Effect of current crowding on void propagation at the interface between intermetallic compound and solder in flip chip solder joints

Zhang, Lingyun; Ou, Shengquan; Huang, Ju; Tu, King‐Ning; Gee, S.A.; Nguyen, Luu

doi:10.1063/1.2158702

Cited by 144 publications

(67 citation statements)

References 10 publications

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“…Based on a former study [28], the current density at the anode corner where the electrons entered into the solder joint is about an order of magnitude higher than the average current density in the bulk of the solder joint. We obtain the effective charge number Z * to be 24 when we take the stress gradient = 6 MPa / µm,  Sn = 1.325 × 10 -7…”

Section: Mpamentioning

confidence: 99%

In situ measurement of electromigration-induced transient stress in Pb-free Sn–Cu solder joints by synchrotron radiation based x-ray polychromatic microdiffraction

Chen

Tamura

Kunz

et al. 2009

Journal of Applied Physics

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Electromigration-induced hydrostatic elastic stress in Pb-free SnCu solder joints was studied by in situ synchrotron X-ray white beam microdiffraction. The elastic stresses in two different grains with similar crystallographic orientation, one located at the anode end and the other at the cathode end, were analyzed based on the elastic anisotropy of the β-Sn crystal structure. The stress in the grain at the cathode end remained constant except for temperature fluctuations, while the compressive stress in the grain at the anode end was built-up as a function of time during electromigration until a steady state was reached. The measured compressive stress gradient between the cathode and the anode is much larger than what is needed to initiate Sn whisker growth. The effective charge number of β-Sn derived from the electromigration data is in good agreement with the calculated value.3

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Section: Mpamentioning

confidence: 99%

In situ measurement of electromigration-induced transient stress in Pb-free Sn–Cu solder joints by synchrotron radiation based x-ray polychromatic microdiffraction

Chen

Tamura

Kunz

et al. 2009

Journal of Applied Physics

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“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] BasaranÕs group studied stress and deformation in solder joints under high current stressing. [21][22][23][24][25][26] This study examined thermomechanical stress and strain in the different solder joints during steady-state electromigration.…”

Section: Introductionmentioning

confidence: 99%

Thermomechanical Stress and Strain in Solder Joints During Electromigration

Zhang

et al. 2009

Journal of Elec Materi

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Thermomechanical stress and strain in the solder joints of a dummy area array package were studied as electromigration occurred. A current density of 0.4 9 10 4 A/cm 2 was applied to this package, constructed with 9 9 9 solder joints in a daisy chain, to perform the electromigration test. After 37 h, the first joint on the path of the electron flow broke off at the cathode, and the first three solder joints all exhibited a typical accumulation of intermetallic compounds at the anode. Different solder joints exhibited dissimilar electromigration states, such as steady state and nonsteady state. Finite element analysis indicated that during steady-state electromigration, although the symmetrical structure produced uniform distributions of current density and Joule heating in all solder joints, the distribution of temperature was nonuniform. This was due to the imbalanced heat dissipation, which in turn affected the distribution of thermomechanical stress and strain in the solder joints. The maximum thermomechanical stress and strain, as well the highest temperature and current crowding, appeared in the Ni/Cu layer of each joint. The strain in the Ni/Cu layer was significant along the z-axis, but was constrained in the x-y plane. The thermomechanical stress and strain increased with advancing electromigration; thus, a potential delamination between the Ni/Cu layer and the printed circuit board could occur.

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“…2 During electromigration, some damage, such as the formation of voids at the cathode and the growth of whiskers and hillocks at the anode, will occur in the solder or at the solder/underbump metallization (UBM) interface. [3][4][5] It is known that the formation of whiskers and hillocks in Sn-based solder joints is a stress release process in which solder atoms squeeze out from the broken spot of the solder surface. 6 There are three indispensable conditions for whisker growth: (1) fast diffusion of Sn atoms at room temperature, (2) breaking of the protective surface oxide on the solder, and (3) formation of IMC layers as diffusion barriers.…”

Section: Introductionmentioning

confidence: 99%

Effect of Intermetallic on Electromigration and Atomic Diffusion in Cu/SnAg3.0Cu0.5/Cu Joints: Experimental and First-Principles Study

Zhou

Liu

et al. 2009

Journal of Elec Materi

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0.5 /Cu joint were investigated with current stressing. The special effect of intermetallic compound (IMC) layers on the formation of serious electromigration damage induced by nonuniform current density distribution was discussed based on experimental results. Meanwhile, hillocks were observed both at the anode and near the cathode of the joint, and they were described as the result of diffusion of atoms and compressive stress released along grain boundaries to the relatively free surface. Moreover, the diffusion behavior of Cu at the cathode was analyzed with the electromigration equation, and the stability of Ag atoms in the solder during electromigration was evaluated with a firstprinciples method.

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Effect of current crowding on void propagation at the interface between intermetallic compound and solder in flip chip solder joints

Cited by 144 publications

References 10 publications

In situ measurement of electromigration-induced transient stress in Pb-free Sn–Cu solder joints by synchrotron radiation based x-ray polychromatic microdiffraction

In situ measurement of electromigration-induced transient stress in Pb-free Sn–Cu solder joints by synchrotron radiation based x-ray polychromatic microdiffraction

Thermomechanical Stress and Strain in Solder Joints During Electromigration

Effect of Intermetallic on Electromigration and Atomic Diffusion in Cu/SnAg3.0Cu0.5/Cu Joints: Experimental and First-Principles Study

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