Search Results (61)

The corrosion behaviors of newly developed solder alloys with excellent mechanical properties, Sn-2.5 Ag-1.0 Bi-0.8 Cu-0.05 Ni (SABC25108N) and Sn-1.5 Bi-0.75 Cu-0.065 Ni (SBC15075N), are analyzed to supplement the corrosion behavior of the limited corrosion data in Pb- and Zn-free solder compositions. A potentiodynamic polarization test is conducted on these compositions in a NaCl electrolyte solution, the results of which are compared with those of conventional Sn-3.0 (wt%) Ag-0.5Cu and Sn-1.2Ag-0.5Cu-0.05Ni alloys. The results indicate that SBC15075N exhibits the lowest corrosion potential and highest corrosion current density, thus signifying the lowest corrosion resistance. By contrast, SABC25108N exhibits the lowest corrosion current density and highest corrosion resistance. Notably, SABC25108N shows a slower corrosion progression in the active state and exhibits the longest passive state. The difference in corrosion resistance is affected more significantly by the formation and distribution of the Ag₃Sn intermetallic compound phase owing to the high Ag content instead of by the presence of Bi or Ni. This uniform dispersion of Ag₃Sn IMC phases in the SABC25108N alloy effectively suppressed corrosion propagation along the grain boundaries and reduced the formation of corrosion products, such as Sn₃O(OH)₂Cl₂, thereby enhancing the overall corrosion resistance. These findings provide valuable insights into the optimal design of solder alloys and highlight the importance of incorporating sufficient Ag content into multicomponent compositions to improve corrosion resistance. Full article

Ball Grid Array (BGA) failures are often dominated by stress concentrations at the outer solder joints, particularly under thermomechanical loading. To mitigate this issue, this study investigates the mechanical and reliability implications of optimizing the BGA solder joint array by removing the outermost rows and columns, positioning all connections directly beneath the silicon die. Two commonly used solder alloys—SAC305 and Sn37Pb—were selected to evaluate the effects of this optimized array design. A combined experimental and numerical approach was employed, including accelerated thermal cycling (–40 °C to 125 °C), in situ resistance monitoring, cross-sectional failure analysis, and finite element modeling (FEM) to assess fatigue behavior under the altered layout. The optimized array significantly improved performance for SAC305, yielding a 1.67× increase in mean cycles-to-failure and a 29% reduction in peak von Mises stress, with failure locations shifting from the corners to more evenly distributed areas beneath the die. Sn37Pb assemblies showed only a 1.01× improvement despite an 11% stress reduction, attributed to persistent shear-dominated failures at second-row joints. These results highlight the critical influence of joint array architecture and solder alloy selection on reliability, offering design-level guidance for applications prioritizing thermomechanical robustness with reduced I/O counts. Full article

This study investigates the microstructural changes and micromechanical responses of Pb-containing and Pb-free solder alloys subjected to various annealing conditions, with the goal of elucidating the relationship between microstructure evolution and micromechanical properties. Results indicate that grain size in SAC0307 and SAC305 significantly increases with annealing temperature, while that of Sn63Pb37 remains relatively stable. In Sn63Pb37, the Pb-rich phase coarsens and its area fraction increases with higher annealing temperatures, whereas in SAC0307, the intermetallic compounds (IMCs) phase coarsens but its area fraction decreases. Nano-indentation tests show that the hardness of Sn63Pb37 significantly increases with rising annealing temperature, whereas the hardness of SAC0307 decreases, and that of SAC305 remains relatively unchanged. These variations in these alloys induced by annealing are closely related to the changes in the hardness of individual phases within the grains. For Sn63Pb37, higher annealing temperatures increase the hardness of both the Sn matrix and Pb-rich phases, enhancing overall hardness. Conversely, in SAC0307, increased temperatures reduced the hardness of both the Sn matrix and IMCs phases, resulting in lower overall hardness. The differing trends in mechanical property of individual phases in three alloy are attributed to their distinct evolutions under annealing treatment. This study provides insights into the micromechanical behavior of solder alloys under annealing and offers guidance for optimizing their performance. Full article

Under the dual impetus of environmental regulations and reliability requirements, the Pb–free/Pb hybrid assembly process in aerospace-grade ball grid array (BGA) components has become an unavoidable industrial imperative. However, constrained process compatibility during single or multiple reflow protocols amplifies structural heterogeneity in solder joints and accelerates dynamic microstructural evolution, thereby elevating interfacial reliability risks at solder joint interfaces. This paper systematically investigated phase composition, grain dimensions, thickness evolution, and crystallographic orientation patterns of interfacial intermetallic compounds (IMCs) in hybrid micro-solder joints under multiple reflows, employing electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The result shows that the first reflow induces prismatic Cu₆Sn₅ grain formation driven by Pb aggregation zones and elevated Cu concentration gradients. Surface-protruding fine grains significantly increase kernel average misorientation (KAMave) of 0.68° while minimizing crystallographic orientation preference density (PF_max) of 15.5. Higher aspect ratios correlate with elongated grain morphology, consequently elevating grain size of 5.3 μm and IMC thickness of 5.0 μm. Subsequent reflows fundamentally alter material dynamics: Pb redistribution transitions from clustered to randomized spatial configurations, while grains develop pronounced in-plane orientation preferences that reciprocally influence Sn crystal alignment. The second reflow produces scallop-type grains with minimized dimensions of 4.0 μm and a thickness of 2.1 μm, with a KAMave of 0.37° and PF_max of 20.5. The third reflow initiates uniform growth of scalloped grains of 7.0 μm with a stable population density, whereas the fifth reflow triggers a semicircular grain transformation of 9.1 μm through conspicuous coalescence mechanisms. This work elucidates multiple reflow IMC growth mechanisms in Pb–free/Pb hybrid solder joints, providing critical theoretical and practical insights for optimizing hybrid technologies and reliability management strategies in high-reliability aerospace electronics. Full article

The self-healing characteristics of Al6061 reinforced with CuO have been examined experimentally. The solder alloys 60Pb40Sn and 99.3Sn0.7Cu with low melting points are incorporated to strengthen the Al6061 MMCs’; the self-healing properties have been investigated. Developed self-healing samples have undergone testing for hardness, tensile, and impact characteristics in accordance with ASTM standard test protocols. The findings demonstrate how the solder filling affects the mechanical characteristics of self-healed Al6061 alloy and its MMCs’. The results showed that the composites formed a decent bond between the solder and matrix, confirming successful fabrication. Pb-Sn filled samples demonstrated higher self-healing efficiency for tensile and impact of 90.02% and 90.30% with 6 wt.% of CuO, respectively, and Sn-Cu filled samples witnessed higher self-healing efficiency for tensile and impact of 91.81% and 91.09% with 6 wt.% of CuO respectively. However, the self-healed composite did not split in two when subjected to Charpy impact and tensile strength tests, and the healing efficiency of Sn-Cu-filled composites is higher than that of the Pb-Sn-filled composites. Full article

As semiconductor packaging technologies face limitations, through-silicon via (TSV) technology has emerged as a key solution to extending Moore’s law by achieving high-density, high-performance microelectronics. TSV technology enables enhanced wiring density, signal speed, and power efficiency, and offers significant advantages over traditional wire-bonding techniques. However, achieving fine-pitch and high-density interconnects remains a challenge. Solder flip-chip microbumps have demonstrated their potential to improve interconnect reliability and performance. However, the environmental impact of lead-based solders necessitates a shift to lead-free alternatives. This review highlights the transition from Sn-Pb solders to lead-free options, such as Sn-Ag, Sn-Cu, Sn-Ag-Cu, Sn-Zn, and Bi- or In-based alloys, driven by regulatory and environmental considerations. Although lead-free solders address environmental concerns, their higher melting points pose challenges such as thermal stress and chip warping, which affect device reliability. To overcome these challenges, the development of low-melting-point solder alloys has gained momentum. This study examines advancements in low-temperature solder technologies and evaluates their potential for enhancing device reliability by mitigating thermal stress and ensuring long-term stability. Full article

Resistance Element Soldering (RES) is one of the new methods of joining dissimilar materials by resistance heating using an element. Sn60Pb40 solder, which has been used for decades in tin smithing and the electrical industry, has already been tested for joining galvanized steel sheet with thermoplastic using RES. However, legal restrictions are currently moving towards prohibiting the use of lead in mass production. For this reason, the possibility of replacing Sn60Pb40 solder with Sn91Zn9 lead-free solder was verified. The results showed that with an appropriate choice of flux and resistance heating conditions, it is possible to replace Sn60Pb40 solder with Sn91Zn9 solder when joining galvanized steel sheet with thermoplastic using RES. With a suitable heat input during soldering, good conditions were achieved for wetting the base material with molten solder with a sufficient volume of remelted solder in the core of the Cu/Sn91Zn9 bimetallic element. The strength of the soldered joint made at a heat input of 901 J was measured at the level of 94% of the strength of Sn91Zn9 solder. Full article

Soldering with Sn alloys has always been the essential assembly step of microelectronics. The conductive Sn whiskers, which can spontaneously grow from soldering surfaces, mean a considerable reliability risk for microelectronics due to possible short circuit formation between the leads of the components. Since their discovery in 1951, thousands of research studies have been conducted to unravel their growth mechanisms and find effective prevention methods against them. Till 2006, the Sn whisker problem was solved and partially forgotten due to the very effective whisker suppression effect of Pb alloying into the solder materials. The lead-free change gave new impetus to the problem, which was further enhanced by the application of new material systems, growing reliability requirements, and accelerating miniaturization in the 21st century. Our review would like to give an overview of the Sn whisker’s history from the beginning till the latest results, focusing on the suppression solutions by the modification of the solder alloy compositions. Recently, promising results have been reached by alloying Bi and In, which are metals that are the focus of low-temperature soldering, and by composite solders. Full article

In this paper, In was introduced into SnPb eutectic solder to develop a new low-temperature solder for three-dimensional packaging technology. SnPbIn solders containing 5, 10, 13, 15 and 17 wt.% In were prepared through vacuum induction melting. The effect of the addition of In on the microstructure and thermal and mechanical properties of the SnPbIn solders was investigated. The results showed that the SnPb eutectic solder consisted of Sn(ss) and Pb(ss), but when the In content was higher than 5 wt.%, the SnPbIn solder included Sn(ss) and Pb(ss) and a new InSn4 phase. Solid dissolution of the In element into Sn(ss) and Pb(ss) preferentially occurred. The melting points of the SnPbIn solders gradually decreased with the increasing addition of the In element. The melting point of the Sn-Pb-13In solder decreased to 150.5 °C, which met the requirements of 2.5D packaging. But the cast Sn-Pb-5In solder reached the best tensile strength of 48.8 MPa and elongation of 27.3%. Super-plasticity occurred in the cold-rolled SnPbIn, while the 59.9Sn35.1 Pb5In solder achieved elongation of 382.0% and 408.6%, respectively, at deformation of 70% and 90%. The super-plasticity originated from the recrystallization behavior and soft orientation. Full article

This paper examined the reliability of complex PCB assemblies under random vibration and temperature cycling, which are two primary causes of assembly failure. A combination of finite element simulation and environmental testing was employed to investigate the effects of different reinforcement methods and solder joint morphology on assembly reliability. The linear accumulation of damage was utilized to predict assembly failure, and the predicted failure damage was compared with the damage extracted post-testing to validate the simulation analysis. The results indicate that SAC305 solder exhibits greater strength than Sn63Pb37 solder in withstanding temperature cycling fatigue, yet is weaker than Sn63Pb37 solder in withstanding random vibration fatigue. When the solder is Sn63Pb37, the temperature cycling life of the assembly with the bottom filled and the corners fixed is reduced by 92.3% and 99.3%, respectively, compared to the unreinforced method, while the random vibration life is enhanced by 84 times and 3.9 times, respectively. An increase in pad diameter is advantageous for improving the random vibration life of the assembly, but results in a decrease in the temperature cycling life. When the lower pad diameter ranges from 0.35 mm to 0.55 mm, the assembly temperature cycling life decreases by 28.83%, 82.03%, 90.66%, and 91.22% with the increase of the lower pad diameter, and the random vibration life improves by 4.8 times, 9.5 times, 20.4 times, and 33.6 times, respectively. The predicted locations of vulnerable solder joints for the assembly are consistent with the experimental results, and the failure prediction accuracy of the assembly is 88.89%. Full article

This study proposes a Sn58Bi/SAC305 layered composite solder designed for low-temperature applications. By alternating high-melting SAC305 and low-melting Sn58Bi layers, the composite achieves a liquidus temperature of ~180 °C, comparable to traditional Sn-Pb solder. Synchrotron X-ray imaging reveals dynamic interfacial interactions, including partial dissolution of SAC305 into molten Sn58Bi and Bi diffusion, mitigating segregation and forming defect-free interfaces with cellular structures. The 7-layer composite exhibits a peak shear strength of 44.3 ± 0.8 MPa at 200 °C, surpassing single Sn58Bi (41.8 ± 1.1 MPa) and SAC305 (31.6 ± 1.4 MPa), attributed to the refined microstructure and uniform dispersion of Ag₃Sn phases. Fracture analysis indicates mixed ductile–brittle failure modes influenced by intermetallic compounds (IMCs). This work provides insights into the role of layered structures in controlling element diffusion and interfacial reactions, advancing the design of low-temperature lead-free solders. Full article

The current development of soldering materials focuses on the properties of the solder itself, while the reliability of the joints formed after soldering is evaluated to a lesser extent. It is essential to understand the relationship between the structure and the strength of the solder joint obtained. This article shows that the properties of the material used for soldering only to a certain extent largely translate into the mechanical properties of the joint. The aim of this article is to emphasize the importance of the problem of the selection of the chemical composition of the solder with the simultaneous selection of the parameters of the soldering process, including the width of the solder gap for the selected strength properties of the connection. The purpose of this article is to emphasize that the selection of a chemical composition solder with a simultaneous selection of parameters of the soldering process, including the dimensions of the gaps of the soldered materials, are affected properties of the soldered joint. In this article, the main importance was focused on the chemical composition of a tin-based solder. The influence was analyzed, and the most favorable content of elements, such as Al and Cu, which create intermetallic phases, strengthening the soldered joint, was determined. The properties of the newly developed solder joint for alternator applications due to the specified conditions of the soldering process, including the width of the solder gap permissible for alternators, ensured the correct connections, the strength properties of which differed despite the use of the same soldering material and substrate material, as well as the soldering time and tip temperature. This article presents a change in the cracking model of a solder joint made using a newly developed material due to the width of the permissible solder gap in the production process of alternators. Full article

In order to reduce manufacturing costs, the design of silicon-based solar modules is changing from a super-multi-busbar design to a zero-busbar (0BB) design. In this study, two different 0BB technologies based on heterojunction with intrinsic thin-layer solar cells—conventional soldering, and Integrated Film Covering (IFC)—were investigated. IFC-based 0BB technology was found to have a lower contact resistance, which well matches the theoretical calculations and module power testing results. To further measure module reliability, a series of tests on solders and silver pastes were carried out. The results show that Sn43Pb43Bi14 solder is more suitable for soldering-based 0BB technology, whereas Sn32Pb42Bi26 solder is more suitable for IFC-based technology. Additionally, silver paste, which is used for solder ribbon contact areas (SRCAs), is suitable for soldering-based 0BB technology. When Ag@Cu paste is used in SRCAs with IFC-based 0BB technology, a reliable connection can also be achieved. After optimization, modules using both techniques were subjected to and passed lifetime tests, including the thermal cycling, humidity freeze, and hot-spot tests required in IEC standards, as well as more rigorous tests such as thermal–dynamic and thermal–static mechanical loading. The results show that the two technologies have great potential for future mass production. Full article

Intermetallic compounds (IMCs) growth can simultaneously bring about low-resistance electrical pathways and drastically reduce joint lifetime. Recently, incorporated trace nanoparticles into the free-Pb solder were found to promote the performance of the solder joints. Sn3Ag0.9Zn (SAZ) nano-composite solders were developed by doping 0.5 wt.% Al₂O₃ nanoparticles into the SAZ solder. The IMCs formation and growth behavior at the interfacial reactions between the SAZ-0.5Al₂O₃ nano-composite solder and the Cu substrate during soldering at temperatures ranging from 250 to 325 °C for 30 min were investigated. The results showed that after the addition of Al₂O₃ nanoparticles into the SAZ solder, the elongated-type IMCs layer changed into a prism-type IMCs layer, and Ag₃Sn nanoparticles were absorbed on the grain surface of the interfacial Cu₆Sn₅ phase, effectively suppressing the growth of the IMCs layers. The activation energies (Q) for the IMCs layers (Cu₆Sn₅ + Cu₃Sn) were determined to be 36.4 and 39.1 kJ/mol for the SAZ/Cu and SAZ-Al₂O₃/Cu solders, respectively. Full article

Throughout much of the 20th century, Sn–Pb solder dominated electronics. However, environmental and health concerns have driven the adoption of lead-free alternatives. Since 2006, legislation such as the European Union’s RoHS Directive has mandated lead-free solder in most electronic devices, prompting extensive research into high-performance substitutes. Lead-free solders offer advantages such as reduced environmental impact and improved reliability but replacing Sn–Pb presents challenges in areas like melting point and wetting ability. This transition is primarily motivated by a focus on protecting environmental and human health, while ensuring equal or even improved reliability. Research has explored lead-free solder’s mechanical properties, microstructure, wettability, and reliability. However, there is a notable lack of studies on its long-term performance and lifetime influence. To address this gap, mathematical models are used to predict intermetallic bond evolution from process conditions, validated with experimental tests. This study contributes by extending these models to predict bond evolution under typical operating conditions of devices and comparing the predictions with actual intermetallic thickness values found through metallographic sections. Full article