Copper Connections Research Articles

Wettability in lead-free soldering: Effect of plasma treatment in dependence on flux type

To enhance the solderability, highly active fluxes are commonly employed in lead-free soldering. However, there are industry-wide efforts to use less active fluxes to avoid possible issues associated with corrosion processes and minimize subsequent cleaning processes, thereby reducing potential environmentally harmful waste. Therefore, in this study, the effect of the plasma treatment (N2/H2 97:3) on the wettability of the soldered surface (copper connectors) was investigated. Wettability measurements were conducted using SAC305 solder alloy and six different fluxes. The wetting balance test revealed a significant improvement in wetting for all tested fluxes, regardless of their composition. On the other hand, non-wetting occurred when no flux was applied to the plasma-treated surface, attributed to a thin residual oxide layer detected by X-ray photoelectron spectroscopy. Thus, the plasma treatment of the surface supports the flux effect, which cannot be entirely omitted from the soldering process. However, incorporating plasma treatment in the soldering process allows for the use of much less active or even expired fluxes.

Failure investigation of brazed copper winding bar strands of 250 MW stator

The present failure analysis investigates the failure of copper connectors and bus-bar windings of a 250 MW generator unit, of a steam powered turbine, which failed during service. An exhaustive microstructural and nanomechanical characterization was conducted in-order to determine the failure of copper bus-bar. Microstructure analysis revealed porosities in the brazed region with formation of numerous microconstituent phases. Furthermore, microstructure analysis revealed a network of numerous intergranular porosities on the failed copper side. SEM-EDS analysis of different microconstituents revealed a presence of Ag-rich dendritic phase, Cu-rich phase and lamellar eutectic microconstituents, highlighting a diverse microstructure. Nanoindentation measurements of different microconstituents and phases revealed a stark difference in the indentation hardness, thereby highlighting a strong mismatch between the observed microconstituents and phases.

A Review of the Friction Stir Welding of Dissimilar Materials between Aluminum Alloys and Copper

With the rapid development of various industries, the connection of copper and aluminum is in high demand. However, as a solid-phase connection technology, friction stir welding has a potential application prospect in the connection of copper and aluminum. This paper comprehensively summarizes the most recent 20 years of the literature related to the friction stir welding of copper and aluminum. The application significance of copper and aluminum connectors is introduced, and the research field of the friction stir welding of copper and aluminum is analyzed and explored from the aspects of welding technology, microstructure and mechanical properties, as well as innovations and improvements in the welding process. In view of the research status of this field, the authors put forward their views and prospects for its future, aiming to provide a basis for researchers in this field.

Electron beam welding of rectangular copper wires applied in electrical drives

The so-called hairpin winding technology, which is specially tailored to electrical traction components, deploys rectangular plug-in copper wires in the stator. The fusion welding of the adjacent wire ends is associated with challenges due to the high thermal conductivity as well as the porosity formation of the copper. During this study, the electron beam (EB) welding of electrolytic tough pitch (ETP) and oxygen-free electronic grade (OFE) copper connectors was investigated. Subsequently, the specimens underwent X-ray computed tomography (CT) and metallographic examinations to characterize the joints. It was discovered that the residual oxygen content of the base material is responsible for the pore formation. With only a very low level of oxygen content in the copper, a porosity- and spatter-free welding can be reproducibly realized using the robust EB welding technology, especially for copper materials. By optimizing the parameters accordingly, joints exhibiting a low level of porosity were achieved even in the case of the alloy containing a high amount of residual oxygen. Beyond this, detailed analyses in terms of pore distribution were carried out and a good correlation between technological parameters and welding results was determined.

Laser welding of laser-structured copper connectors for battery applications and power electronics

The electrification of the automobile industry leads to an increasing demand for high-performance energy storage systems. The more complex the battery pack, the more complex the electronic components will become. Very high currents have to be transported in a short time and very fast electrical switching processes have to be made possible. These requirements have an effect on the required quality of the electrical connection. Furthermore, a joining process is required that offers short cycle times and a high degree of automation. Laser micro welding with fibre lasers (1070 nm) meets the requirements placed on joining technology. Due to the high beam quality, very small spot diameters and thus very high intensities can be achieved. Copper materials of high purity are used to achieve the high conductivity of the electrical connection. This material, in turn, poses a great challenge to the welding process, since the reflectance for the beam sources mentioned is above 95%.This paper presents a way of significantly reducing the reflectance for copper connectors and thus making the joining process more efficient. For this purpose, the copper connectors are first pre-processed with an ultrashort pulse laser process, which significantly increases the surface area. In a second step, bead-on-plate welds are carried out on the structured surfaces and the absorption coefficient is determined during the welding process with the aid of a double integrating sphere assembly in comparison to a bare copper sample.

Contacting of 18650 lithium-ion batteries and copper bus bars using pulsed green laser radiation

Lithium-ion cell based battery storages are indispensable in many fields of application such as electromobility and stationary energy storage devices. Cylindrical 18650 cells are regularly utilized and connected by cell connectors made of nickel plated steel. Since this setup suffers from high electrical losses and a poor heat removal during operation, copper connectors are demanded more often. For joining the cells and the connectors, laser beam welding offers great potential due to its low energy input and high flexibility. However, challenges arise, as copper materials show a strong reflectivity for infrared wavelengths. Experimental investigations for the contacting of 18650 cells and copper connectors using a spike pulse welding strategy combined with green laser radiation are presented within this study.

Wireless power transfer using a superconducting capacitor

It has been demonstrated that a high temperature superconducting (HTS) wireless power transfer (WPT) system has the advantages of higher power transfer efficiencies and longer transmission distances. But the resistive losses of the conventional compensation capacitors, the copper connectors and the long copper connecting wires between the HTS coils in the liquid nitrogen and the conventional compensation capacitors outside still exist. Since at low frequencies the power transfer efficiency of a WPT system is dominated by the resistive losses (and at high frequencies by radiation) of the WPT system and the AC loss of superconductors is much lower than that of conventional conductors, using superconducting capacitors as the compensation capacitors is an optional way to further increase the power transfer efficiency. Here, a superconducting capacitor was constructed. Two kinds of HTS WPT experiments were conducted by use of the superconducting capacitor and the conventional capacitor as the transmitting compensation capacitor, respectively. The results are presented and analyzed. It is shown that though the capacitance of our superconducting capacitor changed a little, for the distance up to 1.5 times of the radius of the coils, the efficiency of the WPT system can be increased by 4.25% by using the superconducting capacitor as the transmitting compensation capacitor.

A Novel Transmission Line Structure for High-Speed High-Density Copper Interconnects

This paper introduces a novel transmission line structure that can be employed in high-speed high-density copper interconnects, including both cables and connectors. The proposed structure uses a unique combination of dielectric materials with high and low permittivity values to decouple metal shields from adjacent signal pairs. In addition, the proposed structure employs an absorbing material to suppress any crosstalk resonances that may arise due to signal discontinuities in such highly dense environments. The optimum electrical properties of such an absorbing material in the proposed structure were determined using a simulation-based investigation. This paper also presents measured electrical properties of stereolithography resins suitable for rapid prototyping of high-speed interconnects. The effects of increasing the height of a connector on signal crosstalk and introducing any absorbing materials on signal loss are also discussed. Finally, this paper presents test boards and corresponding prototypes that were modeled and measured to validate the proposed transmission line structure for frequencies up to 40 GHz.

The Stem Heat Balance Method to Measure Transpiration: Evaluation of a New Sensor

The measurement of crop transpiration (Tcrop) under field conditions and throughout the growing season is difficult to obtain. An available method uses stem flow gauge sensors, based on the conservation of energy and mass, where the calculated sap flow (F) is a direct measure of Tcrop. This method has been extensively tested on agronomic, horticultural, ornamental aspects and tree crops and the general consensus is that F is a measure of Tcrop. A new sap flow gauge (EXO-SkinTM Sap Flow) sensor, with different placement and number of thermocouples, compared to the original sensor, was introduced, resulting in a different energy balance equation to calculate F. Our objective was to compare values of Tcrop obtained with the new sensor on cotton (Gossypium hirsutum, L) plants to values measured with lysimeters. For this purpose, cotton plants were grown in 11-liter pots in a greenhouse experiment and hourly and daily values of Tcrop were compared for eight days. We used linear regression analysis to compare the hourly and daily values of Tcrop measured with the sensor to corresponding values measured with lysimeters on the same plant. Using a t-test (p > 0.05) we tested if the slope of the line was significantly different than 1 and if the intercept was significantly different than 0. This test indicated that there were no statistical differences between hourly and daily values of Tcrop measured with the new sensor and with the lysimeters. The main advantage of the new sensor is the flexibility of the new heater, allowing for better thermal contact between the plant stem and the temperature sensors. Further, the new sensor requires less wiring and copper connectors, and the number of channels used in a datalogger to record the output from the sensor is reduced by 25%. We conclude that the new sensor correctly measures Tcrop and that additional experiments with field grown plants are required to test the sensor at higher values of Tcrop.

Conductivity of Nafion® 117 membrane used in polymer electrolyte fuel cells

The membrane electric transport (MC) directly influences the performance of the polymer electrolyte fuel cells (PEMFC). The membrane conductivity is determined by a number of parameters such as: hydration technique, graphite cell geometry and pressure applied when the membrane electrode assembly (MEA) is joined. In addition, the membrane conductivity might be influenced by the electrode position due to the possibility of anisotropic electric conductivity.This paper describes the technique used to measure the normal conductivity of Nafion® 117 applying direct current (DC). The membrane was previously hydrated with two different acid techniques. These two conditioning protocols have identical thermal treatments, the only difference is the acid utilized in each technique. The first treatment involved Nitric Acid while the second one was developed using Sulfuric Acid. The results obtained with the different treatments allowed us to identify the difference in the conductivity, issue that could not be appreciated when we studied only the degree of hydration of the membrane because the quantity of water molecules per sulfonic group was the same using both acids.The conductivity was measured using directly carbon paper/membrane/carbon paper samples fully immersed in deionized water. Carbon papers were previously painted with different graphite inks that allowed us to analyze the results and select the best one.The cell used for measuring conductivity was built with two graphite plates, copper connectors and conductive silver epoxy glue that allowed us to form a device similar to the one proposed in the literature. The results are reproducible and consistent with the published data.

Use of AES in corrosion of copper connectors of electronic devices and equipments in arid and marine environments

PurposeThe electronics industry has grown over the past 50 years, mostly in developed countries, contributing to their economic progress. Particularly in the Baja California State located in the northwest of Mexico, these companies have prospered in the industrial parks of Mexicali considered as an arid zone and Ensenada, a port and city on the Pacific Ocean considered as a marine region. In both environments, during winter and summer, the climate impacts on indoor conditions, affecting humidity and temperature, and generating corrosion which decreases the yields of the electronic devices and industrial machines. The purpose of this paper is to investigate the effects of corrosion on electronic devices in these arid and marine environments.Design/methodology/approachThe paper determines the corrosivity levels inside industrial plants of desertic and coast regions in Mexico, to evaluate the deterioration of electronic metals.FindingsRelative humidity, temperature, time of wetness, are recorded and related to the corrosion process in arid and marine environments.Research limitations/implicationsSome missing information about air pollution in Ensenada from some Environmental Monitoring Stations was a limitation, and the need to use complex atmospheric techniques.Originality/valueThe paper shows that it is very important to control metallic corrosion generated by climate factors and air pollution in indoor industrial plants: the corrosion of electronic devices and equipments depletes their yield and can lead to loss‐making failures.

IBM Project Proposes Using Light to Make Chips Faster

IBM has developed an optical technology that could speed up data transmissions among servers, between chips within a system, or on the chips themselves. The company's SNIPER (silicon nanoscale integrated photonic and electronic transceiver) project uses CMOS integrated nanophotonic technology. This approach employs pulses of light, rather than copper connec tions, to move data at higher speeds. IBM's approach uses wavelength division multiplexing, which is faster because numerous data streams can be carried on multiple wavelengths simultaneously within a single fiber. IBM integrates the photonics and the CMOS electronics circuitry on the same chip during the manufacturing process. This approach is less expensive, yields more chips, and avoids damaging parts during assembly.

Ultrasonic metal welding of AA 6022‐T4 lap joints: Part I – Technological characterisation and static mechanical behaviour

High power ultrasonic technology can currently count on a number of industrial applications. Ultrasonic welding, which is a standard joining technique in many applications on plastics, has few but well established metal applications, such as copper wires, pipes and connectors welding, or, considering spot welding of aluminium thin sheets, is attractive for the automotive industry field, where it could represent a possible cost effective alternative to resistance spot welding, clinching or self‐pierce riveting. The present experimental study is addressed to this kind of application in order to evidence the effects of welding parameters and, most of all, their interactions on the tensile strength of tensile–shear spot welded lap joints. Relevant results have been achieved by dedicated and non‐conventional instrumentations applied to the welder for measuring and controlling the process parameters. The best static performance has been taken as an input for the second part of the study regarding the fatigue behaviour and the joints failure modes.

Metallurgical Investigation on Low Ductility Failures of Cu-ETP Components

In the present paper, the investigation on low ductility failures occurred to ETP copper strips and connectors manufactured from cold stamping of copper tubes is presented. Optical microscopy, SEM/EDS for macro- and microfractography and local elemental analysis along with tensile testing were employed as the principal analytical techniques in the context of the present investigation. Casting defects and microstructural abnormalities associated to hydrogen induced cracking (H.I.C.) are the principal contributors of the examined failures.

Comparative Corrosion and Current Burst Testing of Copper and Aluminum Electrical Power Connectors

Crimped and mechanically bolted aluminum and copper connectors are commonly used for terminating industrial electrical power cables with ratings up to 600 V. Aluminum connectors are available for use with aluminum or copper conductor, and copper connectors are available for use with copper conductor only. The performance of copper and aluminum connectors was compared by conducting accelerated aging under corrosive environmental conditions. The testing consisted of 2000 hours of cyclic salt fog environmental exposure, in conjunction with periodic electrical current burst testing. The connectors were evaluated by comparing the change in resistance of the test samples as the test progressed.

Overheating of flexible tinned copper connectors

Overheating of flexible tinned copper connectors has been observed at a number of power stations. These connectors are used to connect the generator to outgoing busbars and transformers thus serving to counter the effects of vibration and thermal expansion forces. It is shown that the main cause for the observed overheating is a result of a combined action of the high initial contact resistance, fretting, stress relaxation, differential thermal expansion and the formation of intermetallics at the copper-tin interfaces.

High speed plastic networks (HSPN): a new technology for today's applications

Decades ago, glass fiber promised to be the future of communications offering large bandwidth, low attenuation, and electromagnetic compatibility. For the long haul applications, this promise has been fulfilled. Today, glass fibers have yielded simple, reliable, and economic means of communicating worldwide. However, when it comes to shorter distances and rugged environments, glass fiber optics has not been the answer. Unforeseen rapid developments in software and display technology have enabled communications in the form of multimedia, E-mail, web pages, and video conferencing. These developments are pushing data rates higher and higher in application environments that are more severe, uncontrolled and require shorter connected intensive links. To achieve desired data rates and electromagnetic compatibility (EMC) using copper systems, shielded cable and connectors or parallel links are necessary, driving up cost and complexity. Glass fiber optic systems provide more than adequate bandwidth and superior EMC but cannot offer a cost effective, robust, user-friendly system. Recent developments have poised plastic optical fiber (POF) to fill the physical layer gap. This paper will discuss the recent developments in plastic fiber including appropriate application space, types of plastic optical fiber, ARPA-funded HSPN team, and recent POF developments.

Vibration isolation of superconducting magnets

In order to improve image resolution and magnetic field uniformity in a magnetic resonance imaging device, the vibrations and loads produced by the cryocooler are isolated from the superconducting magnet and cryostat. The vibrations and loads are isolated through the use of flexible, laminated copper connectors and rubber mounts.

Fretting damage in tin-plated aluminum and copper connectors : Milenko Braunovic. IEEE Trans. Compon. Hybrids mfg Technol.12(2), 215 (1989)

Fretting damage in tin-plated aluminum and copper connectors : Milenko Braunovic. IEEE Trans. Compon. Hybrids mfg Technol.12(2), 215 (1989)

Fretting damage in tin-plated aluminum and copper connectors

A number of bolted-type tin-plated aluminum and copper connectors commonly used for distribution transformers were examined using scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), Auger electron spectroscopy (AES), X-ray analysis, and optical microscopy. In addition, the contact resistance of the connector contact zones was measured using a point probe. The connectors studied had been removed from service because of unsatisfactory performance under normal operating conditions as manifested either by overheating or instability. The results of the detailed examination show the presence of extensive fretting damage in the contacting surfaces. The fretting debris was composed mainly of tin oxide and oxidized base metal particles. Localized melting and wear of the tin plating down to the underlying substrate were also observed in some of the connectors examined. >