Guy. After concrete pouring and slurry collection, cover the concrete with geotextile for water conservation as soon as possible, so as to keep the concrete surface moist all the time, and the maintenance time is at least 7 days, so as to avoid cracks in concrete due to temperature shrinkage. The main function of cover plate is to improve the drilling quality and yield, and it is an indispensable plate in the process of NC drilling of printed circuit boards at present.