Thermomechanical Fatigue Life Prediction of 63Sn/37Pb Solder

Abstract

Isothermal and thermomechanical fatigue of 63Sn/37Pb solder is studied under total strain-controlled tests. A standard definition of failure is proposed to allow inter-laboratory comparison. Based on the suggested failure criterion, load drop per cycle, the Young’s modulus and the ratio of the maximum tensile to maximum compressive stresses remain constant, and the fatigue response of the solder is stable before failure, although cyclic softening was observed from the beginning. Experimental results of isothermal fatigue tests for a total strain range from 0.3 to 3 percent show that the log-log plot of the number of cycles to failure versus the plastic strain range has a kink at the point where the elastic strain is approximately equal to the plastic strain. In this paper, it is shown how the isothermal fatigue life of near-eutectic solder at lower strain ranges can be predicted by using the experimental data of fatigue tests at high strain ranges and early stage information of a fatigue test at the strain range in question. A thermomechanical fatigue life prediction is also given based on a dislocation pile-up model. Comparison with experimental results shows a good agreement.

Low Cycle Fatigue Properties of Ni added Low Silver Content Sn-Ag-Cu Flip Chip Interconnects

“…On the other hand, the Ni added low silver content alloy has superior fatigue resistance in any displacement regimes, and the life is almost equivalent to that of 3 mass%Ag alloy. Since an increase in silver content up to 2 mass% did not improve low cycle fatigue resistance of Sn-xAg-0.5 mass%Cu alloy in our previous study, 6) the result suggests that small amount of Ni has an effect to enhance low cycle fatigue resistance of low silver content Sn-Ag-Cu alloy.…”

“…8,9) In order to evaluate the mechanical shear fatigue properties of the flip-chip interconnections, the straddle fatigue test was used in this study. 6,10,11) The methodology of the straddle fatigue test is imposition of shear deformation into the solder alloy by mechanical displacement of the substrates as shown in Fig. 4.…”

“…In our previous study, 6) we investigated the relationship between the low cycle fatigue life of Sn-xAg-0.5 mass%Cu flip-chip interconnects and silver content. The fatigue life of 3 mass%Ag solder alloy was longer than that of other alloys tested.…”

Measuring intrinsic elastic modulus of Pb/Sn solder alloys

“…Intrinsic (time-independent) Young's modulus values of 9-48 GPa have been reported in the literature (Basaran and Chandaroy, 1998;Dasgupta et al, 2001;Dun, 1975;Frear et al, 1995;Hacke et al, 1997;Knecht and Fox, 1990;Zubelewicz, 1993;Frear et al, 1994;Harper, 1970;Pecht et al, 1999;Guo et al, 1991;Bonda and Noyan, 1996;Ling and Dasgupta, 2000). In computational mechanics analysis, results vary significantly if 9 GPa is used instead of 48 GPa.…”

A modified energy-based low cycle fatigue model for eutectic solder alloy

“…Strain-based models, notably the Coffin-Manson model (1-2), have been widely used to characterize low cycle fatigue behaviors of engineering materials including solder alloys (3)(4)(5). However, it is practically very difficult to obtain a single plastic strain value in a solder joint because of the complex stress state (6).…”