Thin Copper Strips Research Articles

Study on the forming of complex shaped microparts by progressive micropunching of thin copper strip

In this work, a progressive micropunching technology was proposed to form complex shaped microparts using thin copper strip with a thickness of 200 μm. The mechanical properties, microstructure and texture of the annealed thin copper strip were systematically studied, and the quality of the formed microparts through both 1-step micropunching and progressive micropunching were evaluated and discussed. The results show that annealing temperatures of 500 and 600 °C are beneficial to improve the plasticity and formability of copper strips, thereby enhancing the dimensional and shape accuracy of formed complex shaped microparts. Compared with the formed products after 1-step micropunching, the smooth zone of the microparts by progressive micropunched increases by 25%. Also, progressive micropunching significantly improves the surface finish of the cross section of formed microparts. Overall, the proposed progressive micropunching process is functional to enhance the dimensional and shape accuracy of punched parts, exhibiting superiority in comparison with 1-step micropunching process.

Towards 2D dosimetry using monolithic active pixel sensors and a copper grating

Higher energy and intensity X-ray radiotherapy treatments are coming into wider use, having the benefit of requiring fewer treatment fractions and fewer hospital visits per patient. However, small percentage errors in multileaf collimator positioning and dose become bigger problems with higher doses per fraction. Hence, real-time treatment verification becomes essential. Where devices downstream from the patient suffer from scattering in the patient, upstream devices can disturb the therapeutic beam. Here, a method is proposed for performing dosimetry upstream using monolithic active pixel sensors, which can be made thin enough to disturb the beam by <1%. In order to calculate the dose to the tumour, a verification device needs to make a measurement of the photon field. Some photons will Compton scatter an electron in the silicon and generate a signal. However, this signal is obscured by energy deposits from contamination electrons, originating from Compton scattering in the accelerator head and air. Often extensive build-up material is added to verification devices to reduce the electron contamination and enhance the photon signal. However, this leads to degradation of the beam intensity to the patient. Instead we propose using thin strips of 50 µm thick copper in a grating pattern and measuring the difference in the signal with and without it. The contamination electrons are relatively undisturbed by the presence of the thin copper strips and the photon signal generated via Compton scattering is enhanced under the strips. Hence the difference in the two signals mostly consists of energy deposits originating from the therapeutic photons. From this the dose to the patient can be derived. The 50 μm of copper is thin enough to keep the beam attenuation below 1%, but in itself would give a total signal response which consists of 38% contamination electrons. Using the grating technique, we show that the electron contamination can be reduced to 2.6% of the total signal. This allows the photon signal only to be extracted from the data and thus the dose to patient with a very thin upstream detector can be calculated using a Monte Carlo model to extrapolate the photon flux into the tumour.

A compound pendulum for thrust measurement of micro-Newton thruster

A thrust stand is developed for testing micro-Newton level thrusters on the ground. The stand is composed of a compound pendulum that is symmetrically suspended by two thin beryllium copper strips, and it is precisely calibrated by gravity. The stiffness of the stand can be adjusted in 3 orders of magnitude by a counterweight. When the stiffness is larger than 1 Nm/rad, the stand demonstrates a fast response to thrust. The measured range of the stand reaches 1000 μN, and the noise is less than 0.1 μN/Hz within 1 mHz-1Hz. To calibrate the resolution of the stand, an electrostatic force is applied to the stand with an actuator. The equivalent thrust is determined to be 0.09 μN with a standard uncertainty of 0.02 μN. Using the stand, a micro-Newton colloid thruster is tested. The output of the colloid thruster changes with the applied voltage as 0.015(1) μN/V. When changing the voltage by 50V, the change in thrust is measured to be 0.7 μN with a standard uncertainty of 0.1 μN.

Graphene Growth Directly on SiO2/Si by Hot Filament Chemical Vapor Deposition

We report the first direct synthesis of graphene on SiO2/Si by hot-filament chemical vapor deposition. Graphene deposition was conducted at low pressures (35 Torr) with a mixture of methane/hydrogen and a substrate temperature of 970 °C followed by spontaneous cooling to room temperature. A thin copper-strip was deposited in the middle of the SiO2/Si substrate as catalytic material. Raman spectroscopy mapping and atomic force microscopy measurements indicate the growth of few-layers of graphene over the entire SiO2/Si substrate, far beyond the thin copper-strip, while X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy showed negligible amounts of copper next to the initially deposited strip. The scale of the graphene nanocrystal was estimated by Raman spectroscopy and scanning electron microscopy.

On-Line Quantification of Corrosive Sulphur Content in Large Autotransformers

This paper introduces the use of thin film copper strips as a potential approach for online quantification of corrosive sulphur content in transformer insulating oils. The progression of sulphur corrosion is tracked by means of the changes in resistance of the thin film copper strips which is measured based on low-resistance measurements using the four-wire measurement method. The results show that the change of resistance of thin film copper is a function of the level of corrosive sulphur compounds (i.e. in ppm) and the bulk temperature of the oil.

Development of Rational Reduction Schedules and Roll Profiles in Simulating the Rolling of Thin Copper Strips

Rational reduction and tension schedules and roll profiles for 150/500×400 four-high reversing mill and 350×450 two-high reversing mill were developed and studied to increase the output of strips of high accuracy. For the 150/500×400 mill, increasing the work roll crown from +0.1 to +0.15 mm, the specific back tension from 0.12–0.16 to 0.14–0.18 МРа, and the specific front tension from 0.16–0.18 to 0.18–0.20 MPa appeared to decrease the transverse thickness deviation of strips by 10% compared with the conventional reduction and tension schedules. For the 350×450 mill, increasing the work roll crown from +(0.04–0.07) to +0.09 mm, the specific back tension from 3.3 to 8.7 MPa, and the specific front tension from 4.44 to 10.0 МРа appeared to decrease the transverse thickness deviation of 1-mm strips to 0.039 mm, which may be considered high accuracy. A mathematical model is proposed to analyze the stress-strain state of wavy strips with allowance for hardening. The numerical modeling showed that the tangential stresses are maximum on the upper and lower faces of a 0.5h1 strip, while the radial stresses are maximum in the neutral plane of the strip.

Electrically small folded spherical helix antennas using copper strips and 3D printing technology

Folded spherical helix (FSH) antennas using thin and wide copper strips instead of thick wires as a means of reducing the electrical size of ka is designed. It is found that FSH antennas made of copper strips show comparable radiation properties to FSH antennas made of thick wires. Furthermore, such designs can achieve even smaller size down to ka of 0.11 while keeping the radiation quality factors approaching the lower physical bound. An FSH antenna made of copper strips with ka of 0.21 is fabricated as a prototype using 3D printing technology. The measured resonance occurs at 307 MHz with the radiation efficiency of about 90%, verifying the simulated results and the proposed method of utilising copper strips in designing extremely small yet highly efficient volumetric folded helix antennas.

Damage Evaluation of Lead-Free Solder Joints Based on Micro-Electrical-Resistance Strain Measurement

The relationship between the micro-electrical-resistance strain and the damage was obtained via the theoretical formula deduction, which provides a theoretical foundation for the feasibility of measuring solder joints’ damage based on micro-electrical-resistance strain. Single shear lap creep specimens with a 1 mm2 cross sectional area between thin copper strips were fabricated using lead-free solder (Sn-3.5Ag) to quantify their micro-electrical-resistance strain with in situ micro-electrical-resistance strain measurement under the shear tensile loading. The results showed that the micro-electrical-resistance strain of the solder joints had two stages at the room temperature. And it increased slowly with an almost linear growth trend at the first stage but increased quickly with an almost exponential growth trend at the second stage. The creep damage curves were very similar with the classic creep damage curve.

A strip-shield improves the efficiency of a solenoid coil in probes for high-field solid-state NMR of lossy biological samples

A strip-shield inserted between a high inductance double-tuned solenoid coil and the glass tube containing the sample improves the efficiency of probes used for high-field solid-state NMR experiments on lossy aqueous samples of proteins and other biopolymers. A strip-shield is a coil liner consisting of thin copper strips layered on a PTFE (polytetrafluoroethylene) insulator. With lossy samples, the shift in tuning frequency is smaller, the reduction in Q, and RF-induced heating are all significantly reduced when the strip-shield is present. The performance of 800MHz 1H/15N and 1H/13C double-resonance probes is demonstrated on aqueous samples of membrane proteins in phospholipid bilayers.

The effect of resistive filament interconnections on coupling losses in filamentaryYBa2Cu3O7 coated conductors

The effect of normal metal interfilamentary connections on AC losses was investigated for multifilamentaryYBCO (YBa2Cu3O7) coated conductors. This effect was studied for resistiveinterconnections (thin copper strips) on samples of multifilamentYBa2Cu3O7 coated conductor of two types in an applied harmonic external magneticfield with frequencies between 10 mHz and 0.9 Hz, and amplitudes up to∼0.1 T. For samples with well insulated filaments, the losses were of a purely hysteretic nature.The loss greatly increases when filaments are electrically connected at both ends of thesample due to the coupling losses. Additional normal metal bridges in the center of thesample only minimally increase the coupling losses. We also investigated the losses insamples with an artificially low resistance between the filaments, where the coupling loss iscomparable to the hysteresis loss even at low frequencies. The effect of the bridgeplacement on coupling loss is the same as that for samples with well insulated filaments.For our samples we did not observe a reduction of coupling losses due to the normalmetal bridges. However, they can be used to enable current sharing between thesuperconducting filaments without raising the overall level of losses if appropriatelyplaced.

Size effects of lead-free solder joint thickness under shear creep based on micro-electrical-resistance strain

Single shear lap creep specimens with a 1 mm2 cross sectional area between thin copper strips were developed and fabricated using a lead-free solder (Sn–3.5Ag) to quantify their electrical resistance. The electrical-resistance strain of solder joints with different thicknesses (0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.40, 0.50 mm) were measured by a tailor-made in situ micro-electrical-resistance measurement. The results showed that the solder joints with 0.25 mm thickness yielded a minimum electrical-resistance strain and the longest creep life. Thicker solder joints produced a larger electrical-resistance strain and a shorter lifetime if the thickness >0.25 mm. In contrast, thinner solder joints produced a larger electrical-resistance strain and a shorter lifetime if the thickness <0.25 mm. A quantificational relationship between the electrical-resistance strain and the solder joint thickness was obtained according to the experimental data. On the other hand, solder joints with different thicknesses (corresponding to those used in the experiment) were studied by the finite element method (FEM). The results showed that the creep strain of solder joints was the lowest with 0.25 mm thickness, and the creep strain increased with the increment in the thickness if the thickness >0.25 mm but decreased with the increment in the thickness if the thickness <0.25 mm. The quantificational relationship between the creep strain and solder joints thickness was obtained according to the data of FEM. Finally, the quantificational relationship between the creep strain and the electrical-resistance strain was obtained by combining the experimental data and the FEM data.

Quantification of creep strain in small lead-free solder joints with the in situ micro electronic-resistance measurement

Single shear lap creep specimens with a 1 mm 2 cross sectional area (similar in size to small lead-free solder joints used in electronic packaging and jointing) between thin copper strips were developed and fabricated using lead-free solder (Sn–3.5Ag) to quantify their creep strain with in situ micro electronic-resistance measurement. Where the solder joints’ micro electronic-resistance is in situ measured by an electronic testing system (tailor-made for the micro electronic-resistance and stress measurement) and recorded by a PC via serial port, then all data of micro electronic-resistance and elapsing time are formed in curves. They are used to describe the solder joints’ micro electronic-resistance and electronic-resistance strain varied with time. Most of curves can reveal the continual development of damage and fracture mechanisms which are consistent with observations generated by literatures. The quantitative relationship between electronic-resistance strain and mechanical-creep strain was proved theoretically using a mathematic model. These mean that the in situ micro electronic-resistance measurement can be used as an alternative quantification of creep strain in small lead-free solder joints. Thus, provide an alternative and simplified evaluation method about the reliability of a solder joint.

A Three-Dimensional Numerical Modeling of Atmospheric Pool Boiling by the Coupled Map Lattice Method

In the present paper, the characteristic atmospheric pool boiling curve is qualitatively reproduced for water on a temperature controlled thin copper strip having comparable length and breadth by the coupled map lattice (CML) method using a three-dimensional boiling field model. The basic objective of the work is to improve the prediction of the critical heat flux (CHF) with respect to the 2D CML model of Ghoshdastidar et al. (Ghoshdastidar, P. S., Kabelac, S., and Mohanty, A., 2004, Numerical Modelling of Atmospheric Pool Boiling by the Coupled Map Lattice Method, J. Mech. Eng. Sci., IMechE Part C, 218, pp. 195-205). The work models saturated pool boiling of water at 1 bar on a large (much larger than the minimum wavelength of 2D Taylor waves) and thin horizontal copper strip. The pool height is 0.7 mm, indicating thin film boiling. In the present model, it is assumed that boiling is governed by (a) nucleation from cavities on a heated surface, (b) thermal diffusion, (c) bubble rising motion and associated convection, (d) phase change and (e) Taylor instability. The changes with respect to the 2D model are primarily with respect to 3D modeling of thermal diffusion and 2D distribution of nucleating cavity sizes. The predicted CHF is 1.57 MW/m 2 as compared to the actual value of 1.3 and 0.36 MW/m 2 predicted by the 2D CML model of Ghoshdastidar et al. (see above). It can be said that for the first time a coupled map lattice method which is essentially qualitative in nature has been able to predict the CHF of saturated pool boiling of water at 1 bar very close to the actual value. Furthermore, a sensitivity analysis shows that the model gives physically realistic and stable results.

Material flow in butt friction stir welds in AA2024-T3

The properties of a workpiece joined by friction stir welding (FSW) are directly related to the material flow around the tool. In the present work, the material flow is investigated by traditional metallography as well as X-ray and computer tomography (CT). By introducing a thin copper strip in the workpiece and welding through it, thus, acting as a marker material, detailed information about the flow field is gathered. The two- and three-dimensional CT images are used in parallel with micrographs for visualization of the flow field. Two procedures for estimating the average velocities for material flowing through the shear layer are presented. The procedures depend on the configuration of marker material relative to the welding direction, i.e. longitudinal and transverse. As such, the present work constitutes the first attempt in the literature to estimate flow velocities in FSW based on thorough experimental investigations.

Numerical modelling of atmospheric pool boiling by the coupled map lattice method

In the present paper, the characteristic atmospheric saturated pool boiling curve is qualitatively reproduced for water on a temperature-controlled long and thin copper strip using the coupled map lattice (CML) method known in non-linear spatio-temporal chaos dynamics. The pool height is 0.7 mm, indicating that the boiling is of the thin-film type. The work modifies the basic theoretical model proposed by Shoji in 1998 in terms of nucleation superheat distribution and mixing. The stirring action of the bubbles is modelled by increasing the fluid thermal diffusivity by an enhancement factor. It is assumed that boiling is governed by (a) nucleation from cavities on a heated surface, (b) thermal diffusion, (c) bubble rising motion and associated convection, (d) phase change and (e) Taylor instability. The effectiveness of the enhancement factor approach in the present model is clearly seen in its capability of reproducing the saturated pool boiling curve well and predicting the critical heat flux (CHF) in the same order of magnitude of the actual value.

THz interconnect with low-loss and low-group velocity dispersion

We report the demonstration of a physically flexible, practicable THz interconnect with minimal pulse distortion and loss. The interconnect is a parallel-plate waveguide, with the TEM mode excited, constructed of two thin copper strips. The incoming 0.22 ps THz pulse broadens to 0.39 ps after propagating 250 mm in the waveguide and is also attenuated by a factor of ten. We show that this attenuation is mainly due to the finite conductivity of copper with some additional loss caused by the beam spread in the unguided dimension. The pulse broadening is due to the frequency-dependent loss since the group velocity dispersion is negligible.

Verification of the correspondence between CT-stimulated and treatment beams.

A single phantom technique has been developed to verify the full CT simulation and treatment-beam delivery procedures. The phantom consists of a target delineated by thin copper strips, affixed to therapy verification film, and inserted securely between two slices of water-equivalent material. The target is defined with the aid of the copper strips, and the position of the isocenter and beam parameters such as field size, and gantry and collimator angle are determined by CT simulation. With these parameters, the phantom is subsequently irradiated by the linear accelerator in the treatment position. Correspondence between the planned and the irradiated region is determined by the position of the copper strips on the film. The technique is a simple and practical method for verifying the entire CT simulation and treatment-beam delivery processes, and provides a permanent record of the correspondence between the planning digitally reconstructed radiographs (DRR) and the actual beam delivered.

Low-Cost Hot Stage For Crystal Studies

Abstract I required a hot stage to do some work with iiquid crystals. Hot stages on the market are very expensive. I decided to try using electro-conductive glass, This is the NESA glass used by automotive manufacturers in electrically operated defrosting windows, A local glazier ordered some of the glass for me in 8 x 8 inch squares, i had the squares cut and edge polished into 2 x 2 inch pieces by a filter manufacturer. One sheet of 8 x 8 inch glass cost me about $15.00. Cut down, I got nine 2 x 2 inch pieces suitable for my experiments at an additional cost of $3.00 per cut piece. A piece of 2 x 2 inch electro-conductive glass is prepared with two thin copper strips epoxied to the outer margins. One needs a conductive epoxy, and i used a silver epoxy (40-3900 resin and catalyst) obtained from Epoxies, Etc. of Greenville, Rl.

Analysis of thin copper film planar lines with fractal structure for microwave circuits

We propose modifying the spectral-domain approach to analyze planar lines with a very thin copper strip, presenting a fractal character. We derive, from a fractional derivative electromagnetism formulation, a new modified surface impedance introduced in that numerical technique. The results exhibit very sensitive evolution of the losses and of the relative effective permittivity versus frequency. ©1996 John Wiley & Sons, Inc.

Combined reduction and sintering of preformed cuprous oxide strip

A new method of making thin copper strip direct from cuprous oxide powder by an integrated powder technology route has been outlined. The proposed route consists of making, by a slurry method, a green cuprous oxide strip which is subsequently reduced with hydrogen to produce a porous copper strip. The strip is densified by hot rolling to produce a fully dense structure. The combined reduction and sintering behaviour of the green cuprous oxide strip is reported. The mechanism of reduction of the cuprous oxide with hydrogen at various temperatures is discussed, and the geometry of the reaction zone in the green oxide strip is described.MST/183