Finite-element analysis of a PBGA assembly under isothermal/mechanical twisting loading

In order to reduce the reliability testing time for new electronic products, a new highly accelerated mechanical-thermal (HAMT) test system has been developed. In this system, a cyclic out-of-plane deformation is imposed on a printed circuit board (PCB) assembly by twisting the PCB mechanically inside a thermal chamber. The combined effects of the mechanical deformation and the coefficient of thermal expansion (CTE) mismatch of different materials accelerate the failure of solder joints, so as to reduce the reliability testing time of the PCB assembly. To verify the test method, HAMT tests of plastic ball grid array (PBGA) assemblies were carried out in an isothermal environment. Finite-element (FE) simulations were conducted to predict the reliability of the PBGA assemblies under the isothermal/mechanical twisting (ITMT) loading condition. In this paper, the simulation results are presented. The failure locations in the PBGA solder joints under the ITMT loading condition are investigated, and the fatigue life of the interconnections is predicted using Darveaux's crack initiation and growth model. The simulation results exhibit a good correlation with the test results.