Electrical assembly having impedance controlled signal traces

An electrical assembly having controlled impedance signal traces and a portable electronic device comprising an electrical assembly having controlled impedance signal traces are provided. In accordance with one embodiment, there is provided an electrical assembly, comprising: a chassis for mounting electronic components, the chassis being made from a conductive material and forming a first ground plane; a first dielectric layer overlaying the chassis; a first signal trace overlaying the first dielectric layer; and a second dielectric layer overlaying the first signal trace.