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 a portable electronic device, comprising an electrical assembly, comprising: a chassis made from a conductive material and forming a first ground plane; a first dielectric substrate layer overlaying the chassis; a first signal trace overlaying the first dielectric substrate layer; and a second dielectric layer overlaying the first signal trace.