Silver Fillers Research Articles

Self-Assembly Synthesis of Silver Nanowires/Graphene Nanocomposite and Its Effects on the Performance of Electrically Conductive Adhesive.

Among recent advances in electronic packaging technologies, electrically conductive adhesives (ECAs) attract most researchers’ attention, as they are environment-friendly and simple to apply. ECAs also have a lower operating temperature and volume resistivity compared with conventional electronic conductive adhesives. In ECAs, the conducting fillers play a significant role in improving conductivity and strength. In this work, as filler additives, the silver nanowires/graphene nanocomposites (AgNWs-GNs) were successfully fabricated via a facile self-assembly method. The characteristics of the as-prepared nanocomposites were evaluated by FTIR (Fourier Transform infrared spectroscopy), XRD (X-ray Diffraction), XPS (X-ray photoelectron spectroscopy), TEM (Transmission electron microscope) and Raman tests, demonstrating a successful synthesis process. Different amounts of AgNWs-GNs were used as additives in micron flake silver filler, and the effects of AgNWs-GNs on the properties of ECAs were studied. The results suggested that the as-synthesized composites can significantly improve the electrical conductivity and shear strength of ECAs. With 0.8% AgNWs/GNs (AgNWs to GO (Graphite oxide) mass ratio is 4:1), the ECAs have the lowest volume resistivity of 9.31 × 10−5 Ω·cm (95.4% lower than the blank sample without fillers), while with 0.6% AgNWs/GNs (AgNWs to GO mass ratio is 6:1), the ECAs reach the highest shear strength of 14.3 MPa (68.2% higher than the blank sample).

Stress analysis of the brazing joints of tubular ceramic oxygen-permeable membranes and metal supports

This study investigates the effect of joint structure and temperature dependent mechanical properties on the residual stress states in ceramic/metal brazing joints. A closed-one-end BaCo0.7Fe0.2Nb0.1O3 (BCFN) membrane tube is joined to 310S by using silver filler. Finite element simulation of different BCFN/310S joint assemblies is conducted to evaluate the stresses and deformations of the components at an isothermal state. The results indicate that the outer sleeve structure with low residual stress and good air tightness is more suitable for joining ceramics to metal supports than other joint structures in four joint assemblies. And thermal cycling experiments also verify the functional reliability of the outer sleeve joint assembly. Besides, nonlinear material properties of BCFN can not only cause the sudden change in ceramic stress at 300 °C, but also be the important basis for the stress contrast of different joint structures.

Corrosion behaviors of 316LN stainless steel joints brazed with Sn-plated silver filler metals

AgCuZnSn filler metals were prepared from the BAg34CuZnSn filler metal by a combinative process of brush plating and thermal diffusion, and the prepared filler metals were applied to the induction brazing of the 316LN stainless steel. The corrosion behaviors of the brazed joints was evaluated based on local corrosion analyses, where the morphology of the joints was analyzed by scanning electron microscopy (SEM) after immersion in a 3.5 wt.% NaCl aqueous solution and electrolytic etching in a 10 vol.% oxalic acid solution. The microstructure of the brazed joints with the Sn-plated filler mainly consisted of the Ag phase, Cu phase, CuZn phase, Cu5Zn8 phase, Cu[Formula: see text]Sn[Formula: see text] phase and Ag3Sn phase. The local corrosion analysis results indicated that galvanic corrosion occurred near the interface between the stainless steel base metal and the brazing seam. With increasing local corrosion time, the corrosion rates of both the brazing seam and the base metal first exhibited an increasing trend, followed by a decreasing trend, and the corrosion rate of the brazing seam was slightly greater than that of the base metal. The corrosion behaviors analysis indicated that the corrosion resistance of the brazing seam was reduced, and concave defects emerged after electrolytic etching for 90 s.

Comparative study on thermodynamic characteristics of AgCuZnSn brazing alloys

AgCuZnSn brazing alloys were prepared based on the BAg50CuZn filler metal through electroplating diffusion process, and melting alloying method. The thermodynamics of phase transformations of those fillers were analyzed by non-isothermal differentiation and integration methods of thermal analysis kinetics. In this study, it was demonstrated that as the Sn content increased, the reaction fractional integral curves of AgCuZnSn fillers from solid to liquid became straighter at the endothermic peak. Under the same Sn contents, the reaction fractional integral curve of the Sn-plated filler metal was straighter, and the phase transformation activation energy was higher compared to the traditional silver filler metal. At the 7.2 wt% Sn content, the activation energies and pre-exponential factors of the two fillers reached the maximum, then the phase transformation rate equations of the Sn-plated silver filler and the traditional filler were determined as: k = 1.41 × 1032exp(−5.56 × 105/RT), k = 7.29 × 1020exp(−3.64 × 105/RT), respectively.

Silver Filler Pre-embedding to Enhance Resolution and Contrast in Multidimensional SEM: A Nanoscale Imaging Study on Liver Tissue.

Contemporarily, serial block-face scanning electron microscopy (SBF-SEM) has emerged as an immensely powerful nanoscopic imaging technique, capable of generating large-volume three-dimensional information on a variety of biological specimens in a semiautomated manner. Despite the plethora of insights and advantages provided by SBF-SEM, a major challenge inherent to the technique is that of electron charging, which ultimately reduces attainable resolution and detracts from overall image quality. In this chapter, we describe a pre-embedding approach that involves infiltration of tissue with a highly conductive silver filler suspension following primary fixation. Such an approach is demonstrated to improve overall sample conductivity, resulting in the minimization of charging under high-vacuum conditions and an improvement in lateral resolution and image contrast. The strength of this sample preparation approach for SBF-SEM is illustrated on liver tissue.

Increasing Brazing Joint Strength between Cemented Carbide with Silver Filler Metal

Increasing Brazing Joint Strength between Cemented Carbide with Silver Filler Metal

Conductivity enhancement of polymer composites using high-temperature short-time treated silver fillers

In this work, we develop an easy, convenient and effective high-temperature short-time annealing method to treat silver fillers through decomposing the silver oxide on the surface into silver nanoparticles and also in-situ paralyzing part of the surface lubricants to reduce the length of the tunneling distance between neighboring silver flakes. The modified micro silver flakes play a significant role in improving the electrical conductivity of the corresponding electrically conductive adhesives (ECAs), exhibiting the lowest resistivity of 1.28×10−4Ω·cm at 70wt% filler loading. This work suggests that the high-temperature short-time annealing strategy can greatly enhance the electrical conductivity of as-treated silver flakes based ECAs, which will allow them to be widely used in electronic packaging.

Effect of Filler and Heat Treatment on the Physical and Mechanical Properties of the Brazed Joint between Carbide Tip and Steel

In this study, the effect of filler and heat treatment on the physical and mechanical properties of the brazed joint carbide tip and steel was investigated. Tip carbide YG6 and low carbon steel (SS400) is joining by torch brazing with two filler metals, silver, and copper filler. Heat treatment was performed in induction furnace. Microstructure and shear strength of the brazed joint have been investigated. Many silver filler layer are formed on the surface of the base metal rather then using copper filler. The highest shear strength is achieved using a silver filler metal at temperatur 725°C. The highest shear load is 18.62 kN.

Effect of Silver Nanowires on the Resistivity of Electronically Conductive Adhesives

Large-scale silver nanowires with a length of 30∼90 μm were synthesized by a polyol process. Electronically conductive adhesives (ECAs) were made by adding micro-sized silver flakes and silver nanowires to the polymer composites consisting mainly of epoxy resin, cure agent and catalyst. The volume resistivity of the ECAs was researched as a function of silver filling loading and sintering temperature. The results indicate that the volume resistivity of ECAs first decreases and then increases with the increase of fractions of silver nanowires when the curing temperature is 180 °C. With the increase of curing temperature, the volume resistivity of ECAs decreases. In the condition of the ECAs filled with 65% silver fillers (the ratio of silver micro-sized silver flakes and silver nanowires is 55:10), the volume resistivity of ECAs reaches 6.5×10 −4 and 1.3×10 −4 Ω·cm when cured at 180 and 300 °C, respectively. The dramatic improvement in the conductivity of the ECAs is due to the low-temperature sintering of the silver nanowires at 300 °C. Effect of silver nanowires on the resistivity of ECAs was discussed in terms of the distribution and sintering behavior of silver nanowires and interaction relationship between silver nanowires and micro-sized silver flakes.

Crack repair welding by CMT brazing using low melting point filler wire for long-term used steam turbine cases of Cr-Mo-V cast steels

Surface melting by gas tungsten arc (GTA) welding and overlaying by cold metal transfer (CMT) brazing using low melting point filler wire were investigated to develop a repair process for cracks in worn cast steel of steam turbine cases. Cr-Mo-V cast steel, operated for 188,500h at 566°C, was used as the base material. Silver and gold brazing filler wires were used as overlaying materials to decrease the heat input into the base metal and the peak temperature during the welding thermal cycle. Microstructural analysis revealed that the worn cast steel test samples contained ferrite phases with intragranular precipitates of Cr7C3, Mo2C, and CrSi2 and grain boundary precipitates of Cr23C6 and Mo2C.CMT brazing using low melting point filler wire was found to decrease the heat input and peak temperature during the thermal cycle of the process compared with those during GTA surface melting. Thus, the process helped to inhibit the formation of hardened phases such as intermetallics and martensite in the heat affected zone (HAZ). Additionally, in the case of CMT brazing using BAg-8, the change in the hardness of the HAZ was negligible even though other processes such as GTA surface melting cause significant changes. The creep-fatigue properties of weldments produced by CMT brazing with BAg-8 were the highest, and nearly the same as those of the base metal owing to the prevention of hardened phase formation. The number of fracture cycles using GTA surface melting and CMT brazing with BAu-4 was also quite small.Therefore, CMT brazing using low melting point filler wire such as BAg-8 is a promising candidate method for repairing steam turbine cases. However, it is necessary to take alloy segregation during turbine operation into account to design a suitable filler wire for practical use.

Sintering Behavior and Effect of Silver Nanowires on the Electrical Conductivity of Electrically Conductive Adhesives.

In this paper, two kinds of silver nanowires with a 160 nm average diameter ranging from 30 to 90 µm length and a 450 nm average diameter up to 100 µm length were successfully synthesized by a polyol process with FeCl3 and Na₂S as reaction inhibitor, respectively. The experimental results indicate that the morphologies and sintering behaviors of both of silver nanowires are impacted by glutaric acid and sintering temperature. The isotropically conductive adhesives (ICAs) filled with micro-sized silver flakes and silver nanowires as hybrid fillers were fabricated and the electrical properties were investigated based on the fraction of the silver nanowires of the total of silver fillers and the curing temperature, etc. The in situ monitoring the variation in electrical resistance of the ICAs explores that silver nanowires have influence on the curing behavior of the ICAs. Silver nanowires synthesized with Na2S as reaction inhibitor and treated with glutaric acid can significantly improve the electrical conductivity of the ICAs in the case of the low loading of silver fillers in the appropriate proportion range of the weight ratio of micro-sized silver flakes and silver nanowires, primarily as a result of connecting effect. When the loading of silver fillers in the ICAs is high, the electrical conductivity is also enhanced slightly in the case of the proper fraction of silver nanowires of the total of silver fillers. The effect of the curing temperature on the electrical conductivity relates to the fraction of silver nanowires and the total loading of silver fillers. The electrical conductivity of the ICAs filled with micro-sized silver flakes and silver nanowires synthesized with FeCl₃ as reaction inhibitor is greatly damaged, indicating that the size of silver nanowires also is one of main factor to impact the electrical conductivity of the ICAs doped with silver nanowires. The electrical property of the ICAs filled with micro-sized silver flakes and silver nanowires results mainly from the synergy of silver flakes and nanowires, forming the conductive pathways.

Self-assembled three-dimensional structure of epoxy/polyethersulphone/silver adhesives with electrical conductivity

Diglycidyl ethers of bisphenol-A (DGEBA)/4,4′-diaminodiphenylmethane (DDM)/polyethersulphone (PES) blends were prepared as matrix resins for electrically conductive adhesives containing silver (Ag) fillers. The epoxy/PES blends formed co-continuous phase structures from initial homogeneous solutions via reaction-induced phase separation during the curing process. The Ag fillers were selectively localized in the epoxy-rich phases that had high affinity toward the surface of the Ag fillers. The co-continuous phase structures of the epoxy/PES blends acted as templates for the three-dimensional continuous structures of the Ag fillers. The self-assembled structures of the Ag fillers were connected in a continuous phase that possessed high electrical conductivity using a relatively small amount of Ag filler. In addition, the epoxy/PES/Ag adhesives had excellent shear adhesive strength. The fracture toughness of the epoxy/PES blends was the source of the high adhesive strength.

Effect of Silver Flakes and Particle Shape on the Steady Shear Viscosity of Isotropic Conductive Adhesives

Abstract This study investigated the effect of silver filler particle/flake shape on the rheological behavior of isotropic conductive adhesives (ICAs). Three types of epoxy systems were formulated with the following fillers: silver flakes, silver powder, and a mixture of silver flakes and silver powder. A volume fraction ranging from 0.2 to 0.8 silver fillers was added to the epoxy systems, and the corresponding viscosity of the paste was measured. The relationship between viscosity and volume fraction of ICAs is described through empirical models such as the Krieger–Dougherty, Quemada, and Eilers models. The studies showed that the shape of the filler influenced the viscosity of the suspension. For example, the silver flakes agglomerated at a lower volume fraction than silver flakes. In addition, an increase in the volume fraction reduced the distance between the particles and flakes, resulting in greater viscosity. In addition, the Krieger–Dougherty model yielded the best correlation between the measured viscosities and volume fraction.

Joining of Silver Nanomaterials at Low Temperatures: Processes, Properties, and Applications.

A review is provided, which first considers low-temperature diffusion bonding with silver nanomaterials as filler materials via thermal sintering for microelectronic applications, and then other recent innovations in low-temperature joining are discussed. The theoretical background and transition of applications from micro to nanoparticle (NP) pastes based on joining using silver filler materials and nanojoining mechanisms are elucidated. The mechanical and electrical properties of sintered silver nanomaterial joints at low temperatures are discussed in terms of the key influencing factors, such as porosity and coverage of substrates, parameters for the sintering processes, and the size and shape of nanomaterials. Further, the use of sintered silver nanomaterials for printable electronics and as robust surface-enhanced Raman spectroscopy substrates by exploiting their optical properties is also considered. Other low-temperature nanojoining strategies such as optical welding of silver nanowires (NWs) through a plasmonic heating effect by visible light irradiation, ultrafast laser nanojoining, and ion-activated joining of silver NPs using ionic solvents are also summarized. In addition, pressure-driven joining of silver NWs with large plastic deformation and self-joining of gold or silver NWs via oriented attachment of clean and activated surfaces are summarized. Finally, at the end of this review, the future outlook for joining applications with silver nanomaterials is explored.

English

The aim of this study was to study the effect of reinforcement of acrylic resin denture base polymer with chopped glass fibers and silver filler on the linear dimensional changes, and water sorption. The dimensional changes were measured immediately after processing, after 1, 2, 3, 7 and 14 days of water storage. Water sorption was measured after 7-days of water storage. The results revealed that both types of reinforcement affect the dimensional accuracy and water sorption of the test specimens when compared to the control unreinforced specimens. The greatest dimensional accuracy was found with the glass fibers reinforced test specimens. The lowest amount of water sorption was found with the silver-filled test specimens. It was concluded that both the tested reinforcing materials decreased the linear dimensional changes and water sorption as compared to the control group specimens.

Interfacial Nano-Mechanical Properties of Copper Joints Bonded with Silver Nanopaste near Room Temperature

Sintering of nanomaterials at low temperatures has been demonstrated as an alternative for flexible electronic packaging. Silver nanowires were synthesized via polyol method and used as filler material for bonding copper to copper near room temperature. The experimental results indicated that both silver-to-silver and copper-to-silver formed metallurgical bonds. The elastic modulus and nano-hardness of copper joints at the copper-silver interface were characterized using nanoindentation. A transition layer at the interface was observed and its thickness was determined. Sintered silver filler material showed good elasticity both inside and out of the transition layer. [doi:10.2320/matertrans.MI201412]

Brazing of Alloy Based on Fe3al Aluminide/ Lutowanie Twarde Stopu Na Osnowie Aluminidku Fe3al

Abstract Alloys based on the Fe3Al intermetallic phase belong to a new generation of metallic materials intended for operation at higher temperatures and having properties something between those of metals and ceramic materials. They are characterised by relatively high oxidation resistance, high corrosion resistance, high-temperature creep resistance, high electrical resistivity, high abrasion resistance as well as resistance to erosion and cavitation. Although the material costs of these alloys are relatively low, they belong to materials which are very difficult to join by means of welding methods. For this reason, joining such materials remains an important and current research and technological problem. One of the methods used for joining such materials is brazing. This work shows the results of technological tests concerned with vacuum brazing an alloy based on the Fe3Al (Fe86Al14) phase using silver (Ag72Cu28) and copper-nickel (Cu90Ni10, Cu95Ni5) filler metals as well as presents the results of tests on the mechanical and structural properties of obtained joints.

New insights into silver nanowires filled electrically conductive adhesives

Silver nanowires have drawn remarkable attention owing to their anisotropic electrical and optical properties that differ from those observed in the bulk materials and the interesting applications in various areas such as electronic devices, chemical sensors and photonics. In this paper, silver nanowires with an average diameter of 450 nm and a length of up to 100 μm were successfully synthesized by a polyol process. The experimental results indicate that the morphologies and sintering behaviors of silver nanowires are impacted by glutaric acid and the sintering temperature. The isotropically conductive adhesives (ICAs) were made by adding silver nanowires to the polymer composites consisted mainly of epoxy resin, cure agent and catalyst, and then the electrical properties were investigated based on those physical parameters such like the fraction of the silver nanowires of the total of silver fillers and the curing temperature. The in situ monitoring of the variation in electrical resistance of the ICAs and DSC explore that silver nanowires can affect the curing behavior of the ICAs. Silver nanowires can significantly improve the electrical conductivity of the ICAs when the loading of silver nanowires is low and the curing temperature is less than about 250 °C. There is little difference of the electrical resistivity between the ICAs filled with silver nanowires and micro-sized silver flakes when the loading of silver fillers in the ICAs is 75 wt%, and this phenomenon is related to the curing temperature. The silver nanowires treated by glutaric acid can improve the electrical property of the ICAs.

Sintering behavior and effect of silver nanoparticles on the resistivity of electrically conductive adhesives composed of silver flakes

In this paper, silver nanoparticles with size of 30–50 nm were synthesized by reducing silver nitrate with sodium borohydride and sodium citrate and using PVP as an adsorption agent in the ethanol solution. The experimental results indicate that the morphologies and sintering behaviors of both kinds of silver nanoparticles are impacted by glutaric acid and sintering temperature. The electrically conductive adhesives (ECAs) filled with micro-sized silver flakes and silver nanoparticles as hybrid fillers were fabricated and the electrical properties were investigated based on the fraction of the silver nanoparticles of the total of silver flakes and the curing temperature, etc. The incorporation of the untreated/treated silver nanoparticles into the polymer matrix with 65 wt% silver filler the resistivity increased in almost all cases, especially the high fraction and the low curing temperature. The curing temperature has influence on the resistivity of the ECAs filled with micro-sized silver flakes and the silver nanoparticles due to the sintering of the silver nanoparticles. The addition of 10% treated silver nanoparticles into the ECAs with 60 wt% silver fillers, the resistivity is slightly lower than that of the ECAs with micro-sized silver flakes. In the system of the ECAs with the high loading of silver fillers, the untreated/treated silver nanoparticles have little effect on the electrical conductivity. The results suggest that the morphology and distribution of silver fillers are the key to affect the conductivity of ECAs when nanoparticles are included in the system.

Surface iodination: A simple and efficient protocol to improve the isotropically thermal conductivity of silver-epoxy pastes

Abstract Heat dissipation is a critical issue in many areas such as the high-performance electronic devices. The present work gives a detailed investigation regarding a simple and efficient surface modification method, which can remarkably improve the thermal conductivity of the isotropically thermally conductive adhesives (TCAs). Herein we demonstrate that the thermal conductivity of TCAs based on micron-sized silver fillers can be improved to near eightfold merely through simple surface chemistry treatment of the fillers, without changing the conventional epoxy resin (adhesive) processing conditions. Experimental results show that the thermal conductivity of a TCA sample with iodine modified silver fillers (85 wt%, size 1–2 μm, near-spherical particles) achieved 13.5 Wm−1 K−1 when cured at 150 °C. Compared to the unmodified silver-based TCAs, only 1.7 Wm−1 K−1 was achieved when cured in the same condition. This work suggests that through modulating the filler interface of a TCA, the thermal conductivity of a TCA can be drastically improved. These TCAs with superior isotropic thermal conductivity may find many heat dissipation applications e.g. surface mounted devices (SMDs) and high power (printed circuit) motherboards.