Atmospheric Pressure Plasma Treatment for Direct Sputtering of Copper Seed Layers on Cycloolefin Polymer Films for High‐Frequency Applications

ABSTRACT This study investigates the feasibility of atmospheric pressure plasma (APP) treatment using a nitrogen–air gas mixture as a surface modification technique to enable the direct sputtering of copper seed layers on cycloolefin polymer (COP) films. The APP treatment achieved a peel strength of 0.6 kN/m between the COP film and the copper plating layer, exceeding the 0.5 kN/m threshold required for reliable circuit pattern formation. This result demonstrates the potential of the APP treatment as a cost‐effective and scalable alternative to vacuum‐based surface modification methods for high‐frequency applications, including next‐generation antenna substrates under ambient‐pressure conditions.