Enhanced Corrosion\nProtection of Printed Circuit Board\nElectronics using Cold Atmospheric Plasma-Assisted SiO<sub><i>x</i></sub> Coatings

The miniaturization and widespread deployment of electronic\ndevices\nacross diverse environments have heightened their vulnerability to\ncorrosion, particularly affecting copper traces within printed circuit\nboards (PCBs). Conventional protective methods, such as conformal\ncoatings, face challenges including the necessity for a critical thickness\nto ensure effective barrier properties and the requirement for multiple\nsteps of drying and curing to eliminate solvent entrapment within\npolymer coatings. This study investigates cold atmospheric plasma\n(CAP) as an innovative technique for directly depositing ultrathin\nsilicon oxide (SiO<sub><i>x</i></sub>) coatings onto copper\nsurfaces to enhance corrosion protection in PCBs. A systematic investigation\nwas undertaken to examine how the scanning speed of the CAP deposition\nhead impacts the film quality and corrosion resistance. The research\naims to determine the optimal scanning speed of the CAP deposition\nhead that achieves complete surface coverage while promoting effective\ncross-linking and minimizing unreacted precursor entrapment, resulting\nin superior electrical barrier and mechanical properties. The CAP\ncoating process demonstrated the capability of depositing SiO<sub><i>x</i></sub> onto copper surfaces at various thicknesses\nranging from 70 to 1110 nm through a single deposition process by\nsimply adjusting the scanning speed of the plasma head (5–75\nmm/s). Evaluation of material corrosion barrier characteristics revealed\nthat scanning speeds of 45 mm/s of the plasma deposition head provided\nan effective coating thickness of 140 nm, exhibiting superior corrosion\nresistance (30-fold) compared to that of uncoated copper. As a proof\nof concept, the efficacy of CAP-deposited SiO<sub><i>x</i></sub> coatings was demonstrated by protecting an LED circuit in\nsaltwater and by coating printed circuits for potential agricultural\nsensor applications. These CAP-deposited coatings offer performance\ncomparable to or superior to traditional conformal polymeric coatings.\nThis research presents CAP-deposited SiO<sub><i>x</i></sub> coatings as a promising approach for effective and scalable corrosion\nprotection in miniaturized electronics.