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Acta Metall Sin  2018, Vol. 54 Issue (7): 1077-1086    DOI: 10.11900/0412.1961.2017.00426
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Interaction Between β-Sn Grain Orientation and Electromigration Behavior in Flip-Chip Lead-Free Solder Bumps
Mingliang HUANG(), Hongyu SUN
Key Laboratory of Liaoning Advanced Welding and Joining Technology, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, China
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Abstract  

With the increasing demands for miniaturization, the electromigration (EM)-induced failure by diffusion anisotropy in β-Sn is expected to be more serious than that induced by local current crowding effect, especially with the downsizing of solder bumps. In this work, the effects of Sn grain orientation on intermetallic compound (IMC) precipitation, dissolution of Ni under bump metallurgy (UBM) at the cathode, EM failure mechanism as well as the EM-induced β-Sn grain rotation in Ni/Sn-3.0Ag-0.5Cu/Ni-P flip-chip interconnects undergoing solid-solid EM under a current density of 1.0×104 A/cm2 at 150 ℃ were in situ studied. (Ni, Cu)3Sn4-type IMCs precipitated in these β-Sn grains with a small angle θ (between the c-axis of Sn grain and electron flow direction), i.e., along the c-axis of β-Sn grains. Stress relaxation, squeezing β-Sn whiskers near the anode, was also observed during EM. A mathematical model on the relationship between the dissolution of Ni UBM and β-Sn grain orientation was proposed: when the c-axis of β-Sn grain is parallel to the electron flow direction, excessive dissolution of the cathode Ni UBM occurred due to the large diffusivity of Ni along the c-axis; when the c-axis of β-Sn grain is perpendicular to the electron flow direction, no evident dissolution of cathode Ni UBM occurred. The proposed model agreed well with the experimental results. EM-induced β-Sn grain rotation was attributed to the different vacancy fluxes caused by EM between adjacent grains of various grain orientation, when vacancies reached supersaturation and undersaturation at the interfaces of the anode and the cathode, respectively. Vacancy fluxes went through free surface along the interface, resulting in a normal vacancy concentration gradient. Accordingly, stress gradient produces a torque to rotate the β-Sn grain.

Key words:  electromigration      β-Sn;      anisotropy      cathode dissolution      IMC precipitation      grain rotation     
Received:  13 October 2017     
ZTFLH:  TN405  
Fund: Supported by National Natural Science Foundation of China (Nos.51475072, 51511140289 and 51671046) and Fundamental Research Funds for the Central Universities (No.DUT17ZD202)

Cite this article: 

Mingliang HUANG, Hongyu SUN. Interaction Between β-Sn Grain Orientation and Electromigration Behavior in Flip-Chip Lead-Free Solder Bumps. Acta Metall Sin, 2018, 54(7): 1077-1086.

URL: 

https://www.ams.org.cn/EN/10.11900/0412.1961.2017.00426     OR     https://www.ams.org.cn/EN/Y2018/V54/I7/1077

Fig.1  Schematic of the Ni/Sn-3.0Ag-0.5Cu/ENEPIG lead-free solder joint (ENEPIG—electroless nickel electroless palladium immersing gold, BT—bismaleimide triazine, PCB—printed circuit board, UBM—under bump metallurgy)
Fig.2  Cross-sectional micromorphologies of as-soldered flip chip lead-free solder joint
(a) macrograph (b) interface at the chip side (c) interface at the PCB side
Fig.3  Cross-sectional micromorphologies of No.1 flip chip lead-free solder joint after electromigration at 150 ℃ under the current density of 1.0×104 A/cm2 for 0 h (a), 150 h (b), 250 h (c), 350 h (d), 500 h (e) and the corresponding EBSD map in RD direction (f) (RD—rolling direction)
Fig.4  Cross-sectional micromorphologies of No.2 flip chip lead-free solder joint after electromigration at 150 ℃ under the current density of 1.0×104 A/cm2 for 0 h (a), 150 h (b), 250 h (c), 350 h (d), 500 h (e) and the corresponding EBSD map in RD (f)
Fig.5  Cross-sectional micromorphologies of No.3 flip chip lead-free solder joint after electromigration at 150 ℃ under the current density of 1.0×104 A/cm2 for 0 h (a), 150 h (b), 250 h (c), 350 h (d), 500 h (e) and the corresponding EBSD map in RD (f)
Fig.6  Cross-sectional micromorphologies of No.4 flip chip lead-free solder joint after electromigration at 150 ℃ under the current density of 1.0×104 A/cm2 for 0 h (a), 150 h (b), 250 h (c), 350 h (d), 500 h (e) and the corresponding EBSD map in RD (f)
Fig.7  Cross-sectional micromorphologies of No.5 flip chip lead-free solder joint after electromigration at 150 ℃ under the current density of 1.0×104 A/cm2 for 0 h (a), 150 h (b), 250 h (c), 350 h (d), 500 h (e) and the corresponding EBSD map in RD (f)
Fig.8  Cross-sectional micromorphologies of No.6 flip chip lead-free solder joint after electromigration at 150 ℃ under the current density of 1.0×104 A/cm2 for 0 h (a), 150 h (b), 250 h (c), 350 h (d), 500 h (e) and the corresponding EBSD map in RD (f)
Axis ρ γ E D (150 ℃) / (cm2s-1) DT (150 ℃)
μΩcm 10-6-1 GPa Ag Cu Ni m2s-1
a 13.25 15.45 22.9 5.60×10-11 1.99×10-7 3.85×10-9 8.70×10-13
c 20.27 30.50 68.9 3.13×10-9 8.57×10-6 1.17×10-4 4.71×10-13
Table 1  Anisotropic Properties of β-Sn[8,9,10]
Parameter Valne Unit
Z*[23] 3.5 -
CNi 1.858×1024 atomsm-3
T 423 K
i 1.0×108 Am-2
ρSn 1.18×10-7 Ωm
Ω 6.6×10-6 m3mol-1
l 1.0 μm
δ 0.0125 μm
Table 2  Parameters of the material used in the calculation
Fig.9  The consumption of cathode Ni UBM as a function of angle q
Fig.10  Schematic of grain rotation caused by electromigration in a Sn-3.0Ag-0.5Cu flip chip lead-free solder joint(Jvc and Jva are the self-diffusion vacancy fluxes of Sn atoms along the c-axis and a-axis of Sn grain, respectively; v is vacancy)
[1] Jung Y, Yu J.Electromigration induced kirkendall void growth in Sn-3.5Ag/Cu solder joints[J]. J. Appl. Phys., 2014, 115: 083708
[2] Huang M L, Zhou S M, Chen L D.Electromigration-induced interfacial reactions in Cu/Sn/Electroless Ni-P solder interconnects[J]. J. Electron. Mater., 2012, 41: 730
[3] Chen L D, Huang M L, Zhou S M.Effect of electromigration on intermetallic compound formation in line-type Cu/Sn/Cu interconnect[J]. J. Alloys Compd., 2010, 504: 535
[4] Chen C, Tong H M, Tu K N.Electromigration and thermomigration in Pb-free flip-chip solder joints[J]. Annu. Rev. Mater. Res., 2010, 40: 531
[5] Huang M L, Ye S, Zhao N.Current-induced interfacial reactions in Ni/Sn-3Ag-0.5Cu/Au/Pd(P)/Ni-P flip chip interconnect[J]. J. Mater. Res., 2011, 26: 3009
[6] Kim K S, Huh S H, Suganuma K.Effects of intermetallic compounds on properties of Sn-Ag-Cu lead-free soldered joints[J]. J. Alloys Compd., 2003, 352: 226
[7] Zhang Z J.Liquid-solid electromigration behavior and mechanism of micro interconnect [D]. Dalian: Dalian University of Technology, 2016
[8] Dyson B F, Anthony T R, Turnbull D.Interstitial diffusion of copper in tin[J]. J. Appl. Phys., 1967, 37: 3408
[9] Yeh D C, Huntington H B.Extreme fast-diffusion system: Nickel in single-crystal tin[J]. Phys. Rev. Lett., 1984, 53: 1469
[10] Huang F H, Huntington H B.Diffusion of Sb124, Cd109, Sn113, and Zn65 in tin[J]. Phys. Rev., 1974, 9B: 1479
[11] Lu M H, Shih D Y, Lauro P, et al.Effect of Sn grain orientation on electromigration degradation mechanism in high Sn-based Pb-free solders[J]. Appl. Phys. Lett., 2008, 92: 211909
[12] Huang M L, Zhang Z J, Zhao N, et al.In situ study on reverse polarity effect in Cu/Sn-9Zn/Ni interconnect undergoing liquid-solid electromigration[J]. J. Alloys Compd., 2015, 619: 667
[13] Huang M L, Zhao J F, Zhang Z J, et al.Dominant effect of high anisotropy in β-Sn grain on electromigration-induced failure mechanism in Sn3.0Ag-0.5Cu interconnect[J]. J. Alloys Compd., 2016, 678: 370
[14] Harris K E, Singh V V, King A H.Grain rotation in thin films of gold[J]. Acta Mater., 1998, 46: 2623
[15] Moldovan D, Yamakov V, Wolf D, et al.Scaling behavior of grain-rotation-induced grain growth[J]. Phys. Rev. Lett., 2002, 89: 206101
[16] Lloyd J R.Electromigration induced resistance decrease in Sn conductors[J]. J. Appl. Phys., 2003, 94: 6483
[17] Wu A T, Gusak A M, Tu K N, et al.Electromigration-induced grain rotation in anisotropic conducting beta tin[J]. Appl. Phys. Lett., 2005, 86: 241902
[18] Wu A T, Hsieh Y C.Direct observation and kinetic analysis of grain rotation in anisotropic tin under electromigration[J]. Appl. Phys. Lett., 2008, 92: 121921
[19] Huntington H B, Grone A R.Current-induced marker motion in gold wires[J]. J. Phys. Chem. Solids, 1961, 20: 76
[20] Shi J H, Huntington H B.Electromigration of gold and silver in single crystal tin[J]. J. Phys. Chem. Solids, 1987, 48: 693
[21] Prakash K H, Sritharan T.Interface reaction between copper and molten tin-lead solders[J]. Acta Mater., 2001, 49: 2481
[22] Liu C Y, Ke L, Chuang Y C, et al.Study of electromigration-induced Cu consumption in the flip-chip Sn/Cu solder bumps[J]. J. Appl. Phys., 2006, 100: 083702
[23] Linares X, Kinney C, Lee K O, et al.The Influence of Sn orientation on intermetallic compound evolution in idealized Sn-Ag-Cu 305 interconnects: An electron backscatter diffraction study of electromigration[J]. J. Electron. Mater., 2014, 43: 43
[24] Huntington H B.Diffusion in Solids: Recent Developments [M]. New York: Academic Press, 1975: 303
[25] Huang M L, Zhang Z J, Zhao N, et al.A synchrotron radiation real-time in situ imaging study on the reverse polarity effect in Cu/Sn-9Zn/Cu interconnect during liquid-solid electromigration[J]. Scr. Mater., 2013, 68: 853
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