Electrical connector system

A wafer assembly of an electrical connector system may include a metal center ground plane and a plurality of plastic ribs overmolded on the metal center ground plane. The plastic ribs may be positioned in a configuration that forms a plurality of electrical contact channels on the metal center ground plane. An array of electrical contacts may be positioned substantially within the plurality of electrical contact channels. In some implementations, the electrical connector system may also include a wafer housing and a header module that include guidance components that align the header module with the wafer housing when the wafer housing mates with the header module. The electrical connector system may also include a power contact that passes through aligned openings in the wafer housing and the header module to provide a power transmission path between the first substrate and the second substrate.