Fundamentals of Modern Manufacturing: Materials, Processes and Systems

A review of lead-free solders for electronics applications

The paper presents the description of an experimental complex that has been designed for investigations of high temperature capillarity phenomena by various testing methods (classical sessile drop, pendant drop, dispensed drop, sandwiched drop, transferred drop, drop sucking, drop pushing, drop smearing or rubbing) at a temperature of up to 2100 °C under vacuum of up to 10−7 hPa or in protective atmosphere (static or flowing gas with controlled rate at required level of pressure). Several examples of high temperature wettability tests are discussed in order to demonstrate the wide testing possibilities of the new experimental complex.

Experimental complex for investigations of high temperature capillarity phenomena

Centrifugal-force infiltration was used for obtaining aluminium alloy composites reinforced with carbon fibre by the infiltration of preforms. The lost-wax-casting technique was used during the manufacturing process. Preforms fabricated with different percentages of reinforcement were heated to facilitate their filling with aluminium. Some samples were coated with nickel to favor the reinforcement wetting by the molten aluminium alloy. Composites with volume fraction of reinforcements above 7 vol.% and porosity values lower than 0.5 vol.% were obtained with this technique. The hardness of the composites increased with the volume fraction of reinforcement and the solution and the later precipitation of nickel coating caused an additional hardening effect.

Fabrication of aluminium composites reinforced with carbon fibres by a centrifugal infiltration process

A critical review of phase change material composite performance through Figure-of-Merit analysis: Graphene vs Boron Nitride

The paper discusses the scientific understanding of the role of interfacial phenom- ena in joining of dissimilar materials using liquid-phase-assisted processes. From the exam- ple of the Sn-alloy/Cu system, it is demonstrated that interaction in the liquid solder/substrate couples is accompanied by a number of complex interfacial reactions leading to significant changes in the structure and chemistry of interfaces (solder/substrate, solder/environment, substrate/environment) and remaining solder layer that finally influence the mechanical prop- erties of solder joints. The experimental data on wetting behavior, interface characterization, and mechanical properties of different solder/metal substrate couples are analyzed in order to display the role of such factors as time and temperature of interaction, environment (protective atmosphere, flux), presence of oxide films on interfaces, alloying additions to a solder, formation of inter- facial phases, and porosity.

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Factors affecting wettability and bond strength of solder joint couples

For a successful implementation of newly proposed silicon-based latent heat thermal energy storage systems, proper ceramic materials that could withstand a contact heating with molten silicon at temperatures much higher than its melting point need to be developed. In this regard, a non-wetting behavior and low reactivity are the main criteria determining the applicability of ceramic as a potential crucible material for long-term ultrahigh temperature contact with molten silicon. In this work, the wetting of hexagonal boron nitride (h-BN) by molten silicon was examined for the first time at temperatures up to 1750 °C. For this purpose, the sessile drop technique combined with contact heating procedure under static argon was used. The reactivity in Si/h-BN system under proposed conditions was evaluated by SEM/EDS examinations of the solidified couple. It was demonstrated that increase in temperature improves wetting, and consequently, non-wetting-to-wetting transition takes place at around 1650 °C. The contact angle of 90° ± 5° is maintained at temperatures up to 1750 °C. The results of structural characterization supported by a thermodynamic modeling indicate that the wetting behavior of the Si/h-BN couple during heating to and cooling from ultrahigh temperature of 1750 °C is mainly controlled by the substrate dissolution/reprecipitation mechanism.

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Wetting Behavior and Reactivity of Molten Silicon with h-BN Substrate at Ultrahigh Temperatures up to 1750 °C

The role of aluminium oxidation in the wetting-bonding relationship of Al/oxide couples

The solderability of the SAC305 alloy in contact with printed circuit boards (PCB) having different surface finishes was examined using the wetting balance method. The study was performed at a temperature of 260 °C on three types of PCBs covered with (1) hot air solder leveling (HASL LF), (2) electroless nickel immersion gold (ENIG), and (3) organic surface protectant (OSP), organic finish, all on Cu substrates and two types of fluxes (EF2202 and RF800). The results showed that the PCB substrate surface finish has a strong effect on the value of both the wetting time t
 0 and the contact angle θ. The shortest wetting time was noted for the OSP finish (t
 0 = 0.6 s with EF2202 flux and t
 0 = 0.98 s with RF800 flux), while the ENIG finish showed the longest wetting time (t
 0 = 1.36 s with EF2202 flux and t
 0 = 1.55 s with RF800 flux). The θ values calculated from the wetting balance tests were as follows: the lowest θ of 45° was formed on HASL LF (EF2202 flux), the highest θ of 63° was noted on the OSP finish, while on the ENIG finish, it was 58° (EF2202 flux). After the solderability tests, the interface characterization of cross-sectional samples was performed by means of scanning electron microscopy coupled with energy dispersive spectroscopy.

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Effects of PCB Substrate Surface Finish and Flux on Solderability of Lead-Free SAC305 Alloy

The aluminum recovery from white aluminum dross by a mechanical treatment and sizing followed by remelting process was investigated. The dross was subjected to a ball mill, and the obtained particles were sized in different ranges. They were studied by advanced materials characterization techniques. It was found that the larger particles contain high metallic portions, and most non-metallic components of the dross are in the fine fraction 1 mm) were remelted at 900°C to recover aluminum. It was found that the metal structure after remelting is homogeneous and consisted of a dominant metallic aluminum matrix, containing an average of > 96% Al with around 99% total metallic components. The results show that the applied method is a good economic alternative for the aluminum recovery from white dross, which is important for the valorization/recycling of industrial waste and circular economy.

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Artur Kudyba

Papers

Factors affecting wettability and bond strength of solder joint couples

Wetting Behavior and Reactivity of Molten Silicon with h-BN Substrate at Ultrahigh Temperatures up to 1750 °C

The role of aluminium oxidation in the wetting-bonding relationship of Al/oxide couples

Effects of PCB Substrate Surface Finish and Flux on Solderability of Lead-Free SAC305 Alloy

Aluminum Recovery from White Aluminum Dross by a Mechanically Activated Phase Separation and Remelting Process