Impact of plasma etching on fabrication technology of liquid crystal polymer printed circuit board

Liquid crystal polymer (LCP) has attracted great attention as a potential candidate for high performance micro-wave substrate material in high frequency printed circuit boards (PCB). This is attributed to its low loss behaviour, excellent thermal stability, and outstanding chemical resistance. The use of LCP in PCB, however, is hindered by its extreme chemical inertness, causing fabrication challenges in desmearing and metallization processes. To overcome the challenges, plasma etching is suggested for its capability of smear removal, adhesion improvement and surface activation of PCB material. However, previous experimental and theoretical studies of the effects of plasma etching on LCP PCB at different treatment conditions are lacking. This paper thus evaluates recent developments on plasma etching technologies, involving the plasma etching investigation under different process conditions for manufacturing LCP PCB. Distinct process approaches are developed and proposed based on the illustrations of the experimental outcomes. Finally, examples are shown to demonstrate the effectiveness of the proposed plasma etching approach for controlling the fabrication of LCP PCB.