Comparison of vacuum ultraviolet irradiation and oxygen plasma treatment as pretreatment for copper seed layer on cycloolefin polymer
Akihiro Shimizu1,2, Kazuhiro Fukada 3, Shinichi Endo 1, and Shinji Kambara 2
1 Ushio Inc. (Japan)
2 Gifu University (Japan)
3 Shibaura Machine Co., Ltd. (Japan)
We investigated the adhesion characteristics between a cycloolefin polymer (COP) film and a copper plating layer with a directly sputtered copper seed layer, aiming for application to antenna substrates in next-generation 6G communication systems. We focused on how different surface modification methods—vacuum ultraviolet (VUV) irradiation and oxygen plasma treatment—affect peel strength. VUV irradiation resulted in the formation of a brittle modified layer on the COP surface, leading to substrate failure. In contrast, oxygen plasma treatment produced a very thin modified layer and promoted the formation of Cu2O at the interface by introducing functional groups that chemically bonded with copper, leading to high peel strength and interfacial failure. These results suggest that enhancing peel strength requires suppressing excessive surface brittleness while introducing sufficient functional groups to facilitate interfacial chemical bonding.
