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Research Papers

Effects of Strain Rate and Amplitude Variations on Solder Joint Fatigue Life in Isothermal Cycling

[+] Author and Article Information
Sa'd Hamasha

Department of Engineering Management,
Rose-Hulman Institute of Technology,
Terre Haute, IN 47803
e-mail: hamasha@rose-hulman.edu

Peter Borgesen

Department of Systems Science and
Industrial Engineering,
Binghamton University,
P.O. Box 6000,
Binghamton, NY 13902

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received November 6, 2015; final manuscript received February 19, 2016; published online March 23, 2016. Assoc. Editor: Yi-Shao Lai.

J. Electron. Packag 138(2), 021002 (Mar 23, 2016) (9 pages) Paper No: EP-15-1128; doi: 10.1115/1.4032881 History: Received November 06, 2015; Revised February 19, 2016

The behavior of lead-free solder alloys under realistic service conditions is still not well understood. Life prediction of solder joints relies on conducting accelerated tests and extrapolating results to service conditions. This can be very misleading without proper constitutive relations and without understanding the effects of cycling parameter variations common under realistic service conditions. It has been shown that the fatigue life depends on the inelastic work accumulation, independently of cycling-induced material property variations, which explains the breakdown of damage accumulation rules and allows the development of a modified Miner's rule. This paper discusses the interacting effects of strain rate and amplitude variations on solder joint fatigue life. Individual SnAgCu solder joints with two different Ag contents (SAC305 and SAC105) were tested in low cycling shear fatigue under single and varying amplitudes with different strain rates. Such a shear fatigue experiment allows the measurement of work accumulation and the evolution of solder deformation properties during cycling. The results showed that cycling with a lower strain rate at fixed amplitude causes more damage per cycle. Alternating between mild amplitude at a high strain rate and harsh amplitude at a low strain rate leads to ongoing increases in the rate of damage at the mild amplitude and thus relatively rapid failure. In comparing SAC305 with SAC105, the effect of strain rate on both alloys is almost the same, and SAC305 is still more fatigue resistant than SAC105 in varying amplitude cycling with any strain rate.

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References

Figures

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Fig. 1

Schematic view of the shear fatigue fixture with a solder joint

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Fig. 2

Experimental setup using Instron Micromechanical Tester

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Fig. 3

Load–displacement loops for SAC305 solder joint cycled with amplitudes of 400 gf

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Fig. 4

Load–displacement curves of SAC305 solder joint cycled with two different strain rates

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Fig. 5

The work per cycle of two SAC305 solder joints cycled with a fixed amplitude of 20 MPa and different strain rates

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Fig. 6

The average steady-state work per cycle versus the strain rate on a log–log scale

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Fig. 7

Fatigue life of SAC305 solder joints at 24 MPa as a function of strain rate

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Fig. 8

Correlation between the average damage per cycle (1/fatiguelife) and the average steady-state work per cycle for cycling with different strain rates

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Fig. 9

The work per cycle of SAC305 solder joint cycled with a repeated sequence of 50 cycles at 16 MPa and three cycles at 24 MPa

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Fig. 10

The amplification factor data as a function of the number of intervals for a SAC305 solder joint in a repeated sequence of 50 cycles at 16 MPa and three cycles at 24 MPa

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Fig. 11

The work per cycle of a SAC305 solder joint cycled with a repeated sequence of 50 cycles at 12 MPa with 0.015/s and 15 cycles at 12 MPa with 0.0003/s

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Fig. 12

Work per cycle of SAC305 solder joint in repeated sequence of (16 MPa at 0.3/s + 16 MPa at 0.03/s + 24 MPa at 0.3/s)

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Fig. 13

Amplification factor in fast and slow 16 MPa amplitudes after applying a higher amplitude of 24 MPa with strain rate of 0.3/s on SAC305 solder joint

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Fig. 14

Paired comparison of SAC305 solder joints amplification factor between mild amplitude at 0.3/s and 0.03/s strain rates after applying a higher amplitude at 0.3/s strain rate

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Fig. 15

Paired comparison of SAC105 solder joints amplification factor between mild amplitude at 0.3/s and 0.03/s strain rates after applying a higher amplitude at 0.3/s strain rate

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Fig. 16

Work per cycle of SAC305 solder joint in repeated sequence of (16 MPa at 0.3/s + 24 MPa at 0.3/s + 16 MPa at 0.3/s + 24 MPa at 0.03/s)

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Fig. 17

Amplification factor at a mild amplitude of 16 MPa with 0.3/s after applying a higher amplitude of 24 MPa with strain rates of 0.3/s and 0.03/s on a SAC305 solder joint

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Fig. 18

Paired comparison of SAC305 solder joint amplification factors after higher amplitude at 0.3/s and 0.03/s strain rates for the mild amplitude at 0.3/s

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Fig. 19

Paired comparison of SAC105 solder joint amplification factors after higher amplitude cycling with 0.3/s and 0.03/s strain rates for the mild amplitude with 0.3/s

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Fig. 20

Work per cycle of SAC305 solder joint in repeated sequence of (16 MPa at 0.03/s + 24 MPa at 0.3/s + 16 MPa at 0.03/s + 24 MPa at 0.03/s)

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Fig. 21

Amplification factor at mild amplitude of 16 MPa with 0.03/s after applying a higher amplitude of 24 MPa with strain rates of 0.3/s and 0.03/s on SAC305 solder joint

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Fig. 22

Paired comparison of SAC305 solder joint amplification factors after higher amplitude cycling with 0.3/s and 0.03/s strain rates for the mild amplitude with 0.03/s

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Fig. 23

Paired comparison of SAC105 solder joint amplification factors after high amplitude cycling at 0.3/s and 0.03/s strain rates for the mild amplitude at 0.03/s

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Fig. 24

Average slope of work amplification in combinations of mild and harsh amplitudes with different cycling speeds on SAC305 and SAC105 solder joints

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Fig. 25

The average values of the plastic deformation of SAC305 solder joints

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Fig. 26

The plastic strain of a SAC305 solder joint cycled with a repeated sequence of 50 cycles at 12 MPa with 0.015/s and 15 cycles at 12 MPa with 0.0003/s

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