On the 3-D Shape of Interlaced Regions in Sn-3Ag-0.5Cu Solder Balls

Daszki, A.A.; Gourlay, C.M.

doi:10.1007/s11664-020-08508-w

Cited by 8 publications

(2 citation statements)

References 17 publications

(34 reference statements)

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“…Figure 3a, b shows this using one joint from this study and Fig. 3c confirms {101} macroscopic beachball boundaries from 29 joints reanalysed from EBSD datasets in 29 , 32 . Note in Fig.…”

Section: Resultssupporting

confidence: 72%

The role of microstructure in the thermal fatigue of solder joints

Xian,

Xu,

Stoyanov

et al. 2024

Nat Commun

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Thermal fatigue is a common failure mode in electronic solder joints, yet the role of microstructure is incompletely understood. Here, we quantify the evolution of microstructure and damage in Sn-3Ag-0.5Cu joints throughout a ball grid array (BGA) package using EBSD mapping of localised subgrains, recrystallisation and heavily coarsened Ag3Sn. We then interpret the results with a multi-scale modelling approach that links from a continuum model at the package/board scale through to a crystal plasticity finite element model at the microstructure scale. We measure and explain the dependence of damage evolution on (i) the β-Sn crystal orientation(s) in single and multigrain joints, and (ii) the coefficient of thermal expansion (CTE) mismatch between tin grains in cyclic twinned multigrain joints. We further explore the relative importance of the solder microstructure versus the joint location in the array. The results provide a basis for designing optimum solder joint microstructures for thermal fatigue resistance.

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“…Figure 3a, b shows this using one joint from this study and Fig. 3c confirms {101} macroscopic beachball boundaries from 29 joints reanalysed from EBSD datasets in 29 , 32 . Note in Fig.…”

Section: Resultssupporting

confidence: 72%

The role of microstructure in the thermal fatigue of solder joints

Xian,

Xu,

Stoyanov

et al. 2024

Nat Commun

Self Cite

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“…Extensive studies have been conducted to characterize the mechanical properties of SAC alloys; however, the results vary not only between groups but also between multiple measurements of the same group [3,4]. This is usually attributed to their stochastic microstructure, which typically consists of only a few highly anisotropic grains, in either discrete or interlaced morphology [5][6][7][8]. Moreover, the miniaturization of packages leads to an increase in the number of I/Os and a decrease in pitch size, which also reduces the size and volume of individual solder joints.…”

Section: Introductionmentioning

confidence: 99%

Grain-Scale Anisotropic Analysis of Steady-State Creep in Oligocrystalline SAC Solder Joints

2021

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Heterogeneous integration is leading to unprecedented miniaturization of solder joints, often with thousands of joints within a single package. The thermomechanical behavior of such SAC solder joints is critically important to assembly performance and reliability, but can be difficult to predict due to the significant joint-to-joint variability caused by the stochastic variability of the arrangement of a few highly-anisotropic grains in each joint. This study relies on grain-scale testing to characterize the mechanical behavior of such oligocrystalline solder joints, while a grain-scale modeling approach has been developed to assess the effect of microstructure that lacks statistical homogeneity. The contribution of the grain boundaries is modeled with isotropic cohesive elements and identified by an inverse iterative method that extracts material properties by comparing simulation with experimental measurements. The properties are extracted from the results of one test and validated by verifying reasonable agreement with test results from a different specimen. Equivalent creep strain heterogeneity within the same specimen and between different specimens are compared to assess typical variability due to the variability of microstructure.

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Misorientations and Subgrains in Sn-Ag and Sn-Ag-Cu Solder Balls After Solidification

Sun,

Xian,

Hsieh

et al. 2024

J. Electron. Mater.

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Subgrains and recrystallisation are common microstructural features in solder joints that have been subjected to thermal fatigue or mechanical loading. Here we study similar features in Sn-Ag and Sn-Ag-Cu solder balls after solidification. It is shown that four types of misorientation features exist to different extents in solder balls examined shortly after solidification: (i) small variations in orientation created by dendrite growth and eutectic solidification, (ii) partial polygonisation into subgrains, (iii) small grains with high angle boundaries and (iv) large anomalous grains surrounded by interlacing where the grain boundaries do not correlate with the dendrite growth pattern. The subgrains often have a boundary plane and rotation axis consistent with dislocations from a facile slip system. The recovery and misorientation features were more extensive in regions that solidified at deeper melt undercooling. The findings highlight the importance of distinguishing between the solidification and solid-state components of microstructure evolution when interpreting solder microstructures after solidification.

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On the 3-D Shape of Interlaced Regions in Sn-3Ag-0.5Cu Solder Balls

Cited by 8 publications

References 17 publications

The role of microstructure in the thermal fatigue of solder joints

The role of microstructure in the thermal fatigue of solder joints

Grain-Scale Anisotropic Analysis of Steady-State Creep in Oligocrystalline SAC Solder Joints

Misorientations and Subgrains in Sn-Ag and Sn-Ag-Cu Solder Balls After Solidification

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