Patent ID: 8756804

Claim:
A method of manufacturing a printed circuit board, comprising: providing a base member; forming an insulating layer on each of both surfaces of the base member; forming a through hole in the base member; forming a via in the through hole; forming a circuit layer on each of both surfaces of the base member so that the circuit layer formed on one surface of the base member and the circuit layer formed on the other surface of the base member are connected with each other using the via; and forming a protection layer for covering the circuit layer, wherein the protection layer has an opening for exposing the pad of the circuit layer or the via and is formed by means of a photoresist using a liquid photodefinable material, wherein the opening of the protection layer is formed through photo-exposure and development processes and is subjected to rounding treatment so as to be imparted with a shape which has a diameter that increases as the opening becomes more distant from the base member by using a prebaked process at 60-150° C. for 1-10 minutes and, after the photo-exposure process, a curing at 180-250° C. for a period of time ranging from 30 minutes to 2 hours, and wherein the insulating layer serves to flatten the surfaces of the base member by offsetting the surface roughness.