Patent ID: 8105644

Claim:
A manufacturing method of a printed circuit board comprising the steps of: forming a circuit board having a plurality of conductive pads on an insulating layer of said circuit board; and placing a printing mask, which has a plurality of openings corresponding to said plurality of conductive pads, on said circuit board and applying conductive paste onto said plurality of conductive pads through said plurality of openings, wherein a respective peripheries of each of the openings of said printing mask is bent in a concave shape toward a respective inside of each of the openings to form rectangular recesses, and wherein each of said plurality of openings is composed of a first wide portion, a narrow portion and a second wide portion that are formed in a rectangular region, said first and second wide portions are arranged along both end sides if said rectangular region, said narrow portion is arranged between said first wide portion and said second wide portion so as to extend in parallel with both lateral sides of said rectangular region, said recesses correspond to respective regions between the both lateral sides of said rectangular region and both lateral sides of said narrow portion, when it is assumed that a length of said lateral side of said rectangular region is a, a length of said end side of said rectangular region is b, and an area of said opening is A, said opening satisfies a relation obtained by 0.05<( a×b−A )/( a×b ).