Cyclic bending reliability of wafer-level chip-scale packages

In this paper, both experimental and numerical studies are conducted to investigate board-level reliability of wafer-level chip-scale packages under four-point cyclic bending conditions that combine different deflection amplitudes and excitation frequencies. In addition to the fatigue lives of the test vehicle, locations and modes of fractured solder joints are observed. In the numerical modeling, inertia forces along with rate-dependent material properties of the solder joints are considered in order to capture frequency-dependent characteristics of this particular test methodology. Through the dynamic finite element analysis, plastic strain energy densities accumulated per bending cycle within the critical solder joint are calculated and together with the experimental results, parameters for the Morrow fatigue model are calibrated.