Condensation and Growth of Kirkendall Voids in Intermetallic Compounds

Weinberg, Kerstin; Böhme, Thomas

doi:10.1109/tcapt.2008.2010057

Cited by 34 publications

(8 citation statements)

References 16 publications

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“…7. It is clear that the size of Kirkendall voids increases with both the time and strain rate, which is consistent with the results of the simulation work employing the constitutive model [19]. The growth exponents of Kirkendall voids under different strain rates with the same cyclic period are shown in Fig.…”

Section: B Evolution Of Kirkendall Voids Under Different Strain Ratessupporting

confidence: 87%

Phase field crystal simulation of morphological evolution and growth kinetics of Kirkendall voids at the interface and in the intermetallic compound layer of Sn/Cu soldering system under cyclic loading

Liang

et al. 2015

2015 16th International Conference on Electronic Packaging Technology (ICEPT)

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Kirkendall voids can cause weakening in mechanical properties at the wire bonding and soldering interconnect on integrated circuit packaging, assembly and interconnections. These voids may form at the Cu/Cu3Sn interface and in the CU3Sn layer of the solder interconnect consisting of the Sn-based solder and Cu substrate (Le., SnlCu soldering system). Excessive formation and growth of Kirkendall voids may increase the potential for brittle interfacial fracture, and the existence of voids will reduce the thermal conductivity. Thus, characterization of formation and growth of Kirkendall voids is very important for the evaluation of performance and reliability of solder interconnects. In this paper, a phase field crystal model is utilized to study the morphological evolution of Kirkendall voids in a typical SnlCu soldering system subjected to a periodic tensile stress with different forms. Firstly, a constant tensile stress is applied to the solder joint in the first half cycle, while without imposing stress in the second half cycle. The simulation results show that Kirkendall voids may nucleate and grow at the interface under the cyclic tensile stress, and the coalescence growth of the voids is not obvious. With increasing the strain rate, the growth exponent and void size increase. Secondly, a square-wave form periodic stress with various lengths of cyclic period and a high strain rate is applied perpendicular to the interface, the simulation results show that no significant difference can be observed regarding the growth process of Kirkendall voids. Moreover, with increasing the length of cyclic period, the growth exponent decreases at first and then increases gradually.

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Section: B Evolution Of Kirkendall Voids Under Different Strain Ratessupporting

confidence: 87%

Phase field crystal simulation of morphological evolution and growth kinetics of Kirkendall voids at the interface and in the intermetallic compound layer of Sn/Cu soldering system under cyclic loading

Liang

et al. 2015

2015 16th International Conference on Electronic Packaging Technology (ICEPT)

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“…43 Yet another alternative means of describing vacancy diffusion relies on continuum models. 19,[44][45][46] Within a continuum setting, the vacancy concentration is thought of as a function of space and time, and evolution equations are used to describe its evolution. Continuum models allow the study of very large systems over long periods of time, albeit at some inevitable loss of fidelity relative to discrete models.…”

Section: Kinetic Monte Carlo Simulationsmentioning

confidence: 99%

“…5,[14][15][16][17][18] By design, micromechanical continuum models of porous plasticity either postulate an initial void size and density (e.g., when voids nucleate by decoherence of second-phase particles) or rely on a nucleation model in order to compute the initial void size and density. 19,20 In this model, nucleation corresponds to the onset of plastic cavitation, i.e., to the formation of voids of a size such that subsequent growth can happen by plasticity. In metals at high tensile pressures, the critical void size for plastic cavitation may be in the nanoscale, in which case plastic cavitation occurs by the emission of discrete dislocation loops.…”

Section: Introductionmentioning

confidence: 99%

Nanovoid nucleation by vacancy aggregation and vacancy-cluster coarsening in high-purity metallic single crystals

2011

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A numerical model to estimate critical times required for nanovoid nucleation in high-purity aluminum single crystals subjected to shock loading is presented. We regard a nanovoid to be nucleated when it attains a size sufficient for subsequent growth by dislocation-mediated plasticity. Nucleation is assumed to proceed by means of diffusion-mediated vacancy aggregation and subsequent vacancy cluster coarsening. Nucleation times are computed by a combination of lattice kinetic Monte Carlo simulations and simple estimates of nanovoid cavitation pressures and vacancy concentrations. The domain of validity of the model is established by considering rate-limiting physical processes and theoretical strength limits. The computed nucleation times are compared to experiments suggesting that vacancy aggregation and cluster coarsening are feasible mechanisms of nanovoid nucleation in a specific subdomain of the pressure-strain rate-temperature space.

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“…In [2,3] the authors developed a detailed model for KIRKENDALL voiding in IMCs. The main ideas are sketched here shortly.…”

Section: Constitutive Model For Void Nucleation and Growthmentioning

confidence: 99%

Void nucleation by vacancy condensation

Weinberg¹

2008

Proc Appl Math and Mech

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A computational simulation of Kirkendall voiding in metallic materials is presented. After a brief explanation of the phenomena and its consequences on the reliability of microelectronic components we introduce a constitutive model for void nucleation and growth which is based on vacancy diffusion and rate-dependent inelastic deformation. This model can be used to predict the temporal development of voids in solder during thermal cycling and/or impact loading. A numerical study illustrates the potential of the model for the failure analysis. The ProblemSolder joints of microelectronic circuit units are to an increasing extent made of tin alloys (e.g., Sn-Ag or Sn-Ag-Cu). These joints hold the multi-layered unit in position and, in addition, the solder joints provide electrical conductivity between the metallic (coppered) layers of the units. "Aging" of solder, such as phase separation, coarsening or the formation of InterMetallic Compounds (IMCs), as well as the formation and growth of pores and cracks in the vicinity of heterogeneities significantly effect the life expectation of the joints and considerably influence the reliability of the whole component. During manufacturing the (molten) Sn-rich solder wets the copper pad and IMCs are formed due to an interfacial reaction. These IMCs are relatively stiff and considerable stresses are induced in these regions due to mismatching thermal expansion. Furthermore the IMCs show different diffusion coefficients w.r.t. Cu and, therefore, the diffusion of Cu from the pad via the interface Cu/Cu 3 Sn into Cu 3 Sn is much slower than the diffusion of Cu from Cu 3 Sn into the Cu 6 Sn 5 scallops, which also cannot be "corrected" by the vice versa diffusion of Sn via the Cu 6 Sn 5 /Cu 3 interface. As a consequence vacancies on the lattice sides remain within the Cu 3 Sn compounds, which coalesce due to vacancy diffusion to macroscopic voids. Moreover, primarily initiated by stress peaks in the vicinity of the voids they further grow and merge to cracks, which may proceed such that failure occurs. Constitutive Model for Void Nucleation and GrowthIn [2, 3] the authors developed a detailed model for KIRKENDALL voiding in IMCs. The main ideas are sketched here shortly. To this end we distinct between void nucleation and ∼growth. The nucleation process is understood, beyond the atomic scale, to be the result of vacancy diffusion. The resulting vacancy "cluster" is, if a critical amount of vacancies would be reached, treated as a nucleated macroscopic void. However, these voids do not exclusively grow due to diffusion. In particular, local mechanical stresses or surface energy effects result in proceeding void growth and coalescence.

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Condensation and Growth of Kirkendall Voids in Intermetallic Compounds

Cited by 34 publications

References 16 publications

Phase field crystal simulation of morphological evolution and growth kinetics of Kirkendall voids at the interface and in the intermetallic compound layer of Sn/Cu soldering system under cyclic loading

Phase field crystal simulation of morphological evolution and growth kinetics of Kirkendall voids at the interface and in the intermetallic compound layer of Sn/Cu soldering system under cyclic loading

Nanovoid nucleation by vacancy aggregation and vacancy-cluster coarsening in high-purity metallic single crystals

Void nucleation by vacancy condensation

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