Patent ID: 8227175

Claim:
A method for smoothing a printed circuit board (PCB), comprising: providing a PCB comprising a base, a first electrically conductive layer and a second electrically conductive layer, the PCB defining a plurality of buried holes therein passing through the first electrically conductive layer and a portion of the base while exposing a portion of the second electrically conductive layer, an electrically conductive material filling in each of the buried holes and electrically connected to the first and the second electrically conductive layers, the PCB having a first smooth outer surface on the base and the second electrically conductive layer, and an opposite second outer surface, the second outer surface including a smooth region on the first electrically conductive layer and a plurality of dimples each having an arc cross-section on the electrically conductive material; applying a liquid photoresist layer onto the entire second outer surface of the PCB to fill the dimples; removing the portions of the liquid photoresist layer on the smooth region, with the portions of the liquid photoresist layer corresponding to the dimples remaining, thereby forming protrusions of the liquid photoresist layer; solidifying the remaining portions of the liquid photoresist layer to obtain a solidified photoresist layer; polishing the protrusions of the solidified photoresist layer until a surface of the protrusions is coplanar with the smooth region, with portions of the solidified photoresist layer in the dimples remaining; and polishing the entire second outer surface until the solidified photoresist layer is completely removed, thereby obtaining a plain outer surface parallel to the first smooth outer surface.