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The purpose of this paper is a comparable evaluation of the influence of a particular element (Bi and Sb) added to Sn‐Ag‐Cu and Sn‐Zn alloys on their surface and interfacial tensions, as well as the wetting properties on the Cu substrate expressed by the wetting angle.

The authors applied the L₈ orthogonal Taguchi array to carry out the experiments and discussed the results using analysis of variance (ANOVA).

It was expected, on the base of previous studies, the decrease of the surface and interfacial tensions and thus improving wettability after the Bi and Sb addition to Sn‐Ag‐Cu and Sn‐Zn alloys. Unfortunately, the obtained results on the quinary Sn‐Ag‐Cu‐Bi‐Sb alloys and the quaternary Sn‐Zn‐Bi‐Sb alloys do not confirm these trends. The performed analyses suggest that the compositions of the quinary Sn‐Ag‐Cu‐Bi‐Sb alloys, as well as the quaternary Sn‐Zn‐Bi‐Sb alloys, do not have optimal compositions for practical application. The Cu, Bi and Sb elements in the case of the Sn‐Ag‐Cu‐Bi‐Sb alloys and the Zn, Bi and Sb elements in the case of the Sn‐Zn‐Bi‐Sb alloys show mutual interaction and, in consequence, there is no correlation between the tendency of the surface and interfacial tensions changes and the wettings of the Cu substrate.

It is suggested that further studies are necessary for the purpose of the practical application, but they should be limited mainly to the Sn‐Ag‐Cu‐Bi and the Sn‐Zn‐Bi alloys with the optimal compositions.

The performed analysis suggests that none of the investigated compositions of the quinary Sn‐Ag‐Cu‐Bi‐Sb alloys, as well as the quaternary Sn‐Zn‐Bi‐Sb alloys, have the optimal compositions for practical application.

The quickest way to determine which element of the alloy composition influences the surface tension and the wetting properties, and how, is to apply orthogonal analysis. After choosing the orthogonal array, the experiments were performed and analysis of variance (ANOVA) was used to perform the quantifiable analysis of the measured and calculated results of surface and interfacial tensions, as well as the wetting properties on the Cu substrate.

The purpose of this paper is to investigate the effects of minor addition of the rare earth (RE) element cerium, Ce, on the microstructures and creep properties of Sn-Ag-Cu solder alloys.

The pure Sn, Sn-Cu alloy, Sn-Ag alloy and Cu-Ce alloy were used as raw materials. Sn-Ag-Cu alloys with different contents of RE Ce were chosen to compare with Sn-Ag-Cu. The raw materials of Sn, Sn-Cu alloy, Sn-Ag alloy, Cu-Ce alloy were melted in a ceramic crucible, and were melted at 550°C ± 1°C for 40 minutes. To homogenize the solder alloy, mechanical stirring was performed every ten minutes using a glass rod. During the melting, KC1 + LiCI (1.3:1), were used over the surface of liquid solder to prevent oxidation. The melted solder was chill cast into a rod.

It is found that the microstructure exhibits smaller grains and the Ag₃Sn/Cu₆Sn₅ intermetallic compound (IMC) phases are modified in matrix with the addition of Ce. In particular, the addition of 0.03 wt.% Ce to the Sn-Ag-Cu solder can refine the microstructures and decrease the thickness of the IMC layers of Sn-Ag-Cu solder alloys. Meanwhile, thermodynamic analysis showed that these phenomena could be attributed to the reduction of the driving force for Cu-Sn IMC formation due to the addition of Ce. Results calculated using the thermodynamic method are close to the above experimental data. Thus, the optimum content of Ce in Sn-Ag-Cu solder alloys should be about 0.030 percent. Additionally, the effect of Ce on the creep rupture life of Sn-Ag-Cu soldered joints was studied. It was found that the creep rupture life may be increased up to 7.5 times more than that of the original Sn-Ag-Cu alloy, when Ce accounts for 0.030 percent.

This paper usefully investigates the effects of the RE cerium (Ce), on the microstructures and creep properties of Sn-Ag-Cu solder alloys, optimizing the quantity of Ce in the Sn-Ag-Cu solder alloy through a thermodynamic method and by creep-rupture life testing.

The purpose of this paper is to explore the formation and growth mechanism of bulk Cu₆Sn₅ intermetallic compounds, selecting Sn‐Ag‐Cu‐Ce solders as specimens.

In order to further enhance the properties of SnAgCu solder, trace amount of rare earth Ce was selected as alloying addition into the alloy; in previous investigations, the enhancements include better wettability, physical properties, creep strength and tensile strength. In this paper, the microstructure of Sn‐Ag‐Cu‐Ce soldered joints and its interfacial intermetallic compounds were investigated. Moreover, different morphologies of Cu₆Sn₅ IMCs were enumerated and described, and Ostwald ripening theory was employed to interpret the formation mechanism of bulk Cu₆Sn₅ IMCs.

In addition, based on finite element simulation, it is found that the von Mises stress concentrate around the bulk Cu₆Sn₅ IMCs inside the Sn‐Ag‐Cu‐Ce soldered joints after three thermal cycling loading (−55‐125°C). From the stress distribution, the failure site was predicted to fracture near the bulk Cu₆Sn₅ IMCs interface. This coincides with the experimental findings significantly.

The results presented in this paper may provide a theory guide for developing novel lead‐free solders as well as reliability investigation of lead‐free soldered joints.

This paper presents the analysis of information collected from numerous patent searches on lead‐free alloys. The significance of claim structure and content is discussed in view of the growing number of lead‐free patents. Patent analysis software was developed to effectively compare over 350 lead‐free alloy patents. A case study was conducted to assess Sn‐Ag‐Cu and special purpose lead‐free candidate alloy intellectual property. The results show that there are a number of patents and patent applications that may affect the use of “popular” Sn‐Ag‐Cu formulations.

Viscosity is an important basic physical property of liquid solders. However, because of the very complex nonlinear relationship between the viscosity of the liquid ternary Sn-based lead-free solder and its determinants, a theoretical model for the viscosity of the liquid Sn-based solder alloy has not been proposed. This paper aims to address the viscosity issues that must be considered when developing new lead-free solders.

A BP neural network model was established to predict the viscosity of the liquid alloy and the predicted values were compared with the corresponding experimental data in the literature data. At the same time, the BP neural network model is compared with the existing theoretical model. In addition, a mathematical model for estimating the melt viscosity of ternary tin-based lead-free solders was constructed using a polynomial fitting method.

A reasonable BP neural network model was established to predict the melt viscosity of ternary tin-based lead-free solders. The viscosity prediction of the BP neural network agrees well with the experimental results. Compared to the Seetharaman and the Moelwyn–Hughes models, the BP neural network model can predict the viscosity of liquid alloys without the need to calculate the relevant thermodynamic parameters. In addition, a simple equation for estimating the melt viscosity of a ternary tin-based lead-free solder has been proposed.

The study identified nine factors that affect the melt viscosity of ternary tin-based lead-free solders and used these factors as input parameters for BP neural network models. The BP neural network model is more convenient because it does not require the calculation of relevant thermodynamic parameters. In addition, a mathematical model for estimating the viscosity of a ternary Sn-based lead-free solder alloy has been proposed. The overall research shows that the BP neural network model can be well applied to the theoretical study of the viscosity of liquid solder alloys. Using a constructed BP neural network to predict the viscosity of a lead-free solder melt helps to study the liquid physical properties of lead-free solders that are widely used in electronic information.

The aim of the present study was to gather and review all the important properties of the Sn–Ag–Cu (SAC) solder alloy. The SAC solder alloy has been proposed as the alternative solder to overcome the environmental concern of lead (Pb) solder. Many researchers have studied the SAC solder alloy and found that the properties such as melting temperature, wettability, microstructure and interfacial, together with mechanical properties, are better for the SAC solder than the tin – lead (SnPb) solders. Meanwhile, addition of various elements and nanoparticles seems to produce enhancement on the prior bulk solder alloy as well. These benefits suggest that the SAC solder alloy could be the next alternative solder for the electronic packaging industry. Although many studies have been conducted for this particular solder alloy, a compilation of all these properties regarding the SAC solder alloy is still not available for a review to say.

Soldering is identified as the metallurgical joining method in electronic packaging industry which uses filler metal, or well known as the solder, with a melting point < 425°C (Yoon et al., 2009; Ervina and Marini, 2012). The SAC solder has been developed by many methods and even alloying it with some elements to enhance its properties (Law et al., 2006; Tsao et al., 2010; Wang et al., 2002; Gain et al., 2011). The development toward miniaturization, meanwhile, requires much smaller solder joints and fine-pitch interconnections for microelectronic packaging in electronic devices which demand better solder joint reliability of SAC solder Although many studies have been done based on the SAC solder, a review based on the important characteristics and the fundamental factor involving the SAC solder is still not sufficient. Henceforth, this paper resolves in stating all its important properties based on the SAC solder including its alloying of elements and nanoparticles addition for further understanding.

Various Pb-free solders have been studied and investigated to overcome the health and environmental concern of the SnPb solder. In terms of the melting temperature, the SAC solder seems to possess a high melting temperature of 227°C than the Pb solder SnPb. Here, the melting temperature of this solder falls within the range of the average reflow temperature in the electronic packaging industry and would not really affect the process of connection. A good amendment here is, this melting temperature can actually be reduced by adding some element such as titanium and zinc. The addition of these elements tends to decrease the melting temperature of the SAC solder alloy to about 3°C. Adding nanoparticles, meanwhile, tend to increase the melting temperature slightly; nonetheless, this increment was not seemed to damage other devices due to the very slight increment and no drastic changes in the solidification temperature. Henceforth, this paper reviews all the properties of the Pb-free SAC solder system by how it is developed from overcoming environmental problem to achieving and sustaining as the viable candidate in the electronic packaging industry. The Pb-free SAC solder can be the alternative to all drawbacks that the traditional SnPb solder possesses and also an upcoming new invention for the future needs. Although many studies have been done in this particular solder, not much information is gathered in a review to give better understanding for SAC solder alloy. In that, this paper reviews and gathers the importance of this SAC solder in the electronic packaging industry and provides information for better knowledge.

This paper resolves in stating of all its important properties based on the SAC solder including its alloying of elements and nanoparticles addition for further understanding.

The solder joint reliability of ceramic chip resistors assembled to laminate substrates has been a long time concern for systems exposed to harsh environments. In this work, the thermal cycling reliability of several 2512 chip resistor lead‐free solder joint configurations has been investigated. In an initial study, a comparison has been made between the solder joint reliabilities obtained with components fabricated with both tin‐lead and pure tin solder terminations. In the main portion of the reliability testing, two temperature ranges (−40‐125°C and −40‐150°C) and five different solder alloys have been examined. The investigated solders include the normal eutectic Sn‐Ag‐Cu (SAC) alloy recommended by earlier studies (95.5Sn‐3.8Ag‐0.7Cu), and three variations of the lead‐free ternary SAC alloy that include small quaternary additions of bismuth and indium to enhance fatigue resistance.

The purpose of this paper is to enhance the understanding on the electrodeposition of various lead (Pb)‐free solder alloys, so that new studies can be carried out to solve processing issues.

The paper reviews the available reports on the electrodeposition of tin (Sn)‐based solder systems and identifies the challenges in this area.

Compositional control remains a major challenge in this area, where the achievement of desired composition for binary and ternary alloys is subjected to uncertainties. The use of chelating agents in the bath and optimization of parameters can assist the achievement of near‐desired alloy composition. Acidic plating baths are preferred due to their compatibility with photoresists but oxidation of stannous ions causes poor bath stability. Antioxidants, reducing agents and low oxygen overpotential anodes can suppress the oxidation rate and increase the lifespan of plating baths. Apart from chelating agents and antioxidants, various categories of additives can be added to improve quality of deposits. Surfactants, grain refiners and brighteners are routinely used to obtain smooth, fine‐grained and bright deposits with good thermo‐mechanical properties.

The paper provides information on the key issues in electrodeposition of Pb‐free solder alloys. Possible measures to alleviate the issues are suggested so that the electrodeposition technique can be established for mass production of a wider range of solder alloys.

The purpose of this paper is to carry out a study of the evolution of the microstructure and the microhardness of Sn-Cu-Ag alloys from as-cast condition and under artificial isothermal aging at different temperatures (100ºC and 180ºC) for a treatment time up to 500 h. A comparison with Sn-37% Pb eutectic solder samples was also made.

Sn-3.5%Ag, Sn-0.7%Cu and Sn-3.5%Ag-0.9%Cu were poured in two different cooling rate conditions and then aged at 100ºC (373ºK) and 180 °C (453ºK) during 500 h. Microstructural changes were observed by optical microscopy, scanning electron micrograph and energy dispersive X-ray microanalysis. Differential scanning calorimetry technique (DSC) was also used to confirm the obtained results.

A decrease up to 20% in microhardness respect to the value of the as-cast alloy was observed for both aging temperatures. These changes can be explained considering the coarsening and recrystallization of Sn dendrites present in the microstructures of all the systems studied.

There is no evidence of dissolution or precipitation of new phases in the range of studied temperatures that could be detected by DSC calorimetry technique. The acting mechanisms must be the result of coarsening of Sn dendrites and the residual stresses relaxation during the first stages of the isothermal aging.

The purpose of this paper is to study the effect of copper concentration in near‐eutectic liquid SAC solders on their thermophysical properties: viscosity, surface tension, density; as well as wetting behavior on copper substrates at 523 K.

Viscosity, surface tension, and density were studied over a broad range of temperatures with the recently developed Roach‐Henein method. The obtained results were compared with the data from modified capillary, maximum bubble pressure, wetting balance and dilatometric measurements. Wetting angles measured with wetting balance method were compared with the results of sessile drop measurements.

The results obtained indicate that increasing concentration of copper in the alloy results in higher density, surface tension and viscosity, but differences resulting from copper concentration on wettability are relatively small. At 523 K, the density is: 7.097, 7.186, 7.232 g cm⁻³, the surface tension is: 538.1, 553.5, 556.7 m Nm⁻¹, the viscosity is: 2.173, 2.227, 2.467 mPas, respectively, for alloys containing 0.41, 1.01 and 1.61 wt% of Cu. Wetting angles on copper substrates are similar within a margin of error for all compositions. The results of present study are compared with the available literature data and a relatively good agreement is observed.

This paper provides the data of thermophysical properties of widely‐used SAC solders including viscosity, of which there is little data in the literature. It is confirmed that the increased copper concentration increases viscosity, yet this effect is small and does not correlate with the wetting behavior.