Sn-Pb Solder Alloys Research Articles

Deformation behavior and constitutive equation of Sn-37Pb solder alloy at cryogenic temperature

In this work, the tensile property, ductile-to-brittle transition (DBT) mechanism and constitutive relations of 63Sn-37Pb (Sn-37Pb) solder alloy at cryogenic temperature were studied by uniaxial tensile experiments for different temperatures. The tensile strength of Sn-37Pb solder alloy increases from 38.2MPa (293K) to 178.9MPa (123K) and then declines to 145.2MPa (77K) with decreases of temperature, and its fracture elongation changes from 42.8% (293K) to 10.2% (77K). Mechanical behavior of Pb second phase in Sn-37Pb alloy at low temperatures is illustrated: when the temperature drops to 123K and below, the fracture failure of β-Sn matrix occurs in an open mode. As a result, Sn-37Pb solder alloy fails by brittle fracture mode. Anand model is adopted as a unified viscoplastic intrinsic law to describe the intrinsic relationship of Sn-37Pb solder alloys. Above 123K, Anand model can effectively fit the stress-strain curves of Sn-37Pb solder alloys. When the temperature lower than 123K, the deformation characters of Sn-37Pb solder alloys change from elasto-viscoplastic to elasto-plastic, and Anand model is unable to continue to fit the intrinsic relationship of Sn-37Pb solder alloys. Sn-37Pb solder alloy exhibits more obvious strain hardening at low temperature, and its low-temperature intrinsic response is successfully described by Hollomon’s equation. The research method of the solder alloy is of great significance to solve the reliability problem of low temperature electronic devices.

A study on the quantitative recrystallization of cold deformed copper affected by tin-lead solder

It has been observed that the fractional recrystallization characteristics of commercially pure copper is affected by the presence of individual or both the constituent elements of the Sn-Pb solder alloy. In order to design the experiment, commercially pure Cu, binary copper alloys (Cu-Sn and Cu-Pb) and ternary copper alloy, Cu-Sn-Pb are investigated. Cast alloys are homogenized, solution treated, and then quenched to complete the thermal treatment. In order to recrystallize, alloys are cold rolled to a 75% thickness and then annealed at 700°K isothermally for varying durations, up to 3600 seconds. In this experiment, the fractional recrystallization of annealed samples is evaluated as the normalized difference in microhardness recorded at various time steps. Additionally, in an attempt to verify the experimental results, the well-known Johnson-Mehl-Avrami-Kolmogorov equation is also used to predict the associated recrystallization behavior. From the study, it can be inferred that the presence of Sn-Pb solder-alloy elements have a positive impact on the recrystallization behavior of pure copper due to the solid solution strengthening, in which the effect of tin is greater than that of lead. Quantitative analysis indicates that recrystallization of pure Cu, Cu-Sn, Cu-Pb, and Cu-Sn-Pb alloys attains 99.4%, 95.4%, 98.4%, and 89.5%, respectively. Sn forms intermetallic with Cu but Pb does not. Additionally, Sn forms different intermetallic with impurities and has a BCC crystal structure dissimilar to the FCC of Cu and Pb. As a result, the formation of GP zones and the intermetallic phases during annealing show greater differences in the recrystallization behavior between the two approaches. By combination, microstructural studies of the cold-rolled alloys reveal the elongated grains of the second phases, and the alloys almost completely re-crystallized after 1800 seconds of annealing at 700°K.

Effect of temperature on the low cycle fatigue properties of BGA solder joints

Since the restriction of hazardous substances (RoHS) directive, lead-free soldering has been widely broad adopted. In many applications, lead-free alloys have been substituted for conventional SnPb (Tin-Lead) solder. Among lead-free alloys, SAC305(Sn-3.0Ag-0.5Cu) has gained the highest acceptance as a solder alloy. The fatigue performance of solder joints has become an essential reliability assessment criterion due to the transition to more reliable lead-free alloys from highly predictable lead-based alloys. This study examines the shear fatigue characteristics of sandwich test vehicles for SnPb and SAC305 at different temperatures using both Organic Solderability Preservative (OSP) and Electroless Nickel-Immersion Silver (ENIG) surface finishes. The fatigue experiments were performed using an Instron micromechanical tester at a constant strain rate, and microstructural analysis was carried out using Scanning Electron Microscopy (SEM) to identify the Intermetallic Compound (IMC) morphology and failure mode. The stress-strain (hysteresis) loops of SnPb and SAC305 were measured, and the fatigue life of the specimens was estimated using the strain-life equation at various temperatures. SAC305 was observed to have a better fatigue life than SnPb, particularly at higher strain levels or testing temperatures. The OSP surface finish demonstrated superior fatigue properties compared to the ENIG surface finish. Additionally, elevated testing temperatures were found to accelerate fatigue failure in solder joints. The Arrhenius model was utilized to develop a general empirical model that predicts the fatigue life of SAC305 and SnPb solder alloys with OSP and ENIG surface finishes as a function of the strain level and testing temperature.

Effects of Zn Addition on Dendritic/Cellular Growth, Phase Formation, and Hardness of a Sn–3.5 wt% Ag Solder Alloy

Sn–Ag‐based alloys are considered good alternatives to soldering operations as compared with the traditional Sn–Pb solder alloys. Herein, the effects of 0.5 and 1.0 wt% Zn additions to a Sn–3.5 wt% Ag eutectic alloy on cooling and growth rates, microstructure, and microhardness along the length of directionally solidified (DS) castings are examined. Characterization techniques such as optical microscopy (OM), scanning electron microscopy (SEM), X‐ray fluorescence (XRF), X‐ray diffraction (XRD), and Vickers microhardness are used to examine different samples extracted along the length of the DS castings. The Sn–3.5 wt% Ag alloy is shown to have a fully dendritic microstructure, characterized by a Sn‐rich matrix with the eutectic mixture located in the interdendritic regions. On the other hand, the alloy modified with 1 wt% Zn exhibits a microstructure entirely formed by β‐Sn cells, with a mixture of β‐Sn, ε‐Ag3Sn, and ζ‐AgZn phases in the intercellular regions. The DS Sn–3.5 wt% Ag–0.5 wt% Zn alloy casting exhibits a cellular/dendritic transition at a critical cooling rate of 8.5 °C s−1. The 0.5 wt% and 1 wt% Zn additions to the Sn–3.5 wt% Ag alloy improve hardness by 42.6% and 47.5%, respectively.

Morphological and Structural Properties of Sn-Bi Lead-Free Solder in 6 M Potassium Hydroxide

Sn-based lead-free solder alloys have been explored extensively as an alternative to the conventional Sn–Pb solder alloys. While the miniaturization of electronic devices and the growth of appliance area, the corrosion resistance of solder alloys play a crucial element in the reliability of electronic devices in a prolonged period of service. This paper determines the corrosion effect of Sn-Bi solder lead-free solder, particularly immersed in alkaline solution which is potassium hydroxide. Morphological and elemental analyses reveal the formation of oxides on the surface after immersion after using a scanning electron microscope, dispersive energy X-ray and X-ray diffraction. The result of morphology reveals that the Sn matrix in plateau indicated dark contrast while Bi-rich in the lamellar eutectic structure indicated in light contrast appearance. In addition, phase and elemental analyses revealed the formation of mixed corrosion products of SnO, SnO2 and Bi2O3 on the surface after testing. It is hoped that this finding will provide some helpful evidence in clarifying the corrosion progress of lead-free solder alloys. Furthermore, the remaining corrosion potential and current of Sn-Bi in 6 M potassium hydroxide solutions in this research are proposed.

Tensile, hardness and microstructural properties of Sn-Pb solder alloys

This work investigated the Tensile, Hardness and Microstructural Properties of Sn-Pb Solder Alloys of Pb content 15, 60 and 80%. The Sn-Pb solder alloy was prepared from granulated Sn and Pb. The element was mixed in right proportions, melted in furnace at 350 °C while being held in crucible. The results showed that maximum tensile stresses obtained had specimen containing 60% with the highest value and the alloys had decreased hardness as a result of increased Pb content while ductility of the alloy increased as observed from stress strain curve. The sample alloy with 60% Pb is the preferred solder.

The Effect of Germanium Addition on the Lead-free Solder Alloys: A Short Review

The Restriction of Hazardous Substances (RoHS) has been enforced a law to restrict the use of hazardous materials in electronic and electrical industries. Hence, it leads to the development of lead-free solder among the electronic industry. SnAg, SnCu, SnAgCu, and SnZnBi solders are found to be alternatives to replace SnPb solder alloys. However, they still have many problems, such as large undercooling and large intermetallic compounds are still present in the solder alloys. Later, researchers come up with the idea of adding alloying elements to lead-free solders to further enhance the properties of lead-free solders. This review paper is aimed to analyze and summaries the effects of germanium (Ge) addition to lead-free solders focusing on its microstructure and thermal properties. The Ge has an almost similar crystal structure as pure tin (Sn), so it is expected that the properties of the lead-free solder could be enhanced by adding an appropriate amount of Ge. Nevertheless, Ge has a unique characteristic as it could act as an antioxidant agent in the lead-free solders.

Electrochemical Corrosion of SAC Alloys: A Review

Tin–silver–copper (SAC) solder alloys are the most promising candidates to replace Sn–Pb solder alloys. However, their application is still facing several challenges; one example is the electrochemical corrosion behaviour, which imposes a risk to electronics reliability. Numerous investigations have been carried out to evaluate the corrosion performance of SAC lead-free alloys, regarding the effect of the corrosive environment, the different manufacturing technologies, the effect of fluxes, the metallic contents within the SAC alloys themselves, and the different alloying elements. In these studies, widely used electrochemical techniques are applied as accelerated corrosion tests, such as linear sweep voltammetry and electrochemical impedance spectroscopy. However, there is lack of studies that try to summarise the various corrosion results in terms of lead-free solder alloys including low-Ag and composite solders. This study aims to review these studies by showing the most important highlights regarding the corrosion processes and the possible future developments.

Effect on Shear Strength and Hardness Properties of Tin Based Solder Alloy, Sn-50Bi, Sn-50Bi+2%TiO<sub>2</sub> Nanoparticles

Solder alloys are important joining medium widely used in the electronics industry to connect components to printed circuit board PCB. The Sn-Pb solder alloys have been the cornerstone medium used for a long time. Unfortunately, the use of Pb was banned by the European Union due to the harmful environmental and health issues with Pb. Therefore, in this study, the Sn-50Bi and Sn-50Bi+2%TiO2 nanoparticles lead-free solder alloy is investigated based on their shear strength, Vickers hardness, and melting temperature. The investigation shows that the hypo eutectic Sn-50Bi has a low melting temperature of approximately 145°C, and the 2%TiO2 nanoparticles reinforced Sn-50Bi has a melting temperature of around 182°C, which is lower than the traditional Sn-Pb (Tm=183 °C) and Sn-Ag-Cu (Tm=227°C). Furthermore, the developed Sn-50Bi had a Vickers hardness and shear strength of 26.81 HV and 40.78 MPa respectively, higher than the other leaded and lead-free solders. However, after the reinforcement, the hardness increased by 12% (30 HV) and a slight increase of 2.5% (42.4MPa) in shear strength. Overall, the addition of the TiO2 nanoparticles showed a clear influence on the Sn-Bi properties. The results obtained from this study seem satisfactory to the electronic industry and the environment.

Investigations on the Corrosion Properties of Sn–0.5Cu–Bi–xAg Lead Free Solder Alloys in 3.5% NaCl Solution

Various environment legislations lead to the ban of Pb in solder alloy making. Solder alloy is an integral part of electronic packaging industry. As a result of this researchers were searching for new combinations without lead which can replace Sn–Pb solder alloy. The new lead free solder joint should possess good mechanical properties, good wetting properties and good corrosion resistance properties. Many lead free solder alloys were discovered. Sn–0.5Cu–3Bi is a good candidate for replacing the Sn–Pb alloy with good properties. The addition of Ag into the alloy enhanced the properties, especially 1% by wt. Ag. In this paper, investigations on the corrosion behavior of Sn–0.5Cu–3Bi–xAg (x = 0, 0.5, 1% by wt.) in 3.5% NaCl is carried out using weight loss method. Microstructure and EDAX analysis were also conducted in the analysis. It is found that the corrosion rate is minimum with 1% by wt. addition of Ag. Corrosion rate is less when compared with the SAC (Sn–Ag–Cu). Sn–0.5Cu–3Bi–1Ag can be considered as a potential lead free solder joint with good corrosion resistance.

Environmental Friendly Low Mass 20g-Sn58Bi/Cu Solder Alloy as an Alternative to Lead SnPb and Its Properties Study

The SnBi solder system are argued to be the possible replacement for the lead and hazardous SnPb solder alloy. The features that differs in this study from the other types of Sn58Bi/Cu is the low mass usage of 20g. This low mass serves as to preserve materials and reduce waste. Yet, the main objectives to provide substantial data in term key properties of melting temperature, hardness and contact area properties of this Sn58Bi solder. The melting point of the Sn58Bi solder alloy is 142.25°C, close to the eutectic temperature. The average Vickers hardness value produced by the Sn58Bi was 28.8Hv, considerably high and close to the SnPb. The spreading area of the Sn58Bi solder alloy on the Cu substrate was calculated to 14.85mm2, at the soldering temperature 230°C. These properties are based on 20g of SB that can be predicted to be quite standout, and at the same time provides less waste of materials. Insight discussions are elaborated in this paper.

Corrosion behavior of Sn-based lead-free solder alloys: a review

Sn-based lead-free solder alloys have been investigated widely to replace the traditional Sn–Pb solder alloys. Since the miniaturization of electronic products and the expansion of application field, the corrosion resistance of solder alloys play a key factor in the reliability of electronic products in long-term service. In this article, we review the recent progress on the corrosion behavior of Sn-based lead-free solder alloys by summarizing the results in representative ones of Sn–Bi, Sn–Cu, Sn–Zn, Sn–Ag, Sn–Ag–Cu and other multi-elements lead-free solder alloys. Specifically, the relationship between microstructure morphology and corrosion behavior, the corrosion mechanism of Sn-based lead-free solder alloys after incorporation of alloy elements or particles are summarized. It is hoped that this overview will provide some useful information in clarifying the corrosion mechanism and development of lead-free solder alloys. Furthermore, remaining difficulties and future trends in this research field are proposed.

Development of Geopolymer Ceramic as a Potential Reinforcing Material in Solder Alloy: Short review

Nowadays, the consumption of lead-free solder has been widely used around the world since the utilization of SnPb solder has been banned and restricted by European Union. Variety of studies have been conducted by the researchers to find an alternative to replace the usage of SnPb such as SnCu, SAC, SnAg and etc. However, the development of plain lead-free solder was declared to provide low mechanical, thermal, and electrical properties in terms of interfacial intermetallic compound and wettability towards its solder joint compare to the traditionally monolithic SnPb solder alloy. Mostly, previous studies stated that addition of some additives such as ceramic particles (Si 3 N 4, TiO 2, SiC, NiO and etc) may improves the solder joint reliability. At the same time, no major studies were done using geopolymer ceramic as reinforcing agent in plain matrix alloy. Therefore, this paper reviews the fabrication process of multiple geopolymer-based ceramic such as fly ash, kaolin, and slag as reinforcement in solder alloy. The development process includes the processing method of geopolymer ceramic and the characterization of geopolymer ceramic as reinforcing material consist of; i) chemical composition, and ii) phase identification.

The effect of Aluminium addition on the microstructure of lead-free solder alloys: A short review

The ban on using lead in electronic packaging has been taken effect since the year 2006. The alternative to replacing lead (Pb) based solder has been given highly concerns by the electronic industry. Both Sn- Ag-Cu and Sn-Cu solder alloys were considered to be the most acceptable candidates to replace SnPb solder alloy. From the findings, it showed that β-Sn appears as island-liked shape and eutectic phases appear as a darker shade. The grain size is refined significantly after incorporated with a suitable amount of Al. When exorbitant amount of Al addition will cause Al-rich particles, which has high potential to acts as the heterogeneous nucleation site and result in a lower degree of undercooling. The most desired amount of Al addition is between 0.025 - 0.05 wt%. The primary intermetallic compounds found in Sn-based solder alloy are Cu6Sn5 and Ag3Sn. New intermetallic compouds were found after addition of Al, which are Cu-Al and Ag-Al intermetallic. The formation of new intermetallic compounds causes the formation of Cu6Sn5 and Ag3Sn to be suppressed.

Temperature and strain-rate dependent constitutive model for prediction of thermal cycling life

With temperature cycling as the characteristic working environment of aerospace electronic chips, various constitutive models have been proposed to predict the failure problems of solder joints. However, most researchers adopted only a set of constant parameters to describe the solder joint material properties throughout the temperature cycles, which is obviously unreasonable concerning the possible wide range of working temperature. In fact, with the changing temperature and strain rate, some material parameters will correspondingly evolve as observed in the experiments. In this paper, the framework of the Anand constitutive model is adopted to verify the effect of material parameters of different temperatures and strain rates on the mechanical properties of materials under the scenario of temperature cycling. The lead-containing solder alloy 63Sn37Pb material that is most widely used in aerospace is selected as the solder material for the interconnection structure. In addition, a typical plastic ball grid array (PBGA) packaging structure is used to analyze the influence of the constitutive model parameters on the PBGA thermal fatigue life. Based on experimental data, seven sets of constitutive model parameters with different temperatures (-55°C~125°C) under a region of low strain rate (1×10-4/s) were employed to compare the mechanical properties of the material under temperature cycling. The sensitivity analysis of material parameters is performed and the underlying mechanism are also explained so that the present study can promote the optimization of the constitutive model in numerical simulations in practice.

Fabrication of Novel Geopolymer Reinforced Tin Copper Solder in Suppressing Intermetallic Layer Growth

Currently, lead-free composite solder technology system is the new approach that have been considered as a promising replacement for toxic SnPb solder alloy. Sn-0.7Cu was used as matrix solder alloy while fly ash geopolymer and kaolin geopolymer with different compositions (0.5 wt.%, 1.0 wt.%, and 1.5 wt.%) was added as a reinforcement to increase the properties of solder alloy. The solder composite was prepared by using powder metallurgy method which consist of mixing, compaction, and sintering process via microwave oven. Microwave sintering approach results in more uniform heating, lower pore coarsening with cost-effective and energy efficiency. The chemical composition and morphology of geopolymer reinforcement was analysed by using X-ray Flourescene and Scanning Electron Microscope. The influences of the geopolymer particulates in the monolithic matrix solder on the interfacial intermetallic compound thickness and wettability were investigated by using optical microscope, while the specific value was measured by using J-image software. The melting point temperature were investigated by using differential scanning calorimeter (DSC). The influences of adding types of geopolymer particulates into Sn-0.7Cu lead free solder were investigated in terms of interfacial intermetallic compounds (IMCs) and thermal properties. It is noted that several addition of fly ash geopolymer and kaolin geopolymer particles can remarkably supressed the thickness of intermetallic layer between composite solder and the substrate and thus gives higher melting temperature but somehow certain composition resulted low in mechanical properties. Overall, the addition of 0.5 wt.% of kaolin geopolymer reinforcements into Sn-0.7Cu lead-free improved all the listed properties of the solder materials.

Ratcheting assessment of visco-plastic alloys at ambient temperature by means of the A-V and O-W hardening rule frameworks

The present study evaluates ratcheting response of samples made of Z2CND18.12N Steel, Zircaloy-4, and 63Sn37Pb solder alloys subjected to asymmetric stress cycles with different stress levels and rates by means of the Ohno-Wang (O-W) and Ahmadzadeh-Varvani (A-V) isotropic-kinematic hardening rules. The framework of hardening rules was constructed on the basis of visco-plasticity constitutive equation to account for the effects of stress rate and time-dependency over ratcheting progress. Elements of visco-plasticity were adopted in the hardening rules on the basis of Chaboche's formulation to evaluate stress rate dependent ratcheting of materials at room temperature. The predicted ratcheting curves and stress-strain hysteresis loops on the basis of the O-W and A-V frameworks have compared with those of experimentally obtained. The A-V framework resulted in consistent ratcheting curves and hysteresis loops and better agreement with experimental data than the O-W framework at various stress ratios.

Investigation On Mixing Heat Effect Of Bi-In And In-Sn System At 730 K

Abstract In automotive industries, the circuit boards placed inside the vehicle experience greater thermal stress due to temperature in the excess of 150°C. It can be minimise by replacing hazardous Pb in Sn-Pb solder alloy, which reflect the development of Pb free solder alloy. Formation of alloy depends on its phase diagram followed by measurement of its thermodyanamical properties. In this work, investigation of mixing heat effect (mixing enthalpy) as partial enthalpy and integral enthalpies of mixing in liquid phase Bi-In and In-Sn system have been carried out at ambient temperature (730 K) by a drop Calorimeter over the entire composition of indium. The plot of enthaplyies enthalpies of mixing are plotted against indium and found exothermic in nature for all the compositions. The experimental data were used to determine the binary interaction parameters at 730 K and it is used to calculate the Redlich –Kister polynomial and compared with our experimental data. It has been observed that model value was close to experimental data for all compositions at 730 K

Experimental and numerical investigations of the vibration reliability of BGA and LGA solder configurations and SAC105 and 63Sn37Pb solder alloys

PurposeThis paper aims to investigate and compare the reliability performance of land grid array (LGA) and ball grid array (BGA) solders, as well as the SAC105 and 63Sn37Pb solder alloys, in vibration loading conditions.Design/methodology/approachReliability tests were conducted using a sine dwell with resonance tracking vibration experiment. Finite element simulations were performed to help in understanding the observed failure trends.FindingsReliability results showed that the tin-lead solders out-perform lead-free solders in vibrations loading. Additionally, the LGA solder type could provide a better vibration reliability performance than BGA solders. Failure analysis results showed that in LGAs, the crack is initiated at the printed circuit board side and at the component side in BGAs. In both types, the crack is propagated throughout in the intermetallic compound layer.Originality/valueIn literature, there is a lack of published data in the comparison between LGA and BGA reliability performance in vibration loadings. This paper provides useful insights in the vibration reliability behavior of the two common solder joint types.

Mechanical Property of Sn-58Bi Solder Paste Strengthened by Resin

Sn-58Bi solder has been widely used for microelectronics packaging due to its low melting point temperature, good wetting performance, good mechanical properties, and low cost. Compared with Sn-Bi solder alloy and Sn-Pb solder alloy, the strength and plasticity of Sn-Bi solder are not enough, due to the higher brittleness of bismuth, which thus limits the application of Sn-Bi solder. In order to improve the properties of Sn-Bi solder, a novel solder paste strengthened with resin was developed by mixing epoxy resin (ER) with Sn-58Bi solder, which enhanced the joint strength at a low cost. Aimed at the electronic industry, in this study, the spreadability of the novel solder paste was investigated, and the mechanical properties and microstructure of solder joints after reflow soldering were tested and analyzed. The results showed that when the content of epoxy resin was in the optimum range, the shear strength was significantly higher, reaching nearly twice that of Sn-58Bi solder alone.