Variation Of Contact Resistance Research Articles

A comparative study on the electrical contact behavior of CuZn40 and AgCu10 alloys under fretting wear: Effect of current load

The current load is one of the most significant factors in the reliability of electrical contact under fretting conditions. In this paper, the fretting wear experiments are conducted for CuZn40 and AgCu10 alloys with varied current loads. The variations of electrical contact resistance (ECR), ECR endurance, temperature, and wear volume with the increasing current load of two alloy materials under fretting conditions are investigated, and the differences between their electrical contact behaviors are compared. The microstructures of the surface wear morphology are examined to reveal the mechanisms of fretting wear and electrical contact failure. In addition, the fretting wear volume evolution of both alloys under different fretting cycles is studied. The results show the current load impacts the wear morphology. The wear particles become smaller and the oxide layer becomes stable with the increase of current load. The effect of current load on ECR and temperature is more significant for CuZn40 alloy. The ECR endurance for both materials first increases and then decreases. This is attributed to two competitive mechanisms controlling the evolution of ECR endurance under varied current loads.

Design Technology Co-Optimization for the DRAM Cell Structure With Contact Resistance Variation

Design Technology Co-Optimization for the DRAM Cell Structure With Contact Resistance Variation

Reliability of Bolted Aluminum Busbars for Battery Systems: Effect of Nickel Coating and Corrosive Environment

Bolted busbar connections are a simple and versatile connection method used in battery systems. Copper busbars are widely used for such bolted connections; however, aluminum offers the potential to save weight and cost. To date, the reliability of aluminum connections dimensioned for battery systems and the vulnerability to corrosion accelerants is not established. In this study, bolted aluminum connections were tested under operational and environmental conditions applicable to battery systems. Four bolted configurations (AA1070 and AA6101, with nickel plating or brushed contact surfaces) were exposed to corrosive environments and current-induced thermal cycling. Nickel plating provided a robust contact interface that maintained stable resistance over 6000 cycles across three temperature levels. The nickel plating’s electrical performance was unaffected by the corrosive environments, including humidity, salt mist, and hydrogen sulfide exposure. The brushed aluminum configurations produced connections with greater contact resistance variation and achieving a joint performance factor < 1.5 was critical for long-term reliability. The growing appeal of aluminum in battery systems requires verification methods capable of assessing new contact configurations. Currently, corrosion test environments for evaluating aluminum contacts are lacking in the literature. This study provides insights into the performance of bolted aluminum configurations dimensioned for battery systems and provides methodology for accelerated verification of new configurations.

Sensitive piezoresistive pressure sensor based on micropyramid patterned tough hydrogel

Microstructures are decisive factors of hydrogel-based piezoresistive pressure sensors for excellent performances in flexible electronics. However, the desirable microstructures are still difficult to be completely engineered on the surface of hydrogel, owing to limitations concerning to comprehensive mechanical performances of hydrogels. Herein, we prepared a type of piezoresistive pressure sensor by decorating pyramid microarrays on the surface of a tough and ionically conductive polyacrylamide (PAAm)/poly(vinyl alcohol) (PVA) hydrogel. To achieve high sensing behaviors, sizes and topologies of the recessed pyramid microarrays molded by three-dimensional (3D) printing photosensitive resin were investigated for elaborate fabrication of pyramid microarray hydrogel. The ionically conductive PAAm/PVA hydrogel of excellent comprehensive mechanical performances decorated with pyramid microarrays was able to generate large contact resistance variation to respond to external pressure, achieving a maximum sensitivity to 2.27 kPa−1, low detection limit of 9.0 Pa, as well as good recoverability and stability. Such tough and sensitive device based on micropyramid patterned tough hydrogel have potential applications in the fields of flexible electronics.

3-D coarse-grained reconfigurable array using multi-pole NEM relays for programmable routing

We propose the use of multi-pole nanoelectromechanical (NEM) relays for routing multi-bit signals within a coarse-grained reconfigurable array (CGRA). We describe a CMOS-compatible multi-pole relay design that can be integrated in 3-D and improves area utilization by 40% over a prior design. We then demonstrate a method for placing multiple contacts on a relay that can reduce contact resistance variation by 40× over a circular placement strategy. Additionally, we develop static and dynamic SPICE models (calibrated to accurate finite element models) for predicting circuit-level performance with these devices. Finally, we establish a methodology for integrating these relays into an industry-standard digital design flow. Using our multi-pole relay design, we perform post-layout simulation of a hybrid CMOS-NEMS CGRA processing element (PE) tile in 40 nm technology. We achieve up to 19% lower area and 10% lower power at iso-delay, compared to a CMOS-only CGRA PE tile. The results show a way to bridge the performance gap between programmable logic devices (such as CGRAs) and application-specific integrated circuits using NEMS technology.

Failure Analysis of Power Relays With Multiple Breaks in the Electrical Endurance Experiments

Multiple breaks are favorable for arc extinguishment of relays switching heavy load. However, the existed asynchronous mechanical separation of contact pairs and associated unbalanced arcing behavior limit the electrical lifetime to some extent. In this article, the typical contact voltage and contact current waveforms of double breaks within power relays are presented. Based on the variations in bounce energy, contact resistance, and arc energy as a function of switching cycles, the effect of contact gap on the electrical lifetime of power relays is analyzed explicitly. Furthermore, the failure process of power relays with two bridges is characterized by the recorded breaking time difference of bridges. The observed significant asynchronous breaking phenomena in the end of electrical lifetime experiments attribute to the contact welding failure of power relays.

Modeling Study of Commercial NCA Cylindrical Battery Cells’ Impedance Behavior Under Different Operation Conditions

The classic 18650 and 21700 format cylindrical Li-ion batteries have been widely used today to power electric vehicles (EVs). Their wound jelly-roll structure (in a form of an Archimedean spiral) can provide a relatively higher energy density in the limited EV given space comparing with the battery cells using stacked electrodes. As the rapid development and deployment of EV technology require high performance and reliable Li-ion batteries, it is critical to understand the mechanism and process behind battery cell behaviors under various driving conditions. In this study, a series of impedance experiments is designed to explore the impact of battery state of charge (SOC), temperature, C-rates and other operating conditions. Then, an impedance mathematical model is developed to explore the potential mechanisms behind experimental observations. Our obtained results show that the impedance response of cylindrical NCA battery cells varies with the state of charge in both charge and discharge operation, and the SOC dependent impedance existed in different operating temperatures and C-rates. Through modeling analysis, results indicate the operating temperature and charge-discharge rate could significantly influence the impedance response of the battery cell but could not directly cause the variation of the impedance response at different SOC conditions. Besides, modeling results also show that the contact resistance variation, resulted from the expansion and contraction of cell electrodes during charge and discharge, could lead to a SOC dependent impedance behavior of the commercial cell and influence battery output performance.

Impact of ambient temperature and thermal resistance on device performance of junctionless silicon-nanotube FET

In this article, a comprehensive analysis of the impact of electrothermal characteristics in the junctionless silicon-nanotube (Si-NT) field-effect-transistors is carried out using the Sentaurus TCAD. The combined study of the variation in thermal contact resistance (1 × 10−9 to 1 × 10−8 m2 W K−1), ambient temperature (300–400 K), and spacer length (5–20 nm) are performed. Significant improvements are observed in carrier temperature by 14%, lattice temperature by 13.7%, and gate leakage current from 0.787 nA to 0.218 fA due to the change in the spacer length. Further, a change in the drain current of 25.6% for thermal resistance (R th) and of 11.62% due to ambient temperature is observed. We also show that the junctionless device suffers significantly less from self-heating effects because of the electric field intensity, which is much lower in the channel region.

A study of dielectrics generated by electro-less electrochemical method for semiconductor devices

The aim of this work is to the basic concepts of the varies chemical and electrochemical procedures used m the fabrication of semiconductor devices seems to be useful to provide a suitable background for the present work, a brief review of the same as also the results obtained by earlier workers has been undertaken at the outset. A careful scrutiny of the results obtained by different workers reveals that although the aforesaid methods have a few limitations, they may be satisfice borily used as an alternative to sputter and evaporation techniques for device fabrication. The author carried out experimental investigations on the formation and properties of ohmic contact to silicon using two electroless plating baths - one operated at room temperature and the other at 95°C. In particular, the variation of contact resistance of ohmic contacts formed by electroless Ni-P process on silicon was studied as a function of sintering temperatures with operating point temperatures and pH of the baths as parameters. ^rom these studies it has been shown that both the baths yielded an adherent and dense deposit of nickel-phosphorous alloy on n-Si, which when sintered at very high temperatures give a less value of contact resistance due to the formation of metal-n -n contact. The phosphorous component of the Ni-P deposit diffuses into n-Si during heat treatment and forms the metal-n+ --n contact which behaves as an ohmic contact. As expected, the value of contact resistance was found to decrease with the increase of phosphorous materials in the deposit. The most favourable temperature range of heat treatment was found to be between 600°-700°C. Heats studying above 700°C slightly less increase the contact resistance probably due to the out diffusion of phosphorous from the Ni-P deposit. The barrier height and ideality factor are two important parameters for m-s contacts. The values of these two parameters of electrochemically fabricated Schottky diodes as obtained from the capacitance and current voltage characteristics were found to be in fairly close agreement with those of vacuumevaporated diodes. It is therefore, concluded that the electrochemical method of metal deposition is a valid and convenient technique for the fabrication and study of metalsemiconductor contacts

An Artificial Neural Network Model Based on Experimental Measurements for Estimating the Grounding Resistance

In grounding systems established in rocky and sandy lands where contact resistance with metal electrodes is high, contact resistance is generally the most critical parameter that changes the total grounding resistance value. Therefore, the nonlinear variation of the earth contact resistance according to the soil type cannot be taken into account in determining the grounding resistance with the traditional mathematical formulas given theoretically. This reduces the accuracy of grounding resistance determination. In this study, experimental measurements were made according to soil types and a data set was created. Then, to estimate the total grounding resistance of complex grounding systems, a classification was made using the multi-layer sensor (MLP) type ANN algorithm and the successful results were reported. Thus, according to the data set prepared based on experimental measurements, the proposed general classification algorithm approach can be applied to any grounding system. It presents a different technique from the previous literature as a pre-feasibility study for estimating the grounding resistance, especially before the grounding system installation, which is an early stage of the design process.

Effect of Curing Temperature of Epoxy Matrix on the Electrical Response of Carbon Nanotube Yarn Monofilament Composites

In order to evaluate the capability of carbon nanotube yarn (CNTY)-based composites for self-sensing of temperature, the temperature-dependent electrical resistance of CNTY monofilament composites was investigated using two epoxy resins: one that cures at 130 °C (CNTY/ERHT) and one that cures at room temperature (CNTY/ERRT). The effect of the curing kinetics of these epoxy resins on the electrical response of the embedded CNTY was investigated in prior studies. It was observed that the viscosity and curing kinetics affect the level of wetting and resin infiltration, which govern the electrical response of the embedded CNTY. In this work, the cyclic thermoresistive characterization of CNTY monofilament composites was conducted under heating–cooling, incremental heating–cooling, and incremental dwell cycles in order to study the effect of the curing temperature of the epoxy matrix on the electrical response of the CNTY monofilament composites. Both monofilament composites showed nearly linear and negative temperature coefficients of resistance (TCR) of −7.07 × 10−4 °C−1 for specimens cured at a high temperature and −5.93 × 10−4 °C−1 for specimens cured at room temperature. The hysteresis loops upon heating–cooling cycles were slightly smaller for high-temperature cured specimens in comparison to those cured at room temperature. A combination of factors, such as resin infiltration, curing mechanisms, intrinsic thermoresistivity of CNTY, variations in tunneling and contact resistance between the nanotubes and CNT bundles, and the polymer structure, are paramount factors in the thermoresistive sensitivity of the CNTY monofilament composites.

High-Voltage Wave Induced a Unique Structured Percolation Network with a Negative Gauge Factor.

Nanocomposite percolation networks have attracted increasing attention in the field of wearable devices. Generally, the large junction resistance caused by the small contact area in the percolation network is considered as the bottleneck in preparing high-performance electronics. In such electronics, an applied strain will lead to deformation on the fiber junction, subsequently increasing the sheet resistance. However, taking advantage of the dominant role of the contact resistance in the percolation network, the overall resistance of the network can be controlled by skillfully adjusting the contact area. Here, we designed a combined gold-polycaprolactone (Au-PCL) network with a unique buckling net structure. When the thickness of the gold nanolayer is 50 nm, the network shows typical percolation behavior with high transparency (93%), good conductivity (20 Ω/sq), and good ductility. Moreover, the networks show a unique positive relationship between the conductivity and strain due to the variation of contact resistance. By designing different waving angles, the network can be used as a dynamic strain sensor with a tunable gauge factor ranging from -0.8 to -1.8. Overall, these highly stretchable and transparent Au-PCL networks show promising applications in the field of high-performance electronic and optoelectronic nanodevices.

Contact resistance based tactile sensor using covalently cross-linked graphene aerogels.

A movable electrical contact between two materials is one of the most fundamental, simple, and common components in electronics that is used for binary control of a conducting path in an electrical circuit. Here, variable contact resistance between a highly elastic graphene aerogel and a rigid metal electrode is used for the analysis of non-binary pushing and pulling mechanical forces acting on the contact, enabling superior strain and pressure measurements. The variable contact resistance based electromechanical sensors demonstrate superfast, ultrasensitive and quantitative measurements of compressive and tensile stress from -1.18 MPa to 0.55 MPa. The sensors can operate over the temperature range of -60 to 100 °C, cover the whole skin and human motion range, and determine the weight of a grasped object. The measurement of such high forces has only been possible due to the high-temperature induced covalent cross-linking of graphene in the aerogel that provides high strength, durability, and fast response (<0.5 ms) to the sensing element. The study demonstrates the great potential of the contact resistance-controlled sensing, which enables high-precision and reliable measurement of strain and pressure over a remarkable large sensing range, providing new opportunities for applications in human-machine interfaces, robotics, flexible electronics, and haptic technology.

Study on thermal contact resistance of low melting alloy used as thermal interface material

The development of reliable electronic equipment is a big challenge due to miniaturization and performance characteristics of high speed and high power electronic devices. Thermal control is one of the key roles to meet the above challenge. Thermal Interface Material (TIM) plays a significant role in thermal control. TIM has been extensively used in diverse electronic devices for next generation electronics. To improve or enhance heat transfer performance at the interface region between copper substrates, Low Melting Alloy (LMA) Bi-Sn-Pb is usually used as TIM. In the present work, Thermal contact resistance (TCR) and Temperature variation by TIM is experimentally investigated. In the study, Bi39.4Sn30.8Pb29.8 is used as TIM material. The variation of TCR subjected to heat flow, variation of temperature between the interface and specimen thickness is reported and discussed.

Micro-Flexible-Surface Probe for Determining Spatially Heterogeneous Electronic Conductivity of Lithium-Ion Battery Electrode Films

Lithium-ion battery electrodes are generally made up of porous, thin films that are structurally heterogeneous on multiple length scales due to the manufacturing process. This in turn causes spatial variability in the electrical properties of the film. This work reports development of a low-cost, flexible probe for measurement of film conductivity and contact resistance to the current collector. When mounted on a moveable stage, the probe can quickly produce maps of electrode electrical properties at sub-millimeter resolution. Bulk conductivity and contact resistance are determined by inverting a 2D model of the experiment. The method is validated using a conductive silicone rubber placed on top of plain and corroded steel with significant contact resistance variation. Measurements on commercial quality electrode films, two cathodes and one anode, show statistically significant macro-variations in film properties perpendicular to the rolling direction and micro-variations throughout the film, variations that will impact electrode performance. The flexible-surface probe can be a significant tool to determine and minimize sources of variation in electrode manufacturing.

An Impedance Behavior Study of Commercial NCA Cylindrical Battery Cells at Different SOCs

The impedance behavior of a commercial Nickel-cobalt-aluminum(NCA) cylindrical cell was studied in this work. A series of impedance experiments was designed to explore the impact of battery state of charge (SOC) and other operating conditions. Our results indicated the impedance response of this cylindrical battery varies with the state of charge in both charge and discharge process. Experimental results also showed the SOC dependent impedance existed in different operating temperatures and C-rates. An impedance model was developed to explore the potential mechanisms behind experimental observations. Model results showed that the operating temperature and charge-discharge rate could significantly influence the impedance response of the battery but could not directly cause the variation of the impedance response at different SOC conditions. Results also showed that the contact resistance variation, resulted from the expansion and contraction of cell electrodes during charge and discharge, could lead to a SOC dependent impedance behavior of the commercial cell and influence battery output performance.

Noninvasive Measurements and FEM Analyses for Estimating the Rotor Bar-Lamination Contact Resistance

This research work investigates the phenomenon of interbar currents in induction motors equipped with die-cast aluminum cages. Flowing in the lamination and distorting the bar current distributions, the interbar currents cause additional stray losses as well as an increase of the joule loss in the cage bars. The contact resistance between the bars and the rotor laminations is the key modeling element for a correct prediction of the interbar currents and the related extra losses. The study presents a new noninvasive method to obtain a reliable estimation of the contact resistance. The proposed hybrid approach is based on a mix of experimental data and Finite Element method (FEM)-based simulation results. A reliable three-dimensional FEM model of a four-pole 15-kW induction motor with closed rotor slots has been used to investigate the impact of variable contact resistance on the interbar currents, rotor joule losses, and the voltage drops along the bars, opening a new perspective for this complex phenomenon and its impact on the stray losses. Finally, the proposed methodologies are critically discussed and the obtained results compared with other relevant research works.

Impact of receptacle degradation and loose connection on signal integrity and electrical performance repeatability

Radio frequency (RF) coaxial connectors are important constituents of modern communication systems. The degraded electrical contacts may adversely affect the signal transmission efficiency particularly in the case of loose connections. In this study, a distributed equivalent model of a coaxial connector with degraded receptacle and the loose connection was developed. The scattering parameters were analysed from the perspectives of both experimental testing and model simulation. The equivalent model and experimental results show good agreement. The impact of the degraded receptacle and loose connection on signal integrity was studied along with its electrical performance repeatability for different cases with respect to a degraded and loose connector. In addition, for the same degradation and loose level, the variation of contact resistance and contact capacitance was also investigated. These results are helpful for a better understanding of the intermittent failure of RF connectors. Moreover, these conclusions are also useful for diagnosing circuit faults caused by deteriorated repeatability of degraded and loose connectors.

Flexible Waterproof Piezoresistive Pressure Sensors with Wide Linear Working Range Based on Conductive Fabrics

HighlightsThe laser-engraved method was introduced to fabricate the electrode for the sensor.The sensor showed a wide linear working range, superior sensitivity, and fast response time and also exhibited excellent viability in a wet situation.Wireless integrated network sensors successfully monitored the health states.Developing flexible sensors with high working performance holds intense interest for diverse applications in leveraging the Internet-of-things (IoT) infrastructures. For flexible piezoresistive sensors, traditionally most efforts are focused on tailoring the sensing materials to enhance the contact resistance variation for improving the sensitivity and working range, and it, however, remains challenging to simultaneously achieve flexible sensor with a linear working range over a high-pressure region (> 100 kPa) and keep a reliable sensitivity. Herein, we devised a laser-engraved silver-coated fabric as “soft” sensor electrode material to markedly advance the flexible sensor’s linear working range to a level of 800 kPa with a high sensitivity of 6.4 kPa−1 yet a fast response time of only 4 ms as well as long-time durability, which was rarely reported before. The integrated sensor successfully routed the wireless signal of pulse rate to the portable smartphone, further demonstrating its potential as a reliable electronic. Along with the rationally building the electrode instead of merely focusing on sensing materials capable of significantly improving the sensor’s performance, we expect that this design concept and sensor system could potentially pave the way for developing more advanced wearable electronics in the future.

Ultrathin, Biocompatible, and Flexible Pressure Sensor with a Wide Pressure Range and Its Biomedical Application.

In this research, an ultrathin, biocompatible, and flexible pressure sensor with a wide pressure range has been developed and applied in biomedical applications. The pressure sensing mechanism is based on the variation of contact resistance between an electrode and a three-dimensional microstructured polyimide/carbon nanotube composite film. The sensor has a thickness of about 31.3 μm, a maximum sensitivity of 41.0 MPa-1, and a sensing range of 10-500 kPa. Moreover, in situ temperature measurement by an integrated resistive temperature detector enables data correction for varying temperature conditions. In order to show the advantages of the fabricated sensor, it is attached to the human body and integrated with the surface of a radiofrequency ablation (RFA) needle with small radius of curvature. In the experiments, the proposed pressure sensor measured subtle pressure levels (pulse pressure) and high pressure levels (fingertip pressure) without losing conformal contact with the skin. In addition, when the pressure-sensor-integrated RFA needle was inserted into a bovine liver, successful detection of steam popping phenomenon was observed.