Sn-Ag Alloys Research Articles

Geometrical features and chemical adsorptions of (Ag3Sn)n clusters

The Ag-Sn alloys are famous ancient intermetallics, with the Ag3Sn being a crucial component of the phase diagram. Recently, Ag3Sn nanoparticles showcase efficient catalytic CO oxidation capabilities. Here, structural features and stability of (Ag3Sn)n (n = 1–6) clusters are first analyzed in detail. The results reveal that structures of them evolve from cages to close-packed icosahedra, where Ag are distributed on cores and gradually aggregated, whereas Sn occupy edge positions and become dispersed. Moreover, the icosahedral (Ag3Sn)3 has a higher stability than that of its neighbors and can maintain the structural integrity at 700 K. The molecular orbitals reveal that the (Ag3Sn)3 has an electronic open-shell configuration of 1S21P61D102S21F1, which is confirmed by the density of states. Electrostatic potential surfaces show that (Ag3Sn)n have significant electron-deficient σ-hole regions at Ag sites, which can make CO stretching frequencies and bond lengths have red-shifts. Adsorption energies between (Ag3Sn)n and CO display odd–even oscillations, ranging from (0.43–0.68) eV, and the direction of charge flows is from CO → clusters. Our work provides inferences to structure evolutions and adsorptions of the Ag3Sn alloy at the atomic level.

Reactive diffusion at the interface between Cu and Sn–Ag alloys

This study investigates the microstructural evolution and growth behavior of intermetallic compound (IMC) layers in the Cu/(Sn-yAg, y = 0.29–2.00 wt%) system during isothermal aging within the temperature range of 433–473 K. Through systematic variations in Ag content, aging temperature, and time, the fundamental mechanisms governing IMC formation and growth in Cu/(Sn–Ag) solder joints are elucidated. The results demonstrate that IMC growth kinetics follow a power-law relationship, with IMC layer thickness increasing systematically with annealing time. The addition of Ag significantly influences IMC nucleation and growth, with higher Ag content correlating with faster growth rates. Furthermore, the temperature dependence of IMC growth rates is investigated, revealing higher temperatures leading to increased growth rates, indicative of boundary diffusion-controlled growth. By calculating activation enthalpies, values of 36.4 kJ/mol for Sn-2.00Ag and 30.2 kJ/mol for Sn-0.50Ag were obtained, providing quantitative insights into the faster growth rate of intermetallic compound thickness in the Cu/(Sn-2.00Ag) diffusion couple within the experimental temperature range. These findings offer valuable insights into factors affecting the reliability and performance of solder joints in electronic packaging applications.

EBSD characterization of graphene nano sheet reinforced Sn–Ag solder alloy composites

This research explores the effects of incorporating Graphene Nano Sheets (GNS) on the microstructural characteristics and mechanical behavior of Sn–Ag solder alloys. The research was driven by the need for environmentally friendly, lead-free solder alloys with enhanced mechanical and thermal properties. The methodology involved incorporating graphene into the Sn–Ag alloy through stir casting, followed by a series of surface preparation techniques. The composite samples were then examined using EBSD to analyze crystallographic orientations and SEM/EDS for surface morphology and elemental composition. XRD provided insights into phase transformations and structural changes. Key findings reveal that the addition of GNS significantly refines the grain structure of the Sn–Ag alloy, leading to a bimodal grain size distribution. This refinement is attributed to the role of GNS as a nucleation site during solidification. Moreover, the study demonstrates a pronounced alteration in the texture of the material, with an increase in low-angle grain boundaries post-GNS addition. This texture change is indicative of enhanced mechanical properties. The results also show a shift in the orientation distribution function (ODF), suggesting a stronger crystallographic orientation due to GNS. These findings suggest that GNS incorporation could lead to improved mechanical and thermal properties in Sn–Ag solder, making them suitable for high-performance electronic applications. The study concludes that GNS not only serves as an effective reinforcement in Sn–Ag solder alloys but also significantly alters their microstructural and textural characteristics, contributing to the alloy's potential application in environmentally conscious electronic manufacturing.

Clean and efficient recovery of silver from silver-tin alloys by vacuum evaporation-multistage condensation

The recycling of waste lead-free solder and the tin refining process generates large quantities of silver-tin alloys, which have a very high potential for recovery but for which there is no clean and efficient means of recovery. This study examined the saturation vapour pressure, separation coefficients, prediction of the T-x(y) phase diagram of the silver-tin alloys, and condensation rate to explore the feasibility of using vacuum evaporation-multistage condensation as a method for separating silver-tin alloys. The results suggest that in the process of vacuum evaporation, both silver and tin will evaporate, and the evaporability of silver is slightly greater than that of tin. In the process of multistage condensation, tin condenses before silver. Furthermore, the vacuum evaporation-multistage condensation method was experimentally validated. The results suggest that the TF consists of crude silver, with a silver content of 98.17 wt% and a silver distribution rate of 43.60%. The MP consists of a silver-tin alloy with 7.87 wt% silver content and exhibits a silver distribution rate of 53.06%. The RE is crude tin containing 0.27 wt% of silver content and a silver distribution rate of 5.14%. The separation rate of Ag is 96.64%. This study provides a clean and efficient method that is instructive for the recovery of Ag-Sn alloys.

Effect of non-standard SnAg surface finishes on properties of solder joints

In this study, the effects of nonstandard near-eutectic SnAg surfaces on the wettability, intermetallic compound growth and mechanical properties of solder joints were investigated. Four types of surface finishes based on near-eutectic SnAg alloys with different compositions and numbers of layers were analyzed. Design/methodology/approachThe effect of surface-finishes SnAg5NiP and SnAg7NiP, which were prepared with and without a Ni-P diffusion barrier, was tested. The Ni-P layer was produced either chemically or electrochemically. The effect of the SnAg surface finish on wettability, formation, and growth of intermetallic compound in the solder joint was analyzed. We further explored the impact of different PCB finishes on the quality of soldered joints. This investigation involved a comparative analysis of the behavior of SnAg finishes in comparison to pure copper, as well as the commonly employed HASL, ENIG, and ImSn finishes. FindingsIt was found that SnAg surface finishes with a Ni-P diffusion barrier are wetted by molten solder faster than surface finishes without a diffusion barrier. The mechanical properties of the joints on both surfaces are comparable to those on ENIG. SnAg that include a chemically created Ni-P diffusion layer is characterized by the formation of more thermally stable ternary intermetallic compounds based on (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4. On the contrary, the electrochemically formed Ni layer supports the increase in the rate of intermetallic compound formation, which affects the properties of the soldered joints. OriginalityNonstandard near-eutectic SnAg finishes, which contains a Ni-P diffusion layer can be used as promising replacement of ENIG or other standard finishes.

On the role of complexing agents in co-electrodeposition of SnAg alloy with uniform composition

On the role of complexing agents in co-electrodeposition of SnAg alloy with uniform composition

Nanosilver-Reinforced AgSn Alloys for Dental Applications: Mechanical Behavior and Hardness

Aim: AgSn alloys of different compositions were prepared by direct mixing with silver nanoparticles, synthesized, in turn, by an environmentally-friendly method. Method: The procedure was carried out by following the standard technique for preparing dental materials and devices. A detailed mechanical characterization, including the maximum elongation at break, the ultimate tensile strength and the hardness of the resulting nanocomposites, was obtained and numerically fitted by statistically-significant equations Result: The results show improved mechanical performance, as compared to standard materials used in dentistry, in particular amalgams. Conclusion: The procedure described allows to produce low cost materials with tailored mechanical properties.

Influence of TiO2 nanoparticles content as reinforce material to enhance the mechanical and corrosion resistance properties of Sn and Sn–Ag alloy for dental applications

This study evaluated the influence of the TiO2 nanoparticles (NPs) on the mechanical and chemical performance of Sn and Sn–Ag alloys. The XRD (X-ray diffraction) and HR-TEM (high resolution-transmission electron microscopy) methods were used to characterize the NPs synthesized by the sol-gel microwave process. The chemical composition of the alloys was Sn, Sn+3TiO2 NPs, Sn–5Ag+1.5TiO2 NPs, Sn–10Ag, and Sn–10Ag+3TiO2 NPs, obtained from an experimental factorial design (EFD). A statistical model was used to determine the mechanical and chemical properties, showing the Vickers hardness response surface, tensile strength, wear, and corrosion resistance. The wear and corrosion tests for the various alloy compositions were performed using human artificial saliva solution. The results indicated that the Sn–10Ag+3TiO2 NPs exhibited the highest mechanical performance due to their increased hardness (380 HV), tensile strength (370 N), and wear resistance (0.34 × 10−3 mm3 Nm−1); in all the cases, the inclusion of TiO2 NPs enhanced the corrosion resistance of the alloys. According to the American Dental Association (ADA), Sn–10Ag+3TiO2 NPs alloy could be classified as a possible type IV restorative material.

Ag3Sn Morphology Transitions During Eutectic Growth in Sn–Ag Alloys

Eutectic Ag3Sn can grow with a variety of morphologies depending on the solidification conditions and plays an important role in the performance of Pb-free solders. Here, we study morphology transitions in the β-Sn + Ag3Sn eutectic at increasing growth velocity using a combination of real-time X-ray imaging and analytical electron microscopy. Orthorhombic Ag3Sn grew as faceted plates or rods with [010] growth direction and (001) as the largest facet in all three eutectic growth morphologies: Irregular plate, broken-lamellar, and rod. Reproducible β-Sn + Ag3Sn orientation relationships formed for the latter two morphologies. The mechanisms of spacing adjustment and the reversible transition from plate to rod growth are studied for transient solidification after velocity changes. The transition from fully eutectic growth to β-Sn dendrites plus eutectic is reasonably reproduced using a competitive growth criterion. At the highest velocities, Ag3Sn rods developed perturbations whose break down into particles is discussed in terms of unsteady growth and pinch-off mechanisms.

Preparation and characterization of nano-solder paste with high nanoparticle loading and their thermal and printing properties

A lead-free nano-solder paste has been successfully prepared by dispersing tin-silver (Sn–Ag) nanoparticles within a flux using planetary mixing, with nanoparticle loading up to 50 wt%. An aqueous chemical reduction method was used to synthesize the Sn–Ag alloy nanoparticles. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were used to image the morphology of the nanoparticles and the size was estimated to be an average of 19.6 ± 3.6 nm. Composition of the Sn–Ag nanoparticles was measured using energy dispersive x-ray spectroscopy (EDS) and their crystal structures were analyzed via x-ray diffraction (XRD). Differential scanning calorimetry (DSC) measurements of the Sn–Ag nanoparticles, containing approximately 4 wt% Ag, showed an onset of melting at 219.8 °C and an endothermic peak at 222.5 °C. These measured values for the nanoparticles are slightly lower as compared to the corresponding bulk material. The synthesized Sn–Ag nanoparticles were dispersed within a flux using planetary mixing, forming a uniform nanosolder paste, and as high as 50 wt% nanoparticle loading was achieved. Multiple heating cycles of the Sn–Ag nanosolder paste via DSC showed 1.6 °C increase in the onset of melting between the first and fourth cycles. Thermogravimetric analysis (TGA) of the 50 wt% nanosolder paste showed a 76% retention of initial weight up to 250 °C and 56% up to 500 °C, indicating residual material remaining on solder materials after heating. The nanosolder paste was screen-printed and reflowed on Cu substrates in an inert environment. The cross-section of the interface was observed via FE-SEM for intermetallic compound (IMC) formation between the reflowed nanosolder paste and substrate, confirming that a metallurgical bonding has been achieved. Both Cu3Sn and Cu6Sn5 were observed in the interfacial layer.

Separating Silver from Tin Silver Alloy Residue: Effect of Agitation Rate

In this paper, research on the effects of agitation rate for desilvering tin silver alloy residue by using pyrometallurgy was carried out. SnAg alloy residue with 92 wt.% tin and 3.56 wt.% silver was used in this study, and 99.999 wt.% zinc was added as metal solvent. Residues were melted to a temperature of 400 °C for enriching tin silver alloy. The obtained tin silver alloy was melted in a temperature range of 450 °C to 500 °C by adding zinc to evaluate zinc dissolution. The obtained tin silver zinc was agitated at different agitation rates for 20 min at a temperature of 480 °C, then cooled down while stirring to an eutectic point of tin zinc alloy (198.9 °C) to remove silver zinc dross. X-ray Fluorescent-1800 (XRF-1800) and Field Emission Scanning Electron Microscopy Energy Dispersive Spectroscopy (FE-SEM-EDS) analyses were performed in this research. Different factors including holding time, zinc dissolution, agitation time and agitation rate were evaluated. The results revealed that an agitation rate of 600 RPM, 25% Zn and 60 min at a temperature of 198.9 °C were efficient. Zinc silver was removed as dross every 20 min to get 92% silver separation efficiency, and the use of supergravity centrifuge is highly recommended to get best separation efficiency.

Functions of 2-butyne-1,4-diol in the process of tin-silver alloy electrodeposition from the acidic sulfate solution

The eutectic (at.%) Sn96,7/Ag3,3 alloy (Tmelt 221 °С) is used for assembling electronic products and soldering jewelry. Control of the Sn-Ag alloy composition during its electrodeposition is a challenging task due to significant difference in electrode potentials of tin and silver and the tendency of Sn(II) to oxidation and hydrolysis. In this work the composition of known acidic sulfate electrolyte for electrochemical deposition of Sn‒Ag alloy was modified by the addition of 2-butyne-1,4-diol (BD). The purpose was to study the effect of BD on simultaneous Sn(II) and Ag(I) electrochemical reduction, the nature of side processes which accompany the deposition of Sn‒Ag coatings, their composition and structure. It is shown that the addition of BD to the electrolyte reduces silver content in Sn−Ag alloy and provides obtaining near-eutectic alloy according to its elemental, phase composition and melting temperature. The presence of SnO and SnO2 oxides and the increased silver content in the near-surface zone of the coatings no more than 3 nm deep are distinctive features of the deposited Sn‒Ag alloy coatings. These features are due to the occurrence of side processes of Ag(I) reduction with tin and the alloy corrosion, which accompany simultaneous Sn(II) and Ag(I) reduction. The BD additive in the electrolyte inhibit Ag(I) electroreduction, slightly accelerates Ag(I) cementation with freshly reduced tin, but retards corrosive dissolution of the alloy and hydrogen evolution.

Influence of hot deformation and composition on microstructure development of magnesium-stannide alloys

The microstructural evolution of different compositions of Mg-Sn alloys (30%Sn-70%Mg, 40%Sn-60%Mg and 50%Sn-50%Mg) is studied at first to understand the changes observed with change in tin content and deformation conditions. The Mg2Sn phase increases with increase in tin content and a significant substructure development is found in 50%Sn-50%Mg alloy. The above observation led to further deformation studies on Mg2Sn based thermoelectric materials with higher tin percentage. The microstructure in terms of Electron backscatter diffraction (EBSD) measurements is studied in detail followed by the determination of thermoelectric properties i.e., Seebeck coefficient and electrical conductivity for both as cast and extruded Mg(2+x)Sn-Ag alloys. The electrical conductivity of the extruded Mg(2+x)Sn-.3wt%Ag {x = 1} alloy was found to be more than its as cast counterpart while the Seebeck coefficient values remained almost the same.

A Facile Method for the Production of Sn-Ag Alloy by High Energy Ball Milling

A Facile Method for the Production of Sn-Ag Alloy by High Energy Ball Milling

Chromium improvements on the mechanical performance of a rapidly solidified eutectic Sn–Ag alloy

The eutectic Sn–Ag alloy considered a good replacement to the conventional solders. This study aims to enhance the mechanical performance of the eutectic Sn–Ag alloy in terms of both elasticity and plasticity through investigating the effects of chromium (Cr) content with x = 1, 3, and 5 wt.% on the mechanical and thermal properties of melt-spun Sn–3.5%Ag alloy. Ternary melt-spun Sn–Ag–Cr alloys investigated using x-ray diffractions (XRD), Scanning electron microscope (SEM), Instron machine, Vickers hardness tester, and Differential scanning calorimetry (DSC). The results revealed that the Cr content modifies the microstructure by refining the microstructure of the matrix of Sn solder; suppressing coarse intermetallic compound (IMC) formation; and changing the morphology of the IMC in Sn solder. The high concentration of multi-oriental Ag3Sn that formed with 3 wt.% of Cr, in addition to the compatibility among β-Sn (Tetragonal), Ag3Sn (004) (orthorhombic), and Cr (200) (bcc), enhance the elasticity of melt-spun Sn93.5–Ag3.5–Cr3 solder alloy by 330% (87.98 GPa) and obstructed the fracture process. The tensile test for that melt-spun alloy (3 wt.% of Cr) showed obvious improvements in ultimate tensile strength (UST) by 19% (23.42 MPa), and in toughness by 15.31% (911.15 J m−3) compared to that of the eutectic melt-spun Sn–Ag alloy. Its hardness (Vickers hardness) value has improved by 22.37% (171.50 GPa) compared with that of the eutectic melt-spun Sn–Ag alloy. Slight improvements in thermal performance for that alloy have appeared through thermal conductivity by 8% (49.971 w m−1 k−1) and thermal diffusivity by 85.4% (2.758 × 10–7 m2 s–1) compared to that of the eutectic melt-spun Sn–Ag alloy. All of the above-mentioned improvements are related to the microstructural changes with 3 wt.% of Cr to the eutectic Sn–Ag alloy. The high elasticity, high plasticity, low ∆T, and relatively low melting temperature (Tm) that have been taking place with 3 wt.% of Cr are suggested to increase the mechanical reliability of this alloy to become more desirable in soldering applications and electronic assembly.

Influence of Pd(P) thickness on the Pd-free solder reaction between eutectic Sn-Ag alloy and Au/Pd(P)/Ni(P)/Cu multilayer

Autocatalytic plating deposition of a Pd(P) film over a Ni(P) metallization pad, such as Au/Pd(P)/Ni(P) (electroless nickel/electroless palladium/immersion gold, ENEPIG), has been widely used in microelectronic industry for the past decade. However, the data regarding its soderability with eutectic Sn-Ag (Sn-3.5Ag) is still lacking in the literature. We investigated the effects of Pd(P) thickness (δPd(P)) on the interfacial reaction between Sn-3.5Ag and ENEPIG and the mechanical reliability of the joint system. A slight increase in δPd(P) from 0 μm to 0.2 μm caused the nucleation of a pronounced amount of (Pd,Ni)Sn4 in the solder matrix after reflow, which gradually migrated to the joint interface and formed a (Pd,Ni)Sn4/Ni3Sn4 dual layer after subsequent solid-state aging. The formation of the (Pd,Ni)Sn4 dense layer slowed the growth of Ni3Sn4, facilitated the depletion of the Ni(P) film, and seriously deteriorated the mechanical characteristics of the solder joints. This (Pd,Ni)Sn4-induced embrittlement in solder joints (termed the “Pd-embrittlement phenomenon”) had never been found previously in the Sn-Ag reaction system. The formation and migration of (Pd,Ni)Sn4 was dictated by thermodynamics and could be rationalized using a Pd-Ni-Sn isotherm. The above observations indicated that δPd(P) was an important factor of the ENEPIG solderability and should be strictly controlled to be 0.1 μm or less to prevent the undesired Pd-embrittlement phenomenon in Sn-Ag micro joints.

Mechanical reliability of self-aligned chip assembly after reflow soldering process

Purpose This paper focuses on the reliability of the solder joint after the self-alignment phenomenon during reflow soldering. The aim of this study is to analyse the joint quality of the self-alignment assemblies of SnAg alloy solder joints with varying silver content. Design/methodology/approach The shear strength assessment was conducted in accordance with the JIS Z3 198-7 standard. The standard visual inspection of IPC-A-610G was also performed to inspect the self-alignment features of the solder joint samples. Statistical analysis was conducted to determine the probabilistic relationship of shear strength of the misalignment components. Findings The results from the mechanical reliability study indicate that there were decreasing trends in the shear strength value as misalignment offset increased. For shift mode configuration in the range of 0-300 µm, the resulting chip assembly inspection after the reflow process was in line with the IPC-A-610G standard. The statistical analysis shows that the solder type variation was insignificant to the shear strength of the chip resistor. The study concluded that the fracture occurred partially in the termination metallization at the lower part of the chip resistor. The copper content of the joint on that area shows that the crack occurred in the solder joint, and high silver content on the selected zone indicated that the fracture happened partially in the termination structure, as the termination structure of the lead-free chip resistor consists of an inner layer of silver and an outer layer of tin. Practical implications This study’s findings provide valuable guidelines and references to engineers and integrated circuit designers during the reflow soldering process in the microelectronics industry. Originality/value Studies on the effect of component misalignment on joint mechanical reliability are still limited, and studies on solder joint reliability involving the effect of differing contents of silver on varying chip component offset are rarely reported. Thus, this study is important to effectively bridge the research gap and yield appropriate guidelines in the potential industry.

Three-Dimensional Composition Analysis of SnAg Solder Bumps Using Ultraviolet Femtosecond Laser Ablation Ionization Mass Spectrometry.

The application of a novel UV fs Laser Ablation Ionization Mass Spectrometry approach for chemical depth profiling of low-melting point, high surface roughness SnAg solder bump features is presented. The obtained submicrometer resolved three-dimensional compositional data reveal unprecedented information on the distribution of individual elements inside the solder bump matrix. Moreover, the determination of matrix-matched relative sensitivity coefficients allows the first report on quantitative assessment of the SnAg alloy composition. These results significantly contribute to an in-depth understanding of the SnAg plating process. This experimental procedure may find application in future additive performance screening.

Chromium effects on the microstructural, mechanical and thermal properties of a rapidly solidified eutectic Sn-Ag alloy

PurposeThis study aims to investigate the chromium (Cr) effects on the microstructural, mechanical and thermal properties of melt-spun Sn-3.5Ag alloy.Design/methodology/approachTernary melt-spun Sn-Ag-Cr alloys were investigated using X-ray diffractions, scanning electron microscope, dynamic resonance technique, instron machine, Vickers hardness tester and differential scanning calorimetry.FindingsThe results revealed that the Ag3Sn intermetallic compound (IMC) and ß-Sn have been refined because of the hard inclusions’ (Cr atoms) effects, causing lattice distortion increasing these alloys. The tensile results of Sn96.4-Ag3.5-Cr0.1 alloy showed an improvement in Young’s modulus more than 100 per cent (42.16 GPa), ultimate tensile strength (UTS) by 9.4 per cent (23.9 MPa), compared with the eutectic Sn-Ag alloy due to the high concentration of Ag3Sn and their uniform distribution. Shortage in the internal friction (Q−1) of about 54 per cent (45.1) and increase in Vickers hardness of about 7.4 per cent (142.1 MPa) were also noted. Hexagonal Ag3Sn formation led to low toughness values compared to the eutectic Sn-Ag alloy, which may have resulted from the mismatching among hexagonal Ag3Sn phase with orthorhombic Ag3Sn and ß-Sn phases. Mechanically, the values of Young’s modulus have been increased, with increasing chromium content, whereas the UTS and toughness values have been decreased. The opposite of this trend appeared in Sn95.8-Ag3.5-Cr0.7 alloy, which may have been due to high lattice distortion (ƹ = 16.5 × 10−4) compared to the other alloys. Increase in the melting temperature Tm, ΔH, Cp and ΔT was because of Ag3Sn IMC formation. The low toughness of Sn96-Ag3.5-Cr0.5 and Sn95.8-Ag3.5-Cr0.7 (109.56 J/m3 and 35.66 J/m3), relatively high melting temperature Tm (223.22°C and 222.65°C) and low thermal conductivity and thermal diffusivity (32.651 w.m−1.k−1 and 0.314 m2/s) make them undesirable in the soldering process. The high UTS, high E, high thermal conductivity and diffusivity, low creep rate and low electrical resistivity, which have occurred with “0.1 Wt.%” of Cr, make this alloy desirable and reliable for soldering applications and electronic assembly.Originality/valueThis study provides chromium effects on the structure of the eutectic Sn-Ag rapidly solidified by melt-spinning technique. In this paper, the authors compared the elastic modulus of the melt-spun compositions, which have been resulted from the Static method with that have been resulted from the Dynamic method. This paper presents new improvements in mechanical and thermal performance.

Pulse co-deposition of tin-silver alloy from citric acid plating bath for microelectronic applications

Sn–Ag alloys are gaining importance among microelectronics manufacturers because of their potential benefits, e.g., low melting point, excellent wetting to common metallic substrates, and superior mechanical properties required for microelectronic packaging devices. In this work, Sn–Ag alloy was co-deposited from acidic citric acid bath on copper substrates. The plating solution was composed of SnSO4, Ag2SO4, thiourea, and citric acid as a supporting electrolyte. Further, the influence of current density on the Ag content of the coatings was studied. The results indicate that the citric acid bath produces bright Sn–Ag deposits over a wide range of current densities. The grains of the deposits obtained were bigger at lower current densities (10–30 mA cm−2) and become finer at higher current densities (40–50 mA cm−2). Initially, the coatings were very hard and become soft as the current density increases gradually due to the decreased amount of Ag in the deposit which modified the coating solderability.