Joint Failure Research Articles

Effect of the Electrogalvanized and Galvannealed Zn Coatings on the Liquid Metal Embrittlement Susceptibility of High Si and Mn Advanced High-Strength Steel

The advanced high-strength steels (AHSSs) with high Si and Mn contents are extensively applied in the automobile manufacturing industry. To improve the corrosion resistance, Zn coatings are generally applied to the steel substrate. However, heat input and tensile stress occur during the resistance spot welding (RSW) process; thus, Zn-induced liquid metal embrittlement (LME) can be produced due to the existence of liquid Zn. Unfortunately, the LME occurrence can trigger the premature failure of welded joints, seriously affecting the service life of vehicle components. In this study, the LME behaviors in high Si and Mn RSW joints with electrogalvanized (EG) and galvannealed (GA) Zn coatings were comparatively investigated. Based on the Auto/Steel Partnership (A/SP) criterion, 16 groups of different welding currents were designed. In particular, four typical groups of RSW joints were selected to reveal the characteristics of the LME behaviors. Moreover, these four typical groups of EG and GA high Si and Mn RSW joints were, respectively, etched to measure their nugget sizes. The results indicated that with the increase in the welding current, more severe LME cracks tended form. As determined during the comprehensive evaluation of the 16 groups of EG and GA welded joints, higher LME susceptibility occurred in the EG high Si and Mn steels. It was concluded that the formation of Fe-Zn intermetallic compounds (IMCs) and internal oxide layers during the annealing process could account for the lower LME susceptibility in the GA welded joints.

Dorsoradial ligament reconstruction versus imbrication for restoring trapeziometacarpal joint stability: a comparative biomechanical study

The unique saddle articulation of the trapeziometacarpal joint allows for a wide range of motion necessary for routine function of the thumb. Inherently unstable characteristics of the joint can lead painful instability. In this study, we modified a surgical dorsal ligament reconstruction technique for restoring trapeziometacarpal joint stability. We evaluated and compared the biomechanical efficacy of our reconstruction technique with that of dorsoradial capsulodesis by creating a cadaveric model of rotational instability. Twenty-four specimens were subjected to dorsoradial capsulodesis (n = 12) or dorsoradial ligament reconstruction using the abductor pollicis longus (APL) (n = 12). The modified dorsoradial ligament reconstruction entailed detaching one distally based slip of the APL. The harvested tendon’s proximal end was passed through a bone tunnel created at the dorsoradial ridge of the trapezium. A suture anchor was inserted at the dorsal base of the metacarpal bone. The tendon stump was sutured to the metacarpal bone using fiber wire in figure-of-eight configuration. The load to failure of the trapeziometacarpal joint under compression was higher in the reconstruction group (p = 0.003). The improvement in the rotational arc (observed in all specimens) was significantly greater in the reconstruction group than the capsulodesis group (p = 0.003). Our technique reconstructs only the necessary ligament, requires a smaller incision and relatively simpler surgical procedure, and enables precise determination of the insertion and exit sites of the tendon, making it a promising treatment for trapeziometacarpal joint instability.

Study of friction stir welding effects on the microstructure & mechanical properties of AA3003 pipes

Abstract In the present study, similar Aluminum (AA3003) alloy pipes with a thickness of 5 mm were friction stir welded using a high-speed steel (HSS) tool with a cylindrical pin profile. Welding was done at three different rotational speeds and three traverse speeds corresponding to pipes of three different diameters. Six combinations of rotational speed and traverse speed were used to observe the effect of energy input on the properties, specifically tensile strength and microhardness, as well as grain size of the resulting microstructure. This systematic variation in welding parameters was designed to assess how changes in energy input influence both the mechanical performance and microstructural attributes of the welded joints. The tensile test results indicated that an ultimate tensile strength (UTS) of 84% relative to the base metal was achieved at a rotational speed of 900 rotations per minute(rpm) and a traverse speed of 131.94 mm/min. The impact energy corresponding to these parameters was found to be 38% more than base metal which is a remarkable contribution. This combination of welding parameters facilitated optimal material flow and bonding, resulting in improved tensile properties of the welded joint. Additionally, the tensile results showed a consistent pattern in the tensile failure of the welded samples, where the joint failure occurred at the location with the lowest hardness in the welded region. This correlation highlights the critical influence of hardness distribution on the structural integrity of the welds, indicating that areas with reduced hardness are more prone to failure under tensile loading of FSWed joints.

FAULT-TOLERANT ADAPTIVE CONTROL OF A WALKING HEXAPOD WITH FAILURE OF ONE LEG

The article is devoted to the improvement of the control system of a walking mobile robot with six legs (hexapod) in order to ensure its stable movement in case of damage or failure of one limb. A tripod gait is considered as the basic movement algorithm. The failure of one of the joints is considered as a failure of the limb. To ensure movement in the event of failure of one limb, a tripod walking algorithm has been developed, which ensures that each of the defect-free limbs remains in the stage of stable support during two phases of movement in a row. The evaluation of the possibility of fault-tolerant gait of the hexapod according to the developed algorithm was performed on the basis of support triangles and a quadrangle between the limbs that are in the support phase. The structural and functional synthesis of the system of fault-tolerant adaptive control of the hexapod, which consists of the following modules and subsystems, was performed: module of the dynamic model of the robot; basic gait algorithm module; subsystem of executive elements; diagnosis and decision-making subsystem; a subsystem of alternative gait algorithms. The structural and functional scheme of the control channel was developed and substantiated for the implementation of the algorithm for diagnosing the joint of one limb, making a decision about its condition and switching to the continuation of the basic gait algorithm, if the condition of the joint is assessed as defect-free. The scheme of the control channel for switching to the execution of an alternative gait algorithm, if the condition of the joint is assessed as defective, has been developed and substantiated. The proposed structural and functional solutions are generalized for the case of failure of other joints of the considered limb and other limbs of the hexapod. It is shown that based on the detection and localization of joint failures of the hexapod limbs, the reconfiguration of the gait algorithm and the control system takes place, and in this way a fault-tolerant adaptive control of the movement of the hexapod is realized. The implementation of the proposed alternative tripod gait algorithms and control channels in the fault-tolerant adaptive control system will ensure stable movement of the hexapod in case of failure of one of the limbs.

Research on the Influence of Liquid Metal Embrittlement Cracks on the Strength and Fatigue Life of Spot-Welded Joints of Galvanized Q&P980 Steel.

Galvanized high-strength steel has emerged as a key focus in automotive lightweighting research. During resistance spot welding of galvanized steel, the phenomenon of liquid metal embrittlement (LME) can occur, which is characterized by the appearance of irregular cracks on the weld spot surface. However, the impact of LME cracks on the mechanical properties of joints remains unclear. This study investigates the LME phenomenon and its effects on the performance of spot-welded joints using galvanized QP980 steel as the subject. By combining theoretical analysis, experimental methods, and simulations, the formation and characteristics of LME cracks are explored through resistance spot welding experiments and elemental analysis. The influence of LME cracks on the static strength of joints is assessed through quasi-static tensile tests, fracture surface analysis, and theoretical calculations. Finite element simulations of the static tensile process reveal that LME cracks alter the stress-strain fields during joint failure. Additionally, the study examines how the location and size of LME cracks influence these effects. Finally, fatigue testing and fracture analysis of spot-welded joints demonstrate that LME cracks can negatively impact the fatigue life of joints.

Numerical investigation of existing RC exterior beam-column joints under cyclic loading: case study of 1971 algerian building

Many reinforced concrete (RC) buildings constructed in Algeria before the 1980s may have serious structural deficiencies and are considered substandard according to the Algerian seismic code. Specifically, the failure of the beam-column joints has been the cause of building collapse in many earthquakes in the past: Alasnam October 10, 1980 and Boumerdes May 21, 2003. In this work, the behavior of RC exterior beam-column joints under quasi-static cyclic loading is studied by 3D nonlinear finite element analysis using ANSYS software. To perform the non-linear analysis, the load was applied step by step and the modified Newton-Raphson method was used for the solution. In order to prove that the program successfully captures the necessary response parameters without any modifications to the structure details, some available experimental works were modeled and non-linearly analyzed using ANSYS. Moment-rotation and load-displacement relationships were compared with the experimental data. It was observed that the results are quite similar to each other. Thereafter, a typical RC exterior beam-column joint belonging to a building constructed for residential use in Algeria in 1971 was modeled using ANSYS. The joint was subjected to quasi-static cyclic loading, and its performance was examined in terms of load resistance and failure. The moment-rotation hysteresis curve has been established. The hysteretic loops of the joint, representing the existing structure, showed stiffness degradation and strength deterioration.

Surface/Interface behaviour of atmospheric plasma sprayed NiTi alloy on stainless steel with the variation of critical plasma spray parameter

NiTi equiatomic composition is used in atmospheric plasma spraying (APS) machine to coat the stainless steel substrate. APS was conducted with varying critical plasma spraying parameters (CPSP) using NiTi powder as a coating element. After coating, the surface and interface morphology were characterised by XRD, SEM, and hardness tester. Higher CPSP yields better surface morphology. Surface roughness and porosity percentage decrease, and hardness increases from (455–844) Vickers hardness number with CPSP. The residual stress varies from 73 ± 1.1 MPa to −95 ± 1.9 MPa which shows the stress conversion of coating from tensile to compressive with an increase in CPSP. Coating failure occurs as a combined result of adhesion, cohesion and glue joint failure. At 865 CPSP, coating shows highest adhesion strength 42.13 MPa.

Experimental and theoretical studies of malleable flange joints

This paper presents the results of a study of pliable flange connections in steel frame. Calculation of the load carrying capacity and ductility of flange connections is an important design stage and requires consideration of various factors such as analysis of mechanical properties of materials, geometry, operating conditions and type of loads. The main objective of structural design is to ensure structural safety while minimizing cost. For this purpose, it is necessary to use calculation schemes that correspond to the real physical operation of structures. In solving this problem, the following were used: full-scale experiments, finite element method and analytical method of limit equilibrium (LEM), which is traditionally used in structural fracture mechanics. The influence of bending stiffness of the flange on the process of joint failure is investigated. A new design solution of a pliable beam-column assembly is proposed, which is characterized by simplicity of calculation and assembly.

Failure Analysis of Al 6082 Joints Processed by FSW and SFSW

This paper presents a failure analysis of Al 6082 joints processed by Friction Stir Welding (FSW) and Self-Reacting Friction Stir Welding (SFSW) techniques. Aluminium alloy Al 6082 is commonly used in structural and automotive applications due to its excellent strength, corrosion resistance, and weldability. The study focuses on investigating the failures encountered in FSW and SFSW joints of Al 6082. Macroscopic and microscopic examinations are conducted to analyse the root causes of these failures. Macroscopic observations include visual inspection, dimensional measurements, and identification of fracture locations. Microscopic investigations utilize techniques such as optical microscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) to examine the microstructure, fracture surfaces, and elemental composition of the failed joints. The results of this failure analysis contribute to the understanding of Al 6082 joining processes using FSW and SFSW methods. By identifying the failure mechanisms and proposing preventive measures, this research aids in improving the quality and performance of Al 6082 joints, thereby ensuring the integrity and reliability of joined structures in industries that rely on aluminium alloys for critical applications.

Failure Analysis of AA 7075 Joints Processed by FSW and SFSW

This paper presents a failure analysis of AA 7075 Aluminium 7075 joints processed by Friction Stir Welding (FSW) and Submerged Friction Stir Welding (SFSW) techniques. AA 7075 is a high-strength aluminium alloy commonly used in aerospace, automotive, and other industries due to its excellent mechanical properties. Understanding the failure mechanisms in these joining processes is essential for ensuring the structural integrity and reliability of AA 7075 joints. The study investigates the failures encountered in FSW and SFSW joints of AA 7075. Macroscopic and microscopic examinations are conducted to analyse the root causes of these failures. Macroscopic observations include visual inspection, dimensional measurements, and identification of fracture locations. Microscopic investigations utilize techniques scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) to examine the microstructure, fracture surfaces, and elemental composition of the failed joints. Based on the failure analysis findings, recommendations are provided to enhance the quality and reliability of AA 7075 joints processed by FSW and SFSW. The results of this failure analysis contribute to the understanding of AA 7075 joining processes using FSW and SFSW methods. By identifying the failure mechanisms and proposing preventive measures, this research aids in improving the quality and performance of AA 7075 joints, thereby ensuring the integrity and reliability of joined structures in industries that rely on aluminium alloys for critical applications.

Effect of integrity degradation caused by fatigue damage on impact failure for automotive FSSW Al alloy joints

Effect of integrity degradation caused by fatigue damage on impact failure for automotive FSSW Al alloy joints

Counteracting Effect of Sn Grain Orientation on Current Crowding in Electromigration Failures of Solder Joints

AbstractElectromigration (EM) failure in solder joints is a persistent reliability concern, especially in advanced electronic packaging structures. In this study, we conducted an EM experiment on solder joints with asymmetric under-bump-metallization (UBM) thicknesses. Open failure occurred at the solder joint with no current crowding effect but the highest atomic flux of EM, which is related to Sn grain orientation. Our work tries to reveal a counteracting effect of Sn grain orientation on current crowding and the essential reason for the EM failure mechanism of solder joints. Graphical Abstract

Microstructure degradation and creep failure study of the dissimilar metal welded joint of heat-resistant steel and Inconel 617 alloy tested at 650 °C and applied stress range of 100–150 MPa

The advanced ultra-supercritical (A-USC) power plant system is anticipated to become India's next-generation base-load power station. To adopt AUSC technology, dissimilar welded joints (DWJs) between heat-resistant steels and the nickel-based alloys, using the nickel-based fillers, will need to be implemented. However, failure of dissimilar welded joints from P92 steel base metal or the heat affected zone (HAZ) has been commonly observed under high-temperature creep conditions. In the present study, the creep rupture behaviours and rupture mechanisms of DWJ between the Ni-based alloy Inconel 617 and heat-resistant P92 steel with Inconel 617 (ERNiCrCoMo-1) filler metal were investigated. Creep tests were conducted at 650 °C in the stress range of 100–150 MPa. To examine the creep rupture behaviour of the DWJ samples, optical microscopy (OM), scanning electron microscopy (SEM) and microhardness tests were performed. Cross-sectional images of the fractured creep specimens tested under various operating conditions revealed failures originating from distinct locations, including the P92 base metal and the inter-critical heat affected zone (HAZ). The specimen tested at 650 °C/150 MPa exhibited failure originating from the P92 base metal, whereas the specimen tested at 650 °C under the stress range of 100–130 MPa showed failure from the inter-critical heat affected zone (ICHAZ). The failure from P92 BM was primarily governed by plastic deformation, with the growth and coalescence of dimples ultimately resulting in trans-granular fracture. The specimens tested at 650 °C/100–130 MPa, which failed from the ICHAZ, exhibited a typical Type IV inter-granular failure. This failure mode is primarily attributed to matrix softening in HAZ, weakening of the boundaries, coarsening of the precipitates, and the evolution of intermetallic Laves phases. The specimen that failed in the stress range of 100–130 MPa exhibited a high density of microvoids in the ICHAZ, along with a few microvoids in the FGHAZ. The weld metal showed negligible degradation in microstructure, while the hardness study revealed a significant increase in hardness with an increase in rupture time, i.e., a decrease in applied stress and it was attributed to evolution of the new carbide phases in weld metal. Coarsening of the carbide precipitates was observed in each zone of the HAZ of P92 steel as well as in the base metal. The EDS study of the fracture tip and the FGHAZ/ICHAZ of the specimen that failed under stresses of 100 MPa and 120 MPa confirmed the evolution of intermetallic Laves phases. High magnification SEM images confirmed that triple boundaries are preferential locations for microvoid nucleation. The failed specimen showed the presence of microvoids near the carbide precipitates, with a large density of both coarse and fine precipitates confirmed all around and inside the microvoids. The ICHAZ and FGHAZ confirmed the formation of fine prior austenite grain boundaries (PAGBs) during the welding thermal cycle, which exhibited a lower density of carbide precipitates and this played a major role in Type IV failure.

Metrology of No Fault Found Events: Using Microwave Spectroscopy and 4D X-Ray Computed Tomography to Detect Thermal Fatigue-Caused Damage in Solder Joints

The reliability of semiconductor packages is a cornerstone in the advancement of high-performance electronics. As semiconductor components undergo continuous miniaturization and grow in complexity, traditional methods for inspection and analysis, such as serial sectioning and scanning electron microscopy, have become inadequate due their destructive nature, prohibitive time costs, and limited characterization abilities. Furthermore, while evaluating solder joint failures and solder joint reliability by direct current (DC) methods is potentially useful, this technique often does not capture all incipient failures leading to No Fault Found (NFF) scenarios, which occur when the product fails, but upon checking, no fault is detected. High radio frequency (RF) measurements of signal paths are more sensitive to such incipient circuit (or solder joint) failures. RF methods can capture failures due to mechanical changes, which affect the impedance of the devices under test, through return loss, insertion loss or phase angle. Furthermore, RF methods can catch such incipient failures well before complete solder joint failure. In this talk, we compare the fault detection capabilities and detection speeds, of direct current resistance (R-DC) to RF based fault detection measurements and correlate the electrical data with the results from non-destructive 4D X-ray Computed Tomography (XCT).Historically, non-destructive defect characterization techniques such as optical imaging, radiography, and scanning acoustic microscopy (SAM) have been instrumental in assessing defects in semiconductor packages. However, they lack the resolution and capability to accurately characterize defects in dense packages at the micron scale in 3D. Furthermore, the drive for greater device efficiency and performance has led to more complex thermal stress states in semiconductor packages. Therefore, the detection and analysis of defects goes beyond mere quality control and maintenance; they are fundamental for the chip-package-system co-design itself . Thus, 3D X-ray Computed Tomography (XCT) stands out as an ideal tool for the non-destructive assessment of defects in semiconductor packages.. Figure 1 shows the 3D renderings of preliminary work done on the analyses of defect evolution in thermally cycled packages using X-ray Computed Tomography. By capturing spatial and temporal changes, 4D X-ray CT provides unique perspectives into the package behavior under thermal stress. This enables not only the identification and characterization of defects but advancement of our understanding of their origin and development.As expected, the impedance of the solder joints (i.e., S parameter data) changed over time and temperature cycles as the connectors suffer from wear, even when there are clearly no actual changes to the circuit. The capacitance and associated capacitive reactance that formed by a partial crack in a solder joint was found to be so much larger than the very small resistance of an even tiny remaining amount of intact solder joint that the ultimate effect on the circuit is unmeasurable until the crack is fully open (as indicated by 4D XCT). The results presented in this paper should benefit emerging advanced packing concepts, and traditional components manufacturers to determine the reliability of their components on test boards. Figure 1

Fatigue fracture mechanism and life prediction of steel-aluminium clinched joints under different stress ratios

Vehicle bodies are subject to complex random loads during travelling, making it imperative to investigate the effects of different stress ratios on the body joining structure. To investigate the fatigue performance of steel-aluminium clinched joints under different stress ratios, fatigue experiments were conducted on these joints subjected to different load levels at stress ratios of -0.4, 0.1, and 0.4. The fracture mechanism of steel-aluminium clinched joints under different stress ratios was investigated through analysis of the joint's fracture morphology and the composition of abrasive chips using Scanning Electron Microscope and Energy Dispersive Spectroscopy. A fatigue life prediction model for steel-aluminium clinched joints was developed by employing the modified Paris formulation of the Wallker equation. The results indicate that joint failure can be classified into three main forms: lower sheet fracture, upper sheet pull-off accompanied by lower sheet fracture and reaching infinite life (2 million times). The lower sheet of a fatigue failure specimen in a steel-aluminium clinched joint exhibited a novel form of fretting damage known as lower sheet inter-plate fretting wear. Furthermore, the application of Walker's improved Paris formula proved to be highly effective in accurately predicting the fatigue life of steel-aluminium clinched joints under different stress ratios, with the predicted results demonstrating excellent agreement with experimental findings.

Fatigue Failure of Adhesive Joints in Fiber-Reinforced Composite Material Under Step/Variable Amplitude Loading—A Critical Literature Review

Most fatigue-loading research has concentrated on constant-amplitude tests, which seldom represent actual service conditions. Because of the significant time and expense associated with variable-amplitude experiments, researchers often employ block/step-loading tests to evaluate the effects of variable-amplitude loading. These tests utilize various sequences of low-to-high and high-to-low loads to simulate real-world scenarios. Empirical investigations have shown inconsistencies in the damage accumulation under different load sequences. Although literature reviews exist for simulation and experimental methods, there is limited research examining the impact of step/variable-amplitude loading on adhesive joints in composite materials. This review aims to address this gap by comprehensively analyzing the effects of load sequence and block loading on fatigue damage progression in fiber-reinforced polymer composites. Additionally, the applicability of various step-loading fatigue damage accumulation models to adhesive materials is evaluated through numerical simulation to study its suitability in predicting fatigue failure. This review also explores recent theoretical advancements in this field over the past few years, examining more than 100 fatigue damage accumulation models categorized into seven subcategories: (i) linear damage rules, (ii) nonlinear damage curve and two-stage linearization models, (iii) life curve modification models, (iv) models based on crack growth concepts, (v) continuum damage mechanics-based models, (vi) material degradation models, and (vii) energy-based models. Finally, numerical simulations using the most common nonlinear cumulative fatigue damage accumulation models were conducted to predict fatigue failure in adhesively bonded joints under four step-loading tests, and the results were compared with the experimental data. Numerical simulations revealed the need and scope of further development of a fatigue failure model under step/variable loading. This comprehensive review offers valuable insights into the complex nature of fatigue failure in adhesive joints under variable loading conditions and highlights current state-of-the-art nonlinear fatigue damage accumulation models for adhesive materials.

Recent Advances in Aluminum Alloy Surface Treatment Technology and Bonding Properties

Aluminum alloys are widely used in lightweight automotive structures due to their excellent properties. To deeply explore the development of surface bonding technology, aluminum alloy is selected as the object, and current research status of aluminum alloy surface treatment methods is reviewed. The adhesion mechanism during joint preparation, the method of adhesive selection, and the bonding process are summarized. This overview discusses the impact of different surface treatment processes on aluminum alloy joints from two perspectives: substrate characteristics and joint failure modes. It examines how these processes affect surface roughness, surface morphology, surface contact angle, surface free energy, surface chemical composition, and bonding performance. Additionally, it looks ahead to key directions for future research on adhesive joint performance. The results indicate that surface treatment increases the surface roughness of aluminum alloys, reduces the contact angle, and improves surface wettability. Moreover, chemical elements or functional groups that enhance adhesion are introduced on the surface, improving the bonding capability between the adhesive and the substrate. Compared to single‐surface treatment methods, hybrid treatment methods significantly enhance the surface characteristics of aluminum alloys and are expected to become a primary focus for future research on bonded joint performance.

Study on Damage Index for Beam–Column Joints with Flush End-Plate Connections

Experimental results from 109 flush end-plate (FEP) connections were analyzed to investigate the failure modes and damage index of FEP connections across various damage states. The present study was conducted in accordance with the performance design objectives specified in China’s GB50011-2010 Code for Seismic Design of Buildings. The observed rotation angles and corresponding rotation factors were systematically categorized using a probabilistic statistical approach, with the 95% confidence lower limit as the primary constraint. The damage states of FEP connections were classified as virtually undamaged, lightly damaged, moderately damaged, severely damaged, and joint failure. A minimum plate thickness of 12 mm and a minimum high-strength bolt diameter of 20 mm are recommended to be used for the FEP connections, in accordance with building codes in China, the United States, and Europe. Quasi-static tests of six FEP connections were conducted to validate the damage-state categorization. The results revealed that for connections undergoing moderate and severe damage, the mean rotation factor deviated from the theoretical values proposed in this study by 3.7% and 9.4%, respectively. Therefore, the damage state of FEP connections can be reliably predicted based on different rotation angles using the damage-state categorization presented herein.

First-principles calculation of the effects of In doping on η-Cu6Sn5 structure, elastic anisotropy, electronic properties and fracture toughness

During the welding and service stages, the anisotropy of Cu6Sn5 between tin solder / Cu solder joints will lead to abnormal grain growth and fracture of Cu6Sn5, which will eventually lead to solder joint failure, so it is very important to study the alloying element indium (In) to reduce the anisotropy of Cu6Sn5. The effects of indium doping on the crystal structure, electronic structure and mechanical properties of η-Cu6Sn5 have been studied systematically by means of first-principles density functional theory. Through calculation, it is found that with the change of indium doping position, the crystal structure is slightly deformed, but remains stable. Indium doping changes the electronic structure of η-Cu6Sn5, and a new bonding peak is formed by the hybridization of Cu-d and In-s around −5.9 eV. In addition, indium doping can significantly increase the mechanical properties of η-Cu6Sn5, including elastic modulus and hardness. Indium significantly reduces the anisotropy of η-Cu6Sn5, and the anisotropy decreases by nearly 80 % at most. At the same time, the addition of indium can increase the fracture toughness of η-Cu6Sn5.

Deformation behavior study of SAC305 solder joints under shear and tensile loading by crystal plasticity finite element method

Micro solder joints experience various loads during operation, and the failure of a single micro solder joint can impact the overall reliability of the entire microsystem. This study utilized the Crystal Plasticity Finite Element Method (CPFEM) to create a polycrystalline model that accurately represents the shape of solder joints. By calibrating the crystal plasticity characteristics of SAC305 material solder joints using macroscopic stress-strain curves, the model successfully simulates the deformation mechanisms of micro-solder joints under both tensile and shear loads. This paper highlights that equivalent plastic strain serves as a key indicator of solder joint fracture behavior, revealing that strain components have varying effects on cracking: shear strain was found to cause crack initiation, while normal strain was found to promote crack extension. Moreover, Grain boundary features and orientation lead to uneven plastic strain by affecting the slip system and the Schmidt factor, especially small Schmidt factor grains at triple grain boundary intersections are more susceptible to crack initiation. Additionally, the study found that solder joints exhibit more pronounced mechanical responses under tensile loading compared to shear loading. These insights offer valuable guidance for the design and manufacturing of micro-solder joints.