High copper loading metal organic decomposition paste for printed electronics

A screen-printable metal organic decomposition (MOD) paste with a high copper loading has been developed. Copper precursor (copper hydroxide and copper formate) and copper flasks are used as copper sources in the paste. The copper precursor is reduced to copper nanoparticles during sintering at a temperature of 200 °C for 3 min and forms a conductive film, whereas the copper flakes are added to increase the conductivity of the printed film. The optimal formulation of the screen-printing MOD paste was obtained with a copper hydroxide to formic acid ratio of 0.875 and by adding copper flakes to reach a total copper loading of 30 wt%. The printed film after sintering had a sheet resistance of 39 mΩ/sq and a volume resistivity of 21 μΩ cm.     

Effect of size and shape of metal particles to improve hardness and electrical properties of carbon nanotube reinforced copper and copper alloy composites

Utilizing the extra-ordinary properties of carbon nanotube (CNT) in metal matrix composite (MMC) for macroscopic applications is still a big challenge for science and technology. Very few successful attempts have been made for commercial applications due to the difficulties incorporating CNTs in metals with up-scalable processes. CNT reinforced copper and copper alloy (bronze) composites have been fabricated by well-established hot-press sintering method of powder metallurgy. The parameters of CNT–metal powder mixing and hot-press sintering have been optimized and the matrix materials of the mixed powders and composites have been evaluated. However, the effect of shape and size of metal particles as well as selection of carbon nanotubes has significant influence on the mechanical and electrical properties of the composites. The hardness of copper matrix composite has improved up to 47% compared to that of pure copper, while the electrical conductivity of bronze composite has improved up to 20% compared to that of the pure alloy. Thus carbon nanotube can improve the mechanical properties of highly-conductive low-strength copper metals, whereas in low-conductivity high-strength copper alloys the electrical conductivity can be improved.     

Surfactant-stabilized copper paticles for low-temperature sintering: Paste preparation using a milling with small zirconia beads: Effect of pre-treatment with the disperse medium

Copper paste is considered as a promising candidate for printed electronics in replacement for silver paste. This is owing to copper which has anti-electromigration property, lower cost, and similar conductivity and compared with silver. We synthesize a copper nanoparticle (NP) paste that can be sintered at low temperature for high conductivity. The copper NP paste composes of 50 wt% copper NPs and dipropylene glycol (DPG) as the disperse medium. The effect of DPG coating and various conditions of milling with small beads on improving the dispersity of copper NPs has been investigated. The optimum conditions for milling are at 1000 and 2000 rpm for 30 min. This results in a volume resistivity of 6.62 × 10^-6 Ω·cm after sintering the copper NP paste at 200 °C.     

Determination of copper(II) by displacement substoichiometric extraction with radiolabeled cobalt(II)

A substoichiometric radiochemical displacement technique has been employed for the quantification of trace amounts of copper from complex matrices. The procedure is based on higher stability of copper bipyridine complex compared to its cobalt analog, which leads to the displacement of spiked (⁶⁰Co) cobalt from its bipyridine complex in n-butanol by Cu(II). The amount of labeled cobalt stripped back into the aqueous phase is proportional to the amount of copper incorporated into the organic phase and is monitored for the quantitative estimation of copper. The interferences from various allied ions were critically examined. The proposed method has been successfully employed for the estimation of copper from various certified alloys.     

Application of vacuum refining in copper production

Abstract

his literature review was prepared in order to determine the state of the art with respect to the vacuum refining of copper. There have been numerous reported laboratory investigations of copper refining by vacuum treatment since the 1940s. Most studies have been carried out with the aim of eliminating deleterious impurities, such as arsenic, antimony, bismuth, lead, sulphur, and oxygen, from copper to levels appropriate to marketable grades, thereby improving the quality of the copper produced. It is interesting to note that the majority of work in this area has been carried out by Japanese and Soviet researchers: Japanese authors have generally tried to explain their results by means of kinetic or thermodynamic analyses, whereas the Soviet ones have merely given experimental results. This review contains three sections. In the first, the theory of vacuum treatment is discussed. The second presents information currently available (to 1980) on vacuum refining and is divided into three subsections, based on the type of copper treated, namely: (i) treatment of blister copper (or crude copper); (ii) treatment of anode copper and/or cathode copper; and (iii) treatment of copper matte. Finally, a patent survey has been carried out, which is reported in the third section.

MST/54     

Preparation of a copper-polymer composite through the thermolysis of copper(II) succinate

A procedure has been proposed for the preparation of copper/polymer composites through Cu(C₄H₄O₄) · H₂O succinate thermolysis. Three types of copper nanoparticles have been incorporated into a fibrous carbon-polymer matrix of the composite: cubic (350 × 350 nm) and needle-like (40–80 nm in diameter and 4.5–5.5 μm in length) crystals and spherical copper particles (5 to 45 nm). We have compared copper succinate and copper maleate decomposition processes. The composites obtained through thermolysis have been shown to differ drastically.     

A new approach to joining of bulk copper using microwave energy

Metallurgical joining of high thermal conductivity materials like copper has been technically challenging. This paper illustrates a novel method for joining of bulk metallic materials through microwave heating. Joining of copper in bulk form has been carried out using microwave energy in a multimode applicator at 2.45 GHz and 900 W. Charcoal was used as susceptor material to facilitate microwave hybrid heating (MHH). Copper in coin and plate forms have been successfully joined through microwave heating within 900 s of exposure time. A sandwich layer of copper powder with approximately 0.5 mm thickness was introduced between the two candidate surfaces. Near complete melting of the powder particles in the sandwich layer does take place during the microwave exposure leading to metallurgical bonding of the bulk surfaces. Characterisation of the joints has been carried out through microstructure study, elemental analysis, phase analysis, microhardness survey, porosity measurement and tensile strength testing. X-ray diffraction (XRD) pattern indicates that some copper powder particles got transformed into copper oxides. XRD analysis also reveals that the dominant orientation (3 1 1) in starting copper powder got transformed into a preferential orientation (1 1 1) in the joint. A dense uniform microstructure with good metallurgical bonds between the sandwich layer and the interface was obtained. The hardness of the joint area was observed to be 78 ± 7 Hv, while the porosity in the joint was observed to be 1.92%. Strength character of the copper joints shows approximately 29.21% elongation with an average ultimate tensile strength of 164.4 MPa.     

Modeling and experimental study for horizontal twin‐roll casting of copper/aluminum clad sheet

A mathematical model has been developed and validated for the horizontal twin‐roll casting of copper/aluminum clad sheet. The influences of the heat transfer coefficient for copper/roll interface, casting speed and clad sheet thickness on the sump depth and temperature distribution of the copper/aluminum interface were studied. The interface morphologies and chemical compositions of the intermetallic compound layers were analyzed. The results showed the sump depth decreased with the increase of heat transfer coefficient for copper/roll interface and moved to the outlet with the increase of the casting speed. Casting speed was linear with the sump depth ratio to set‐back distance on the centerline for different clad sheet thicknesses. The thickness of the intermetallic compound layer increased with the increase of the clad sheet thickness. Only Al₂Cu layer formed on the copper/aluminum interface with clad sheet thickness of 6 mm, and the second layer of Al₄Cu₉ formed near the copper side with the increase of the thickness.     

Preconcentration and separation of trace amount of copper (II) on N, N-bis(4-fluorobenzylidene)ethane-1,2-diamine loaded on Sepabeads SP70

A sensitive and simple method for the preconcentration of copper (II) ions has been reported. The method is based on the adsorption of copper ion N¹, N²-bis(4-fluorobenzylidene)ethane-1,2-diamine loaded on Sepabeads. The sorpted copper content was eluted by 8 ml of 4 M nitric acid in acetone. The influences of the analytical parameters including pH and sample volume were investigated. The interference effects of matrix ions on the retentions of the copper (II) ions were also examined. The recovery of understudy analyte was generally higher than 95%. The method has been successfully applied to the evaluation of copper contents in some real samples including water samples, vegetable samples and milk samples.     

Preparation and conductive mechanism of copper nanoparticles ink

One step and large-scale synthetic method of copper nanoparticles (NPs), with a yield of 91.36 %, has been first developed. The as-prepared oblate-shape copper NPs with a size 80 nm showed good antioxidation. The ink of the copper nanoparticles (20 wt%) onto glass slides easy formed a favorable conductive film at 300 °C. Interestingly, the coffee ring like structure, which often goes with the films by organic conductive inks, has been effectively suppressed. The experiments revealed that the size and connection of interparticles, as well as the elimination degree of organic molecules are three key factors for the conductivity of the copper films.     

静标测压铜柱静动差修正方法研究

介绍了静标铜柱二次预压测压方法及其使用特点,分析了其产生静动差的原因。将二次预压铜柱放入测压器中和电子测压器组成一个测试组在模拟炮上进行了试验,从试验数据的分析看出静动差可高达18%左右。为了减小静动差,以8mm×13mm铜柱为例,采用量纲分析和相似理论,建立了二次预压静标铜柱静动态修正公式,并对测量结果进行了修正。结果表明,该修正公式可将静动差减小到3%以内,并可恢复大量的同批次铜柱的测压结果,为各类兵器及弹药的研制提供可信的压力数据。     

Lattice distortion and thermal stability of nano-crystalline copper

Molecular dynamics simulations of high temperature annealing of copper bicrystals with varying grain sizes in nano-meter range have been carried out. Planar 1 1 1-tilt CSL grain boundaries are set. An EAM potential of FS type is used for calculating inter-atomic forces in copper. For comparison, similar simulations for aluminum and tungsten have been conducted. The results show that in the copper bicrystals of present grain boundary geometry, mismatch between the {1 1 1} planes of the neighboring grains occurs at the grain boundary, resulting in a general shear lattice distortion within the grains. The shear strain is inversely proportional to the grain size. The energy of such mismatched grain boundary is found lower than that of the mismatch-free grain boundary. For aluminum such kind of mismatch is much smaller, and for tungsten no such mismatch appears. The nano-sized copper bicrystals with grains smaller than a critical size are found instable at high temperature, where grain boundary motion and atomistic reconstruction lead to annihilation of the grain boundaries after an incubation time.     

Kinetic behaviour of Duolite ES 468 in the cosorption of non-ionic surfactant and copper(II)

Kinetic behaviour of the hydrogen form of Duolite ES 468 polyacrylic acid-functionalised cation exchanger with respect to the sorption of non-ionic surfactant alkylmonoethers (ALM-10) and copper(II) has been investigated; kinetic curves have been obtained, using spectrophotometric determination for ALM-10 and complexometric one for copper(II). Kinetic coefficient (B), intraparticle diffusion coefficient (D; m(2)s(-1)) and overall rate constant (k(o); s(-1)) for non-ionic surfactant and copper(II) depend on the solution composition, pH and the maximum sorption at the equilibrium. On increasing the solution acidity from pH 5 to pH 3 a decrease in both D and the equilibrium sorption for copper(II) although an increase in D for ALM-10 is observed. The action of copper(II) results in an increase in both D for ALM-10 and the maximum sorption at the equilibrium, whereas the action of ALM-10 leads to a decrease in the corresponding parameters for copper(II). Hydrogen form of Duolite ES 468 polyacrylic acid-functionalised cation exchanger is suitable for the simultaneous removal of non-ionic surfactant and copper(II) from waste water.     

An electroanalytical study of chemiplated thin films of copper sulphide

Thin films of copper sulphide have been deposited from aqueous solution onto glass, platinum and cadmium sulphide by two new methods: first, chemiplated Cu₂O films have been subjected to anion exchange with S_2- ions and second, copper (I) thiourea complexes have been hydrolysed in sodium tetraborate solution. The copper sulphide films Cu _x S have been analysed electrochemically andx has been found to have values within the range 1.83 to 1.93. The dominance of the digenite phase (Cu_1.8S) in these films has been confirmed by optical measurements.     

Growth of copper on diatom silica by electroless deposition technique

In this study, the growth of copper on porous diatom silica by electroless deposition method has been demonstrated for the first time. Raman peaks of copper (145, 213, and 640 cm^?1) appeared in the copper-coated, Amphora sp. and Skeletonema sp. diatom samples, confirming the successful deposition of copper. Scanning electron microscopy (SEM) indicated the presence of copper on the diatom silica surface. The 3D intricate structure of diatom was still evident by optical and scanning electron microscopy analyses when the diatom samples were immersed in the copper bath for only 5 hours. Incubating the diatom samples in the copper bath for 24 h produced a dense coating on the diatom surface and covered the intricate 3D structure of the diatom silica. These results present possibilities of the fabrication of hierarchically organized copper with 3D diatom replica structures.     

Strengthening mechanisms of aluminum matrix composite containing Cu-coated SiC particles produced by friction stir processing

ABSTRACT

A friction stir processing (FSP) method has been developed to fabricate a locally reinforced aluminum matrix composite (AMC) by stirring electroless-copper-coated SiC particles into AA6061 matrix. The interfacial bonding between particulate reinforcement and the matrix was enhanced by the copper coating. Effective improvement in hardness and in tensile strengths has been proved. Microstructural investigation and analyses were conducted to correlate the microstructural evidences with the possible strengthening mechanisms. The effect of copper coating on the bonding between SiC particles and Al-matrix; the role of the dispersed Cu debris and the increased Cu content in solid solution on the strengthening; and the effect of friction stir on dislocation density and on the recrystallization behavior were analyzed. Multiple strengthening mechanisms due to diffusion between copper film and matrix; dispersion of fine copper debris and Al-Cu intermetallic compounds (IMCs) in the matrix; solid solution due to increased copper content and dislocation punching were four major mechanisms in interpreting the strengthening phenomena in AMC containing copper coated SiC reinforcements.     

Thermodynamic investigation of the MOCVD of copper films from<Emphasis Type="Italic">bis</Emphasis>(2,2,6,6-tetramethyl-3,5-heptadionato)copper(II)

Equilibrium concentrations of various condensed and gaseous phases have been thermodynamically calculated, using the free energy minimization criterion, for the metalorganic chemical vapour deposition (MOCVD) of copper films usingbis(2,2,6,6-tetramethyl-3,5-heptadionato)copper(II) as the precursor material. From among the many chemical species that may possibly result from the CVD process, only those expected on the basis of mass spectrometric analysis and chemical reasoning to be present at equilibrium, under different CVD conditions, are used in the thermodynamic calculations. The study predicts the deposition of pure, carbon-free copper in the inert atmosphere of argon as well as in the reactive hydrogen atmosphere, over a wide range of substrate temperatures and total reactor pressures. Thin films of copper, grown on SiO₂/Si(100) substrates from this metalorganic precursor by low pressure CVD have been characterized by XRD and AES. The experimentally determined composition of CVD-grown copper films is in reasonable agreement with that predicted by thermodynamic analysis.     

Active Soldering of ZnS-SiO2 Sputtering Targets to Copper Backing Plates Using an Sn56Bi4Ti(Ce, Ga) Filler

ZnS-SiO₂ targets have been directly soldered to copper backing plates at 180°C in air using an Sn56Bi4Ti(Ce, Ga) filler. The affinity of cerium to oxygen protects titanium from oxidation, allowing titanium to react with ZnS-SiO₂ sputtering target. The shear strengths are 1.7, 8.7, and 1.3 MPa for ZnS-SiO₂/ZnS-SiO₂, copper/copper and ZnS-SiO₂/copper joints, respectively. EPMA elemental mapping shows that aging test at 120° for 100 hours enhanced the segregation of titanium at the ZnS-SiO₂/solder interfaces. The shear strength of ZnS-SiO₂/copper joint after aging test is 1.3 MPa that shows no trace of degradation compared to the initial quality of the samples.     

TSV转接板硅通孔的热应力分析

硅通孔(TSV)技术作为实现三维(3D)封装的关键而被广泛关注。该文研究了在温度载荷作用下TSV转接板上铜和硅的应力状态,给出了通孔为完全填充铜和部分填充铜两种情况下的应力解析解,并讨论了孔距对转接板应力的影响。建立了TSV转接板的二维有限元模型,并用于验证解析解的适用性。结果表明:当TSV孔距达到孔直径的3倍以上时,解析解可以给出准确的转接板上铜和硅的应力结果;通过减薄镀铜层可以减小硅上的应力;转接板上应力与加载的温度变化成线性关系。     

Studies on the formability of powder metallurgical aluminum–copper composite

Formability is concerned with the extent of deformation that the materials undergo before failure; thus its investigation is critical for successful processing of materials during bulk deformation. The present investigation has been undertaken to generate the forming limit diagrams for powder metallurgical aluminium–copper composites for different initial relative densities and copper contents. Sintered aluminium–copper composite compacts of 2%, 4% and 6% copper content with different initial relative densities have been prepared by applying recommended powder compaction pressures. The material properties such as apparent strain hardening exponent and strength coefficient were determined using stage wise compression test to generate the formability limit diagram. Densification curves were plotted to investigate the effect of initial relative density and copper content on the pore closure phenomena during deformation. Theoretical and experimental investigations using standard ring compression test were carried out to determine friction factor between tool and work piece interfaces for different initial relative density and copper content. The critical transition densities vide the forming limit diagram were found to be 84%, 85.3%, 86% and 87.5% for pure sintered aluminium, Al–2%Cu, Al–4%Cu and Al–6%Cu composites respectively. The friction factor between tool and work piece interfaces has showed increasing pattern for all the cases with decrease in the initial relative density and increase in the copper content of the composite.