A PECVD fabricated ultra-thin bilayer coating with superior corrosion resistance and low signal loss for high-frequency PCBs

Abstract

Undesirable high thickness, terrible loss of high-frequency signal and poor adhesion of the traditional coating had plagued the anticorrosive field of high-frequency circuit boards (PCBs). Herein, a novel ultra-thin bilayer anticorrosive coating was manufactured. The initial Poly (butyl acrylate) coating (~30 nm) was firstly fabricated on the PCBs by plasma enhanced chemical vapor deposition (PECVD). Immediately, the Poly (dodecafluoroheptyl methacrylate) coating, as an external protective coating with low surface energy, was fabricated onto the initial Poly (butyl acrylate) coating via a similar approach. The bilayer anticorrosive coating showed the convex structure of bionic lotus leaf, which caused the water contact angle raised from 62.3° to 108.7°. After a 96-hour corrosion test, the circuit of the high-frequency PCBs with the coating (only 250 nm) can be perfectly protected. Simultaneously, the cross-cut test and molecular dynamics simulations showed the coating had an excellent interface adhesion with the PCB substrate. Importantly, compared with the commercial coating, the bilayer anticorrosive coating exhibited little signal loss over a wide frequency range, even up to 0.63 dB (250 nm, 20 GHz). This work provided clear guidance and a strong impetus for the development of corrosion-resistant coating for high-frequency PCBs.