A manufacturing method of PCB back drill hole

The invention discloses a manufacturing method of PCB back drill hole, which comprises the following steps: laminating, drilling through holes, chemical copper precipitation, electroplating copper, whole plate tin plating, drilling back drilling, tin removing, pre-drying plate, resin plug hole, drying plate and grinding plate; Wherein the back drill hole is a back drill hole having a special structure, wherein the depth ratio of the back drill hole depth to the through hole depth is greater than or equal to 1, and the depth of the back drill hole is greater than or equal to 0.5 mm; The pre-drying plate retains the residual temperature of the plate surface, and the residual temperature is higher than the ambient temperature for resin plug holes; The resin plug hole is plugged in such a waythat resin ink flows into the back hole from the through hole of the plate, and the whole back hole and the through hole are filled. The invention increases the plumpness of the plug hole of the backhole with the special stru