Thermo-mechanical analysis of solder joint fatigue and creep in a flip chip on board package subjected to temperature cycling loading

Thermo-mechanical stress analysis was conducted on a flip-chip-on-board (FCOB) package with underfill encapsulation. The solder joint fatigue and creep deformation response were modeled for a typical temperature cycling loading of -55 to 125 C. Two temperature cycling loading models with and without the curing part of the temperature history for the encapsulation process were investigated. Two-dimensional plane-strain finite element models of the FCOB package were employed. Elasto-plastic and creep deformation behavior of solder was simulated under the temperature cycling conditions to obtain the stress and strain results. The finite element strain results were used in fatigue life prediction models