This study examines the reliability of solder joints with voids under thermo mechanical loading. Nondestructive and destructive failure analysis has been done to inspect the presence and distribution of voids in a BGA component with 100 IO connections. Characteristic voiding scenarios have been created and implemented in a three dimensional finite-element model representing the component. The results of the nonlinear finite element analysis (FEA) are compared to the experimental thermal cycling results. A refined model including a critical joint of the package is then used to focus on the influence of voids. It will be shown that voids can increase a joint's reliability, have negligible impact or heavily reduce the lifetime all depending on the location and size within the solder volume.