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The creep-fatigue life evaluation of Sn-3.5Ag solder under-push pull loading is studied using fast-fast, fast-slow, slow-fast, slow-slow and strain-hold strain waves. Extensive creep-fatigue data are generated using these strain waves and the applicability of four conventional creep-fatigue damage rules, the linear damage rule, the frequency modified fatigue life, the ductility exhaustion model, and the strain range partitioning methods are examined.

This paper studies creep-fatigue life prediction under shear loading by making extensive torsion creep-fatigue experiments using four kinds of strain waves. The linear damage rule, strain range partitioning method, frequency modified fatigue life, and ductility exhaustion model were applied to the experimental data, but no methods accurately predicted the creep-fatigue life. A new method based on the strain rate ratio, which predicted the creep-fatigue life within a factor of 4 scatter band, was developed. [DOI: 10.1115/1.2070091]

This paper describes the tensile strength and inelastic constitutive relationship of six types of Sn-Pb solders. Static tension tests were carried using 5Sn-95Pb, 10Sn-90Pb, 40Sn-60Pb, 60Sn-40Pb, 63Sn-37Pb, and 62Sn-36Pb-2Ag solders at the strain rates of 0.001-10.0%/s between temperatures of 313 K and 398 K. Strain rates faster than 2.0%/s were needed to obtain the time-independent Young modulus and yield stress of the solders. Tensile strength increased with increasing strain rates up to 10%/s. Parametric equations for predicting tensile strength, Young's modulus and yield stress of Sn-Pb solders were developed as a function of temperature and Sn content. Plastic and creep constitutive equations were also proposed as a function of temperature and Sn content. The stress amplitude predicted by these equations agreed with the experimental results within [+ or -] 2 MPa. [DOI: 10.1115/1.1533058]

A study examines the notch effect on low cycle fatigue of Sn-3.4Ag solder by carrying out push-pull low cycle fatigue tests and an a.c. potential method. Results show that there was a decrease in cycles to failure, to crack initiation, and for propagation with elastic stress concentration factor but cycles to crack initiation were significantly reduced with elastic stress concentration factor.

This paper describes the life assessment of flip chip joints. Flip chip joints of 63Sn-37Pb and 5Sn-95Pb solders on a printed circuit board were stressed thermally for fatigue. Fatigue lives of the joints were determined by an electrical potential drop method and the effect of encapsulation on fatigue life was discussed. The encapsulation had a significant effect of prolonging the fatigue life of the joints. Thermo-mechanical finite element analyses proved that the encapsulation lowered the strain amplitude of the joints by distributing the strain over a whole package and bending effect. Cracking location was also discussed in relation with the strain concentration in the joints. Fatigue lives of the flip chip joints were compared with those of bulk round bar specimens and the difference in fatigue life between two types of specimens was discussed from the specimen dimensions and ratchet effect. [S1043-7398(00)00203-6]