The electromagnetic modeling and parameter extraction of digital packages and PCB boards for system signal integrity applications are presented. A systematic approach to analyze complex power/ground structures and simulate their effects on digital systems is developed. First, an integral equation boundary element algorithm is applied to the electromagnetic modeling of the PCB structures. Then, equivalent circuits of the power/ground networks are extracted from the EM solution. In an integrated simulation scheme, the equivalent circuits are combined with signal nets, package models, device circuits, and other external circuitry for system level signal integrity analysis and simulation. This methodology has been implemented as software tools and applied to practical design problems. Effects related to power/ground networks, such as simultaneous switching noises, crosstalk, and ground discontinuity are analyzed for realistic designs.