Low fractal dimension modified drilling-hole wall for PTFE high-frequency board copper plating with plasma treatment

摘要

The development of fifth generation communication has raised the demand of advanced polytetrafluoroethylene (PTFE) board in high-frequency signal transmission. Drilling holes are fabricated on PTFE substrate for subsequent copper plating to achieve interlayer electrical connection between the thin dielectric layers. In this article, we propose O-2/CF4 plasma treatment to clean the after-drilling PTFE hole, achieving highly activated surface for following copper plating. The plating results, in contrast with control experiments which were performed without plasma treatment, demonstrate multiple advantages of O-2/CF4 plasma treatment including qualified copper plating, excellent thermal shock reliability, and improved wettability. X-ray photoelectron spectroscopy analysis for plasma-treated samples confirms the emergence of hydrophilic groups such C(sic)O and COO/COF on PTFE hole wall. In addition, optimized parameters with particle gas flow combination and process time were obtained through parameter sweeping. The best qualified sample was associated with the lowest roughness (fractal dimension) of PTFE hole wall, indicating its promising application in high-frequency signal transmission in PTFE board. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48052.