considering the cause of the CPE behavior in the impedance spectrum. In this study, the anti-corrosion performance of the coating applied to an actual oil storage tank is evaluated by using impedance measurements. The CPE behavior of the coating is explained based on the distribution of the coating resistivity along the thickness. The field impedance data was obtained by the two-electrode impedance measurement setup, as shown in Figure 1. The impedance spectra were obtained over a frequency range from 200 Hz to 10,000 Hz with a 1 Vp-psinusoidal potential. Figure 2 shows the representative impedance spectrum in the obtained data. The fitted curve analyzed with the electrical equivalent circuit consisting of a parallel combination of the CPE and the resistance R pcorresponding to conductive pathways [1] are noted in the figure as dotted lines. The fitted curve was in good agreement with the field data, as can be seen Figure 2. Thus, the impedance spectrum can be interpreted by using the CPE. In subsequent discussions, this CPE behavior is explained by the distribution of the coating resistivity according to a power-law along the thickness, which results from an electrolyte solution permeation in the coating [4][5]. The obtained results in this study will contribute the establishment of an evaluation method for heavy-duty coatings. Acknowledgement: This research was performed with financial support from Japan Oil, Gas and Metals National Corporation.

Analysis of Flip Chip Bonding for Performance Stability of UHF RFID Tags

Thermocompression bonding is one of the most important procedures in radio frequency identification tag fabrication because the electrical and mechanical properties of the joint greatly influence the overall tag performances. The characteristics of the joint are determined by the alignment between the microchip and antenna pads, the adhesives used, and various bonding parameters (temperature, pressure, and time). This paper uses an electrical equivalent circuit analysis, electromagnetic full-wave simulations, and environmental tests to investigate the factors that influence the reading performance of the flip chip bonding process. First, based on an equivalent circuit analysis of the bonded tag, the effect of the parasitic impedance on impedance matching and power transfer is analyzed. The parasitic impedance is then estimated by comparison with the measured impedance of the bonded chips. Second, we investigate the variation in the reading performance of the tag when various geometrical errors are generated at the joint between the microchip and the antenna. Finally, the bonding parameters for stable reading performance are studied by completing environmental tests. The results provide useful information for achieving stable reading performance of tags in flip chip bonding.

The influence of the PANI structure on the conductive mechanism and on the electrical equivalent circuit analysis

The influence of the PANI structural changes during the oxidation of PANI on conductive mechanism and on the electrochemical impedance analysis was investigated. The results obtained by the electron spin resonance (ESR), Raman spectroscopy, ac electrogravimetry and probe beam deflection were used to explain the influence of the PANI structural changes on conductive mechanism. It was explained that the ingress of water molecules that occurs in the potential region of the current peak A, has an important influence on the PANI structure i.e., the PANI chain stretching process. The water molecules increase the distance between the positive charge (polaron) and the negative charge (counter-ion), which facilitates the potentially dependent PANI chain stretching process. The increase in opposite charge distance was explained to be crucial for the process of PANI chain stretching i.e., the chain is transformed from coil type to expanded coil type chain. The influence of the stretching process to the ESR signal properties was commented. It was explained that a decrease in the interaction between polarons, which was promoted by the stretching process, leads to the narrow ESR signal. The influence of structure and/or PANI chain ends on polaron to bipolaron transition was clarified. It was found that the polaron to bipolaron transition is hindered in the condition when the thicker PANI layer is investigated, which leads to greater structural disorder and/or the higher population of the chain ends. The calculated experimental impedance response of the different thickness PANI layers was successfully used in the EIS analysis. The correlation between the PANI structure and physical meaning of EEC parameters was effectively applied to approve or disprove the application of the proposed electrical equivalent circuit (EEC). The structural PANI changes and the EEC analysis of impedance data were used to test the proposed method that examines the interaction of the χ 2-value and obtained EEC parameters, which are related to the PANI structure properties. The proposed method discarded EEC, which resulted in the lowest χ 2-value, from the further analysis due to different trends of experimental and simulated data presented in the low frequency region of Nyquist spectra. In addition, the proposed method rejected EEC from further analysis if its parameters have not shown the correlation with the changes in the PANI structure. The presentations of data in Bode and admittance spectra were found to be especially useful when investigating systems that have pronounced capacitive behavior in the low frequency region.

Impedimetric sensing of cells on polypyrrole‐based conducting polymers

Polypyrrole (PPy) is a conducting polymer that may be electrochemically generated with the incorporation of any anionic species, including net-negatively charged biological molecules such as proteins and polysaccharides. In this article, dermatan and chloride-loaded PPy films were prepared on gold sputter-coated coverslips and various skin derived cells were studied on them by electrochemical impedance spectroscopy. Impedance spectra in the frequency range 1-100 kHz were either determined at specific times or impedance was monitored continuously at specific frequencies. An equivalent impedance circuit was fitted to the recorded impedance spectra to obtain parameters whose contributions could be mapped to intracellular and intercellular current pathways, and the membrane properties of cells. Results show cell-induced impedance changes were detected over PPy modified electrodes and were dependent on cell density and type, monitoring frequency, material composition, and treatment. Lower cell densities were detected on PPy when compared with bare gold. Keratinocyte confluence, as determined by impedimetric analysis, was reached more rapidly on PPy than on gold. This was consistent with previous, more cumbersome, biochemical assays. Electrical equivalent circuit analysis provided evidence that the technique may be extended to discriminate cell type because of the intracellular and intercellular resistance, and cell membrane capacitance being related to cell morphology.

Revolving-field polygon technique for performance prediction of single-phase induction motors

This paper presents a new analytical technique for improving the performance prediction of single-phase induction motors, especially capacitor motors. The technique uses the split-phase motor electrical equivalent circuit analysis together with electrical and magnetic parameters whose variation is computed from the equivalent balanced polyphase motor, so that the same magnetic circuit analysis can be used for both. (The term split-phase is used to cover motors operating from a single-phase supply but with the phase windings split into two orthogonal windings, one of which may have a capacitor in series with it during running or starting.) The technique accounts for the elliptical envelope of the magnetizing field vector and results in improved precision, since the three-phase electromagnetic model is considered to be more precise than the normal split-phase motor analysis. An important result is the computation of vector polygons of flux density for each section of the magnetic circuit, providing a better basis for core loss prediction. The double-frequency torque ripple is also obtained from the stator magnetomotive force and flux-density polygons. Three different electrical equivalent circuit methods for the split-phase motor (based respectively on the cross-field theory, forward- and backward-revolving fields, and symmetrical components) are evaluated to determine the method best suited for incorporating the variation of the circuit parameters from the polyphase magnetic circuit analysis, and it is discussed how the core losses can be included in these circuits to obtain the best overall performance prediction.

A new disc-type ultrasonic motor

Abstract A new approach to establish a design rule for a new disc-type ultrasonic motor (LEMUM) is proposed. In this design rule, an elastic model of lateral elliptical motion induced by exciting piezoelectric ceramics embedded on an elastic metal disc is setup to estimate the frictional driving force between the rotor and stator of the ultrasonic motor. Furthermore, we evaluate the coupled interaction between mechanical vibration and electrical excitation by electrical equivalent circuit analysis. For the confirmation of the proposed design rule, we measure the characteristics of the new disc-type ultrasonic motor. As a consequence, the proposed design rule is very adaptive for disc-type ultrasonic motor.

Analysis of electrical equivalent circuit of quartz crystal resonator loaded with viscous conductive liquids

An electrical equivalent circuit of quartz crystal resonator (QCR), with modified electrodes, loaded with a viscous conductive liquid is proposed. The electrode in contact with the liquid is modified so as to create an unmetallized crystal surface in contact with the liquid and thus to introduce an acoustoelectric interaction at the crystal | liquid interface. The admittance—impedance characteristics of the equivalent circuit of the loaded QCR are analyzed to obtain expressions for the changes in the series and parallel resonant frequencies in terms of the liquid viscosity η L, density ϱ L, dielectric constant ϵ L, and conductivity σ, as well as the quartz parameters and electrode area geometry. Using a network analyzer, the S parameters of the equivalent circuit of various conductive liquid-loaded QCRs are measured and analyzed. It is shown that in addition to being a well-known detector of mechanical properties of liquids, a QCR, when properly designed, can be used to monitor the electrical properties of dilute ionic solutions.

障害波遮断変圧器に関する基礎的検討

A fundamental study of noise reduction transformers is discussed. Such transformers have a filter function for line noise. We prepared three kinds of transformer: a noise reduction transformer, a constant voltage transformer, and a conventional power transformer. In this paper, we discuss the characteristics of noise attenuation of these transformers, determined by experiment and by electrical equivalent circuit analysis utilizing SPICE, to determine a method for the optimum design of the noise reduction transformer.