Dominant effects of Sn orientation on serrated cathode dissolution and resulting failure in actual solder joints under electromigration

Yang, Ting; Yu, Jinran; Li, C.C.; Kao, C. R.

doi:10.1016/j.jallcom.2014.11.222

Cited by 40 publications

(16 citation statements)

References 17 publications

(28 reference statements)

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“…BGA joints on cobalt substrates will suffer the same problem as on copper substrates where the small number of grains per joint have their βSn c-axis oriented differently in each joint which will give variable joint-to-joint reliability due to the highly anisotropic properties of βSn. For example, the electromigration resistance will vary substantially from joint to joint since it depends on the βSn c-axis orientation(s) [69][70][71][72][73][74][75][76]. 4.…”

Section: Outlook For Cobalt Substratesmentioning

confidence: 99%

Nucleation, grain orientations, and microstructure of Sn-3Ag-0.5Cu soldered on cobalt substrates

Gourlay

2017

Journal of Alloys and Compounds

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The potential of cobalt substrates to control the microstructure of 550 μm Sn-3Ag-0.5Cu ball grid array (BGA) joints is explored. It is shown that cobalt substrates give a small and reproducible nucleation undercooling for tin and prevent the formation of large primary Ag3Sn blades and Cu6Sn5 rods. βSn dendrites grew from the CoSn3 reaction layer and the βSn grains are shown to inherit their orientation from the CoSn3 layer due to heterogeneous nucleation with the following orientation relationship: (100)Sn||(100)CoSn3 with [001]Sn||[001]CoSn3. Changes in the dendrite and eutectic microstructure are shown to be caused by the reduced nucleation undercooling for βSn and the altered solidification path due to cobalt substrate dissolution

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Section: Outlook For Cobalt Substratesmentioning

confidence: 99%

Nucleation, grain orientations, and microstructure of Sn-3Ag-0.5Cu soldered on cobalt substrates

Gourlay

2017

Journal of Alloys and Compounds

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“…The variable undercooling causes the microstructure to vary from joint to joint [12] and the small number of grains per joint is a concern because βSn is tetragonal and has highly anisotropic properties such as thermal expansion [13] stiffness [14], and the diffusion of Ni and Cu [15,16]. The orientation of the βSn grain(s) plays an important role in electromigration resistance [17][18][19][20][21] and in the lifetime of a joint during thermal cycling [22,23]. The presence of few βSn grains that are oriented differently in each joint makes every joint unique which is a problem for predicting reliability.…”

Section: Introductionmentioning

confidence: 99%

Grain refinement of electronic solders: The potential of combining solute with nucleant particles

Shang

Belyakov

et al. 2017

Journal of Alloys and Compounds

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Sn-Ag-Cu electronic solder joints typically solidify from a single nucleation event producing either a single βSn grain or twinned grains. With so few and variable βSn orientations, each joint is mechanically unique due to the anisotropy of tetragonal βSn. Here we explore the potential of increasing the number of βSn orientations in solder joints by promoting heterogeneous nucleation during solidification. It is shown that large (60 g) samples can be grain refined effectively by combining growth restricting solute with potent heterogeneous nucleant particles introduced by alloying additions of Zn, Ti, Co, Ir, Pd, or Pt. These mechanisms are discussed with reference to the grain refinement of structural casting alloys.In 500 μm solder balls, these grain refinement approaches were less effective and a relatively high cooling rate of 17 K/s combined with solute and nucleant particles were required to trigger multiple nucleation events. With this approach, up to 12 independent grains formed in 500 μm balls of Sn-3Ag-0.5Cu alloyed with Pt, Co, or Ti, compared with one independent grain in balls without nucleant particle additions.

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“…[19]. For instance, the calculated anisotropy ratio for Ni could reach as high as 30,000 [34]. Thus, it was not surprising to see that outdiffusion of Cu (or IMC) was accelerated because the c-axis of the grain was almost aligned with the current flow direction in the monocrystalline structure (seen in Figure 6a).…”

Section: Resultsmentioning

confidence: 99%

Microstructure and Grain Orientation Evolution in SnPb/SnAgCu Interconnects Under Electrical Current Stressing at Cryogenic Temperature

En²,

Zhou³

et al. 2019

Materials

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Electromigration was characterized at the cathode Cu/solder interface—without the effect of Joule heating—by employing scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) analyses. Rapid (Cux,Ni1−x)6Sn5 intermetallic compound (IMC) growth was observed at the anomalous region at the cathode end due to the effect of current crowding. The abnormal isotropic diffusion and parallel distribution of Pb were characterized in an ultra-low temperature environment in a monocrystalline structure stressed at −196 °C. The interesting results were attributed to crystallographic transformation due to the simultaneous effect of cryogenic and electrical stressing. The diffusion behavior of Pb atoms in face-centered cubic lattices performed isomorphism. As a result, Pb atoms of the bump gathered at the high-energy grain boundaries by diffusing through the face-centered cubic lattices around the long grain boundary, eventually forming a long-range distribution and accumulation of Pb elements. Our study may provide understanding of cryogenic electromigration evolution of the Cu/solder interface and provide visual data for abnormal lattice transformation at the current stressing.

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Dominant effects of Sn orientation on serrated cathode dissolution and resulting failure in actual solder joints under electromigration

Cited by 40 publications

References 17 publications

Nucleation, grain orientations, and microstructure of Sn-3Ag-0.5Cu soldered on cobalt substrates

Nucleation, grain orientations, and microstructure of Sn-3Ag-0.5Cu soldered on cobalt substrates

Grain refinement of electronic solders: The potential of combining solute with nucleant particles

Microstructure and Grain Orientation Evolution in SnPb/SnAgCu Interconnects Under Electrical Current Stressing at Cryogenic Temperature

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