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The purpose of this paper is to investigate the morphology of intermetallic (IMC) compounds and the mechanical properties of SAC305 solder alloy under different cooling conditions.

SAC305 solder joints were prepared under different cooling conditions/rates. The performance of three different etching methods was investigated: simple chemical etching, deep etching based on the Jackson method and selective removal of β-Sn by a standard three-electrode cell method. Phase and structural analyses were conducted by X-ray diffraction (XRD). The morphology of etched solder was examined by a field emission scanning electron microscope. The hardness evaluations of the solder joints were conducted by a Vickers microhardness tester.

The Ag₃Sn network was significantly refined by the ice-quenching process. Further, the thickness of the Cu₆Sn₅ layer decreased with an increase in the cooling rate. The finer Ag₃Sn network and the thinner Cu₆Sn₅ IMC layer were the results of the reduced solidification time. The ice-quenched solder joints showed the highest hardness values because of the refinement of the Ag₃Sn and Cu₆Sn₅ phases.

The reduction in the XRD peak intensities showed the influence of the cooling condition on the formation of the different phases. The micrographs prepared by electrochemical etching revealed better observations regarding the shape and texture of the IMC phases than those prepared by the conventional etching method. The lower grain orientation sensitivity of the electrochemical etching method (unlike chemical etching) significantly improved the micrographs and enabled accurate observation of IMC phases.

This paper aims to cover the recent (2010-2016) techniques for carrying out hardness evaluation on lead-free solders. Details testing configuration/design were compiled and discussed accordingly to each of the measurement techniques: Vickers microhardness, Brinell microhardness and nanoindentation.

A brief introduction on lead-free solders and the concept of hardness testing has been described at the beginning of the review. Equipment setup, capabilities, test configuration and outcomes were presented for each technique and discussed in parallel along with the case studies from selected articles.

Comparison, outcomes and insight regarding each of the methods were highlighted to observe the recent trends, scientific challenges, limitations and probable breakthroughs of the particular hardness testing methods.

The compilation of latest reports, technical setup plus with the critics and perception from the authors are the main key value in this review. This provides an in-depth understanding and guidance for conducting hardness evaluation on lead-free solders.

The purpose of this paper is to review and examine three of the most common corrosion characterization techniques specifically on Sn-Zn solders. The discussion will highlight the configurations and recent developments on each of the compiled characterization techniques of potentiodynamic polarization, potentiostatic polarization and electrochemical impedance spectroscopy (EIS).

The approach will incorporate a literature review of previous works related to the experimental setups and common parameters.

The potentiostatic polarization, potentiodynamic polarization and EIS were found to provide crucial and vital information on the corrosion properties of Sn-Zn solders. Accordingly, this solder relies heavily on the amount of Zn available because of the inability to produce the intermetallic compound in between the elements. Further, the excellent mechanical properties and low melting temperature of the Sn-Zn solder is undeniable, however, the limitations regarding corrosion resistance present opportunities in furthering research in this field to identify improvements. This is to ensure that the corrosion performance can be aligned with the outstanding mechanical properties. The review also identified and summarized the advantages, recent trends and important findings in this field.

The unique challenges and future research directions regarding corrosion measurement in Sn-Zn solders were shown to highlight the rarely discussed risks and problems in the reliability of lead-free soldering. Many prior reviews have been undertaken of the Sn-Zn system, but limited studies have investigated the corrosive properties. Therefore, this review focuses on the corrosive characterizations of the Sn-Zn alloy system.

The purpose of this study is to know the influence of palm oil fuel ash and metakaolin on the strength of concrete and crack resistance of reinforced concrete beam. An ordinary portland cement has been used in the concretes production where it is an important material to be considered due to its nature that reacts with every substance present. During the cement production, a significant amount of carbon dioxide is emitted from the clinker in rotary kiln and lot of energy is required in the production processes. Such an event can be prevented by replacing the part of cement with metakaolin (MK) and palm oil fuel ash (POFA). Aside from being a cementitious alternative, the materials can also contribute to a greener environment and more sustainable building, as POFA is available in Malaysia and may be used to substitute cement and minimize pollution.

This study assesses the effect of MK and POFA on the concrete in terms of compressive strength and cracks pattern of the reinforced concrete beam based on the relevant previous studies.

From this study, the compressive strength of concrete containing MK and POFA was higher than the control mix with the percentage of improvement in the range of 0.8%–78.2% for MK and 0.5%–14%, respectively. The optimum content of MK and POFA is between the range of 10% and 15% and 10% and 20%, respectively, to achieve high strength of concrete. Other than that, the inclusion of MK to the concrete mix improves the strength of reinforced concrete beams and reduces cracks on the surface of reinforced concrete beams, whereas the inclusion of POFA to the concrete mix increases the cracks on reinforced concrete beams. The cracks appeared within the flexure zone of every beam containing the MK and POFA.

It was found that the fineness of MK and POFA has a significant influence on the mechanical properties of concrete.