Sn-Bi Solder Research Articles

Correction: Effect of cobalt nanoparticles on mechanical properties of Sn–58Bi solder joint

Correction: Effect of cobalt nanoparticles on mechanical properties of Sn–58Bi solder joint

Growth behavior and reliability of interfacial IMC for Sn58Bi/Cu and Sn58Bi–AlN/Cu solder joints applied in IGBT modules

The IMC (interfacial intermetallic compound) produced by the metallurgical reaction between the solder and the Cu plate enables the packaging of IGBT (insulated gate bipolar transistor) modules. In this paper, the growth behavior of IMCs of Sn58Bi/Cu and Sn58Bi-0.05AlN/Cu at different times (10, 30 and 60 min) and temperatures (200, 250 and 300 °C) was investigated, which can provide a reference for the connection of IGBT. It was shown that the interfacial IMC thickness of both solders increased with time and temperature, but the growth of interfacial IMC was suppressed for Sn58Bi solder containing 0.05 wt% AlN. The effect of AlN on the inhibition of grain growth was also observed by EBSD testing. Because of the adsorption effect of AlN nanoparticles, they can adhere to the surface of IMC layer and decrease the effective the diffusion path of unreacted Cu atoms, thereby inhibiting the growth of interfacial IMC. And the effect of AlN particles on interfacial IMC was analyzed via phase field simulation. In addition, under the heating conditions with high temperature and long time, there were fewer cracks in the solder joints containing AlN particles, compared to the Sn58Bi solder. Therefore, AlN nanoparticles can enhance the reliability of Sn58Bi/Cu solder joints.

Effect of cobalt nanoparticles on mechanical properties of Sn–58Bi solder joint

Effect of cobalt nanoparticles on mechanical properties of Sn–58Bi solder joint

Effects of tin particles addition on structural and mechanical properties of eutectic Sn–58Bi solder joint

Effects of tin particles addition on structural and mechanical properties of eutectic Sn–58Bi solder joint

Understanding the surface segregation of solute atoms in Sn-Bi–based solder from first principles

Low-temperature Sn-Bi solder has wide application in the field of electronic packaging due to its low melting point and good wettability. The formation of Bi-rich phase and intermetallic compound is the major concern for the reliability of Sn-Bi solder joints. We employed first-principles calculations to understand the segregation of Bi and the third elements to the surface of Sn. The effects of alloying elements on inhibiting the Bi surface segregation were described. Our calculations show that the Bi surface segregation could be effectively alleviated by the addition of Ag, Ga, Ni, and In, along with the reduction of further possible formation of intermetallic compounds in the Sn-Bi–based solders. The results could be interpreted by the enhanced bond orders between Bi and its neighboring Sn, alloying elements.

Damping properties of Sn58Bi and Sn3.0Ag0.5Cu solders with different thicknesses and preparation directions

PurposeThis study aims to experimentally assess the effect of thickness and preparation direction on the damping properties of Sn58Bi and Sn3.0Ag0.5Cu solders.Design/methodology/approachSn58Bi and Sn3.0Ag0.5Cu solder strips with different thicknesses were prepared from the bulk in longitudinal and horizontal directions, and the ratio of loss modulus and storage modulus of the samples was measured by the dynamic mechanical analysis method as the index of damping properties.FindingsSn58Bi and Sn3.0Ag0.5Cu solders exhibited viscoelastic relaxation, and their damping properties decreased with decreasing thickness. The damping properties of both solders had no obvious difference in longitudinal and horizontal directions. Sn58Bi has a more obvious high-temperature damping background than Sn3.0Ag0.5Cu solder. In addition, compared with Sn58Bi solder, Sn3.0Ag0.5Cu solder had an obvious internal friction peak, which moved toward high temperature with increasing frequency. The activation energies of Sn58Bi solder with a thickness of 0.5 mm at the longitudinal and horizontal directions were 0.84 and 0.67 eV, respectively, which were 0.39 and 0.53 eV, respectively, for the Sn3.0Ag0.5Cu solder.Originality/valueThe damping properties of Sn58Bi and Sn3.0Ag0.5Cu solder decreased with decreasing thickness, while their damping properties changed insignificantly when they were prepared from different directions. The internal friction peak of Sn3.0Ag0.5Cu solder moved to higher temperatures with increasing frequency.

Effects of Mo nanoparticles addition on the evolution of microstructure in Cu58Bi-xMo/Cu solder joints during aging

A novel composite lead-free solder was prepared by adding Mo nanoparticles in Sn58Bi solder. Microstructure evolution of Sn58Bi-xMo(x = 0, 0.5%,1%)/Cu solder joints were investigated during aging process at different temperature. The results reveal that Mo nanoparticles significantly inhibited the growth of Cu6Sn5 compounds layer in solder joints, but had little influence on Cu3Sn compounds layer. The diffusion coefficients of atoms at different aging temperature were calculated. It was observed that several Cu6Sn5 compounds layer began to separate and diffuse into solder when Sn58Bi-0.5%Mo/Cu and Sn58Bi-1%Mo/Cu joints were aged for 240 h at 130 ℃. The influence mechanisms of Mo nanoparticles on the growth of Cu6Sn5 and Cu3Sn compounds were analyzed.

Microstructure and mechanical properties of Sn–Bi solder joints reinforced with Zn@Sn core–shell particles

Microstructure and mechanical properties of Sn–Bi solder joints reinforced with Zn@Sn core–shell particles

Board Level Drop Test for Evaluating the Reliability of High-Strength Sn–Bi Composite Solder Pastes with Thermosetting Epoxy

The Sn–Bi solder paste is commonly used in electronic assembly and packaging, but its brittleness causes poor reliability in shock environments. In this study, the mechanical reliability of Sn–Bi solder paste and Sn–Bi composite solder paste with thermosetting epoxy (TSEP Sn–Bi) was investigated with the board level drop test. The crack characterizations of solder joints were evaluated using a stereomicroscope after the dye and pull test. The microstructure characterization and failure types of solder joints were analyzed by a scanning electron microscope (SEM), and an energy dispersive spectrometer (EDS) was employed to investigate the initial phase identification and elemental analysis. Compared with Sn–Bi solder paste, the results show that the TSEP Sn–Bi solder pastes reduced the proportion of the complete failure and partial failure of the solder joints during the drop test. The microstructure observation of the crack path showed that the Sn–Bi/TSEP Sn–Bi solder joints were reinforced through the cured epoxy resin. The number of drops of the Sn–Bi/TSEP Sn–Bi-x (x = 3, 5, 7) solder joints had 1.55, 2.57, and over 3.00 times that of Sn–Bi/Sn–Bi solder joints after the board level drop test.

Effect of remelting heat treatment on the microstructure and mechanical properties of SnBi solder under high-speed self-propagation reaction

The heat source based on the self-propagation reaction of Al/Ni thin foil has the characteristics of concentrated heat, fast temperature rise/fall rate and small heat-affected zone; it can complete the melting and solidification crystallization of solder within milliseconds to realize solder interconnection, which can solve the problems of damage to heat-sensitive materials and components caused by monolithic heating of package structure. However, due to the highly non-stationary interconnection process, the resulting microstructure morphology may affect the service performance of the interconnected joints. In view of this, to investigate the post-solder microstructure of solder based on the self-propagation reaction, this paper analyzes the effect of the initial microstructure on the post-solder microstructure by heating 300-μm-thick SnBi solder with a 40-μm Al/Ni thin foil. The results indicated that the short melting time could resulted in the incomplete melting of heterogeneous phases and the non-uniform distribution of elements during the melting process, which had a significant effect on the morphology and composition distribution of the solidified microstructure, as well as the hardness distribution of the melted zone. The above conclusions have the potential to improve the interconnection process based on the self-propagation reaction, which is critical for both theoretical guidance and engineering application.

Enhancement of structure and properties of Sn58Bi solder by AlN ceramic particles

The Sn58Bi composite solders reinforced by AlN ceramic particles was prepared by mechanical mixing method. The melting characteristics, wettability, microstructure, interfacial intermetallic compounds (IMC) layer, and mechanical properties of Sn58Bi-xAlN (x = 0, 0.03, 0.05, 0.07, 0.1, 0.2 wt.%) composite solders were systematically investigated, and influence mechanism of AlN ceramic particles on the Sn58Bi solder was analyzed. The experimental results show that the wetting area and shear strength of Sn58Bi–AlN composite solders present a trend of first increasing and then decreasing. At the AlN ceramic particles content of 0.05 wt.%, the wettability and mechanical properties of the Sn58Bi are enhanced considerably. However, the wettability, mechanical properties of Sn58Bi are reduced when the content of AlN ceramic particles is high. The melting temperature of Sn58Bi-0.07AlN composite solder is increased slightly. The addition of AlN particles can inhibit the growth of interfacial IMC, where the inhibition effect is more obvious for AlN content of 0.05 wt.% and 0.07 wt.%. Therefore, the addition of an appropriate amount of AlN ceramic particles can improve the comprehensive performance of Sn58Bi solder to a certain extent.

A New Low-Temperature Solder Assembly Technique to Replace Eutectic Sn-Bi Solder Assembly.

We successfully achieved low-temperature assembly by reflowing the 13.5Sn-37.5Bi-45In-4Pb quaternary eutectic solder paste and the SAC 305 solder ball together at 140 °C for 5 min. The wetting angle of the mixed solder joint is 17.55°. The overall atomic percent of Pb in the mixed solder joint is less than 1%, which can be further reduced or eliminated. Moreover, after aging at 80 °C for 25 days, we observed no obvious decrease in shear strength of the fully mixed solder joint, which is the most advantage of this assembly technique over Sn58Bi solder assembly. The Bi phase segregation at the interface is slowed down compared with Sn-Bi solder joint. This low-temperature assembly is promising to be applied in advanced packaging technology to replace the eutectic Sn-Bi solder.

Effects of alloying element on mechanical properties of Sn-Bi solder alloys: a review

PurposeThis paper aims to review recent reports on mechanical properties of Sn-Bi and Sn-Bi-X solders (where X is an additional alloying element), in terms of the tensile properties, hardness and shear strength. Then, the effects of alloying in Sn-Bi solder are compared in terms of the discussed mechanical properties. The fracture morphologies of tensile shear tested solders are also reviewed to correlate the microstructural changes with mechanical properties of Sn-Bi-X solder alloys.Design/methodology/approachA brief introduction on Sn-Bi solder and reasons to enhance the mechanical properties of Sn-Bi solder. The latest reports on Sn-Bi and Sn-Bi-X solders are combined in the form of tables and figures for each section. The presented data are discussed by comparing the testing method, technical setup, specimen dimension and alloying element weight percentage, which affect the mechanical properties of Sn-Bi solder.FindingsThe addition of alloying elements could enhance the tensile properties, hardness and/or shear strength of Sn-Bi solder for low-temperature solder application. Different weight percentage alloying elements affect differently on Sn-Bi solder mechanical properties.Originality/valueThis paper provides a compilation of latest report on tensile properties, hardness, shear strength and deformation of Sn-Bi and Sn-Bi-X solders and the latest trends and in-depth understanding of the effect of alloying elements in Sn-Bi solder mechanical properties.

The Effects of Temperature and Solute Diffusion on Volume Change in Sn-Bi Solder Alloys

The different rates of thermal expansion of the many materials that make up an electronic assembly combined with temperature fluctuations are the driver of the thermal fatigue failure of solder joints. A characteristic of the Sn-Bi system, which provided the basis for many of the low process temperature solder alloys that the electronics industry is now adopting, is the very temperature-sensitive solubility of Bi and Sn in the other phase. In this study, in situ synchrotron powder x-ray diffraction was used to characterize the temperature dependence of the lattice parameters of the βSn and Bi phases in Sn-57wt%Bi and Sn-37wt%Bi. The effects of temperature and solute were separated by comparing with the data from pure βSn and pure Bi and verified using density functional theory calculations. Furthermore, the coefficients of thermal expansion of βSn and Bi during heating were also derived to reveal the thermal expansion behavior.

Impact of 3% Molybdenum(Mo) nanoparticles on the interfacial and shear properties of lead-free Sn58Bi/Cu solder joint

The research investigates the impact of 3 % molybdenum (Mo) nanoparticles onthe interfacial properties and shear stress of the leadfree Sn58Bi (SB) solder joint. The research aims to providea resemblance between the interfacial and shear properties withthe additions of Mo nanoparticles. The interfacial between Mo added to the solder joint comprises of the common intermetallic (IMC) layer of Cu6Sn5andadditional IMCs of MoSn2. that acted as further strengthening mechanism for the joint. Therefore, the shear strength of Mo reinforced solder joint was 32% higher compared to the pristine solder. The introduction of Mo into the SB solder resulted in an advantageous outcome.

Effect of temperature on shear properties of Sn-3.0Ag-0.5Cu and Sn-58Bi solder joints

Microelectronic devices with advanced capabilities, such as multi-functions, high input/output densities, and high capacities, have recently found extensive application in areas such as servers, big data, data centers, IoT, and supercomputing. Owing to the diverse operating conditions of these applications, the reliability of the microelectronic packaging depends on the integrity of the soldered joints at various (high) operating temperatures. In this study, the mechanical shear properties of Sn-3.0Ag-0.5Cu (SAC305) and Sn-58Bi (in wt%) solder joints were studied using a ball shear test at various temperatures on substrates with two types of surface finish: organic solderability preservative (OSP) and electroless nickel-electroless palladium-immersion gold (ENEPIG). The joint strength, force-displacement curve, and fracture energy were measured and calculated for each joint, and the correlations between solder alloys, operating temperatures, and joint mechanical behaviors were revealed. In the case of the SAC305 solder, regardless of the substrate, with increasing temperature, the shear force decreased, fracture distance increased, and the fracture energy decreased. In addition, the fracture was predominantly ductile. In the case of the Sn-58Bi solder, with increasing temperature, the shear force decreased, and the fracture distance increased slightly and then decreased (OSP substrate) and kept constant then decreased (ENEPIG substrate), and the fracture energy decreased. Although ductile fracture occurred at low temperatures, the brittle fracture proportion gradually increased as the temperature increased. Further, the microstructure significantly affected the mechanical properties and fracture behavior of the SAC305 and Sn-58Bi solder joints.

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.

A Study on Transmission properties of AuNi coated polymer ball joint and Sn58Bi solder joint for flex-on-board interconnection

Flex-on-board (FOB) interconnection plays an important role in display applications. Due to the thinness of the interconnect, the contact resistance of anisotropic conductive film (ACF) joints is very small; however, the transmission property of ACF joints are still unknown. In this study, we designed a novel coplanar waveguide structure to characterize the transmission properties of ACF joints in FOB interconnections. Specifically, we compared the differences between the Au/Ni coated polymer ball joint and low melting point Sn58Bi solder ball joint in terms of their high frequency performance. Both were bonded under the same conditions of 200 °C for 10 s at 2 MPa. A high frequency test was then carried out in the range of 300 MHz to 20 GHz. The results showed that 14 GHz was the resonant frequency of FOB package that contained the Au/Ni coated polymer ball joints, while 1 GHz increased by using Sn58Bi solder joints in FOB package. To our knowledge, there is the first study to determine the high frequency performance of flex-on-board interconnections using ACFs joints and the coplanar waveguide method.

Isothermal Aging Effect on Sn-58Bi Solder Interconnect Mechanical Shear Stability

Isothermal Aging Effect on Sn-58Bi Solder Interconnect Mechanical Shear Stability

Microstructural Evolution of Cu/Sn-58Bi/Sn-3.0Ag-0.5Cu Composite Solder Joint during Isothermal Aging

A composite solder joints made of Cu/Sn-58Bi/Sn-3.0Ag-0.5Cu (in weight percent) was successfully fabricated. The composite solder was made from combining a Sn-3.0Ag-0.5Cu solder ball and Sn-58Bi solder paste. The composite solder was reflowed on Cu-OSP (copper-organic solderability preservatives) substrate to form a composite solder joint. The microstructure evolution of the composite solder joints under different reflow temperature and thermal aging conditions were investigated using an optical microscope. This study shows that a composite solder joint of SAC305/Sn-58Bi can be assembled at lower temperature (160 °C) and gradually mixed through isothermal aging.