Conductive Material
Copper sheets with a treated surface roughness of less than one point five micrometers provide the interface for high frequency signal propagation on advanced laminates. Using hyper very low profile foil reduces the skin effect losses that occur when signals travel along the surface of a trace. The smooth topography of the metal ensures consistent impedance across the board.
Adhesion remains a primary concern because flatter surfaces offer fewer mechanical anchoring points for the resin.
Fabrication Advantage
Etching precision improves when the base material has a minimal tooth structure. Because hyper very low profile foil lacks deep protrusions into the dielectric, the chemistries remove unwanted copper more uniformly during the patterning process. This leads to sharper trace edges and tighter spacing tolerances.
Boards designed for millimeter wave applications require this level of geometric accuracy to maintain signal phase.
Adhesion Requirement
Chemical treatments compensate for the lack of mechanical grip between the metal and the prepreg. A hyper very low profile foil undergoes silane coating or other bonding enhancements to prevent delamination during lead free reflow cycles. Testing for peel strength ensures the bond meets the requirements of the industry standard.
Higher frequencies make the trade off between electrical performance and structural integrity more critical. This material choice defines the loss budget for the entire signal path.
