Electrical properties of conductive adhesives as affected by particle compositions,particle shapes,and oxidizing temperatures of copper powders in a polymer matrix

The effects of particle compositions, particle shapes, and oxidation temperatures on the electrical properties of conductive adhesives have been investigated. Silver‐coated copper powders and uncoated copper powders with spherical and flake‐shaped particles are oxidized at temperatures such as 30, 175, 240, 300°C and 350°C for 2 h and dispersed in an epoxy matrix. The results of this study indicate that the electrical properties of the conductive adhesives are strongly affected by the particle compositions and oxidation temperatures and only slightly affected by the particle shapes. Silver‐coated copper powders show significantly greater oxidation resistance than uncoated copper powders. To understand how silver‐coated copper powders show such oxidation resistance, they are analyzed by the techniques of thermogravimetric analysis (TGA), X‐ray diffraction (XRD), and Auger spectroscopy to observe how metal oxides such as AgO, Cu₂O, and CuO affect the electrical properties of the conductive adhesives. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2045–2053, 2004     

Epoxy‐based adhesives filled with flakes ag‐coated copper as conductive fillers

The flake core–shell Cu‐Ag powders are prepared and characterized. Isotropic conductive adhesives (ICAs) filled with flake silver‐coated copper was prepared by using epoxide resin as matrix and tetraethylenepentamine as curing agent. The flake silver‐coated copper was characterized by scanning electron microscopy, X‐ray diffraction, energy dispersive X‐ray spectroscopy, and TG‐DTA. The results show Ag content in the surface of coated copper is up to 96.32%. Oxidation resistance of flake Cu‐Ag powders with high surface Ag content is improved greatly investigated by TG‐DTA. And bulk resistivity and shear strength of ICAs are measured. It was found that the percolation threshold of ICAs filled with flake Cu‐Ag powders is as low as 40 wt%. The ICAs have good overall performances. And the main influence factor on electric resistivity was analyzed. POLYM. COMPOS., 38:846–851, 2017. © 2015 Society of Plastics Engineers     

Enhancement of electrical properties of anisotropically conductive adhesive joints via low temperature sintering

The electrical properties of anisotropically conductive adhesives (ACAs) joints through low temperature sintering of nano silver (Ag) particles were investigated and compared with that of the submicron‐sized Ag‐filled ACA and lead‐free solder joints. The nano Ag particles used exhibited sintering behavior at significantly lower temperatures (<200°C) than at the bulk Ag melting temperature (960°C). The sintered nano Ag particles significantly reduced the joint resistance and enhanced the current carrying capability of ACA joints. The improved electrical performance of ACA was attributed to the reduced interfaces between the Ag particles and the increased interfacial contact area between nano Ag particles and bond pads by the particle sintering. The reduced joint resistance was comparable to that of the lead‐free (tin/3.5 silver/0.5 copper) metal solder joints. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1665–1673, 2006     

Silver‐coated copper nanowires with improved anti‐oxidation property as conductive fillers in low‐density polyethylene

Silver‐coated copper nanowires (AgCuNWs) are prepared by chemical plating method with copper nanowires (CuNWs) and Ag‐amine reagent. The prepared AgCuNWs with silver content of 66.52 wt.%, diameter 28–33 nm exhibited improved anti‐oxidation behaviour. The silver coating on AgCuNWs can effectively reduce the formation of copper oxide under room temperature. The temperature at which nanowires begin to gain weight can be improved from 85 to 230°C and the maximum weight gain can be decreased from 20.3% to 3.2% by applying silver coating. The volume electrical resistivity of the AgCuNWs filled low‐density polyethylene nanocomposites is lower than that of the CuNWs filled low‐density polyethylene nanocomposites with same volume percentage of fillers because the silver content in the AgCuNWs is not oxidised during compression moulding. © 2012 Canadian Society for Chemical Engineering     

The Sintering Behavior of Electrically Conductive Adhesives Filled with Surface Modified Silver Nanowires

Electrically conductive adhesives (ECAs) filled with sintered silver nanowires were prepared and the effect of different curing conditions on the electrical property of the ECAs was discussed. Silver nanowires with a diameter of 50–60 nm and a length of 2–3 μm were successfully synthesized through a polyol process and surface functionalized with dicarboxylic acid. Morphology studies showed that surface modified silver nanowires began to sinter at 200°C and became shorter and thicker, and eventually formed large chunks at higher temperatures. The conductive adhesives filled with 75 wt% of silver flakes and nanowires (3:2 weight ratio) were cured at different temperatures using two kinds of catalysts. The volume resistivity of the conductive adhesives cured at 300°C without a catalyst reached 5.8 × 10 ^–6 Ω cm. The dramatic improvement in the conductivity of the ECA is due to the sintering of silver nanowires and the high solid content resulting from the partial evaporation of polymer components.     

Formulation and characterization of UV-light-curable electrically conductive pastes

UV-light-curable electrically conductive pastes have been formulated from granular silver particles and flake-shaped silver and epoxyacrylate, ethylene glycol and photo-initiator in this study. These conductive pastes were analyzed using photo-DSC, TGA and conductivity metry for reaction rate during photo-polymerization process, thermal resistance and conductivity, respectively. It is shown that (1) the rate of photo-polymerization can be regulated by varying the exposure dose and time depending on the particle size and particle loading; (2) the resistance of the paste containing 60 wt% silver with mean particle size from 0.6 to 1.5 μm is reduced to 5.63 × 10^?7 Ωcm; and (3) with granular-shaped silver with 0.6 to 3.5 μm in diameter the decomposition temperature of electrically conductive paste is 424°C, while the temperature of thermal decomposition is 397°C for the same solid content of flake shape silver with length 0.5 to 5 μm, after photo-polymerization using a radiation dose of 500 mJ/cm².     

Effect of gas environment on properties of particles prepared by spray pyrolysis of metal nitrates

Particles in different states of oxidation were prepared by spray pyrolyses of aqueous solutions of silver and copper nitrates under different gas environments: air, nitrogen or mixture gas of 10 vol%H₂-N₂, respectively. Silver nitrate was converted to phase-pure silver at temperatures below 500 °C whose densification and crystallization were completed around 500 °C, irrespective of the gas environment. On the other hand, phase-pure copper(II) oxide was formed from copper nitrate up to 1,000 °C with air, but below 800 °C with nitrogen, above which copper(I) oxide was produced. Phase-pure copper particles were obtained with the mixture gas at temperatures above 400 °C. Copper(I) oxide was sintered and crystallized more easily than copper(II) oxide. The rates of the metallization, sintering and crystallization of copper were between those of silver and nickel.     

Copper-based Conductive Polymers: A New Concept in Conductive Resins

The history of making plastic materials conductive to both electric currents and to the transfer of thermal energy has traditionally been accomplished by the addition of metallic particles into a resin matrix. Principally, such metals as aluminum, silver, gold, nickel and copper have been used. Copper has had a limited success due to its tendency to form a non-conductive oxide surface layer and currently such adhesives depend primarily on silver for high conductivity.

An intense research effort to eliminate the problems associated with copper-filled conductive polymers resulted in a treatment and preparation of copper flake that allows the stable formation of a conductive structure within a polymer matrix. Once the activated copper particles are in the resin, the formulation is stable. Most of the resins evaluated have been epoxy resins although certain thermoplastic resins have also been made conductive. Volume resistivities as low as 10^?5 ohm-cm have been achieved.     

Oxidation of Polymer‐Derived HfSiCNO up to 1600°C

Oxidation behavior of HfSiCNO ceramics for Hf/Si ratio of 0.09 at 1400°C–1600°C in ambient air is reported. Quantitative X‐ray analysis of oxidized powders shows crystalli‐zation of the amorphous phase into tetragonal hafnia, hafnon, and cristobalite (carbides, seen in inert atmosphere heat treatments are absent). Cross‐sectional SEM shows the oxide overgrowth on the particles to contain precipitates of hafnia/hafnon, while the interior of the particles is decorated with nanoscale grains of hafnia in a necklace‐like formation. The oxidation kinetics of these materials, determined both from weight‐change measurements and from direct observation of oxide overgrowth, are shown to be comparable to the oxidation of SiC single crystals. Oxidation of SiC–SiC minicomposites (straight fiber bundles infiltrated with a SiC matrix), coated with thin films of HfSiCNO prepared by dip‐coating was studied. The overgrowth thicknesses for oxidation time of 1000 h at 1600°C are compared for uncoated, SiCN(O)‐coated, and HfSiCNO‐coated minicomposites.     

Preparation and application of silver nanoparticles on silk for imparting antimicrobial properties

Silver nanoparticles were produced by a chemical reduction method that reduced silver nitrate with reducing agents such as hydrazine and glucose. The silver nanoparticles were characterized with transmission electron microscope, scanning electron microscope, and optical microscope. The effects of process parameters such as the stirring speed, temperature, type of reducing agent, and dispersing agent on the particle size were studied. The particle size decreased with an increase in the stirring speed and a decrease in the process temperature. Smaller particles were formed when the silver nitrate was reduced by glucose versus those that were formed by reduction with hydrazine. Silver nanoparticles with average sizes of 10 and 35 nm, produced by reduction with hydrazine at 5 and 40°C, were applied to silk by an exhaust method. Silk fabrics treated with 40 ppm silver hydrosol produced at 5°C and 60 ppm silver hydrosol produced at 40°C showed 100% antimicrobial activity against the gram‐positive bacterium Staphylococcus aureus. The durability of the antimicrobial property of the treated silk fabric to washing was also examined and is presented. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Copper-based Conductive Polymers: A New Concept in Conductive Resins

The history of making plastic materials conductive to both electric currents and to the transfer of thermal energy has traditionally been accomplished by the addition of metallic particles into a resin matrix. Principally, such metals as aluminum, silver, gold, nickel and copper have been used. Copper has had a limited success due to its tendency to form a non-conductive oxide surface layer and currently such adhesives depend primarily on silver for high conductivity.

An intense research effort to eliminate the problems associated with copper-filled conductive polymers resulted in a treatment and preparation of copper flake that allows the stable formation of a conductive structure within a polymer matrix. Once the activated copper particles are in the resin, the formulation is stable. Most of the resins evaluated have been epoxy resins although certain thermoplastic resins have also been made conductive. Volume resistivities as low as 10^-5 ohm-cm have been achieved.     

The effect of thermal stresses on the EMI (electromagnetic interference) shielding of conductive plastics

The electrical properties of a number of filled and coated plastics were examined after subjecting the materials to rigorous thermal cycling between −20 and 80°C. Filled compounds that obtained their conductivity through the addition of carbon based conductive fillers maintained their conductivity throughout the thermal cycling. Compositions which contained metal fillers were able to maintain their conductivity only when a high temperature thermally stable polymer was used as the polymer matrix. Plaques coated by a zinc arc spray or with acrylic paints containing graphite, silver, and nickel particles were unaffected by thermal cycling. Plaques coated with an acrylic paint containing copper particles lost most of their conductivity during the changes in sample temperature.     

Sol‐gel preparation and properties of Ag‐containing bioactive glass films on titanium

Ag‐containing bioactive glass films (Ag/Ca atomic ratios of 0, 5% and 10%) were sol‐gel prepared for bioactive and antibacterial modification of titanium. The gel powders calcined at 610°C are mainly amorphous confirmed by x‐ray diffraction, but small diffraction peaks of Ca₃SiO₅ and silver are detected. The film surface is porous with the pore size of ~200 nm. Silver‐rich sub‐micro particles with sizes of 100‐480 nm are present at the surface of Ag‐glass films. CaP phase, metallic silver and silica are detected by x‐ray photoelectron spectroscopy. The mean apparent bonding strength of the films is as high as 21±1 MPa measured by the pull‐off test. The potentiodynamic polarization test shows that the coated samples have better corrosion resistance than the polished sample. The Ag‐glass coatings and their wafer samples exhibit antibacterial activity against S. aureus. The coated samples are covered by apatite layer after soaked in the simulated body fluid for 2 weeks, demonstrating their bioactivity.     

Mullite formation from the pyrolysis of aluminium-loaded polymethylsiloxanes: The influence of aluminium powder characteristics

Polymethylsiloxane (PMS) filled with a range of aluminium powders of different size and morphology have been used to produce precursor mixtures to form mullite bodies. The size and shape of the Al powder is shown to have a strong influence on the temperature and mechanism of mullite formation, on the final microstructure and phase composition of the product. The reaction proceeds by decomposition of the PMS producing amorphous SiO₂. Al oxidation occurs both by reaction with the atmosphere and by reduction of the amorphous SiO₂ to produce α-Al₂O₃. Crystallisation of cristobalite was also observed prior to mullitisation. It is these components of the microstructure that react to produce mullite. The onset of mullite formation occurs at different temperatures, depending on the initial Al powder size and morphology. Large, flake morphology Al powders produced the greatest quantity of mullite and showed the lowest temperatures for mullite formation. XRD analysis identified 3:2 mullite in samples using large Al particles after heating to 1400 °C and at 1700 °C in samples using small Al powders.     

Effects of Copper Coating on the Crystalline Structure of Fine Barium Titanate Particles

We have investigated the effect of a metal coating—copper—on the tetragonal structure of fine barium titanate (BaTiO₃) particles. The BaTiO₃ particles were synthesized by a sol-gel method and heat treated at temperatures >900°C for various amounts of time before coating. The copper coating was achieved by an electroless coating technique. The transmission electron microscopy micrographs revealed that the coated powder contained fine BaTiO₃ particles that were embedded in copper patches. The X-ray diffractometry patterns showed that the copper coating increased the c/a ratio of the fine BaTiO₃ particles. For powders that were heat treated at 900°C for 10 h and were initially cubic, the copper coating changed the c/a ratio, from 1 to 1.0034. For powders that were calcined at 900°C for 20 h and were initially tetragonal, the copper coating further enhanced the c/a ratio, from 1.0028 to 1.0043. When the copper-coated BaTiO₃ particles were oxidized, the c/a ratio was reduced to a value that was approximately equal to or below that of the uncoated powders. A conductive coating can eliminate the depolarization energy of an insulating polar particle. The fact that the copper coating promoted the polar tetragonal phase but the nonconductive copper-oxide coating did not was consistent with the interpretation that the presence of the cubic phase (nonpolar) in small BaTiO₃ particles was caused by the depolarization effect.     

电磁屏蔽导电涂料用片状镀银铜粉的研究

介绍了电磁屏蔽导电涂料用镀银铜粉的生产方法,对其性能指标进行测试.同时,将本研究制得镀银铜粉应用于导电涂料的配制,制得电磁屏蔽导电涂料,并对导电涂料性能指标进行测试.并对行业的发展进行了展望.     

抗静电环氧树脂胶粘剂的制备与性能研究

以导电碳黑和银粉为导电填料制备了抗静电环氧树脂(EP)胶粘剂,考察了导电填料的种类和用量对胶粘剂导电性能和力学性能的影响。研究结果表明,导电填料的种类对胶粘剂导电性能和力学性能的影响显著不同;以导电碳黑作为导电填料时,当w(导电碳黑)=5.0%时EP胶粘剂开始具备抗静电能力,当w(导电碳黑)≈7.1%时胶粘剂的体积电阻率发生突跃式下降;而以银粉作为导电填料时,当w(银粉)=0～38%时EP胶粘剂不具备抗静电能力。EP胶粘剂的拉伸强度和剪切强度随着导电碳黑用量的增加呈线性下降的趋势,而随着银粉用量的增加则呈线性上升的趋势。     

Electrical characterization of individual metal‐coated polymer spheres used in isotropic conductive adhesives

Isotropic conductive adhesives (ICAs) filled with metal‐coated polymer spheres (MPS) have been proposed to improve the mechanical reliability compared to conventional ICAs filled with silver flakes. The electrical properties of MPS play an important role in the electrical performance of macroscopic MPS‐based ICAs. This article deals with the electrical characterization of individual MPS using a nanoindentation‐based flat punch method, in which the resistance and the deformation of single MPS were monitored simultaneously. Four groups of silver‐coated polymer spheres (AgPS) with identical polymer cores but different silver coating thicknesses were tested. The resistance of AgPS decreases gradually with increasing deformation degree of particles, and increases when the deformation of particles is reduced. In addition, the resistance of individual AgPS is dependent on the physical properties of the silver coating, such as thickness, uniformity, and porosity. The thicker the silver coating is, the lower and more stable the resistance of AgPS is. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43764.     

Influence of process parameters on SAC305 lead-free solder powder produced by centrifugal atomization

In the present work, a centrifugal atomizer was constructed in order to study the effects of operating parameters: rotating speed, melt feed rate, shape and size of atomizer, and oxygen content in the atomizer chamber, on the characters of SAC305 powder. It was evidenced from the experimental results that the median size of the atomized powders became smaller with increasing rotating speed, decreasing melt feed rate, and the use of larger atomizer. At same operating conditions, a cup shaped atomizer was able to give approx. 11% finer powder compared to that from a flat-disk shaped one. Median particle size appeared to be smaller with decreasing oxygen content in the chamber. SEM micrographs revealed that SAC305 particles atomized under atmospheric condition were found to form various shapes: ligament, teardrop, flake, and irregular. The shape of powder particles tends to be rounder with decreasing oxygen content in the chamber. Fine particles of SAC305 powder (− 45 μm) containing oxygen less than 100 ppm could be synthesized by purging nitrogen gas into the atomizing chamber. Production yield of the SAC305 powder increased with increasing atomizer's rotating speed, lower melt feed rate, and larger atomizer.     

Behavior of Pressure-Sensitive Adhesives Filled with Metallized Inorganic Particles

The electrically conductive pressure-sensitive composite adhesives based on acrylic polymer and silver-coated inorganic particles have been investigated in this article. The electrical conductivity of the pressure-sensitive adhesives containing silver coated spherical inorganic particles is lower at the same concentration of the filler in comparison with silver coated inorganic fibers, the strength of adhesive joint to aluminum being higher in the case of the pressure-sensitive adhesive containing silver-coated inorganic fibers. After the thermal treatment the strength of adhesive joint to aluminum of electrically conductive pressure sensitive adhesives increases significantly. The suitable concentration proposition of the silver-coated inorganic filler in the pressure-sensitive adhesive requires a compromise solution of the problem taking into account the ultimate adhesive and electrical properties of the investigated pressure-sensitive adhesives composites.