Thin Copper Wire Research Articles

Topographical change of high-temperature copper surface bombarded by Ar ions

Topographical changes of thin copper wires (chemical purity 99.9%, 30–50 μm in diameter) during 20 keV argon ion bombardment up to 4 × 10 19 ions cm −2 at several temperatures between room temperature and 1073 K have been studied using the Scanning Electron Microscope. It is observed that there is a notable difference in the surface topography of copper wires below 423 K and above 573 K. This experimental observation is related to the diffusion of metal atoms in near-surface layers of samples.

Welding Characteristics of Thin Copper Wire Using Complex Vibration Ultrasonic Wire Bonding Systems

Welding characteristics of thin copper wire using complex vibration ultrasonic wire bonding are studied. The welding systems used have a complex transverse vibration welding tip which is driven by two longitudinal vibration systems crossed at a right angle. Welding tip vibration locus shape is controlled by regulating these vibration systems. Welding specimens used are 0.025 mm diameter copper wire and 1.0 mm thick copper plate. These specimens are welded successfully with smaller vibration amplitude and shorter weld time than a conventional welding system. Weld strength is independent of specimen wire direction.

Length dependence of the resistance in thin copper wires

The resistance of thin copper wires, area 4 × 10 −12 cm 2 to 1 × 10 −10 cm 2, has been measured at low temperatures. For wires with lengths greater than about 5 μm, the resistance begins to increase as the temperature decreases below about 6 K as predicted by the theory of Anderson localization and electron-electron interactions. For wires with lengths less than 5 μm, the temperature dependence of the resistance deviates from the behavior observed for long wires and this deviation increases as the length of the wire decreases. A thermal cutoff length of < 1.0 μm is found which is consistent with both the temperature dependence and the length dependence. A characteristic length of < 1.4 μm is found for localization theory.

Development of sputter-induced cones on thin copper wires

Thin copper wires, approximately 50 μm in diameter, were irradiated by a 20-keV Ar ion beam in directions parallel and perpendicular to their axes and studied by scanning electron microscopy (SEM). It was found that overall shape of the wire approaches that of a cone and that small subsidiary cones observed at low ion doses persist through higher doses. To examine the evolution of both kinds of cones, irradiation by Ar ions alternated with observation by SEM was performed. Two kinds of apex angles of the cones were found. The evolution of the cones is possibly affected by the cold work present in the wires. Erosion rates were estimated from observations at typical parts of the surface and showed striking local differences.

Fatigue of very thin copper and gold wires

Fatigue of very thin copper and gold wires

Positive and negative surface induced deviations from Matthiessen's rule in thin copper wires

We have measured the electrical resistivity ϱ (d, T) of polycrystalline copper wires with diameter d comparable with the residual electron mean free path 1 E = 71 μm in the temperature range 4.2–35 K. The deviation from Matthiessen's rule caused by the surface scattering of the conduction electrons is examined and found to be negative in samples with d > 1 E. The magnitude of the surface-induced T 2 contribution to the resistivity of samples with d < 1 E increases linearly with (d/1 E) − 2 3 and supplement our recent results on high purity copper single crystals.

Normal modes and dispersion relations in a beaded string: An experiment for an undergraduate laboratory

Normal modes and dispersion relations are studied in a beaded string by forming stationary waves. Thin copper wire, with brass beads mounted on it, works as a one-dimensional medium possessing a granular structure. The beaded string carrying a sinusoidal current is forced to oscillate under the action of an external magnetic field. Various normal modes are conveniently excited and the observed ω vs k relationship agrees well with the theoretical predictions. Simplicity of the apparatus, tractibility of the mathematical analysis, and the correspondence between theoretical predictions and measurements make the experiment suitable for an undergraduate laboratory.

On sample positioning at low temperatures

A method is presented to measure the position of a small solid sample which is suspended by thin copper wires, from a microbalance, in a dewar that has been described earlier [1]. The shrinkage of the wires at low temperatures is reproducible to within ± 0.15 mm.

A Hot-Wire Liquid Water Device Having Fully Calculable Response Characteristics

Abstract A liquid water sensor consisting of a thin copper wire wound on a hollow 1.5 mm diameter cylinder is described. Slave coils on either side of the master sensing coil reduce axial heat losses to an acceptable level, and allow for a simple relationship between power supplied to the wire and liquid water content. Wet wind-tunnel tests show that the system response to liquid water is easily calculable from a knowledge of the geometrical dimensions of the cylinder and the operating temperature of the hot wire. When operated at 100°C, the device has a sensitivity of 0.02 g m−3, a response time of better than 0.05 s and an accuracy of 5% at 1 g m−3.

KONDO-LIKE RESISTIVITY IN SINGLE CRYSTALS OF dhcp Pr AT MILLIKELVIN TEMPERATURES

Resume._ La resistance electrique de Pr dhcp a ete mesure e entre 15 m K et 5 K dans la direction C. En-dessous de 0,4 K nous avons observe une contribution de type Kondo. L'ordre nucleaire, comme l'indique le temps de relaxation thermique, est observe vers 25 m K dans un cristal, mais parait ab ­sent dans un autre. Abstract- Electrical resistance of dhcp Pr has been measured between 15 m K and 5 K in the c-direc-tion. Below 0.4 K a Kondo-like behaviour is observed. Cooperative ordering indicated by the thermal time constant, which has been observed near 25 m K in one crystal, seeme d to b e absent in the presen t sample. INTRODUCTION.- In dhcp Pr the crystal fiel d ground states of the ions are singlets, i.e., non-magnetic. The ratio between effective exchange interactions and crystal field level splitting, however, appears to be close to the critical valu e for spontaneous magnetic order , sinc e polycrystalline materia exhil ­bits a n ordere d state with transition temperature above 20 K /l/, while no such transition has bee n found in magnetic studies of single crystals down to 0.4K 111. Murao /3/ an d Triplett an d White /4/ predicte d that at low enoug h temperatures a subcritical system would order as a consequency of an effective nuclear exchange interaction mediated by hyperfine induced ionic moments and conduction electrons. In specific heat measurements, Lindelof et al./5/ have approa­ched this nuclear cooperative ordering and estima­ted a transistion temperature T„ between 25 and 30 mK. Since the transition involves a polarization of ions by nuclei it woul d be interesting to detect possible effects in the resistivity . RESISTANCE MEASUREMENTS.- Our sample wa s a single crystal of dhcp Pr, approximate lenght 7 m m an d cross section 1mm , cu t alon g the c-direction. Cur ­rent and potential lead s were tinned, thin copper wires attached by ultrasonic soldering. The crystal was mounted directly in the mixin g chamber ofe thdilution refrigerator and supported only by the leads so as to minimiz e strain. Temperature was mea ­sured with Speer carbon resistors also immersed in the liquid. Work supported by the Danis h Natural Science Re ­search Council.

Determination of scattering widths of a long thin wire using an open resonator

Using an open-resonator method, the scattering widths of a set of thin copper wires have been measured. The results are in agreement with theory to within about 9%.

Deviations from Ohm's law for a metal at high current densities

High current pulses were generated in thin copper wires and the specific resistance for different current densities as the same temperature was determined. The measured values show an increase of resistance with current density reaching nearly a factor 3 at 1.6 × 10 8 A/ cm 2

The effect of annealing on the mechanical properties of electroplated NiFe films

Cylindrical magnetic films of a NiFe alloy (7–8% Fe) have been electroplated on thin copper wire substrates, annealed and subjected to tensile tests, to determine the effect of thermal stabilization treatment on the films' mechanical properties. Microhardness tests and X-ray diffraction experiments have also been carried out. It is found that with rising annealing temperature there is at first an improvement of ductility, with the tensile strength ( R m) remaining almost constant. In films annealed between 100° and 200°C the proportionality limit ( R p) and the R p/ R m ratio are increasing, while the elongation falls. Above 200°, a visible embrittlement is observed, with tensile strength, proportionality limit, hardness and elongation all rapidly decreasing. Possible mechanisms underlying the observed changes are discussed.

Contact resistance as a measure of the superconducting order parameter

We have shown experimentally that the electrical contact resistance between a thin copper wire and a bulk superconductor contains a small contribution that varies with temperature below Tc. The observed temperature dependence is always close to that of the energy gap in the superconductor.

A simple apparatus for the determination of g by free fall

The apparatus is of the ball-attached-to-an-electromagnet type with an electronic timer to measure time of descent through a known distance. The accuracy has been improved by attaining a thin copper wire to the ball and arranging the circuits in such a way that the timer does not start until the ball actually leaves the electromagnet (not when its field is cut off and starts decaying) and a circuit is completed when the ball strikes a metal pad at the end of its fall. The accuracy of the measurement is 0.3%.

The mechanism and kinetics of central cavity formation during the growth of thick layers of copper sulfides on the metal

A study of the sulfidation kinetics of thin copper wires and whiskers showed that cavity formation caused by metal consumption starts at the metal-sulfide interface and grows inwards as the reaction proceeds. The cavity does not start in the middle and expand outwards. An exterior honeycombed region is formed which is traversed by metal bridges and filaments linking the internal metal core to the sulfide. The bridges assure the metal supply and only disappear when conversion is virtually completed. The authors suggest a theoretical interpretation which accounts for these observations.

Untersuchung des elektrischen widerstandes und des weglängeneffektes der leitungselektronen an dünnen kupferdrähten

The mean free path of the conduction electrons is determined by the size effect on thin copper wires. The value ϱ·λ being a temperature-independent constant according to the model of the free electron gas for different metals is evaluated for copper from the results of the measurements.

Exploding wires in strong axial magnetic fields

Thin copper wires, typically No. 27 and No. 33, were exploded in magnetic fields up to 72 kG. The ambient gas was atmospheric pressure air. The wire lengths were 0.5–1.35 cm, the applied voltage 3–7 kV, the peak currents 3.5–39 kA, and the ringing frequency 300 kHz. The effect of the magnetic field was generally to increase the pause length and to damp the ringing discharge more.

Instabilities of electrically exploded wires

The experimental results summarized in this paper, which have been obtained with thin tungsten, copper, and constantan wires, give further evidence that electromagnetic macroinstabilities may develop near the melting point of thin wires which are heated by the sudden release of electrical energy and lead to their disintegration. At low-energy-input rates, screw-type instabilities develop in all the wire materials used. On the other hand, at high-energy-input rates, the copper and constantan wires show striations after the explosion, while tungsten wires are not striated but are split into tiny fibers which emerge along the whole wire. At the beginning the restrike channel of copper and constanstan wires has an helicoidal form. Annealed wires show the same results. Helical channels were not observed in tungsten wires. By twisting the copper and constantan wires in the opposite direction to the channel helix, it was possible to change the direction of the helix. Thus, the helical shape of the channel may be an effect produced by the twisting of the wire in mounting it betwen the electrodes. The possibility that the helicoidal shape of the channel is due to some other effect is also discussed.

An Improved Technique to Induce a Standardized Functional Stenosis of a Coronary Artery

A simple technique to induce a reproducible functional stenosis of a coronary artery in acute experiments is described. The artery is narrowed by stepwise twisting of a thin copper wire until a zero f