Effect of SiO2 nanoparticle addition on growth of interfacial Ag3Sn intermetallic compound layers between lead-free solder and silver conductor

This study investigated the effects of silver powder modification on intermetallic compound (IMC) formation and silver leaching during soldering at high temperatures. Silica nanoparticles (NPs) were deposited onto a silver powder surface to inhibit silver leaching, which can lead to soldering joint failure during high-temperature soldering. The NPs were deposited through hydrolysis and a condensation reaction of tetraethyl orthosilicate (TEOS) based on the Stöber method. Fourier transform infrared spectroscopy and scanning electron microscopy were used to observe the microstructures of silver powders after the deposition of silica NPs with various TEOS concentrations and various deposition times. As the deposition time increased, the amount of silica NPs on the surface of the silver powder increased. The transmission electron microscopy results show that silica NPs were located at the IMC grain boundaries, which can hinder the dissolution of IMCs by lead-free solder melt along grain boundaries during soldering, retarding silver leaching. The growth kinetics and mechanism of IMCs during soldering were investigated. The results show that the growth of IMCs is mainly dominated by bulk diffusion. The activation energy for IMC growth increased and the growth rate decreased with increasing silica NP addition and deposition time.

Fine Silver Powders Production

The article lays out the findings aimed to develop the fine silver powder production technique for electronics industry by selecting the variable parameters whereby a number of powder grades can be produced in the existing production environment (JSC “Uralelektromed”, Russia). The tests for significance of the parameters of silver recovery by ascorbic acid such as pH level of nitrate silver solution, dispersant flow rate, initial concentration of silver, mixing rate and solution temperature made it possible to choose optimum conditions to produce powders of 0.8-6.3 μm in particle size, of 3.0-4.2 g/cm3 in tapped density and with the specific surface area of 2300-4300 cm2/g. Crystalline silver of 99.98 % purity served as a raw material for obtaining silver powders.

Tuning the Electrical Resistivity of Conductive Silver Paste Prepared by Blending Multi-Morphologies and Micro-Nanometers Silver Powder

As an important interconnection material in electronics, conductive silver paste has attract much research interest in chip packaging and printed circuit board due to its predominant properties like high conductivity and flexible interconnection. In this paper, the silver nanoparticles, the silver sphere particles and flake silver powder are fabricated by various methods. Different proportions of silver powder are selected to prepare micro-silver paste and mn silver paste (fabricated by silver nanoparticles : sphere particles : flake silver powder=1:1:1). Compared to traditional silver paste (containing 80wt% silver), the electrical resistivity of micro-silver paste containing 66.67wt% silver and cured at 200℃ for 45min in air is about (3.31±0.73)×10-5Ω·cm when the ratio of sphere particle to flake silver powder is 1:1, the resistance of silver paste doesn’t also increase dramatically after bending ten times. The addition of nano-silver particles can reduce the resistivity in lower temperature curing. The folding endurance of mn silver paste is comparable to that of micro-silver paste with sphere : flake=1:1.

Synthesis of micro-sized silver particles suitable for thick film contacts on solar cells

The main goal of the study was to determine parameters for the production of the micro-sized silver powder applicable to the pastes that are in use in solar cell production and maintenance. In all experiments, silver nitrate solution and ascorbic acid were used, as a silver source and reducing agent, respectively. Polyvinylpyrrolidone and gelatine were used as dispersants. The dispersant in this system acts as a protective agent in a way that prevents agglomeration and aggregation processes. The influence of used agents was different, and one of the aims in the research was to determine the pros and cons of them. The optimal parameters of the synthesis were the solution temperature of 45 °C, pH=7, and concentrations of silver and ascorbic acid of 45 g/l and 30 g/l, respectively. Although PVP has proved to be a suitable protecting agent for the goals of the study, the best results were obtained with the use of gelatine as a dispersant in the concentration ratio against the silver ions of 2.5 wt. %.

Laboratory-based study of novel antimicrobial cold spray coatings to combat surface microbial contamination

Objective:To investigate the touch-contact antimicrobial efficacy of novel cold spray surface coatings composed of copper and silver metals, regard to their rate of microbial elimination.Design:Antimicrobial time-kill assay.Setting:Laboratory-based study.Methods:An adapted time-kill assay was conducted to characterize the antimicrobial efficacy of the developed coatings. A simulated touch-contact pathogenic exposure to Gram-positive Staphylococcus aureus (ATCC 25923), Gram-negative Pseudomonas aeruginosa (ATCC 27853), and the yeast Candida albicans (ATCC 10231), as well as corresponding resistant strains of gentamicin-methicillin–resistant S. aureus (ATCC 33592), azlocillin-carbenicillin–resistant P. aeruginosa (DSM 46316), and a fluconazole-resistant C. albicans strain was undertaken. Linear regression modeling was used to deduce microbial reduction rates.Results:A >7 log reduction in microbial colony forming units was achieved within minutes on surfaces with cold spray coatings compared to a single log bacterial reduction on copper metal sheets within a 3 hour contact period. Copper-coated 3-dimensional (3D) printed acrylonitrile butadiene styrene (ABS) achieved complete microbial elimination against all tested pathogens within a 15 minute exposure period. Similarly, a copper-on-copper coating achieved microbial elimination within 10 minutes and within 5 minutes with the addition of silver powder as a 5 wt% coating constituent.Conclusions:In response to the global need for alternative solutions for infection control and prevention, these effective antimicrobial surface coatings were proposed. A longitudinal study is the next step toward technology integration.

Production of sub-micro sized silver particles by chemical reduction method in an environmentally-friendly manner

Silver nitrate in the solution was reduced in the presence of the dispersants by ascorbic acid, and silver particles were generated. The main goal was to examine the influence of different dispersants. The purpose was to improve the production process of the micro-sized silver powder for thick film silver pastes for applications in the photovoltaic sector and the printed electronics. Relatively high concentrations of the reagents were used to achieve a high yield of silver particles. It was a strict request for highly economic production. This paper shows the possibilities for the routes for future large-scale synthesis and potential industrial production. The particles were analyzed by the X-ray diffraction (XRD), scanning electron microscopy (SEM), and laser diffraction particle size analyzer.

Effect of Venting on the Explosion of Aluminium-Silver Powder Mixtures

Dust explosion is considered as a serious threat for the industry that use or handle combustible materials as it may lead towards a significant economic loss in terms of damage to the facilities and suspension of activities, severe workplace injuries and fatalities. The rapid pressure developed during a dust explosion can be mitigated by venting. The present work explored the effects of venting on the explosion of different mixing weight ratios of aluminium and silver powder mixtures. The explosion characteristics of aluminium-silver mixtures were assessed in a 0.0012 m3 confined and vented cylindrical vessel. It was found that the application of 0.1 bar static burst pressure (Pstat) venting membrane gives one tenth reduction on explosion pressure and maximum rate of pressure rise for 70:30 and 50:50 mixing weight ratios of aluminium-silver mixtures explosion, respectively. This finding suggests that besides the venting application effect, the oxidation reaction of aluminium could be disrupted due to the presence of silver powder in the metal mixtures which results in lower heat transfer and reduction of the mass burning rate, hence, lessen flame speeds and explosion severity. However, the venting effectiveness is reduced when the Pstat increases. In order to assess the applicability of the dust explosion venting standard; NFPA 68 and EN 14491, the experimental results were compared with the calculated values according to the standards. The comparative results show that, both NFPA 68 and EN 14491 give underestimated values for explosion venting as compared with the experimental results.