Sn Ag Research Articles

Mineralization of the Daolundaba Cu–Sn–W–Ag deposit in the southern Great Xing'an Range, China: Constraints from geochronology, geochemistry, and Hf isotope

Abstract The Daolundaba deposit, located in the southern Great Xing'an Range, is a medium-sized Cu–Sn–W–Ag deposit dominated by Cu. The intrusive rocks in the ore district mainly include the Early Permian Qianjinchang medium-grained biotite monzogranite and the Early Cretaceous Zhangjiayingzi fine-grained granite and porphyritic granite. Cassiterite U–Pb dating for two Cu–W–Sn ore samples yielded ages of 134.7 Ma and 136.8 Ma, respectively. Zircon U–Pb dating for fine-grained granite and porphyritic granite of the Zhangjiayingzi intrusion yielded ages of 134–136 Ma and 135 Ma, respectively. The Zhangjiayingzi intrusion is high-K calc-alkaline and featured by enrichment of Rb, Th, U, K, Nd, Zr, Hf, and Sm and steady depletion of Ba, Sr, P, Eu, and Ti, with extremely negative Eu anomalies and noticeable tetrad effect of rare earth elements, indicating the intrusion has a highly fractionated granite affinity. The Zhangjiayingzi intrusion has high zircon eHf(t) values (4.1–10.2) and relatively young zircon Hf two-stage model ages (541–929 Ma), suggesting that it dominated originated from the partial melting of a Neoproterozoic juvenile lower crust. The geochronology and geochemistry indicate that the mineralization of the Daolundaba deposit is closely related to Early Cretaceous highly fractionated granites. Fractional crystallization of granitic magmas is the important controlling factor for the formation of the Zhangjiayingzi highly fractionated granite and the Daolundaba Cu–W–Sn–Ag deposit.

Ore-Bearing Magmatic Systems with Complex Sn–Au–Ag Mineralization in the North-Eastern Verkhoyansk–Kolyma Orogenic Belt, Russia

This paper reports the results of a study of magmatic rocks with Sn–W–Au–Ag mineralization from the Kuranakh, Elikchan, and Istekh ore fields in the Northern batholith belt of the north-eastern Verkhoyansk–Kolyma orogenic belt in Eastern Russia. Using petrographic, mineralogical, geochemical, and isotopic methods, we determined the mineral compositions, petrochemistry, and geochemistry of magmatic rocks, the P–T conditions of their generation and crystallization, and their geodynamic affinity. The studied magmatic rocks have common geochemical characteristics that likely reflect the influence of fluids supplied from a long-lived, deep-seated mantle source. The ore fields are characterized by Sn–W–Au–Ag–Pb polygenetic mineralization. The magmatic and metallogenic evolution comprised five stages for the formation of magmatic rocks and ores. During the first stage (Berriasian–Barremian), arc-related magmatic rocks formed in an active continental margin setting and were associated with Au–Ag mineralization. The second, third, and fourth stages (Aptian–Campanian) took place in a crustal extension and rift setting, and were accompanied by Au–Ag and Sn–W mineralization. During the fifth (post-magmatic) stage, Sn–Ag–Sb and Pb–Ag mineralization occurred.

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.

Comparative study between the Sn–Ag–Cu/ENIG and Sn–Ag–Cu/ENEPIG solder joints under extreme temperature thermal shock

The interfacial reactions and the growth behavior of interfacial intermetallic compounds (IMCs), as well as their effects on the mechanical properties of the Sn-3.0Ag-0.5Cu (SAC305)/electroless nickel-electroless palladium-immersion gold (ENEPIG) solder joints under extreme temperature thermal shock between − 196 °C and + 150 °C were investigated, and compared with those of the SAC305/electroless nickel-immersion gold (ENIG) solder joints. The morphology of (Cu, Ni)6Sn5 IMCs formed at the SAC305/ENIG interface transformed from column-type to polygon-type during extreme temperature thermal shock, while the needle-type and thin-layer-type (Cu, Ni, Pd)6Sn5 IMCs at the SAC305/ENEPIG interface completely transformed to chunk-type. The growth rate of interfacial IMCs in the SAC305/ENEPIG joint was slower in contrast to that in the SAC305/ENIG joint, since the Pd(P) layer in the ENEPIG surface finish inhibited the formation and growth of interfacial IMCs. After thermal shock for 400 cycles, the shear force of the SAC305/ENIG and SAC305/ENEPIG joints decreased about 29.06% and 9.79%, respectively. Moreover, the shear force of the SAC305/ENEPIG joints was consistently higher than that of the SAC305/ENIG joints. The SAC305/ENEPIG joints always fractured in the solder matrix, regardless of thermal shock cycles, while the fracture location of the SAC305/ENIG joints transferred from inside the solder matrix to partially inside the solder matrix and partially at the solder/IMC layer interface with increasing thermal shock cycles.

IMC microstructure modification and mechanical reinforcement of Sn–Ag–Cu/Cu microelectronic joints through an advanced surface finish technique

Intermetallic compound(s) (IMC) that nucleates at the interface between solder and Cu trace during a soldering reaction, is one of the most crucial factors for microelectronic packaging reliability. This study was conducted to modify the IMC microstructure and to reinforce the mechanical strength of Sn–Ag–Cu/Cu microelectronic joints through various surface finish coatings, including organic solderability preservative (OSP), immersion Ag (ImAg), immersion Sn (ImSn), Au/Pd (electroless palladium/immersion gold, EPIG), and Au/Pd/Au (IGEPIG) layer(s). We confirmed that the type of surface finish dominated the IMC growth morphology and mechanical characteristics of the Sn–Ag–Cu/Cu solder joints, even though these surface finishes were eliminated in a few seconds of the soldering process. A dense Cu6Sn5 layer with a scallop-like appearance was obtained for the traditional OSP case, while a prismatic, loose Cu6Sn5 microstructure was produced for the alternative cases (metal films). This loose Cu6Sn5 microstructure offered numerous molten solder channels for the in-diffusion of Sn to Cu, retarding undesired Cu3Sn growth at the Cu6Sn5/Cu interface; consequently, a brittle-to-ductile transition in the joint fracture mode with a high shear strength and fracture energy was obtained in the high-speed ball shear (HSBS) test. A significant mechanical reinforcement of the Sn–Ag–Cu/Cu microelectronic joints can be achieved with the replacement of the traditional OSP coating by the newly developed IGEPIG trilayer surface finish.

Novel low Ag-content Sn–Ag–Cu–Sb–Al solder alloys with enhanced elastic compliance and plastic energy dissipation ability by applying rotating magnetic field

The main scope of this research is to investigate the impact of rotating magnetic field (RMF) on the physical properties of the Sn–0.5Ag–0.5Cu–2.0Sb–0.1Al (SAC0505SbAl) solder alloy. The application of RMF during molten alloy cooling showed prominent effect on the morphology, thermal properties, and the consequent mechanical characteristics. It was shown that the dendritic morphology was changed from columnar dendrites to equiaxed grains with the application of RMF. In addition, RMF processing modified the eutectic phases in the alloy matrix. These notable modifications have resulted in a substantial increase in ductility (~ 30%) with a slight decrease in tensile parameters (UTS and YS). Such effects could enhance elastic compliance and plastic energy dissipation ability of solder alloys, which plays superbly fundamental function in drop-impact reliability. Differential scanning calorimetry (DSC) analysis reveals that significant decrease in pasty range (from 10.8 to 7.5 °C) and undercooling (from 13.1 to 9.0 °C) was attained after applying RMF. The stress exponent (n), the activation energy (Q), and deformation mechanism of the SAC0505SbAl alloy processed with and without RMF were discussed in detail. The obtained results are certainly expected to fill the knowledge gap about the behavior of these recently developed solder alloys under the effect of RMF that are potential alternatives as Pb-free interconnecting material in microelectronic packaging industry.

Thermal Fatigue Life Prediction of BGA Solder Joints Using a Creep Constitutive Equation Incorporating Microstructural Coarsening Effect

A thermal fatigue life prediction method is proposed for Sn–Ag–Cu solder joints that incorporates the effect of creep strength reduction due to microstructural coarsening of the solder during thermal cycling. The proposed method was used to predict the thermal fatigue life of solder joints in a BGA (ball grid array) semiconductor package. In the study, the thermal fatigue life was calculated through as follows. A creep constitutive equation for the solder that incorporates the strain-enhanced growth of the intermetallic compounds in the solder was used to update the constitutive equation at each given cycle and the relationship between inelastic strain energy density range and the number of cycles of the solder joint was obtained to calculate the fatigue life. As the number of thermal cycles increased, the intermetallic compounds grew, and in conjunction with this, the inelastic strain energy density range increased, causing the thermal fatigue life of the solder joint to decrease compared with that without the microstructural coarsening effect. Since the growth of intermetallic compounds under field conditions with a long dwell time is large compared with that during accelerated tests, the decrease in thermal fatigue life due to microstructural coarsening was found to be significant under field conditions with a long dwell time.

Surface tension of liquid mixtures and metal alloys. Thermodynamic conditions for the occurrence of a positive temperature coefficient

The atypical increase of surface tension when the temperature of a liquid alloy increases, is addressed using Butler’s thermodynamic model for an ideal surface phase. A rigorous expression for this temperature coefficient at fixed bulk alloy composition, requiring only pure-metal density and surface tension data and no arbitrary simplifying assumptions, is worked out. This theoretical development predicts the occurrence of positive temperature coefficients whenever a combination involving large difference of pure-metal surface tensions, temperatures close to the alloy melting point and molar surface area of the surface-active metal larger than that of the other component, is met. The proposed method is applied to the alloys Cu–Sn, Cu–In, Ag–Bi, Ag–Pb and Ag–Sn for which experimentally measured positive temperature coefficients have been reported. An acceptable agreement between theoretical and experimental values is documented. This theoretical approach predicts a negative temperature coefficient of the surface tension at fixed surface-phase composition, which is in fact the typical behaviour for this dependence. It is concluded that the temperature and composition ranges over which a certain binary alloy may exhibit positive temperature coefficient of the surface tension can be established beforehand using the proposed methodology.

Impact of in situ current stressing on Sn-based solder joint shear stability

This paper reports experimental observations showing that a current flow produces an effect of strengthening a solder joint against a shear load. This conclusion is found from a single-joint shear test conducted on Sn–1Ag–0.5Cu wt% (SAC 105) joints with in situ current stressing varied from 700 to 1400 A/cm2 at room temperature. To isolate the current effect from the Joule heat effect, the same type of tests were conducted at room temperature, 40, 50, and 80 °C, without current applied to the joint, thus mimicking the condition of steady-state temperature resulting from Joule heating. Comparative testing was also conducted after aging the samples at 150 °C for 200 h. These tests produced indications suggesting that the current flow causes the maximum shear load to increase, while the rise in temperature by the Joule heat effect results in the opposite effect. Experimentally, as much as a 9.5% increase in the maximum shear load was observed from the isothermally aged sample tested under a current density of 700 A/cm2, while an ~ 25% reduction was estimated to result from a temperature increase by Joule heating. The potential mechanism for these observations is discussed.

Utilizing E-Waste for Construction of Magnetic and Core-Shell Z-Scheme Photocatalysts: An Effective Approach to E-Waste Recycling.

The increasingly large stream of e-waste is seriously threatening the environment; meanwhile, global energy shortage is on the rise. Based on the principles of energy regeneration and waste utilization, we introduced a win-win approach to utilize waste capacitors for construction of magnetic and core-shell Z-scheme Nb-Pb-codoped BaTiO3/Ni-Pd@graphite-like carbon nitride (g-C3N4) photocatalysts for H2 evolution. Using simple ball-milling, waste capacitors were transformed to Nb-Pb-codoped BaTiO3/Ni-Pd-Ag-Sn nanoparticles and g-C3N4 was coated on the nanoparticles, forming a core-shell structure. The Ni-Pd acted as the electron mediator in the Z-scheme, and Ag-Sn also facilitated the electron transfer. Moreover, Ni made the Z-scheme magnetically separable. The Z-scheme showed a remarkably enhanced photocatalytic H2 evolution rate, which was 22.2 times higher than that of g-C3N4. Such an enhanced photocatalytic performance was attributed to the special Z-scheme and core-shell structure, improving the light adsorption, increasing the Brunauer-Emmett-Teller (BET) surface area, facilitating the efficient separation of electron-hole pairs, and maintaining the strong redox ability of charge carriers. Furthermore, the photoluminescence analysis combined with density functional theory (DFT) calculations provided the basis for the Z-scheme mechanism. This study adequately utilized the composition of e-waste to construct a highly efficient and magnetically separable Z-scheme for H2 generation, which realizes energy regeneration, waste recycling, and environmental protection.

Electrical resistivity of Sn–3.0Ag–0.5Cu solder joint with the incorporation of carbon nanotubes

The main objective of this study is to investigate the electrical properties of Sn–3.0Ag–0.5Cu solder joint with the incorporation of carbon nanotube instead of solder bulk. Sn–3.0Ag–0.5Cu solder paste with the incorporation of carbon nanotube up to 0.04 wt% was fabricated by using mechanical mixing method. Fabricated solder pastes were then soldered on printed circuit board via reflow soldering at 260°C peak temperature. Electrical resistivity of Sn–3.0Ag–0.5Cu-carbon nanotube solder joints was measured by the four-point probe method at room temperature. Microstructure properties were observed by optical microscope and field emission scanning electron microscope. Electrical resistivity of Sn–3.0Ag–0.5Cu solder joint was found to increase with the incorporation carbon nanotube up to 0.03 wt% and slightly decrease at 0.04 wt%. Incorporation of carbon nanotube in the solder matrix apparently changes the microstructure of Sn–Ag–Cu solder alloys. Microstructural observation found that electrical resistivity correlated with the distribution area of eutectic phase in the solder matrix due to the existence of carbon nanotube. It was revealed that eutectic phase area increases with the increasing of carbon nanotube wt% up to 0.03 and then slightly decreases at the incorporation of 0.04 wt% carbon nanotube as parallel with the trend of electrical resistivity values.

Study on self-adaptive lubrication mechanism of surface micro-dimple structure filled with multiple lubricants

In view of the high temperature and heavy load operating conditions of M50 aviation bearings, it is of great significance to explore how to improve its friction performance at high temperature or heavy load. The surface micro-dimple structure filled with multiple lubricants Sn–Ag–Cu/TiO2 is prepared by laser additive manufacturing in this paper. It is found that in high temperature environment, Sn–Ag–Cu/TiO2 in micro-dimples is removed to worn surfaces and are continuously pulverized, oxidized, agglomerated, deformed and compacted under the action of friction, finally forming the lubrication structure, which makes the tribological properties of M50 greatly improved at a wide load range. Under heavy load condition, the slip behavior and high load-bearing properties of TiO2 nanoparticles make M50 still maintain excellent anti-friction and wear resistance. The results can provide guidance for the research of self-adaptive lubrication behavior of materials.

Effect of strain rate on mechanical behavior of Sn0.3Ag0.7Cu solder at macro- and micro-scales

At present, there have been many researches on the effect of trace elements on the mechanical properties of Sn–Ag–Cu solder, and the methods used are mainly shear test or nanoindentation test. However, the size of structural solder joints in electronic packaging has reached the order of micrometers, and the mechanical behavior characteristics related to the strain rate of solder at the micro-scale are obviously more needed for the application of small-scale structural solder joints. For this reason, this paper selects Sn0.3Ag0.7Cu solder with superior comprehensive properties such as ductility and shear strength and low cost, and uses universal testing machine and Split Hopkinson Pressure Bar to perform quasi-static and dynamic compression tests on it. After fitting the Johnson–Cook constitutive model parameters of Sn0.3Ag0.7Cu, the dynamic indentation process at the micro-scale was simulated by ABAQUS, and the effect of strain rate on the mechanical behavior of the material at the macro-scale and micro-scale was analyzed, respectively. Our macro test results show that the yield strength of Sn0.3Ag0.7Cu solder is about 28.74 MPa. Under quasi-static load, the rate of increase of the stress value in the strain hardening stage will increase with the increase of the strain rate; while under dynamic load, the stress value corresponding to different strain rates does not increase significantly, and the main difference lies in the magnitude of plastic strain. In our numerical simulation of dynamic indentation, the result shows that when Sn0.3Ag0.7Cu solder is subjected to a high strain rate load at the micro-scale, a certain degree of hardening occurs in the middle and late stages of indentation propagation. At the same time, the calculated load–displacement curves indicate that the plastic flow ability of Sn0.3Ag0.7Cu solder in the micro-scale increases with the increase of the indentation expansion rate.

Controlling Ag3Sn Plate Formation and Its Effect on the Creep Resistance of Sn–3.0Ag–0.7Cu Lead-Free Solder by Adding Minor Alloying Elements Fe, Co, Te and Bi

Preventing the formation of large platelets of Ag3Sn intermetallic compounds (IMCs) during solidification of solder joints has become a significant challenge in the design of Sn–Ag–Cu lead-free solder alloys. Large platelets of Ag3Sn are generally considered as undesirable as their presence can create solidification defects and causes mechanical property anisotropy. In the present work, the synergetic effects of adding 0.1 wt% of Fe, Co, Te and 2 wt% Bi to Sn–3.0Ag–0.7Cu (SAC 307) solder are studied in terms of the growth of large platelets Ag3Sn IMCs and the resulting alloy’ creep resistance as well as their thermal behavior. Although minor Fe, Co, Te and Bi alloying elements addition causes large increase in the degree of undercooling from 3.4 to 22.3 °C with maintaining the pasty range and melting temperature at the same levels, the modified SAC307–FeTeCoBi alloy exhibits considerable increase in creep resistance (~ 10 times) and large fracture life-time than SAC (307) solder at same stress levels and testing temperatures. This is attributed to the transition of Ag3Sn IMCs from large platelets into fine needle-like morphology and formation of new (Cu,Co)6Sn5, FeSn2, SnTe IMCs and Bi particles, which could provide more obstacles for dislocation movement at the interphase boundaries.

Phase diagram of Ag–Pb–Sn system

The Ag–Pb–Sn ternary system is an important material system for both electronic packaging and thermoelectric applications. However, there is no experimental phase equilibria information of the ternary system. Ag–Pb–Sn alloys are prepared and their phase equilibria at various temperatures were determined. The focus was on the 500, 350, and 200 °C isothermal sections. Additional information was also obtained for 400, and 300 °C. Several samples were studied by DSC studies. No ternary compounds were found in the ternary system. The Ag–Sn binary compounds, Ag3Sn(ε) and Ag4Sn(ζ) at 350 °C and Ag4Sn(ζ) at 500 °C, exhibit very small Pb solubility. The thermodynamic assessment of the ternary Ag–Pb–Sn system was carried out using the above mentioned experimental data.

Ag–Sn dual-modified LiNi0.8Co0.1Mn0.1O2 as cathode for lithium storage

The structural decomposition and inevitable capacity decay during cycling hinder the further commercial application of LiNi0.8Co0.1Mn0.1O2 (NCM811). In this paper, Ag–Sn dual-modification is first adopted to promote the structural stability and the electrochemical property of NCM811. First, there form Li2SnO3 phase coated NCM811, and most Li2SnO3 phases exist on the outer surface of NCM811 sphere during the first-step Sn modification. Then, a slightly uneven Ag coating layer generate on the surface of Li2SnO3 coated NCM811 and more Li2SnO3 phase diffuses into the NCM811 sphere after the second-step of Ag-modification. Meanwhile, the mixing degree of Li+/Ni2+ and residual lithium on the surface of NCM811 are reduced by the Ag–Sn dual-modification. After proving, the Ag–Sn dual-modification is beneficial for improving the electronic conductivity, accelerating the diffusion of Li+ and suppressing the decomposition of electrolyte, thereby enhancing the electrochemical performance. Consequently, the Ag–Sn dual-modified NCM811 reveals a splendid discharge capacity of 193.3 mA h g−1 at 1 C rate, and with retention of 89.4% after 90 cycles between 2.8 and 4.3 V, exhibiting well-enhanced cycling stability with the comparison of pure NCM811 (183.7 mAh g−1, 87.9%). This efficient dual-modification strategy provides a reference scheme for the commercial application of NCM811.

An effective method to retard Cu–Sn intermetallic compounds formation on the sidewall of microbumps by thermal oxidation

The formation of intermetallic compound (IMC) on the sidewall of Cu-pillar microbumps brings potential reliability threats. To inhibit its formation, a thin CuO layer was fabricated on the sidewall of Cu pillars by thermal oxidation first. Then, we verified that the CuO layer effectively retarded Sn–Ag solder sidewall wetting in the reflow process and exhibited a strong inhibition effect on Cu–Sn IMCs formation on the sidewall of microbumps during aging process. Secondly, microstructural evolution of copper oxides layer during aging was discussed studied. Results showed that the initial simple CuO layer became complex as Cu2O/CuO, fully covered the whole solder cap and formed a continuous reticulation structure on the polyimide layer after 2000 h aging. Then, the formation mechanism of copper oxides layer was proposed according to its oxidation kinetics. The growth behaviors of copper oxides layer around microbumps and its inhibition ability of IMC growth on the sidewall of microbumps are of great importance to electronics reliability.

Influence of Ni, Bi, and Sb additives on the microstructure and the corrosion behavior of Sn–Ag–Cu solder alloys

Sn–Ag–Cu solder alloys were usually modified using trace elements to achieve various properties. This paper investigated the effect of additives of Ni, Bi, and Sb on the microstructure and corrosion behavior of SAC alloys under application condition. Investigation was carried out using both solder alloy ingots and reflow-soldered surface insulation resistance interdigitated patterns by electrochemical methods under humid and corrosive conditions. Microstructure analysis was performed using X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy etc. Volta potential distribution in the bulk of the alloy was analyzed by Scanning Kelvin Probe Force Microscopy. Results show the passivation domain of five tested solder alloys did not influence the susceptibility of electrochemical migration under 5 V DC bias loading. Ni and Bi additives resulted in lower susceptibility of electrochemical migration due to homogeneity of the IMCs distribution in the bulk alloys. Bi precipitates in InnoLot alloy participated micro-galvanic corrosion as cathode rather than Ag containing phase as known before.

Relationship between Nanomechanical Responses of Interfacial Intermetallic Compound Layers and Impact Reliability of Solder Joints

This study aims to evaluate solder joint reliability under high speed impact tests using nanoindentation properties of intermetallic compounds (IMCs) at the joint interface. Sn–Ag based solder joints with different kinds of interfacial IMCs were obtained through the design of solder alloy/substrate material combinations. Nanoindentation was applied to investigate the mechanical properties of IMCs, including hardness, Young’s modulus, work hardening exponent, yield strength, and plastic ability. Experimental results suggest that nanoindentation responses of IMCs at joint interface definitely dominates joint impact performance. The greater the plastic ability the interfacial IMC exhibits, the superior impact energy the solder joints possess. The concept of mechanical and geometrical discontinuities was also proposed to explain brittle fracture of the solder joints with bi-layer interfacial IMCs subject to impact load.

Numerical computation of wetting angles of Sn–(3−x)Ag–0.5Cu−x(Bi,In) quaternary Pb-free solder alloy systems on Cu substrate

This paper was aimed to study of the wetting angle ([Formula: see text]) of Sn–Ag–Cu, Sn–([Formula: see text])Ag–0.5Cu–([Formula: see text])Bi and Sn–([Formula: see text])Ag–0.5Cu–([Formula: see text])In ([Formula: see text], 1 and 2 in wt.%) Pb-free solder alloy systems at various temperatures (250, 280 and 310∘C) on Cu substrate in Ar atmosphere. The new Sn–([Formula: see text])Ag–0.5Cu–xBi and Sn–([Formula: see text])Ag–0.5Cu[Formula: see text]([Formula: see text]) In systems, low Ag content quaternary Pb-free solder alloys, were produced by adding 0.5%, 1% and 2% Bi and In separately to the near-eutectic Sn-3[Formula: see text]wt.%Ag–0.5[Formula: see text]wt.%Cu (SAC305) alloy. The wetting angles of new alloys, Sn[Formula: see text]2.5[Formula: see text]wt.%Ag[Formula: see text]0.5[Formula: see text]wt.%Cu[Formula: see text]0.5[Formula: see text]wt.%Bi (SAC-0.5Bi), Sn[Formula: see text]2[Formula: see text]wt.%Ag[Formula: see text]0.5[Formula: see text]wt.%Cu[Formula: see text]1[Formula: see text]wt.%Bi(SAC-1Bi), Sn[Formula: see text]1[Formula: see text]wt.%Ag[Formula: see text]0.5[Formula: see text]wt.%Cu[Formula: see text]2[Formula: see text]wt.%Bi(SAC-2Bi), Sn[Formula: see text]2.5[Formula: see text]wt.%Ag[Formula: see text]0.5[Formula: see text]wt.%Cu[Formula: see text]0.5[Formula: see text]wt.%In (SAC-0.5In), Sn[Formula: see text]2[Formula: see text]wt.%Ag[Formula: see text]0.5[Formula: see text]wt.%Cu[Formula: see text]1[Formula: see text]wt.%In (SAC-1In) and Sn[Formula: see text]1[Formula: see text]wt.%Ag[Formula: see text]0.5[Formula: see text]wt%.Cu[Formula: see text]2[Formula: see text]wt.%In (SAC-2In) were measured by sessile drop method. Experimental results showed that additions of Bi and In separately to SAC305 resulted in a continuous decrease in the [Formula: see text] up to 1[Formula: see text]wt.% above which the [Formula: see text] value was increased and it is appeared that a correlation among the [Formula: see text], alloys compositions and the test temperatures exists which recommended an empirical model to estimate the [Formula: see text] at a given Bi and In content and temperature for a given alloy systems. The numerical model estimates the [Formula: see text] understandably well with the present work.