What is Access Hole Exposure (Dew through, Under Hole)

Access Hole exposes the hole (through the exposed hole, exposed bottom hole) ---- often refers to the protective layer Coverlay of the outer surface of the soft board (to be first punched through the exposed hole), used to fit on the surface of the soft board as a solder mask the use of. However, it is necessary to deliberately reveal the hole ring wall or square pad required for welding in order to facilitate the welding of the parts. The so-called "Access Hole" text means that the surface has been exposed, so that the outside world can be "close" to the meaning of the surface of the board surface solder joints. Some multilayer boards also have this exposed hole.