Slip, Crystal Orientation, and Damage Evolution During Thermal Cycling in High-Strain Wafer-Level Chip-Scale Packages

Zhou, Bowen; Zhou, Quan; Bieler, T. R.; Lee, Tae kyu

doi:10.1007/s11664-014-3572-9

Cited by 41 publications

(20 citation statements)

References 41 publications

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“…The major failure mode of solder joints in thermal cycling is cracking during heterogeneous microstructure evolution, i.e. polygonization and crack nucleation, in the bulk solder near the solder/substrate interface on the Si chip-side, observed in ref [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] . The crack propagates in the region where the mismatch of CTE is large and the induced thermal strain is high in comparison to the surroundings (larger misfit on the Si chip side than PCB side of joint [2,[20][21][22] ).…”

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confidence: 99%

“…When the solder is deformed by thermal cycling, the lattice misorientation within the solder joint is increased continuously by lattice rotation resulting from crystal slip along a single rotational axis (Figure 2f). This lattice rotation indicates higher straining and more highly stored energy in the region, which causes formation of significant subgrain boundaries and is vital for generation of HAGBs (recrystallization) and crack nucleation in the later stages of thermal cycling [7,8,[14][15][16]18] .…”

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confidence: 99%

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In-situ electron backscatter diffraction of thermal cycling in a single grain Cu/Sn-3Ag-0.5Cu/Cu solder joint

Gourlay

et al. 2020

Scripta Materialia

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The heterogeneous evolution of microstructure in a single Cu/SAC305/Cu solder joint is investigated using in-situ thermal cycling combined with electron backscatter diffraction (EBSD). Local deformation due to thermal expansion mismatch results in heterogeneous lattice rotation within the joint, localised towards the corners. This deformation is induced by the constraint and the coefficient of thermal expansion (CTE) mismatch between the β-Sn, Cu6Sn5and Cu at interfaces. The formation of subgrains with continuous increase in misorientation is revealed during deformation, implying the accumulation of plastic slip at the strain-localised regions and the activation of slip systems (110)[1 ̅ 11]/2 and (11 ̅ 0)[111]/2.

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confidence: 99%

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confidence: 99%

In-situ electron backscatter diffraction of thermal cycling in a single grain Cu/Sn-3Ag-0.5Cu/Cu solder joint

Gourlay

et al. 2020

Scripta Materialia

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“…23,[67][68][69] As expected, the behavior of the highly anisotropic joints is seen to vary strongly with orientation. Most recently, an experiment also including long periods of room-temperature aging between cycling seems to cast doubt on the assumption of a simple correlation between the general level of recrystallization and cracking.…”

Section: Discussion and Summarymentioning

confidence: 68%

A Mechanistic Thermal Fatigue Model for SnAgCu Solder Joints

Børgesen

Wentlent

Hamasha

et al. 2018

Journal of Elec Materi

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The present work offers both a complete, quantitative model and a conservative acceleration factor expression for the life span of SnAgCu solder joints in thermal cycling. A broad range of thermal cycling experiments, conducted over many years, has revealed a series of systematic trends that are not compatible with common damage functions or constitutive relations. Complementary mechanical testing and systematic studies of the evolution of the microstructure and damage have led to a fundamental understanding of the progression of thermal fatigue and failure. A special experiment was developed to allow the effective deconstruction of conventional thermal cycling experiments and the finalization of our model. According to this model, the evolution of damage and failure in thermal cycling is controlled by a continuous recrystallization process which is dominated by the coalescence and rotation of dislocation cell structures continuously added to during the hightemperature dwell. The dominance of this dynamic recrystallization contribution is not consistent with the common assumption of a correlation between the number of cycles to failure and the total work done on the solder joint in question in each cycle. It is, however, consistent with an apparent dependence on the work done during the high-temperature dwell. Importantly, the onset of this recrystallization is delayed by pinning on the Ag 3 Sn precipitates until these have coarsened sufficiently, leading to a model with two terms where one tends to dominate in service and the other in accelerated thermal cycling tests. Accumulation of damage under realistic service conditions with varying dwell temperatures and times is also addressed.

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“…The stored energy in the crystal lattice is reduced by deformation phenomena, namely polygonisation and recrystallisation, and these are precursors to crack nucleation and propagation in the strain-concentrated regions. [26][27][28][29][30][31] In service, the SAC305 solder works at a sufficiently high homologous temperature (> 0.6) such that deformation results in microstructural evolution, including dynamic recovery and recrystallisation. During recovery processes the solders deform by continuous lattice and rigid body rotation, where the stored energy or the driving force can be released by forming subgrains with misorientation between 2°and 15°.…”

Section: Introductionmentioning

confidence: 99%

The Role of Lengthscale in the Creep of Sn-3Ag-0.5Cu Solder Microstructures

Gourlay

Britton

2021

Journal of Elec Materi

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Creep of directionally solidified Sn-3Ag-0.5Cu wt.% (SAC305) samples with near-<110> orientation along the loading direction and different microstructural lengthscale is investigated under constant load tensile testing and at a range of temperatures. The creep performance improves by refining the microstructure, i.e. the decrease in secondary dendrite arm spacing (λ2), eutectic intermetallic spacing (λe) and intermetallic compound (IMC) size, indicating a longer creep lifetime, lower creep strain rate, change in activation energy (Q) and increase in ductility and homogeneity in macro- and micro-structural deformation of the samples. The dominating creep mechanism is obstacle-controlled dislocation creep at room temperature and transits to lattice-associated vacancy diffusion creep at elevated temperature ($$ \frac{T}{{T_{M} }} $$ T T M > 0.7 to 0.75). The deformation mechanisms are investigated using electron backscatter diffraction and strain heterogeneity is identified between β-Sn in dendrites and β-Sn in eutectic regions containing Ag3Sn and Cu6Sn5 particles. The size of the recrystallised grains is modulated by the dendritic and eutectic spacings; however, the recrystalised grains in the eutectic regions for coarse-scaled samples (largest λ2 and λe) is only localised next to IMCs without growth in size.

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Slip, Crystal Orientation, and Damage Evolution During Thermal Cycling in High-Strain Wafer-Level Chip-Scale Packages

Cited by 41 publications

References 41 publications

In-situ electron backscatter diffraction of thermal cycling in a single grain Cu/Sn-3Ag-0.5Cu/Cu solder joint

In-situ electron backscatter diffraction of thermal cycling in a single grain Cu/Sn-3Ag-0.5Cu/Cu solder joint

A Mechanistic Thermal Fatigue Model for SnAgCu Solder Joints

The Role of Lengthscale in the Creep of Sn-3Ag-0.5Cu Solder Microstructures

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