Shear and Fatigue Properties of Lead-Free Solder Joints: Modeling and Microstructure Analysis

Wei, Xin; Belhadi, Mohamed El Amine; Hamasha, Sa’d; Alahmer, Ali; Zhao, Rong; Prorok, Barton C.; Sakib, Nazmus

doi:10.1115/1.4055318

Cited by 12 publications

(5 citation statements)

References 24 publications

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“…The presence of Sn was detected using EDS analysis, indicating a ductile failure mode. This observation was in line with other studies, where the SAC305 with OSP surface failure mechanism was studied [ 6 , 30 ]. In this case, the cracks propagated throughout the bulk solder.…”

Section: Resultssupporting

confidence: 92%

“…It was observed that the greater the Ag content, the better the fatigue and shear strengths achieved [ 4 ]. Xu et al [ 5 , 6 ] studied the fatigue characteristics of SAC and SnPb-based alloys under isothermal fatigue conditions. Shear fatigue tests were conducted using plastic ball grid array (PBGAs) to evaluate their reliability over a wide strain range.…”

Section: Introductionmentioning

confidence: 99%

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Analysis and Modeling of Aged SAC-Bi Solder Joints Subjected to Varying Stress Cycling Conditions

et al. 2023

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Solder joints are subjected to varied stress cycle circumstances in the electronic packaging service life but are also influenced by aging. There has been limited investigation into the influence of aging and varying cycles on SnAgCu-Bi (SAC-Bi) solder joint fatigue. Cyclic fatigue tests were performed on solder joints of several alloys, including SnAgCu (SAC305), SnAgCu-Bi (SAC-Q), and SnCu-Bi (SAC-R). Individual solder joints were cycled under varying stress levels, alternating between mild and harsh stress levels. At least seven samples were prepared for each alloy by alternating between 25 mild stress (MS) cycles and three harsh stress (HS) cycles until the solder joint broke off. The impact of aging on Bi-doped solder joints fatigue under varied amplitude stress was examined and predicted for 10 and 1000 h under 125 °C. Because of the “Step-up” phenomenon of inelastic work, a new fatigue model was developed based on the common damage accumulation (CDA) model. The experimental results revealed that aging reduced the fatigue life of the tested solder alloys, particularly that of SAC305. According to the CDA model, all solder alloys failed earlier than expected after aging. The proposed model uses the amplification factor to assess inelastic work amplification after switching between the MS and HS cycles under varying stress amplitude conditions. The amplification factor for the SAC-Bi solder alloys increased linearly with fracture initiation and substantially followed crack propagation until the final failure. Compared with existing damage accumulation models, the proposed fatigue model provides a more accurate estimation of damage accumulation. For each case, the cut-off positions were examined. The SAC-Q amplification factor increased linearly to 83% of its overall life, which was much higher than that of SAC305 and SAC-R. This study identified three distinct failure modes: ductile, brittle, and near intermetallic compound (IMC) failure. It was also observed that SAC-Q with an organic solderability preservatives (OSP) surface finish was more susceptible to brittle failure owing to the excessive brittleness of the alloy material.

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Section: Resultssupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Analysis and Modeling of Aged SAC-Bi Solder Joints Subjected to Varying Stress Cycling Conditions

et al. 2023

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“…Over the past decades, the electronics industry has witnessed a rapid evolution toward smaller and more complex devices, leading to increased demands on the reliability and durability of solder joints (Bani Hani et al , 2023a; Arriola et al , 2022; Samavatian et al , 2020a, 2022a; Xiong et al , 2023). One of the significant challenges faced by electronic instruments is low-cycle fatigue (LCF) in solder joints, which has emerged as a critical failure mechanism (Wei et al , 2023b). In general, LCF refers to the phenomenon of structural degradation and eventual failure of a material subjected to cyclic loading at relatively high stress levels, typically below the material's yield strength (Su et al , 2019).…”

Section: Introductionmentioning

confidence: 99%

Low-cycle fatigue life assessment of SAC solder alloy through a FEM-data driven machine learning approach

Ruiz-Jacinto,

Gutiérrez-Valverde,

Aslla-Quispe

et al. 2023

SSMT

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Purpose This paper aims to present the novel stacked machine learning approach (SMLA) to estimate low-cycle fatigue (LCF) life of SAC305 solder across structural parts. Using the finite element simulation (FEM) and continuous damage mechanics (CDM) model, a fatigue life database is built. The stacked machine learning (ML) model's iterative optimization during training enables precise fatigue predictions (2.41% root mean square error [RMSE], R2 = 0.975) for diverse structural components. Outliers are found in regression analysis, indicating potential overestimation for thickness transition specimens with extended lifetimes and underestimation for open-hole specimens. Correlations between fatigue life, stress factors, nominal stress and temperature are unveiled, enriching comprehension of LCF, thus enhancing solder behavior predictions. Design/methodology/approach This paper introduces stacked ML as a novel approach for estimating LCF life of SAC305 solder in various structural parts. It builds a fatigue life database using FEM and CDM model. The stacked ML model iteratively optimizes its structure, yielding accurate fatigue predictions (2.41% RMSE, R2 = 0.975). Outliers are observed: overestimation for thickness transition specimens and underestimation for open-hole ones. Correlations between fatigue life, stress factors, nominal stress and temperature enhance predictions, deepening understanding of solder behavior. Findings The findings of this paper highlight the successful application of the SMLA in accurately estimating the LCF life of SAC305 solder across diverse structural components. The stacked ML model, trained iteratively, demonstrates its effectiveness by producing precise fatigue lifetime predictions with a RMSE of 2.41% and an “R2” value of 0.975. The study also identifies distinct outlier behaviors associated with different structural parts: overestimations for thickness transition specimens with extended fatigue lifetimes and underestimations for open-hole specimens. The research further establishes correlations between fatigue life, stress concentration factors, nominal stress and temperature, enriching the understanding of solder behavior prediction. Originality/value The authors confirm the originality of this paper.

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“…The structural characteristics of the solder joint are influenced by thermal cycling. After thermal cycling, different failure modes, such as fatigue/creep processes and failure owing to shear stress, were detected in the microstructure [ 2 ]. Aging exacerbates this problem by affecting the mechanical and physical characteristics of the solder substance.…”

Section: Introductionmentioning

confidence: 99%

“…However, the drop shock test indicated the detrimental effect of Ag with the reduction in the ductility [ 12 ]. The other micro-alloying elements, such as Bi, Ni, and Sb, were also reported to improve the reliability of solder joints [ 2 , 6 , 16 ]. Meanwhile, these elements could prevent the degradation of properties during aging [ 6 , 14 , 15 ].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Micro-Alloying and Surface Finishes on the Thermal Cycling Reliability of Doped SAC Solder Alloys

et al. 2022

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The surface finish (SF) becomes a part of the solder joint during assembly and improves the component’s reliability. Furthermore, the SF influences the solder joint’s reliability by affecting the thickness of the intermetallic compound (IMC) layer at the solder interface and copper pads. In this experiment, five different alloys are used and compared with the SAC305 alloy, two of which, Innolot and SAC-Bi, are bi-based solder alloys. This study includes three common SFs: electroless nickel immersion gold (ENIG), immersion silver (ImAg), and organic solderability preserve (OSP). The performance of three surface finishes is examined in terms of component characteristic life. All of the boards were isothermally aged for twelve months at 125 °C. The boards were then exposed to 5000 cycles of thermal cycling at temperatures ranging from −40–+125 °C. Most of the current research considers only one or two factors affecting the reliability of the electronic package. This study combines the effect of multiple factors, including solder paste content, SF, isothermal aging, and thermal cycling, to ensure that the test conditions represent real-world applications. In addition, the electronics packages are assembled using commercialized alloys. The current study focuses on a high-performance alloy already present in the electronic market. The failure data were analyzed statistically using the Weibull distribution and design of experiments (DOE) analysis of variance (ANOVA) techniques. The findings reveal that the micro and uniformly distributed precipitates in solder microstructures are critical for high-reliability solder joints. Re-crystallization of the thermally cycled solder joints promotes the local formation of numerous new grains in stress-concentrated zones. As the fracture spreads along these grain boundaries and eventually fails, these new grains participate in crack propagation. Aging significantly worsens this situation. Finally, although the ENIG surface finish with its Ni layer outperforms other SFs, this does not imply that ENIG is more reliable in all solder paste/sphere/finish combinations.

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Shear and Fatigue Properties of Lead-Free Solder Joints: Modeling and Microstructure Analysis

Cited by 12 publications

References 24 publications

Analysis and Modeling of Aged SAC-Bi Solder Joints Subjected to Varying Stress Cycling Conditions

Analysis and Modeling of Aged SAC-Bi Solder Joints Subjected to Varying Stress Cycling Conditions

Low-cycle fatigue life assessment of SAC solder alloy through a FEM-data driven machine learning approach

The Effect of Micro-Alloying and Surface Finishes on the Thermal Cycling Reliability of Doped SAC Solder Alloys

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