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The purpose of this paper is to investigate the creep properties of Sn‐0.7Cu composite solder joints reinforced with optimal nano‐sized Ag particles in order to improve the creep performance of lead‐free solder joints by a composite approach.

The composite approach has been considered as an effective method to improve the creep performance of solder joints. Nano‐sized Ag reinforcing particles were incorporated into Sn‐0.7Cu solder by mechanically mixing. A systematic creep study was carried out on nano‐composite solder joints reinforced with optimal nano‐sized Ag particles and compared with Sn‐0.7Cu solder joints at different temperatures and stress levels. A steady‐state creep constitutive equation for nano‐composite solder joints containing the best volume reinforcement was established in this study. Microstructural features of solder joints were analyzed to help determine their deformation mechanisms during creep.

The creep activation energies and stress exponents of Ag particle‐enhanced Sn‐0.7Cu lead‐free based composite solder joints were higher than those of matrix solder joints under the same stress and temperature. Thus, the creep properties of nano‐composite solder joints are better than those of Sn‐0.7Cu solder joints.

The findings indicated that nano‐sized Ag reinforcing particles could effectively improve the creep properties of solder joints. A new steady‐state creep constitutive equation of nano‐composite solder joints was established. Deformation mechanisms of Sn‐0.7Cu solder and nano‐composite solder joints during creep were determined.

The purpose of this paper is to investigate the influence of silver nanoparticle additions on the wetting properties of Sn‐Ag‐Cu (SAC) solder paste. In this investigation, the basic solder paste contained 85 wt.% of commercial Sn 96.5 Ag 3 Cu 0.5 powder (with the particle sizes in the range of 20‐38 μm) and 15 wt.% of self‐prepared middle activated rosin flux. To this paste was added 0.5, 1, 2 and 4 wt.% of self‐prepared silver nano‐powders of different grain sizes (from 9 to 138 nm). After the pastes had stabilized, their wetting properties were tested. The main goal of these investigations was to improve the wetting properties of SAC solder paste and to find correlations between the results of the wetting of solder paste with nanoparticles on the copper substrate with the microstructure of the solder joints.

The following methods were applied for the wetting solder paste investigation: spreading on the copper substrate, contact angle measurement on the copper and wetting on a FR‐4 laminate double sided with an 18‐μm thick copper foil. The investigations were performed at temperatures of 220, 230, 240 and 250°C. Cross‐sectioning was performed on the solder paste after reflow on the copper substrate. For the microstructural analysis of the “nano” modified solder joints obtained at 250°C, standard metallographic procedures were applied. Changes in the microstructure, the thickness of the inter‐metallic compounds (IMCs) and their chemical compositions were observed by means of scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS).

As expected, a higher silver nanoparticle addition to the SAC solder paste resulted in better wetting properties on copper. The results indicated the possibility of an improvement of the reflow soldering process by using SAC solder paste with silver nanoparticles and by lowering its soldering temperature. An improvement was also observed in the wettability with a decrease in the silver nanoparticle grain size. Also, the wettability proceeded at a lower temperature (20°C lower) than that for the SAC paste, without the nano‐additives. For the 4 per cent silver nanoparticle addition, Ag₃Sn star‐like IMCs were also found, which grew with the lowering of the silver nanoparticle grain size.

Further studies are necessary for confirmation of the practical application, especially of the mechanical properties, as well as the reliability properties of the solder joints, for the chosen solder paste with silver nanoparticles.

Taking into account the wetting data, the best results of the “nano” SAC solder pastes were obtained for the highest addition of the silver nanoparticles. It was found that the spreading on copper was higher and the contact angles were lower for the SAC solder paste with 4 per cent (by wt.) of 138‐nm grain size silver nanoparticles. A comparison of SAC solder pastes with a 4 per cent silver nanoparticle addition but of a different grain size (138‐9 nm), suggested a further improvement in wetting properties with lowering of the silver nanoparticle grain size. The results suggested the possibility of an improvement in the reflow soldering process by using SAC solder paste with silver nanoparticles and by lowering its soldering temperature.

Spreading, wetting and contact angle measurement methods were used for the wetting determination of the SAC solder paste with the silver nanoparticles on copper under the same temperature conditions. Also, the microstructure of the solder joints obtained at 250°C was determined with the use of SEM and EDS methods. The results obtained made it possible to draw conclusions regarding the correlation between the output of the wetting results and the amount and the grain size of the added silver nanoparticles, and also the microstructure and thickness of the IMCs of the “nano” solder joints.

The purpose of this paper is to improve anti-corrosion, self-cleaning, hydrophily and sterilization properties of aluminum (Al) alloy.

A multifunctional coating for medical external application on Al alloy had been prepared by anodic oxidation, electrolytic coloring silver (Ag) and sealed in boiling water with nano-sized titanium dioxide (TiO₂) particles. The multifunctional coating was characterized by X-ray diffraction, scanning electron microscope and energy dispersive spectroscopy. Other properties such as corrosion-resistance, wipe-resistance, hydrophilicity, photochemical decomposition and bactericidal antiseptic effect were also investigated.

The results demonstrate that a golden film with multi-function had been obtained for medical external application. The main phase of coating is amorphous Al₂O₃, and nano-sized silver particle is electrodeposited in bottom of film hole, while nano-sized TiO₂ is sealed on the external surface of coating. The properties of film, such as anti-corrosion, self-cleaning, hydrophily, sterilization are better than those of Al alloy substrate.

Considering about this usage for medical external application, a multifunctional coating which has the properties such as decoration, anti-corrosion, sterilize and self-cleaning has been first prepared on Al alloy surface in the study. This coating would meet the requirements of medical external using and provide theoretical and practical foundation about Al alloy for medical use.

Nowadays, the usage of antibacterial textiles is very popular for different type of textiles. The silver (Ag) and zinc oxide (ZnO) are the most popular materials in order to improve antibacterial properties of textiles. The purpose of this paper is to investigate the possibility to produce Ag nanoparticle (NP), ZnO NP, Ag/ZnO NP composite materials in this experimental study.

It was investigated whether it was possible to produce Ag NP, ZnO NP, Ag/ZnO NP composite materials by hydrothermal method which was known as in-situ approach on the fiber. In addition, the colloidal silver (Ag+) was produced by electrolysis method, and used instead of process water which was necessary during generating of NPs on the fiber by this method. After whole applications, the samples were characterized by SEM, XRD, EDX analyses and the antibacterial activity of specimens was tested according to the ASTM E 2149-01 (gram-negative Escherichia coli). In addition, the resistance to the repeated washes of these antibacterial samples was investigated.

The production of NPs on the fiber was achieved. The results showed that the samples had sufficient antibacterial activity and this activity did not reduce depending on repeated washing treatments.

Because of usage of one type of fiber, it would be necessary to make researches on the different type of fiber, testing procedure (with different bacteria), washing replications and prescriptions.

During the process the temperature control is very important for the produced fiber. In addition chosen antibacterial test method is crucial for the testing of activity of product. Fiber must be washed at least once to remove unfixed NPs on the fiber.

The technical antibacterial polyester fiber was in-situ coated by hydrothermal method with Ag, ZnO, Ag/ZnO composite NPs.

The purpose of this paper is to focus on the fabrication of SnAgCu (SAC) nanocomposites solder and study the effect of Cu nanopowders (nano-Cu) addition on the microstructure evolution of resultant nanocomposite solder after reflow and thermal aging.

Mechanical mixing is used in this work to incorporate nanoparticles into the solder and produce more homogeneous mixture. Standard metallographic procedures are applied for microstructural analysis of solder joints.

It is found that nano-Cu doped into Sn0.7Ag0.5Cu-BiNi solder has no appreciable influence on melting temperature of the composite solder. The addition of Cu nanoparticles refines the microstructure of bulk solder and suppresses the growth of interfacial intermetallic compound (IMC) layers. However, interfacial IMC grain size increases slightly after 1.0 per cent nano-Cu added.

The paper demonstrates a method of nano-composite solder paste preparation by means of mechanical mixing and a comparison study of the microstructure evolution of composite solder with the basic SAC solder.

The purpose of this paper is to develop and test the thermal interface materials (TIM) for application in assembly of semiconductor chips to package. Good adhesion properties (>5 MPa shear strength) and low thermal interface resistance (better than for SAC solders) are the goal of this research.

Mechanical and thermal properties of TIM joints between gold plated contacts of chip and substrate were investigated. Sintering technique based on Ag pastes was applied for purpose of this study. Performance properties were assessed by shear force tests and thermal measurements. Scanning electron microscopy was used for microstructural observations of cross-section of formed joints.

It was concluded that the best properties are achieved for pastes containing spherical Ag particles of dozens of micrometer size with flake shaped Ag particles of few micrometers size. Sintering temperature at 230°C and application of 1 MPa force on the chip during sintering gave the higher adhesion and the lowest thermal interface resistance.

The new material based on Ag paste containing mixtures of Ag particles of different size (form nanometer to dozens of microns) and shape (spherical, flake) suspended in resin was proposed. Joints prepared using sintering technique and Ag pastes at 230°C with applied pressure shows better mechanical and thermal than other TIM materials such as thermal grease, thermal gel or thermally conductive adhesive. Those material could enable electronic device operation at temperatures above 200°C, currently unavailable for Si-based power electronics.

The purpose of this paper is to study the reliability of sintered nano-silver joints on bare copper substrates during high-temperature storage (HTS).

In this study, HTS at 250 °C was carried out to investigate the reliability of nano-silver sintered joints. Combining the evolution of the microstructure and shear strength of the joints, the degradation mechanisms of joints performance were characterized.

The results indicated that the degradation of the shear properties of sintered nano-silver joints on copper substrates was attributed to copper oxidation at the silver/copper interface and interdiffusion of interfacial elements. The joints decreased by approximately 57.4% compared to the original joints after aging for 500 h. In addition, severe coarsening of the silver structure was also an important cause for joints failure during HTS.

This paper provides a comparison of quantitative and mechanistic evaluation of sintered silver joints on bare copper substrates during HTS, which is of great importance in promoting the development of sintered silver technology.

The purpose of our paper is to investigate thermal and mechanical properties of Ag sintered layers used for assembly of SiC diode to Direct Bonding Copper (DBC) interposer. How SiC devices are assembled to ceramic package defines efficiency of heat transfer and mechanical support.

Ag microparticles, sized 2-4 μm and flake shaped, were used as joining material. The parameters of sintering process were as follows: temperature 400°C, pressure 10 MPa and time 40 min. It was found that after sintering and long-term aging in air at 350°C the adhesion is in the range of 10 MPa, which is enough from a practical point of view. The thermal properties of the SiC die assembled into a ceramic package were also investigated. In the first step, the calibration of the temperature-sensitive parameter VF (IF = 2 mA) was done and the relation between VF and temperature was found. In the next step, the thermal resistance between junction and case was determined knowing junction and case temperature.

For SiC diode with Au bottom metallization joined to the DBC interposer by Ni/Au metallization by Ag microparticle layer, R_th j-c is in the range of 2-3.5°C/W, and for SiC diode with Ag bottom metallization joined to DBC interposer with Ag metallization by Ag microparticle layer, R_th j-c is in the range of 4.5-5.5°C/W.

In the future, research on thermal resistance of SiC diodes assembled onto the DBC interposer with Au and Ag metallization in the temperature range up to 350°C needs to be carried out. To do this, it necessary to find a solution for the attaches that leads to ceramic package able to work at such high temperature.

Obtained results are comparable with results mentioned by other studies for eutectic Au/Sn or SAC solder joints; however, the solution proposed by us can properly work at significantly higher temperatures.

This paper aims to find proper technological parameters of low-temperature joining technique by silver sintering to eventually use this technique for reliable electronic packaging.

Based on the literature and author’s own experience, the factors influencing the nanosized Ag particle sintering results were identified, and their significance was assessed.

It has been shown that some important technological parameters clearly influence the quality of the joints, and their choice is unambiguous, but the meaning of some parameters is dependent on other factors (interactions), and they should be selected experimentally.

The value of this research is that the importance of all technological factors was analyzed, which makes it easy to choose the technological procedures in the electronic packaging.

This paper aims to use nano-silver paste to design a new bonding method for super-large-area direct-bonded-aluminum (DBA) plates. It compared several frequently used bonding methods and proved the feasibility of an optimized low-pressure-assisted double-layer-printed silver sintering technology for large-area bonding to increase the thermal conductivity of power electronic modules with high junction temperature, higher power density and higher reliability.

The bonding profile was optimized by using transparent glasses as substrates. Thus, the bonding qualities could be directly characterized by optical observation. After sintering, the bonded DBA samples were characterized by nondestructive X-ray computed tomography system, scanning electron microscopy equipped with an energy dispersive spectrometer. Finally, bonding stress evolution was characterized by shear tests.

Low-pressure-assisted large-area double-layer-printed bonding process consisting of six-step was successfully developed to bond DBA substrates with the size of 50.8 × 25.4 mm. The thickness of the sintered-silver bond-line was between 33  and 74 µm with the average porosity of 12.5 per cent. The distribution of shear strength along the length of DBA/DBA bonded sample was from 9.7  to 18.8 MPa, with average shear strength of 15.5 MPa. The typical fracture primarily propagated in the sintered-silver layer and partially along the Ni layer.

The bonding stress needs to be further improved. Meanwhile, the thermal and electrical properties are encouraged to test further.

If nano-silver paste can be used as thermal interfacial material for super-large-area bonding, the thermal performance will be improved.

The paper accelerated the use of nano-silver paste for super-large-area DBA bonding.

The proposed bonding method greatly decreased the bonding pressure.