Search results

The dissolution rate of a solid metal such as Cu, in contact with molten solder can be calculated with the use of the Nernst‐Brenner equation. We describe how this equation should be correctly used in cases when the solder is in contact with both the base metal and any intermetallic compounds that have formed. We also show that the concentration of solute in the solder will generally lie between the metastable solubility limit and the equilibrium solubility limit, illustrating these ideas with reference to a system comprising Nb as the base metal and eutectic In‐Sn as the solder, where the concentration levels can be directly correlated to the crystal growth rate.

Detailed studies to characterise the coarsening behaviour of eutectic Sn‐Ag and near‐eutectic Sn‐Pb‐Ag solder joints were carried out on samples reflow soldered and solidified at various cooling rates. Light and scanning electron microscopy as well as EDS were used to study the microstructural evolution, while microhardness measurements were used to monitor the change in the mechanical properties. Samples consisting of copper substrates and solder paste were reflow soldered about 30 °C above their melting points and then solidified at cooling rates ranging from furnace cooling to rates associated with water quenching. Analysis of some of these samples showed that increasing the cooling rate increased the quantity (volume fraction) of primary Sn‐dendrites, decreased the (EQ) intermetallic phase in the bulk solder, and resulted in finer microstructures with higher hardness. The microstructural evaluation involved characterisation of bulk intermetallica and dendrite/eutectic ratios. Subsequent isothermal annealing of these reflow soldered joints at 125 °C for times between 0.25 h and 8 days resulted in an initially fairly rapid decrease in hardness to a given level for each alloy and each cooling rate.

This paper examines the moderating role of firms’ litigation environment on the association between gender diversity and financial reporting quality.

This study draws on a sample of US firms to examine the moderating role of firms’ litigation environment on the association between gender diversity and financial reporting quality. Firm-specific financial data come from Compustat. To measure the firms’ litigation environment, we use state-level datasets from the Lawsuit Climate Survey conducted for the US Chamber Institute for Legal Reform by the Harris Poll.

Findings suggest that firm litigation environment moderates gender diversity, as defined by female members on the board to subdue our first proxy for financial reporting quality (accruals-based earnings management), but our second proxy for financial reporting quality (real-activities manipulations) increases in a firm’s litigation environment. To the extent that our results hold after controlling for firms’ reputation indicates that female members on the board are sensitive to reputational loss and protect firms’ reputation in a litigation environment.

The study is based on a specific country, limiting the generalizability of the findings.

The findings provide support for promoters and advocates of gender diversity in corporate boards. Specifically, it shows the importance of gender diversity policies in business and society.

This study is the first to examine the moderating role of firms’ litigation environment on the association between gender diversity and financial reporting quality. The study provides novel evidence and shows that the litigation environment moderates gender diversity to improve financial reporting quality in the short-term (by decreasing accruals manipulation). In firms’ litigation environment, when female members on the board are restrained from engaging in accruals earnings management, they shift to value-destroying and costly real activities to maintain reputation and firm performance. To the extent that we control for the potential effects of firms’ reputation and financial performance, our findings suggest that ethical concerns are likely to drive female members on the board to produce high-quality financial reports.

The paper's purpose is to provide a solution to a problem on dissolution and disappearance of copper electrodes in solder bath in lead free soldering on printed circuit board (PCB).

The influence of the copper concentration, temperature, and flowing velocity of molten solder on the copper dissolution have been estimated, and it has been found that the dissolution rate of copper electrodes in Sn‐3.0Ag‐xCu solder alloys is defined by temperature and copper concentration in solder.

It was found that increasing the copper concentration to 1.5 mass% in Sn‐3.0Ag‐xCu solder could lower the rate of copper dissolution to the equivalent level as that of the conventional Sn‐Pb eutectic alloy at the temperature of 560 K.

In this paper, a dissolution phenomenon has been studied on Sn‐Ag‐Cu system alloys. It is interesting about the effect of other elements for controlling the dissolution.

The method to control the copper electrode dissolution in wave soldering is clarified. The copper dissolution rate for Sn‐3.0Ag‐1.5Cu solder can be lowered to the equivalent level as that of conventional Sn‐Pb eutectic solder, even at 560 K.

In this paper, a dissolution phenomenon has been evaluated by flowing molten solder which is close to one in a practical soldering. It is the most different point from earlier study.

Understanding crack growth in solder joints is important for predicting the fatigue life of solder interconnects. In this paper, crack propagation in solder joints made of two solder alloys, 62Sn/36Pb/2Ag (by weight), a commonly used solder paste for SMT reflow applications, and 96.5Sn/3.5Ag (by weight), a lead‐free solder alloy, was examined during thermal cycling. Based on these observations, the rate of crack propagation was estimated. Microstructural changes in the solder during thermal cycling were also studied.

This chapter introduces the subject matter of this book and clearly depicts the dichotomous nature of plastic: it is both problematic because of the pollution caused and beneficial because of the benefits it provides. This is set within the context of sustainability, being probably the key concern of the present. It highlights the volume on plastic in existent and the possible consequences from a lack of biodegradability. In doing so, it sets the context for the contents of the book.

This study aims to examine the association between institutional investors’ ownership (IOW), politically connected firms (POCF) and audit report lag (AUDRL).

This study employs a feasible generalised least squares (FGLS) model for panel data to examine the association between IOW, POCF and AUDRL for Malaysian publicly listed companies.

The findings reveal a statistically significant negative relationship between IOW and AUDRL, with this negative relationship being more pronounced amongst POCF. Additionally, the results demonstrate that the relationship between IOW and AUDRL varies depending on the domicile of IIs (local vs. foreign). Specifically, local institutional investors exhibit a negative and statistically significant relationship with AUDRL, whilst foreign institutional investors show a positive and statistically significant relationship with AUDRL.

The results of this study provide a new understanding of auditor responses to institutional investor monitoring and political connections (PCs) in an emerging economy.

The purpose of this paper was to develop a physics-based mathematical model to estimate the amount of substrate metal lost during the wet soldering process.

A mathematically rigorous model depicting the actual physics of the substrate/solder interaction and dissolution has been proposed to simulate the dissolution of the substrate metal in the liquid lead-free solder. The basic mass diffusion equation with the implementation of interface reaction kinetics was solved numerically using the finite volume approach. The moving interface was tracked by utilizing the coordinate transformation technique.

It was observed that the process of metal dissolution in the liquid solder was governed by two important parameters, viz., interface kinetics and long-range diffusion in the liquid solder. Non-equilibrium behavior was observed in the early stage of the process. The early stage of the dissolution process was seen as governed by interface kinetics, while diffusion became the rate-controlling mechanism at the later phase of soldering.

Substrate dissolution can be accurately estimated for a particular substrate–solder combination and for the given process conditions. This early estimation will help in ensuring the reliability and health of the solder joint.

A model based on actual physics is proposed, and interface reaction kinetics has been introduced to capture the actual behavior of the process. The model will serve as the basis for two- and three-dimensional analysis, including the formation of an intermetallic compound in the solder joint.

As a literature review article, the purpose of this paper is to highlight the intricate interaction and correlation between the interconnection microstructure and the failure mechanism. It is therefore critical to summarize all the challenges in understanding solder solidification of interconnections.

Literature review.

Solidification of solder interconnections is therefore critical because it is the process during which the solder interconnection is formed. The as‐solidified microstructure serves as the starting point for all failure modes. Because of the miniaturization of electronics, the interconnection size decreases continuously, already to such a range that solder solidification takes place remarkably differently from the bulk ingot, on which solidification studies have been focused for decades. There are many challenges in understanding the solidification of tiny solder interconnections, including the complex metallurgical system, dynamic solder composition, supercooling and actual solidification temperature, localized temperature field, diverse interfacial IMC formation, and so on, warranting further research investment on solder solidification.

This paper provides a critical overview of the concerns in solidification study for lead‐free solder interconnection. It is probably an article initiating more attention towards solidification topics.