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RESEARCH PAPERS

Inelastic Deformation and Fatigue of Solder Alloys Under Complicated Load Conditions

[+] Author and Article Information
J. Liang1

School of Materials Science & Engineering, Chongqing University, Chinajliang@alum.MIT.EDU

N. Dariavach, P. Callahan

 EMC Corporation, Hopkinton, MA 01748

D. Shangguan

 Flextronics, San Jose, CA 95131

1

Currently on sabbatical leave from EMC Corp, is a specially appointed guest professor at Chongqing University, China.

J. Electron. Packag 129(2), 195-204 (Jun 23, 2006) (10 pages) doi:10.1115/1.2721593 History: Received March 14, 2006; Revised June 23, 2006

Fundamental study of deformation and fatigue fracture behavior of solder alloys under complex load conditions is a key to enabling implementation of sophisticated three-dimensional (3D) time-dependent nonlinear finite-element stress and strain analyses for the life assessment for electronic packages and assemblies. In this study, the rate-dependent deformation and fatigue fracture behavior of Sn3.8Ag0.7CuPb-free alloy and SnPb eutectic alloy was investigated with thin-walled specimens using a biaxial servo-controlled tension–torsion material testing system, with solder alloys subjected to a variety of complex load conditions: pure shearing at strain rates between 6.7×107s and 1.3×101s, creep at temperatures ranging from room temperature up to 125°C, and cyclic loading with frequencies of 0.001Hz to 3Hz. Biaxial stress conditions were imposed to investigate the effects of multiaxial stresses on deformation behavior. The effects of frequency and temperature on cyclic deformation and fatigue facture were investigated for lead-free Sn3.8Ag0.7Cu and SnPb eutectic solder. Fractography of fatigue tested samples was also conducted to determine possible fatigue failure mechanisms.

Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 3

Comparison of shear stress–strain curves for the Sn–Pb eutectic and SAC 387 alloys at strain rate of 6.7×10−7∕s

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Figure 4

Comparison of shear stress–strain curves for the Sn–Pb eutectic and SAC 387 alloys at strain rate of 1.3×10−1∕s

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Figure 5

Variable strain rate tests, increasing rates from 1.3×10−4∕s to 1.3×10−2∕s

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Figure 6

Variable strain rate tests, decreasing rates from 1.3×10−2∕s to 1.3×10−5∕s

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Figure 11

Axial stress effect on shearing at controlled shear rate of 1.3×10−4∕s for the Sn–Pb eutectic alloy

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Figure 12

Axial stress effect on shearing at controlled shear rate of 1.3×10−2∕s for the Sn–Pb eutectic alloy

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Figure 13

Shear creep curves of the SAC 387 lead-free solder at room temperature

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Figure 14

Shear creep curves of the Sn–Pb eutectic solder at room temperature

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Figure 15

Shear creep rates versus stress for the SAC 387 alloy

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Figure 16

Shear creep rates versus stress for the Sn–Pb eutectic alloy

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Figure 17

Temperature effects on creep rates for the SAC 387 alloy

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Figure 18

Temperature effects on creep rates for the Sn–Pb eutectic solder

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Figure 19

LCF S–N curves for the Pb-free SAC 387 alloy at RT

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Figure 20

LCF S–N curves for the Sn–Pb eutectic alloy at RT

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Figure 21

Fatigue damage process comparison of the Sn–Pb eutectic and SAC 387 alloys at 0.1Hz

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Figure 22

Fatigue damage process comparison of the Sn–Pb eutectic and SAC 387 alloys at 3Hz

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Figure 23

Temperature effects on LCF damage process (f=3Hz, strain amplitude of 0.24%)

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Figure 24

Temperature effects on LCF damage process (f=0.1Hz, strain amplitude of 0.24%)

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Figure 25

Surface cracking on Sn–Pb sample (0.48%, 3Hz)

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Figure 26

Surface cracking of SAC 387 (0.24%, 0.1Hz)

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Figure 27

Intergranular surface cracking on Sn–Pb sample with 0.48% strain amplitude, 0.1Hz

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Figure 28

Intergranular surface cracking on SAC 387 sample, with 0.24% strain amplitude, 0.01Hz

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Figure 29

Transgranular crack growth on Sn–Pb sample with 0.48% strain amplitude, 0.1Hz

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Figure 30

Transgranular crack growth on SAC alloy sample with 0.24% strain amplitude, 0.01Hz

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Figure 2

Strain rate effects on shear deformation of the Pb-free SAC 387 solder

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Figure 1

Strain rate effects on shear deformation of the Sn–Pb eutectic solder

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Figure 10

Shearing strain versus stress with axial stress of 0ksi, 1.5ksi, and 3.0ksi at a higher shear rate of 1.3×10−2∕s for the Pb-free SAC 387 alloy

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Figure 9

Shearing strain versus stress with axial stress of 0ksi, 1.5ksi, and 3.0ksi at controlled shear rate of 1.3×10−4∕s for the Pb-free SAC 387 alloy

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Figure 8

Simultaneous axial tension creep deformation under 1.5ksi and 3.0ksi axial stress during shearing tests along the thin-wall circumferential direction

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Figure 7

Biaxial test profiles with fixed axial tensile stress (1.5ksi or 3.0ksi) and controlled shear rate along the thin-wall circumferential direction

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