Patent ID: 8083123

Claim:
A method of manufacturing a printed wiring board having at least one solder bump thereon, the method comprising: forming a solder resist layer on a conductor layer, the solder resist layer having at least one opening that exposes a connection pad of the conductor layer, the at least one opening in the solder resist layer having a depth D, from the solder resist layer to the exposed connection pad, of from 3 μm to 18 μm, wherein the depth D of the opening in the solder resist layer is selected and meet the following equation: D≦R −√{square root over (R 2 −( W /2) 2 )} wherein R is a radius of the solder ball and W is a diameter of the at least one opening in the solder resist layer; loading a solder ball into each of the at least one opening in the solder resist layer; and forming a bump on the exposed connection pad by heating the solder ball to a reflow temperature.