Topographic Metric
Arithmetic mean deviation represents the average absolute departure of a surface profile from a mean centerline over a specific sampling length. The term copper surface roughness sa quantifies the texture of conductive foils used in printed circuit board fabrication. Manufacturers measure this value to determine how effectively a dielectric layer anchors to the metallic base.
High values increase the interface area while low values facilitate higher frequency signal transmission through the conductive traces.
Process Requirement
Fabricators apply this parameter during the lamination stage to control the mechanical bond strength between the epoxy resin and the metallic surface. Chemical etching or mechanical treatments modify the profile before the layup process begins to reach target values. Insufficient height results in delamination under thermal stress during assembly, while excessive height introduces impedance variations at high data speeds.
Verification typically occurs using optical profilometry or contact stylus instruments before the circuit pattern formation.
Signal Impact
Electromagnetic performance fluctuates as a direct result of skin effect losses at high frequencies where current travels primarily along the outer layer of the conductor. Conductive paths with high peak to valley height exhibit increased resistance because the signal path length grows relative to a perfectly smooth surface. Engineers select specific copper profiles to align with performance goals for high speed digital or radio frequency applications.
Signal attenuation rises in proportion to the severity of these surface deviations.
