Abstract: Parylene and plasma-enhanced chemical vapor deposition (PECVD) nano coatings were prepared on printed circuit board (PCB) surfaces by vacuum chemical vapor deposition technology (CVD). The effects of coating thickness and PCB surface ion concentration on the protective performance of the coatings were investigated. The results show that the protective performance of the parylene nano coatings was observed to degrade with increasing PCB surface ion concentration and decreasing coating thickness. The PECVD nano coating demonstrated significantly superior protective effectiveness compared to the parylene nano coating, exhibiting minimal dependence on variations in both PCB surface ion concentration and coating thickness. The selection and application of PCB surface protection materials should comprehensively consider both hydrophobicity and barrier performance to achieve optimal surface protection.