Mechanical characterization of Sn–Ag-based lead-free solders

Amagai, Masayuki; Watanabe, Miki; Omiya, Masaki; Kishimoto, Kikuo; Shibuya, Toshikazu

doi:10.1016/s0026-2714(02)00017-3

Cited by 226 publications

(57 citation statements)

References 13 publications

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“…Current constitutive relations for solder typically predict inelastic rates of deformation that vary with the stress to a power of 6 or more. [48][49][50][51][52][53][54][55] However, simple calculations (''Appendix'') show how this cannot lead to work during the hightemperature dwell that varies faster than the DNP. Only a linear dependence of the inelastic strain rate on the stress is compatible with a variation of the life span with DNP…”

Section: Constitutive Relationsmentioning

confidence: 99%

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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Section: Constitutive Relationsmentioning

confidence: 99%

A Mechanistic Thermal Fatigue Model for SnAgCu Solder Joints

Børgesen

Wentlent

Hamasha

et al. 2018

Journal of Elec Materi

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“…In reality this volume change is split into a volume expansion on the Sn side and a volume contraction on the Cu side. For simplicity, we take (31)- (35) have been calibrated to experiments by Champion et al [33] for the Cu phase and by Amagai et al [34] for the Sn phase, respectively. In addition, the parameters are calibrated so that the hardening behavior, (32), matches the behavior predicted by the Taylor equation,…”

Section: Choice Of Parametersmentioning

confidence: 99%

Coupled diffusion-deformation multiphase field model for elastoplastic materials applied to the growth of Cu6Sn5

et al. 2016

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A coupled diffusion-deformation, multiphase field model for elastoplastic materials is presented. The equations governing the evolution of the phase fields and the molar concentration field are derived in a thermodynamically consistent way using microforce balance laws. As an example of its capabilities, the model is used to study the growth of the intermetallic compound (IMC) Cu 6 Sn 5 during room-temperature aging. This IMC is of great importance in, e.g., soldering of electronic components. The model accounts for grain boundary diffusion between IMC grains and plastic deformation of the microstructure. A plasticity model with hardening, based on an evolving dislocation density, is used for the Cu and Sn phases. Results from the numerical simulations suggest that the thickness of the IMC layer increases linearly with time and that the morphology of the IMC gradually changes from scallop-like to planar, consistent with previous experimental findings. The model predicts that plastic deformation occurs in both the Cu and the Sn layers. Furthermore, the mean value of the biaxial stress in the Sn layer is found to saturate at a level of −8 MPa to −10 MPa during aging. This is in good agreement with experimental data.

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“…In our previous study, the SnAg-Cu UBM solder exhibits the microstructural complexity owing to the rapid quenching rate resulting from small feature size under few tens of micrometers, including various crystal phases, nanoeutectic dendrite structure, and those complex multilayers~Bali et al, 2008!. Therefore, it is a critical issue to investigate thermal degradation behaviors of the UBM solder, which can crucially affect the mechanical failure and electrical properties at high temperaturẽ Amagai et al, 2002;Kang et al, 2002;Deng et al, 2005;Keller et al, 2011!. However, research results on the mechanisms of microstructural change and phase transition induced by thermal aging of solder have not been reported so far, because it is practically very hard to fabricate a transmission electron microscopy~TEM! sample of the micro-sized UBM bump by conventional TEM sampling methods.…”

Section: Introductionmentioning

confidence: 99%

In Situ Heating Transmission Electron Microscopy Observation of Nanoeutectic Lamellar Structure in Sn–Ag–Cu Alloy on Au Under-Bump Metallization

et al. 2013

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Abstract:We investigated the microstructural evolution of Sn 96.4 Ag 2.8 Cu 0.8 solder through in situ heating transmission electron microscopy observations. As-soldered bump consisted of seven layers, containing the nanoeutectic lamella structure of AuSn and Au 5 Sn phases, and the polygonal grains of AuSn 2 and AuSn 4 , on Au-plated Cu bond pads. Here, we found that there are two nanoeutectic lamellar layers with lamella spacing of 40 and 250 nm. By in situ heating above 1408C, the nanoeutectic lamella of AuSn and Au 5 Sn was decomposed with structural degradation by sphering and coarsening processes of the lamellar interface. At the third layer neighboring to the lamella layer, on the other hand, Au 5 Sn particles with a zig-zag shape in AuSn matrix became spherical and were finally dissipated in order to minimize the interface energy between two phases. In the other layers except both lamella layers, polycrystal grains of AuSn 2 and AuSn 4 grew by normal grain growth during in situ heating. The high interface energy of nanoeutectic lamella and polygonal nanograins, which are formed by rapid solidification, acted as a principal driving force on the microstructural change during the in situ heating.

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Mechanical characterization of Sn–Ag-based lead-free solders

Cited by 226 publications

References 13 publications

A Mechanistic Thermal Fatigue Model for SnAgCu Solder Joints

A Mechanistic Thermal Fatigue Model for SnAgCu Solder Joints

Coupled diffusion-deformation multiphase field model for elastoplastic materials applied to the growth of Cu6Sn5

In Situ Heating Transmission Electron Microscopy Observation of Nanoeutectic Lamellar Structure in Sn–Ag–Cu Alloy on Au Under-Bump Metallization

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