Abstract: A method for forming ball pads of a BGA substrate is disclosed. A substrate is provided with a plurality of pad terminals on its surface. A solder mask is formed on the surface and has a plurality of openings to expose the pad terminals. A metal layer for redefining ball pads is formed on the solder mask. An etching mask is formed on the metal layer, the etching mask has a plurality of covering portions which are aligned with the pad terminals and larger than the openings of the solder mask. The metal layer is etched to form a plurality of redefined ball pads under the etching mask. The redefined ball pads cover the pad terminals of the substrate and extend around the openings of the solder mask so that solder balls can be jointed with the redefined ball pads to avoid contacting the solder mask and the pad terminals by redefinition of bonding area of solder balls.

Abstract: A ball grid array package substrate includes a substrate body having a surface. A least a ball pad and a solder mask are formed on the surface of the substrate body. The solder mask has an opening corresponding to the ball pads to enable the ball pad to have an exposed surface out of the opening of the solder mask. A patterned reinforcing metal layer is formed on the exposed surface of ball pads along a sidewall of the opening of the solder mask so that the sidewall of the opening will not directly contact the solder balls. Solder balls can be reflowed on the ball pads and the patterned reinforcing metal layers to increase jointing area and improve the shear strength of the solder balls.