Copper Foil Profile

Electrical Impact

Signal propagation at frequencies above 10 GHz is restricted to the outer skin of the conductor due to the skin effect. When the copper foil profile is deep, the signal path length increases as electrons follow the contours of the jagged surface, which leads to higher conductor loss. This physical lengthening of the path also introduces phase variation in high speed differential pairs.

Smooth foils prevent this loss.

Adhesion Boundary

Peel strength decreases as the topography becomes smoother. While a very low profile reduces insertion loss, it raises the risk of delamination during thermal cycling or lead free soldering. Chemical treatments are applied to smooth foils to provide chemical bonding where physical interlocking is absent.