Characterization of elasto-plastic behavior of actual SAC solder joints for drop test modeling

This paper focuses on the characterization of the elasto-plastic properties of actual Sn–1.0 wt.%Ag–0.5 wt.%Cu (SAC105), Sn–3.0 wt.%Ag–0.5 wt.%Cu (SAC305) and Sn–4.0 wt.%Ag–0.5 wt.%Cu (SAC405) solder joints for drop test modeling. Several actual ChipArray® BGA (CABGA) packages were cross-sectioned, polished and used as the test vehicles. The drop tests were performed with various impact amplitudes using a specially designed mini drop table along with a conventional drop table to generate plastic deformations in the solder joints. The plastic deformations in the solder joints were measured after each drop using microscope imaging in conjunction with the digital image correlation (DIC) technique. The coefficients of the Ramberg–Osgood elasto-plastic model for the solder alloys were extracted from the experimental results using a finite element method (FEM) modeling-based iteration process. An application and validation of the developed model were carried out using pendulum tests.