Shearing Mechanism of Straight Thin Copper Wires at Connecting Terminal due to Lightning Current

When a lightning current is impressed through a copper wire, the copper wire would be melted. A straight thin copper wire with a diameter of 0.1 mm,~ is melted due to the specific melting Joule heating （j^2t）m in an adiabatic condition. However, it has been recognized in the experiment that the thicker copper wires of φ1 mm are not completely melted, but sheared mainly at the connecting terminal by a relatively low impulse current. Electro-magnetic mechanical shearing stress, etc. are discussed in addition to the conventional Joule heating. New broken mechanisms were presumed and proved in the additional experiments.

A novel integrated microfluidic chip for on-demand electrostatic droplet charging and sorting

On-demand droplet sorting is extensively applied for the efficient manipulation and genome-wide analysis of individual cells.However,state-of-the-art microfluidic chips for droplet sorting still suffer from low sorting speeds,sample loss,and labor-intensive preparation procedures.Here,we demonstrate the development of a novel microfluidic chip that integrates droplet generation,on-demand electrostatic droplet charging,and high-throughput sorting.The charging electrode is a copper wire buried above the nozzle of the microchannel,and the deflecting electrode is the phosphate buffered saline in the microchannel,which greatly simplifies the structure and fabrication process of the chip.Moreover,this chip is capable of high-frequency droplet generation and sorting,with a frequency of 11.757 kHz in the drop state.The chip completes the selective charging process via electrostatic induction during droplet generation.On-demand charged microdroplets can arbitrarilymove to specific exit channels in a three-dimensional(3D)-deflected electric field,which can be controlled according to user requirements,and the flux of droplet deflection is thereby significantly enhanced.Furthermore,a lossless modification strategy is presented to improve the accuracy of droplet deflection or harvest rate from 97.49% to 99.38% by monitoring the frequency of droplet generation in real time and feeding it back to the charging signal.This chip has great potential for quantitative processing and analysis of single cells for elucidating cell-to-cell variations.

Effect of ultrasonic power and bonding force on the bonding strength of copper ball bonds

Copper wire, serving as a cost-saving alternative to gold wire, has been used in many high-end thermosonic ball bonding applications. In this paper, the bond shear force, bond shear strength, and the ball bond diameter are adopted to evaluate the bonding quality. It is concluded that the ef/~cient ultrasonic power is needed to soften the ball to form the copper bonds with high bonding strength. However, excessive ultrasonic power would serve as a fatigue loading to weaken the bonding. Excessive or less bonding force would cause cratering in the silicon.

Expansion of Plasma of Electrically Exploding Single Copper Wire Under 4.5kA～9.5kA/Wire

The experimental system for electrically exploding single metal wire has been designed and manufactured. Expansion of the dense plasma column formed from an electrically exploding Cu wire of diameter 30 μm has been studied with a high-speed photographer to obtain the time-dependent radius (R-t) curve. The experimental results demonstrate that the mean expansion rate of the dense plasma column is 1.94 μm/ns, 2.6 μm/ns and 3.75 μm/ns according to the peak pulse current 4.5 kA, 7 kA and 9.5 kA respectively. The results can be beneficial to giving a profound understanding of the early stage of wire-array Z-pinch physics and to improvement on their design.

Modified Coated Copper Wire as a New Fiber for SPME-GC Analysis of Some Polycyclic Aromatic Hydrocarbons

In this study for the first time, a novel copper Solid Phase Microextraction (SPME) fiber has been introduced for removal of naphthalene, phenanthrene and anthracene from aqueous solution. Copper was used as a solid support, which was at first coated by 3-mercaptopropyltrimethoxysi- lane. A stationary phase of oxidized multi walled carbon nanotube (MWCNTs)) was bonded to the surface of the copper wire. The developed SPME was characterized by IR and Scanning Electron Microscopy (SEM) and coupled to gas chromatography for separation of the analytes. Stability of the fiber, the effect of coating thickness and recovery time were optimized. The MWCNTs film thickness was about 5 μm which was perfect for a rapid mass transfer. The detection limits were at the range of 0.005 to 0.1 μg·L-1. The calibration curves were linear R2 > 0.9813 in the range of 0.01 to 5 μg·L-1. The method has been successfully applied for real samples with standard addition of 5 μL-1 of each sample. Stability study of the fiber to acid and alkali shows that it can be used for more than 50 times.

High-performance carbon fiber/gold/copper composite wires for lightweight electrical cables

In this study,we synthesized high-performance Carbon Fiber/Gold/Copper(CF/Au/Cu)composite wires by using a 2-step deposition method via sputtering and electrodeposition.After Au was sputtered on PANbased CFs as a pre-treatment,the wettability and surface reactivity of the CFs were improved,resulting in a homogeneous deposition of Cu on their surface.At different Cu electrodeposition time,the resulting CF/Au/Cu composite wires could possess a high strength of up to 3.27 GPa(~10 times stronger than copper wires)while their electrical conductivity could be as high as 4.4×10^5 S/cm(~75%of that for copper).More importantly,since the composite wires were lightweight(up to 70%lower than Cu mass density),they are a promising candidate to substitute conventional heavy metal wires in the future electrical applications.

Comparison of the copper and gold wire bonding processes for LED packaging

Wire bonding is one of the main processes of the LED packaging which provides electrical interconnec- tion between the LED chip and lead frame. The gold wire bonding process has been widely used in LED packaging industry currently. However, due to the high cost of gold wire, copper wire bonding is a good substitute for the gold wire bonding which can lead to significant cost saving. In this paper, the copper and gold wire bonding processes on the high power LED chip are compared and analyzed with finite element simulation. This modeling work may provide guidelines for the parameter optimization of copper wire bonding process on the high power LED packaging.

金属细丝扭转中的尺寸效应与钝化效应

本文对直径在25-50微米、有无钝化层的微尺度铜丝进行了扭转测试,开展了尺度效应与钝化效应的实验研究.通过磁控溅射制备了镀钛铜丝试样,在扭转测试中观察到直径减小和钝化层存在引起的屈服强度和流动应力的增加.与未钝化铜丝相比,钝化铜丝中存在更加明显的尺度效应,钝化铜丝的规范化扭矩随着直径减小而增加更为显著.基于Fleck-Hutchinson应变梯度塑性理论对铜丝的扭转响应进行了预测,数值结算结果与实验数据吻合较好,并阐明了钝化层对铜丝扭转变形影响的物理机制。

Role of electrodes in ambient electrolytic decomposition of hydroxylammonium nitrate (HAN) solutions

Decomposition of hydroxylammonium nitrate (HAN) solution with electrolytic decomposition method has attracted much attention in recent years due to its efficiencies and practicability.However,the phenomenon has not been well-studied till now. By utilizing mathematical model currently available,the effect of water content and power used for decomposition was studied. Experiment data shows that sacrificial material such as copper or aluminum outperforms inert electrodes in the decomposition of HAN solution. In the case of using copper wire to electrolyse HAN solutions, approximately 10 seconds is required to reach 100℃ regardless of concentration of HAN. In tem of power consumption,100W-300W was found to be the range in which decomposition could be triggered effectively using copper wire as electrodes.