Transmission line attenuation is known to be influenced by conductor surface profile (Rrms), an effect that worsens as frequency increases. In this paper, copper conductive losses are characterized from 0.03–30 GHz in low-loss materials incorporating various copper types and tracewidths, using microstrip transmission lines. Differing copper types are also evaluated in stripline structure using the Bereskin method. This comparison allows the relationship between Rrms and conductor loss to be quantified. The advantages of packaging low-loss materials with low profile copper foil are discussed.