Electrical Contact Performance Research Articles

Study on the Lumped Evaluation Model of Sliding Electrical Contact Performance of Railgun

The sliding electrical contact performance of electromagnetic railgun is the main factor affecting the launch accuracy, launch efficiency, and working life of electromagnetic railguns. The research on the evaluation of sliding electrical contact performance of electromagnetic railgun is crucial for the research of electromagnetic railgun theory and engineering design. In this paper, a lumped evaluation model based on the normalized index of the resistance heat loss and frictional resistance loss of the electromagnetic railgun armature–rail interface is established, and the actual launch test of a certain launcher is evaluated to verify the lumped evaluation model. It can provide a reference for the theoretical and engineering application research of the sliding electromagnetic contact performance of the subsequent electromagnetic railgun.

Research on Segmentation Evaluation Model of Sliding Electrical Contact Performance of Electromagnetic Railgun

The sliding electrical contact performance of the electromagnetic railgun is the main factor affecting the launch accuracy, launch efficiency, and working life of the electromagnetic railgun. The objective evaluation of the sliding electrical contact performance of the electromagnetic railgun is crucial for the research of the electromagnetic railgun theory and engineering design. Because the sliding electrical contact process of the electromagnetic rail gun is complex, the mechanism and performance requirements of the launcher in different phases are different, so it is difficult to evaluate according to the unified standard. In this paper, the whole launch process is divided into three phases: dry friction, liquefaction layer, and high-speed instability. The sliding electrical contact mechanism of these three phases is analyzed separately, and the evaluation model is established, respectively. Then, the theoretical analysis, expert evaluation, and experimental data statistics are used to comprehensively determine the weight system of the three phases. Finally, the comprehensive evaluation model of the three phases is established. The validity of the above-mentioned model is verified by the actual launch test. The evaluation method of this model has practical significance for the scientific research, engineering design, and model development of the electromagnetic rail gun.

Simulation and Experimental Study of the Influence of Temperature Stress on the Intermittent Fault of an Electrical Connector

The electrical connector is an important basic element, and its electrical contact performance is easily changed by ambient factors, such as temperature, resulting in various intermittent and permanent faults of the electrical connector. The intermittent faults of the electrical connector are difficult to reproduce, raising serious challenges to equipment availability and mission success. This paper addresses the problem of the intermittent faults of electrical connectors caused by ambient temperature stress and provides qualitative analyses of the impacts of temperature stress on electrical contacts. A finite element simulation model of the contact pairs of electrical connectors is established. The characteristics of intermittent faults at different temperature stress levels for electrical connectors with different contact pair sizes and materials are simulated and analysed. Based on this simulation analysis, experimental studies are conducted on the mechanisms of different temperature stress levels, different contact pair sizes and materials on the intermittent faults of electrical connectors. The results show that external temperature stress and temperature impacts obviously influence the contact performance of the electrical connector and that random intermittent faults occur. The more extreme the temperature and the higher the temperature change rate are, the more obvious their influences.

Influence of Wear Test Parameters on the Electrical Contact Performance of Brass Alloy/Copper Contactors Under Fretting Wear

Fretting of mated electronic connectors may be due to extreme increase in contact resistance. We present a detailed analysis of contact resistance by fretting experiments using brass alloys/copper contact pairs. The relationship between wear mechanisms and contact resistance was determined. The influence of fundamental factors such as normal load, displacement amplitude, and current on contact resistance change was also evaluated. It was found out that displacement amplitude, normal load, and current are important parameters for infinite lifetime or stable electrical resistance during fretting condition. Influence of displacement amplitude on the electrical contact performance might be affected by wear debris in the contact area. Electric contact performance could be improved by increasing the power current, which could break down the thick oxide film formed. The predicted working lifetime and reliability requirements of the connector were determined to optimize and extend the service life under the working condition.

Contrastive Research on Electrical Contact Performance for Contact Materials of Cu-SnO2 and Cu-ZnO2 Alloys

Herein, SnO2- and ZnO2-doped (1.5 wt.%) composite Cu powder was prepared by mechanical alloying (MA) respectively, and both the contact materials of oxide-doped Cu alloys were subsequently obtained by canned hot-pressing powder sintering with hot extrusion combined. Scanning electron microscopy (SEM), laser scanning confocal microscopy (LSCM) and self-designed electrical breakdown device were used for investigating the microstructure and properties including electric conductivity and hardness, especially for electrical contact performance of the Cu-SnO2 alloy and in compared with the Cu-ZnO2 alloy. The experimental results show that the hardness of Cu-SnO2 and Cu-ZnO2 contact materials are 103.5±1 HV and 192.7±1 HV, respectively, which meet the hardness standard of national standard electrical contact materials. Meanwhile, the relative conductivity %IACS are 7.24% and 6.20%, respectively, which are higher than the traditional Cu-based contact materials. This electrical life simulation test system was designed independently, and the results indicate that the switching times of Cu-SnO2 contact materials are much more than that of Cu-ZnO2. The addition of SnO2 can effectively improve the arc extinguishing characteristics and the anti-welding performance of the contact materials is enhanced. In summary, SnO2-doped Cu-based contact materials possess excellent comprehensive properties, which can provide reference for potential applications in contact materials.

Design and Launching Performance of Armature Coating with Low Melting Point Alloy

Hydrodynamic lubrication is an effective method to improve the sliding electrical contact performance for electromagnetic railguns. A kind of U-shaped aluminum armatures coated with low melting point alloy was designed, and the solid coating could melt and form a fluid dynamic lubrication film during initial launching process. A series launching experiments were comparatively conducted about armatures with and without coating, the current waveform, the muzzle velocity, and the contact resistance were collected. The experiments results reached three aspects. First, the variation of the sliding electrical contact resistance of the armature/rail can be divided into three stages: rapid reduction stage, stabilization stage, and oscillation and rising stage. And the coating works mainly in the first stage. Second, with the increasing number of repeated launching, the amplitude of oscillations in the last stage gradually decreases, and the muzzle velocity tends to be stable. And in the last stage, with the increase of rail depositions, contact resistance gradually tends to stability. Third, compared with common armature, the armature coating with low melting point alloy occupies a shorter launching time interval and gets a higher muzzle speed. That work has some reference significance to the sliding electrical contact of the electromagnetic railgun.

Arc erosion behavior of the Al2O3-Cu/(W, Cr) electrical contacts

Al2O3-Cu/(25)W(5)Cr and Al2O3-Cu/(35)W(5)Cr electrical contact materials were fabricated by vacuum hot-pressing sintering and internal oxidation. The relative density, electrical conductivity, and Brinell hardness were measured. The microstructure was analyzed by scanning electron microscopy and transmission electron microscopy. JF04C electrical contact testing apparatus were used to investigate the electrical contact performance of composites. Arc erosion morphologies were analyzed by scanning electron microscopy and three-dimensional profilometer. The material transfer as well as electrical contact performance were studied during contact make and break operations at 30 V DC with current between 10 and 30 A. It indicates that the nano-Al2O3 particles pinned dislocations. Material transfers from the cathode to the anode. With the melting, evaporation, and sputtering of Cu during arcing, W particles gather and generate needle-shaped skeletons. Finally, liquid droplets, needle-like structures, craters, and bulges were formed on electrode surfaces after arc erosion. Furthermore, their quantity and morphology are affected by tungsten content. When the content of W in the dispersed copper matrix increases from 25 wt% to 35 wt%, welding force is reduced during the steady operations. In addition, when the arc duration is greater than 8.86 ms, the Al2O3-Cu/(35)W(5)Cr contact material has a shorter average arc duration than Al2O3-Cu/(25)W(5)Cr at the same arc energy.

Improving the Electrical Contact Performance for Amorphous Wire Magnetic Sensor by Employing MEMS Process.

This paper presents a novel fabrication method for amorphous alloy wire giant magneto-impedance (GMI) magnetic sensor based on micro electro mechanical systems (MEMS) technology. In this process, negative SU-8 thick photoresist was proposed as the solder mask due to its excellent properties, such as good stability, mechanical properties, etc. The low melting temperature solder paste was used for the electrical connections with the amorphous alloy wire and the electrode pads. Compared with the conventional welding fabrication methods, the proposed micro electro mechanical systems (MEMS) process in this paper showed the advantages of good impedance consistency, and can be fabricated at a low temperature of 150 °C. The amorphous alloy wire magnetic sensor made by the conventional method and by the micro electro mechanical systems (MEMS) process were tested and compared, respectively. The minimum resistance value of the magnetic sensor made by the conventional welding method is 19.8 Ω and the maximum is 28.1 Ω. The variance of the resistance is 7.559 Ω2. The minimum resistance value of the magnetic sensor made by micro electro mechanical systems (MEMS) process is 20.1 Ω and the maximum is 20.5 Ω. The variance of the resistance is 0.029 Ω2. The test results show that the impedance consistency by micro electro mechanical systems (MEMS) process is better than that of the conventional method. The sensor sensitivity is around 150 mV/Oe and the nonlinearity is less than 0.92% F.S.

Effect of different atmospheres on the electrical contact performance of electronic components under fretting wear

The effects of oxide etch on the surface morphology of metals for industrial application is a common cause of electrical contacts failure, and it has becomes a more severe problem with the miniaturization of modern electronic devices. This study investigated the effects of electrical contact resistance on the contactor under three different atmospheres (oxygen, air, and nitrogen) based on 99.9% copper/pogo pins contacts through fretting experiments. The results showed the minimum and stable electrical contact resistance value when shrouded in the nitrogen environment and with high friction coefficient. The rich oxygen environment promotes the formation of cuprous oxide, thereby the electrical contact resistance increases. Scanning electron microscope microscopy and electron probe microanalysis were used to analyze the morphology and distribution of elements of the wear area, respectively. The surface product between contacts was investigated by x-ray photoelectron spectroscopy analysis to explain the different electrical contact properties of the three tested samples during fretting.

Effect of roughness on electrical contact performance of electronic components

This study investigated the effects of electrical contact resistance (ECR) on pogo pins used in mobile phones, chargers, digital cameras, Bluetooth headsets, medical equipment, and other electronic products with different surface roughness. Experimental results revealed that metallic wear debris is generated by fretting motion and formation of a third body on rough surfaces without removal by fretting motion, thus increasing ECR. Wear debris does not easily form the third body at contact areas of smooth surfaces and causes formation of metal–metal contact pattern. Results showed low ECR with fretting motion. 3D and 2D profiles of contact area verified the definition of contacting high spots, further explaining increases in ECR.

Fretting Behavior of Gold-Plated Contact Materials Used in High-Frequency Vibration and Different Temperature Environment

Using an electrodynamic-shaker-based test setup, experiments were performed on gold-plated contacts under a variety of fretting conditions, including different vibration frequencies, vibration amplitudes, and different environment temperatures. The variations in contact resistance with fretting cycles are recorded explicitly. The fretted surface is examined using a scanning electron microscope, energy-dispersive X-ray spectroscopy, and a con-focal laser scanning microscope to assess the surface morphology, extent of oxidation, and elemental distribution across the fretted zone. It was found that fretting damage is a complex phenomenon for electrical contact applications. Different fretting regimes, including the robust electrical contact performance, the oxidation-dominated failure, and the transient unstable conductivity failure are determined. Finally, the degradation mechanisms of gold-plated contacts are proposed.

Investigation of the Effect of Different Current Loads on the Arc-Erosion Performance of Electrical Contacts

In this study, arc-erosion experiments using contactors were performed under inductive loads for up to 40000 switching operations to investigate the effect of different current loads on the arc-erosion performance of electrical contacts. Determination of the mass loss was performed after every 5000 operations. The arc-eroded surfaces were examined using scanning electron microscopy. The chemical composition near the arc was determined by energy dispersive X-ray spectroscopy. The results show that the contact surfaces are greatly affected by arc-erosion, resulting in mass loss due to material migration and/or evaporation. In addition, the arc-affected zones become bigger with the increase in the number of switching operations, especially at 20 A. However, electrical cleaning improves the contact performance by reducing the contact resistance due to breakdown of the non-conducting oxide films formed between 20000 and 25000 switching operations at 20 A. The stationary contacts experience major erosion, whereas the movable contacts suffered less contact erosion under each current load.

Electrical contact performance of MEMS acceleration switch fabricated by UV-LIGA technology

This paper expanded a micro-contact resistance model to investigate the contact performance for a acceleration switch fabricated by UV-LIGA (Ultra-violet Lithographie, Galvanoformung and Abformung) technology. Based on the relationship between the contact radius a and electron mean free path ?, three different contact resistance models have been analyzed. The material properties (elastic modulus E, hardness H and Poisson's ratio v) and surface topographic parameters (asperity summit radius r, standard deviation of height distribution ?, and surface density of asperity) have been studied to evaluate the contact resistance-load characteristics. The results show that the theoretical prediction of contact resistance-load characteristics correlates well with the experimental results except there exists experimental discrepancy. The discrepancy between theoretical predictions and experimental results mainly is due to the contaminations, errors from assumptions, surface oxidation and external environmental conditions.

Study of Some Influencing Factors of Armature Current Distribution at Current Ramp-Up Stage in Railgun

Current ramp-up is an important stage for a railgun electromagnetic launch system. In lots of launching experiments, a big chunk of deposit aluminum can be found on the rail surface at the start-up position of the armature-rail contact area, sometimes, erosion is even emerged. The transition at current ramp-up is mainly related to local degradation of armature. The larger value of maximum current densities at the rail/armature (A/R) interface would lead to armature local temperature increasing rapidly, which deteriorates the material property of armature, degrades the static electrical contact performance, and reduces the railgun lifetime significantly. In this paper, for restraining start-up transition, several influencing factors of armature degradation and melt are studied based on current concentration. Rail resistivity, rail dimensions, armature resistivity, and the shape of current supply are considered and simulated. At current startup, skin effect and induced current are analyzed, which are considered as the direct factors of armature's current distribution. Armature current distribution and the maximum current density are obtained and compared for each factor. Finally, launching experiments are carried out as the same condition with simulation. On the rail surface at the start-up position of the A/R interface, the depositions reflect the current distribution on armature with different factors influence at the current ramp-up. The results of experiments are in reasonable agreement with simulation description.

Corrosion Study of Electrodeposited Co-Ni-Fe Protective Coating on Electroless Nickel Immersion Gold (ENIG) Flexible Printed Circuit

Abstract Flexible Printed Circuits (FPCs) have been vastly used in electronic devices such as mobile phones and sensors. This multi-layer polymer is used in electronic packaging to interconnect high performance devices. Electroless Nickel Immersion Gold (ENIG) is the final finishing method commonly applied on FPCs due to its excellent planarity, wear or abrasion resistance and electrical contact performance. However, corrosion problem on FPCs surface may influence the electrical conductivity, performance and thus affect the functionality of the end product. Previous published literature showed that Co-Ni-Fe enhanced the corrosion behavior of metals. Therefore, ternary Cobalt alloys (Co-Ni-Fe) have been synthesized as the protective coating on ENIG FPCs in this research. A low cost electrodeposition method is applied to produce a Co-Ni-Fe protective coating to improve the corrosion resistance of ENIG FPCs. The result will be compared between FPCs with and without protective coating. Co-Ni-Fe solution for electrodeposition process was prepared at pH 1. The current applied to coat the FPCs is 0.6 ± 0.05 A. The experiment conducted at 50 °C ± 0.5 and performed at 30s and 60s of deposition time. Irregular shape of microstructure with grain size range from 46 nm to 88 nm was observed under FESEM micrographs. Corrosion test was performed by using Potentiodynamic Polarization technique under acidic environment. The corrosion rate per year of the FPCs after coated with electrodeposited Co-Ni-Fe showed lower corrosion rate than ENIG FPC. The corrosion behavior and surface morphology studies have shown that the electrodeposited Co-Ni-Fe coating improved the corrosion rate of ENIG FPCs.

Based on Grey Theory of Prediction on Electrical Contact Reliability of Relay

Electrical contact reliability is an important aspect of contactor electric products reliability,so assessment of electrical contact performance and reliability and prediction its failure time to improve operational reliability of contactor electrical apparatus products have important application value.Aiming at the complexity of the relay failure reasons,prediction of electrical contact reliability is put forward based on gray theory.By establishing of a single variable prediction model GM(1,1),preferable forecasting the electrical contact failure problems.And HH52P type electromagnetic relays failure detection test is done using dynamic contact resistance measurement system,it proves the accuracy of the grey prediction models.

电磁轨道发射器连续发射的滑动电接触

电磁轨道发射器连续发射的滑动电接触

Improving the contact resistance at low force using gold coated carbon nanotube surfaces

Investigations to determine the electrical contact performance under repeated cycles at low force conditions for carbon-nanotube (CNT) coated surfaces were performed. The surfaces under investigation consisted of multi-walled CNT synthesized on a silicon substrate and coated with a gold film. These planar surfaces were mounted on the tip of a PZT actuator and contacted with a plated Au hemispherical probe. The dynamic applied force used was 1 mN. The contact resistance (Rc) of these surfaces was investigated with the applied force and with repeated loading cycles performed for stability testing. The surfaces were compared with a reference Au–Au contact under the same experimental conditions. This initial study shows the potential for the application of gold coated CNT surfaces as an interface in low force electrical contact applications.

The Relationship Between Contact Resistance and Contact Force on Au-Coated Carbon Nanotube Surfaces Under Low Force Conditions

Carbon nanotube (CNT)-coated surfaces are investigated to determine the electrical contact performance under low force conditions. The surfaces under investigation are vertically aligned multiwalled CNTs formed on a silicon substrate and coated with an Au film. These planar surfaces are mated with a hemispherical Au plated probe mounted in a nanoindentation apparatus. The maximum contact force used is 1 mN. The contact resistance of these surfaces is investigated as a function of the applied force and is also studied under repeated loading cycles. The surfaces are compared with a reference Au-Au contact under the same experimental conditions and the results compared to established contact theory. The results show that the vertically aligned multiwalled CNT surface provides a stable contact resistance. This paper shows the potential for the application of CNT surfaces as an interface in low force electrical contact applications.

Silicon cantilever arrays with by-pass metal through-silicon-via (TSV) tips for micromachined IC testing probe cards

In this paper, an integrated probe card is proposed and developed for wafer-level IC testing. Based on micromachining technology, totally about 26,000 cantilever-tip probes can be formed simultaneously in one 4-in. silicon wafer, with the minimum pitch of 35 μm for adjacent probing tips. The probe card is designed with a novel composite structure that combines both single-crystalline silicon and electroplated metals. In the composite structure, a novel bypass through-silicon-via with a low aspect ratio can be high-yield fabricated for transferring the testing signals from the probing sided (at the wafer bottom side) to the I/O interface (at the front side). The probe card makes full use of the advantages of the single-crystal silicon and the electroplated nickel and copper. Bulk micromachined silicon cantilevers behave uniform probing height and a good elastic deformation property, while the electroplated nickel probing tips promise high hardness and satisfactory electric contact performance with the dies-under-test (DUT). Measurements show that the fabricated cantilever is able to withstand a contact force of 80mN by a tip displacement of 20 μm. The measured contact resistances on metal pads (Al, Cu, and Au) are all below 1 Ω, whereas the maximum current leakage is 64 pA for 3.3 V voltage across two adjacent tips. After a probing reliability test of 100,000 cycles, the cantilever-tip shows no sign of any performance degradation.