Signal Loss
Electromagnetic wave propagation along printed circuit board transmission lines experiences progressive signal amplitude degradation as frequency increases. High frequency attenuation measures total signal power loss resulting from dielectric absorption and conductor surface resistance along RF trace paths. Signal degradation limits maximum achievable trace length for gigabit data channels.
Conductor Loss
Electric current at high frequencies shifts toward the outer skin of metallic conductors, reducing effective cross-sectional conduction area and elevating AC resistance. Surface roughness at the copper dielectric interface lengthens the physical current path, aggravating conductor losses at microwave frequencies. Smooth copper foils decrease surface resistance but lower mechanical bond strength between metal layers and substrate resin.
High frequency attenuation rises sharply when copper surface profile heights exceed skin depth values at target operational frequencies. Trace width expansion reduces conductor resistance but increases substrate area requirements and capacitive coupling to adjacent ground planes.
Dielectric Loss
Substrate polymer molecules reorient continuously under high-frequency alternating electric fields, converting electromagnetic energy into thermal heat within the dielectric material. Dissipation factor values of resin systems govern energy absorption rates along transmission paths. Dielectric losses dominate total signal attenuation above multi-gigahertz thresholds where conductor skin losses flatten out.
Low loss dielectric resins minimize signal amplitude reduction across long backplane channels.
