Variation of stress across the length and thickness of a cantilever during creep allows obtaining multiple pairs of strain rates and stress under steady-state condition. This work applies digital image correlation (DIC) and conjugate analytical models to obtain several such “strain rate–stress” pairs during steady-state creep by testing a single cantilever at a constant applied load. Furthermore, these strain rate–stress pairs are used to accurately determine the stress exponent of the material (e.g., Al and Pb). In addition, an empirical observation of plotting strain rate as a function of stress at fixed strain during primary creep for estimating stress exponent is extended to bending creep, wherein strain rates of the points in the cantilever lying on an iso-strain contour were plotted against the moment at the point to determine stress exponent. This study, thereby, proves that the “bending creep–DIC” combination is a high throughput test methodology for studying steady-state creep.

The effective lifetimes of electronic packages are affected by various thermos-mechanical deformations. Creep is considered the most salient mechanism in the failure of solder joints. Many researchers have conducted reasonable studies to portray the behavior of creep deformation using numerical models and further extended their research scope to forecast the lifetimes of packages with the results obtained from creep models. Many studies have identified particular creep and lifetime models to be nominal based on experimental data.

In this study, the characteristics of familiar creep models were examined in detail, and their significance was made known. Lifetime prediction models that seem prominent among researchers were discussed in detail. Finite element analysis of a wafer level chip-scale package (WLCSP) used to figure out the engagement of different creep models and their capability of materializing creep deformation was investigated via simulation. The results from the simulation were applied to different lifetime prediction models, and their predictions were examined carefully. After considering the various factors that affected the reliability study of the solders, the Garofalo-Arrhenius creep model and modified strain energy density model seemed to be convincingly productive for studying the reliability of various electronic packages.