Binary Solder Alloy Research Articles

Electrochemical behaviour of lead-free Sn-In-Al solders alloys in 3.5 wt.% NaCl solution

The corrosion properties of lead-free solder alloy can not be ignored in the field of the electronic industry. However, there is no literature on the effect of aluminium on Sn-In binary solder alloys. This study looked at the corrosion of a lead-free solder alloy in a 3.5 wt.% NaCl simulated seawater environment. Three isopleths were created with varying aluminium content in the Sn-In-Al system while maintaining Sn and In radio constant (1:1). The vacuum sealing process was used to create the samples. The corrosion resistance of this lead-free solder ware was investigated at room temperature in a 3.5 wt.% NaCl solution. Corrosion resistance improves with Al content, according to the potentiodynamic polarization test. By lowering the current density (Icorr), the inclusion of aluminium refines the microstructure. It enhances the corrosion resistance of Sn-In-Al solder alloys, resulting in high resistance of the passive layer produced by lowering the current density (Icorr). Scanning electron microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDS) was used to analyze of surface morphology of the non-corroded and corroded Sn-In-Al solder alloys. Intermetallic compound (IMC) of non-corroded and corrosion products on the surface corroded solder alloys were studied using X-ray diffraction (XRD). According to XRD analysis, the composition of corrosion products altered as the aluminium content changed, forming phases such as Sn3O(OH)2Cl2, oxides, and chlorides of Sn.

Influence of bismuth (Bi) addition on the structure and properties of annealed Sn-9Zn eutectic binary solder alloy

ABSTRACT The Sn-9Zn eutectic alloy has been considered as a potential replacement for toxic lead-based solders for its lower melting point (198 °C) and improved mechanical properties compared to traditional lead-based solder alloys. This paper investigates the influence of bismuth (Bi) addition as a surface-active element on the structural, thermal, mechanical, and electrical properties of eutectic Sn–9Zn alloy. Different amounts of Bi were added (x = 0.5, 1, 2, 3, wt %) to study the characteristics of Sn-9Zn-xBi ternary alloys followed by annealing at 150 °C for 60 minutes. Microstructures and phase constituents of developed alloys were examined and compared using optical microscopy and XRD respectively. The melting point and coefficient of linear thermal expansion were determined by differential thermal analysis and thermo-mechanical analysis. Tensile Properties (ultimate tensile strength, elongation, %), microhardness (HV), and electrical conductivity (% IACS) were measured. The results indicated that the addition of Bi decreased the melting point by about 10 °C, the heat of fusion, coefficient of thermal expansion, electrical conductivity than Sn-9Zn eutectic alloy. Bi addition enhanced the ultimate tensile strength and hardness by about 65% by 50% respectively. SnBi inter-metallic compound (IMC) precipitates were formed and extracted from the β-Sn matrix with a non-uniform microstructure.

Microstructural Aspects of Fatigue Parameters of Lead-Free Sn-Zn Solders with Various Zn Content

Abstract The study includes the results of research conducted on selected lead-free binary solder alloys designed for operation at high temperatures. The results of qualitative and quantitative metallographic examinations of SnZn alloys with various Zn content are presented. The quantitative microstructure analysis was carried out using a combinatorial method based on phase quanta theory, per which any microstructure can be treated as an array of elements disposed in the matrix material. Fatigue tests were also performed using the capabilities of a modified version of the LCF method hereinafter referred to in short as MLCF, which is particularly useful in the estimation of mechanical parameters when there are difficulties in obtaining many samples normally required for the LCF test. The fatigue life of alloys was analyzed in the context of their microstructure. It has been shown that the mechanical properties are improved with the Zn content increasing in the alloy. However, the best properties were obtained in the alloy with a chemical composition close to the eutectic system, when the Zn-rich precipitates showed the most preferred morphological characteristics. At higher content of Zn, a strong structural notch was formed in the alloy because of the formation in the microstructure of a large amount of the needle-like Zn-rich precipitates deteriorating the mechanical characteristics. Thus, the results obtained during previous own studies, which in the field of mechanical testing were based on static tensile test only, have been confirmed. It is interesting to note that during fatigue testing, both significant strengthening and weakening of the examined material can be expected. The results of fatigue tests performed on SnZn alloys have proved that in this case the material was softened.

Simulating surface tension of Sn-based lead free solder using an artificial neural network

PurposeBecause of the complexity of relationship between surface tension and its decisive factors, such as temperature, concentration, electronic density, molar atomic volume and electro-negativity, a reasonable predicting model of surface tension of Sn-based solder alloys has not been developed yet. The paper aims to address the surface tension issue that has to be considered if the new lead free solder will be applied for electronics.Design/methodology/approachUsing an artificial neural network (ANN) model with back-propagation (BP) algorithm, the surface tension for Sn-based binary solder alloys was simulated, and the comparison between the simulating results and data from experiments and literatures was analyzed as well. In addition, the relationship between surface tension and its decisive factors would be discussed based on the ANN and orthogonal design methods.FindingsIt is shown that the predicting model of surface tension of Sn-based solder alloys is constructed according to the BP–ANN theory, and the predicted value from the BP–ANN is in excellent agreement with the experimental results. The surface tension of Sn-based solders is determined by five factors, i.e. temperature, concentration, electronic density, molar atomic volume and electro-negativity. Among of the factors, molar atomic volume is major factor, and the order of degree of influence on surface tension is molar atomic volume > electro-negativity > electronic > density > concentration > temperature. Moreover, a simply reasonable equation is proposed to estimate the surface tension for Sn-based solders.Originality/valueThe five decisive factors of surface tension for Sn-based binary solder alloys have been analyzed theoretically, and a reasonable model of surface tension for Sn-based binary solder alloys is proposed as well. It is shown that ANN theory will be applied well to simulate the surface tension of Sn-based lead free solder.

Numerical simulation of coarsening in binary solder alloys

Coarsening in solder alloys is a widely accepted indicator for possible failure of joints in electronic devices. Based on the well-established Cahn–Larché model with logarithmic chemical energy density (Dreyer and Müller, 2001) [20], we present a computational framework for the efficient and reliable simulation of coarsening in binary alloys. Main features are adaptive mesh refinement based on hierarchical error estimates, fast and reliable algebraic solution by multigrid and Schur–Newton multigrid methods, and the quantification of the coarsening speed by the temporal growth of mean phase radii. We provide a detailed description and a numerical assessment of the algorithm and its different components, together with a practical application to a eutectic AgCu brazing alloy.

Reduced Electrical Resistivity of Ternary Solder Alloy of Tin–Copper–Sulfur: An Anti-Oxidative Role of Sulfur in Binary Solder Alloy of Tin–Copper

Reduced Electrical Resistivity of Ternary Solder Alloy of Tin–Copper–Sulfur: An Anti-Oxidative Role of Sulfur in Binary Solder Alloy of Tin–Copper

Theoretical and experimental investigations of microstructural changes in lead-free solders

Experiments show that the microstructure of solders changes over time. From a materials science point-of-view this phenomenon considerably affects the reliability and lifetime of microelectronic products. It is, therefore, important to quantitatively predict the amount of microstructural change. In the present paper we concentrate on a theoretical and experimental description of spinodal decomposition as well as subsequent phase growth in binary solder alloys. We present experimental results and a theoretical description, which is based on an extended diffusion equation of the phase field type, and which can be interpreted as an generalization of the Cahn–Hilliard equation. Moreover, it takes diffusion of the Fickian type, surface tensions along the phase boundaries as well as local thermo-mechanical stresses into account. In particular we turn our attention to the determination of the required material parameters, which can all be obtained consistently from atomistic models or adopted from literature. As an example the FCC-structured lead-free solder alloy Ag–Cu is considered and numerical results are presented.

Modeling Phase Separation and Coarsening in Ag‐Cu

AbstractThe ongoing miniaturization and environmental trends in microelectronics recently turn the attention to new materials the properties of which still have to be studied. Of fundamental importance for material properties is the temporal development of the microstructure which can experimentally be observed in several solder alloys. Starting with a detailed overview on coarsening phenomena and intermetallic growth as observed in lead‐free solders we concentrate on the description of nucleation and spinodal decomposition in these alloys. An extended diffusion equation of the phase field type is presented in which all required material parameters are determined either from the literature / databases or from calculations based on the Embedded‐Atom Method (EAM). We will restrict to the one dimensional case of diffusion and consider as an example the FCC‐structured lead‐free binary solder alloy Ag‐Cu. Furthermore a numerical study is performed in order to arrive at a quantitative description of temporal micromorphological development. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)