A wiring substrate having variously sized ball pads, a semiconductor package including the wiring substrate, and a stack package using the semiconductor package, to improve board level reliability (BLR) of a semiconductor package or stack package mounted on a mother board are shown. Outer ball pads are formed to have relatively greater surface areas at the corners of the semiconductor package as compared to those at other areas and are formed to have the greatest surface area within a designable range. Additionally, occurrence of cracks may be inhibited at junctions of other solder balls by forming dummy solder pads at the outermost corners among the outer ball pads formed proximate to the corners of the wiring substrate. Stress arising during a board level reliability test is absorbed without product failure at junctions between the dummy solder pads and dummy solder balls.