Copper Balls Research Articles

A strategy that combines the adhesion and hydration of polydopamine to realize targeted water lubrication

Water has many natural advantages for using as an ecological lubricant in engineering. However, how to ensure the efficiency and stability of water lubricating film with low viscosity has been always the key point of practical applications. For this, a strategy is given to improve lubricating capacity of water under loads by combining the biomimetic adhesion and hydration lubrication of polydopamine (PDA). The PDA nanoparticles were polymerized and purified, and its aqueous suspensions were used to solve the difficult problem of lubrication failure when using water as lubricant. The morphology characteristics and lubrication performance of PDA nanoparticles were experimentally tested and analyzed. The results showed that PDA nanoparticles can form an adhesive-lubricating film on the copper balls and effectively reduce the tribological behaviors in rubbing processes. This strategy that combines the biomimetic adhesion and hydration lubrication of PDA provides a novel method to realize targeted hydrated film and excellent water lubrication under load bearing conditions.

Analysis of the Formation Mechanism of Short Circuit Marks

In this study , short -circuit processes were analyzed via simulations and experiments by applying a principle that can interpret the short-circuit marks, which are the most basic inspection criteria in fire-scene investigation. According to Fleming's left-hand rule, a Lorentz force is generated when current and magnetic fields are applied. Railgun, one of the typical applications, utilizes the same basic principle for generating trajectories. Using the same concept, it was interpreted that the molten copper balls generated during a short-circuit process scatter in the load direction similar to a ballistic launch. The simulation and experimental results also confirmed that the copper balls were scattered in the load direction owing to the Lorentz force. Although it is impossible to examine the source and load during a fire-scene investigation process, the study findings will aid in predicting the load by observing the portion where the copper bulbs are relatively frequent. Thus, based on an estimation of the cause of fire, it will be possible to infer reliable results through fire-scene investigation.

Triprotic Ammonium Oleate Ionic Liquid Crystal Lubricant for Copper-Copper Friction and Wear Reduction

The triprotic ammonium carboxylate ionic liquid crystal (2-hydroxyethyl)ammonium oleate (MO) has been studied as a neat lubricant and as a lubricant additive in two base oils, PAO6 and 100N. The lubricants have been used in commercially pure copper-OFHC copper balls on disk reciprocating sliding contact at room temperature. Neat MO presents a very good lubricating performance, with a friction coefficient of 0.06 and a wear rate of OFHC copper disk of 4.15 × 10−7 mm3/N·m. These results are, respectively, 94% and 98% lower than those obtained for PAO6, with similar reductions obtained with respect to 100N. MO has also been studied as an additive in 2wt.% proportion. The severe abrasive wear mechanism that takes place in the presence of neat base oils is reduced by the MO additive.

Behavior characteristics of Janus particles impacting bubbles

In order to better apply amphiphilic Janus particles to phase change heat transfer, the hydrophilic-superhydrophobic Janus particles are prepared with copper balls. The particle size is 1.0 mm and the bubble diameter is 3.0 mm. The behavior of Janus particle with small bubbles impinging on bubbles at different heights is studied. The falling heights are 0, 10.0, 20.0, 30.0 and 40.0 mm. The results show that there are obvious differences in behavior characteristic among Janus particles with different wettability surfaces when they hit the bubble. When the superhydrophobic side contacts the bubble, it will slide to the bottom of the bubble without rotation along the bubble surface; when the hydrophilic side contacts the bubble, it will first slide along the bubble surface for a certain distance, and then rotate, resulting in strong disturbance to the bubble. When the interface between hydrophilic and superhydrophobic contacts the bubble, the particle will start to rotate at the moment of contact. When Janus particle impacts the bubble at a certain height, the hydrophilic surface generally contacts bubble first. With the increase of height, the degree of deformation of Janus particles pulling bubbles increases. The force analysis shows that the main reason for the rotation of Janus particles is that the action points and directions of capillary force acting on different wettable surfaces are different, resulting in corresponding rotation torque.

A SiC Double-Sided Stacked Wire-Bondless Power Module for High-Frequency Power Electronic Applications

Abstract This article reports a double-sided stacked wire-bondless power module package for silicon carbide (SiC) power devices to achieve low parasitic inductance and improved thermal performance for high-frequency applications. The design, simulation, fabrication, and characterization of the power module are presented. A half-bridge module based on the SiC power MOSFETs is demonstrated with minimized parasitic inductance. Double-sided cooling paths are used to maximize heat dissipation. Besides conventional packaging materials used in the power module fabrication, a low-temperature cofired ceramic (LTCC) and nickel-plated copper balls are used in this module package. The LTCC acts as an interposer providing both electrical and thermal routings. The nickel-plated copper balls replace bond wires as the electrical interconnections for the SiC power devices. The electrical and thermo-mechanical simulations of the power module are performed, and its switching performance is evaluated experimentally.

Study on the microstructure and properties of a phosphor copper ball during its formation process

Microcrystalline phosphor copper balls with a diameter of 28 mm were prepared via continuous extrusion upsetting. Optical microscopy and electron backscatter diffraction were used to study the microstructural evolution of phosphor copper balls during the formation process. In addition, the hardness distribution and tensile properties were tested. The results show that fine dynamic recrystallisation grains and twins were formed after continuous extrusion and that the grains were further refined after upsetting. After continuous extrusion upsetting, there were typical 〈111〉, 〈100〉, and 〈110〉 fibre textures, and the proportions of these three textures in the individual samples were different. The change in microhardness was affected by the microstructure. The increase in the hardness value from casting and continuous extrusion upsetting was owing to pronounced grain refinement. The grain sizes from the centre to the edge were similar, and the grain refinement was more uniform. Notably, the grain size of the extruded rod was still fairly uniform from the centre to the edge in the radial direction. It can be concluded that the continuous extrusion-upsetting phosphor copper anode is more conducive to the formation of black film, that is, it is more suitable for electroplating anode material.

Expansion of the Beamforming Coverage Area in an Elevation Plane for 60 GHz Band 3-D Beamforming

This letter proposes a novel antenna structure for 60 GHz band 3-D coverage beamforming. By using the proposed antenna structure, the coverage area can be expanded in an elevation plane. Dipole and patch subarray antennas were packaged into one structure by using the copper balls interconnection technique. A simple idea to utilize dipole and patch elements enables endfire and broadside radiations resulting in the coverage area expansion in the elevation plane. Two 2 × 4 array antennas were made up of eight multilayered substrate. Six metal layers were used for each multilayered substrate.

Experimental research on energy dissipation based on damping of magnetic fluid

Energy dissipation of tall building structures suffering frequent violent shaking under strong excitation is a key research topic for the safety of such buildings. In this paper, a new-type tuned magnetic fluid damper with copper balls immersed is proposed to reduce the vibration under different excitation frequencies. First, the natural frequency of the damper was deduced by the Kinetic equations of magnetic fluid, and the sizes of the copper balls in the damper were determined by constructing the equivalent damping ratio model. Meanwhile, the viscosity changes of the magnetic fluid with different magnetic fields were obtained by establishing the finite element simulation of the magnetic field and carrying out the magnetic-viscous experiment about the magnetic fluid. The kinetic energy of magnetic fluid and copper balls were obtained by constructing dynamic finite element simulation model. The vibration experiment was carried out to verify the damping effect of the damper. Finally, the conversion of dissipated energy in the process of energy dissipation was analyzed by building fitting functions, and then analyzed in combination with the simulation results. The experimental results showed that the amplitude attenuation of horizontal vibration was obvious under the action of the damper when the excitation frequency was close to the natural frequency of the damper. In addition, most dissipated energy was converted into the kinetic energy of magnetic fluid and copper balls.

Experimental Verification of Excavated Structure on Multi-Layered Substrates for Millimeter-Wave Signal Vertical Transition Using Copper Balls

This paper presents a vertical transition of millimeter-wave signal for interconnection between multi-layered substrates, which utilizes copper balls for vertical interconnection, as both for electrical connection and physical support. In particular, the copper balls were used to configure a quasi-coaxial transmission line at the vertical interconnection. The key idea was to create an excavated structure at the location of the copper balls to fix it, given that the copper balls slightly fluctuate during reflow soldering when simply placed on a flat surface. Such activity of the copper balls defines large variation in transmission characteristics at millimeter-wave band that produce low yield rate. Practically, with the proposed method of an excavated structure, the location error of the copper balls can be minimized, leading to high reproducibility in determining the copper balls location, and small variation of the transmission characteristics. To verify the method's effectiveness, a prototype having three vertically stacked multi-layered substrates with the excavated structure was fabricated. The excavation had a depth of 90 μm and diameter of 0.45 mm. The copper balls used had a 0.3-mm diameter. Five samples were fabricated and then evaluated by X-ray images and S-parameter measurements. Based on the results, the reflection characteristics of the measurement were less than -10 dB from dc to 97GHz in the best-case scenario, whereas the variation in the S-parameters was comparatively small up to 70 GHz. Moreover, the X-ray images showed relatively small copper balls location error. These results indicate that the proposed excavated structure is effective for millimeter-wave vertical interconnections using copper balls, in small wireless terminal applications.

Performance Analysis of Latent Heat Thermal Energy Storage using Phase Changing Material in a Circular Orientation

The enormous consumption of energy has led to the fact of saving it at large. To negate the loss of energy, the present work commences research in the field of Thermal Energy Storage in its latent form incorporating Phase Changing Material (PCM) in circular oriented copper Ball Structure. Heating of PCM (by an electric heater) inferred in these copper balls continues till 85˚C(well beyond the melting point of selected PCM), and then when disconnected, PCM discharges gradually giving off the heat accumulated within. Considering 30litres of water in Latent Heat Thermal Energy Storage Tank(LHTES), for a family of four, the research intends to investigate the prolonged duration of time required to keep the water warm. The consequence presents that the time required to charge(heat) water is 4.6 hours(270minutes) and discharge(heat is given off) is 29hours(1740 minutes). Thus proving significant potential in keeping water warm for better performance in a circular orientation.

Optimized Electromagnetic Fields Levitate Bulk Metallic Materials

The bulk metallic electromagnetic levitation technique has a promising application prospect in condensed physics and materials science. In order to resolve the problem of weak levitation force and the small size of samples, an optimized solution based on finite element analysis (FEA) is developed to seek the best electromagnetic field distribution in the levitation zone. The influence of material properties on the distribution of magnetic flux density, surface pressure, and the Lorentz force were studied by the FEA method with various sample sizes of titanium and copper balls. The levitation capability of cylindrical coil system which consists of a single-layer coil with an inner diameter of 30 mm and the levitated object with a diameter of 20 mm was analyzed. To keep a balance between the turn number and increment efficiency of force, the best number of 7 turns is confirmed. Then, two types of optimized coils were predicted by numerical simulations, and the levitation force is improved drastically. The double-layer coil displays an outstanding levitation capability owing to the strong electromagnetic field generated by multilayer turns. In addition, 5 to 50 g aluminum, titanium, copper, and nickel are levitated by the above three kinds of coils and the levitation capacities are validated from the recorded data of the minimum operating current that can levitate the samples. The experimental results show good agreements with the simulation results, and the minimum current for optimized coils is reduced efficiently.

Performance characteristics of a new hybrid solar cooker with air duct

A new hybrid solar box cooker (SBC) has been developed and tested for thermal performance evaluation in climatic condition of western Uttar Pradesh, India. The uniqueness of new box cooker is an integrated trapezoidal duct and its other integrated elements. The objective of the study is to enhance the heat transfer rate and to reduce the cooking timings by consumption of minimum heat energy. For this purpose, a 200 W halogen lamp has been placed inside the duct to enhance the heat transfer. Besides this, 450 of small hollow balls of copper have also been used to improve thermal performance of SBC especially on forced convection mode. The performances testing have been carried to evaluate the thermal efficiency, figures of merit (F1 and F2), cooking power, heat transfer and overall heat loss coefficient. After completion of experiments, thermal efficiency of SBC has been observed 45.11%, cooking power is estimated to be 60.20 W and overall heat loss coefficient is obtained around 6.01 W/m2 C. Results shows that the present design follow the BIS standards and can cook almost edibles in poor ambient conditions by consuming only 210 W. Discussion has also been made on the significance of the use of copper balls, fan and halogen lamp over the performance of SBC. The present solar cooker has been found as first kind of SBC which can efficiently perform on forced convection in any type of climatic conditions.

Aluminum-Scandium: A Material for Semiconductor Packaging

A well-known aluminum-scandium (Al-Sc) alloy, already used in lightweight sports equipment, is about to be established for use in electronic packaging. One application for Al-Sc alloy is manufacture of bonding wires. The special feature of the alloy is its ability to harden by precipitation. The new bonding wires with electrical conductivity similar to pure Al wires can be processed on common wire bonders for aluminum wedge/wedge (w/w) bonding. The wires exhibit very fine-grained microstructure. Small Al3Sc particles are the main reason for its high strength and prevent recrystallization and grain growth at higher temperatures (>150°C). After the wire-bonding process, the interface is well closed. Reliability investigations by active power cycling demonstrated considerably improved lifetime compared with pure Al heavy wires. Furthermore, the Al-Sc alloy was sputter-deposited onto silicon wafer to test it as chip metallization in copper (Cu) ball/wedge bonding technology. After deposition, the layers exhibited fine-grained columnar structure and small coherent Al3Sc particles with dimensions of a few nanometers. These particles inhibit softening processes such as Al splashing in fine wire bonding processes and increase the thickness of remnant Al under the copper balls to 85% of the initial thickness.

Heat Production of Stored Canola Seeds under Airtight and Non-Airtight Conditions

Abstract. Heat production by 14.0% moisture content (MC) canola seeds was determined at 30°C and 20°C under airtight and non-airtight storage conditions by using a transient method. The 14.0% MC canola seeds were placed inside copper balls (15 cm diameter with 1.5 mm wall thickness). The balls were located at the center of cubic plywood boxes (50 cm long in each inner dimension) which were filled with 8.0% MC canola seeds. The plywood boxes were insulated with Styrofoam (14.5 cm thickness). Thermocouples were installed inside and outside the boxes and balls at 27 locations. The heat production rate was calculated by using finite element, analytical, and Fourier law methods. The heat production rate calculated by the finite element method was the heat production rate of the 14.0% MC canola, while the analytical and Fourier law methods overestimated and underestimated the heat production rate, respectively. The mean heat production rates at 30°C non-airtight, 30°C airtight, and 20°C non-airtight conditions were 0.102 ±0.001, 0.084 ±0.003, and 0.036 ±0.001 W kg -1 , respectively. Accumulated heat increased with increase of temperature and decrease of airtightness. The dry mass loss of canola seeds due to respiration of microflora was in accordance with heat production, moisture content increment under airtight condition, and microorganism infestation. The measured heat production ratios were higher than or equal to the theoretical value when only glucose was used as substrate for decomposition.

ChemInform Abstract: Fast, Solvent‐Free Asymmetric Alkynylation of Prochiral sp3 C—H Bonds in a Ball Mill for the Preparation of Optically Active Tetrahydroisoquinoline Derivatives.

AbstractThe asymmetric cross‐dehydrogenative coupling between tetrahydroisoquinolines and terminal alkynes is performed in a ball mill (2 copper balls) with silica gel as grinding agent.

Fast, solvent-free asymmetric alkynylation of prochiral sp3 C–H bonds in a ball mill for the preparation of optically active tetrahydroisoquinoline derivatives

Solvent-free asymmetric cross-dehydrogenative-coupling (CDC) reaction between the sp3 C–H bond of prochiral CH2 and terminal alkynes was first studied under High-Speed Ball-Milling conditions. A series of optical active 1-alkynyl tetrahydroisoquinoline derivatives were achieved by using recoverable copper balls together with PyBox chiral ligand in the presence of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). All coupling products were obtained in good yields at short reaction time with enantiomeric excesses up to 79%.

Application of ultra-smooth composite diamond film coated WC–Co drawing dies under water-lubricating conditions

A specific revised HFCVD apparatus and a novel process combining HFCVD and polishing technique were presented to deposit the micro- and nano-crystalline multilayered ultra-smooth diamond (USCD) film on the interior-hole surface of WC–Co drawing dies with aperture ranging from d1.0 mm to 60 mm. Characterization results indicate that the surface roughness values (Ra) in the entry zone, drawing zone and bearing zone of as-fabricated USCD coated drawing die were measured as low as 25.7, 23.3 and 25.5 nm, respectively. Furthermore, the friction properties of USCD films were examined in both dry sliding and water-lubricating conditions, and the results show that the USCD film presents much superior friction properties. Its friction coefficients against ball-bearing steel, copper and silicon nitride balls (d4 mm), is always lower than that of microcrystalline diamond (MCD) or WC–Co sample, regardless of the lubricating condition. Meanwhile, it still presents competitive wear resistance with the MCD films. Finally, the working lifetime and performance of as-fabricated USCD coated drawing dies were examined under producing low-carbon steel pipes in dry-sliding and water-lubricating conditions. Under the water-lubricating drawing condition, its production significantly increases by about 20 times compared with the conventional WC–Co drawing dies.

Shear Strength and Failure Modes of As-Bonded Gold and Copper Ball Bonds on Aluminum Metallization

The shear test failure modes of “as-bonded” gold and copper ball bonds are fundamentally different. Soft gold balls are typically sheared by the tool, leaving a lower section of the ball bonded to the aluminum metallization. In contrast, copper balls do not undergo appreciable plastic deformation and are sheared completely away from the bond pad. Evidence is presented to show that the different failure modes of gold are copper are due to the relative strength of the balls. Copper balls are generally harder than gold balls, and the failure mode changes to the weakest interface, which is at the ball– aluminum bond pad. Gold ball bonds fail due to plastic deformation of the ball, while copper ball bonds fail by a process of plastic deformation in the aluminum bond pad.

60-GHz Band Copper Ball Vertical Interconnection for MMW 3-D System-in-Package Front-End Modules

In order to realize millimeter-wave (MMW) 3-D system-in-package (SiP) front-end modules, we propose a 60-GHz band copper ball vertical interconnection structure, which interconnects between vertically stacked substrates. The structure enables ICs to be placed between the vertically stacked substrates. Since the diameter of the copper balls must exceed the thickness of the ICs, the distance between the substrates in the modules is larger than that of the flip-chip interconnection widely used in the MMW-band. Therefore, the conventional flip-chip interconnection does not scale for the interconnection between the substrates in MMW 3-D SiP front-end modules. The layout of grounded copper balls and the patterns of inner ground layers in the upper/lower substrates are designed using 3-D electromagnetic field simulation. The designed structure allows less than 1dB transmission loss up to 71.1GHz, compared with a through transmission line. The result is verified with fabrication and measurement and confirms the feasibility of MMW 3-D SiP front-end modules.

Solvent-Free Cross-Dehydrogenative Coupling Reactions under High Speed Ball-Milling Conditions Applied to the Synthesis of Functionalized Tetrahydroisoquinolines

Solvent-free reaction using a high-speed ball milling technique has been first applied to cross-dehydrogenative coupling (CDC) reactions between tetrahydroisoquinolines and three types of pronucleophiles such as nitroalkanes, alkynes, and indoles. All coupling products were obtained in good yields at short reaction times (no more than 40 min). When alkynes and indoles were used as pronucleophile, the reactions can be catalyzed efficiently by recoverable copper balls without any additional metal catalyst.