Abstract: Provided is a method of fabricating a semiconductor package. The method includes providing a package substrate including a pad, mounting a semiconductor chip with a solder ball on the package substrate to allow the solder ball to be disposed on the pad, filling a space between the package substrate and the semiconductor chip with a underfill resin including a reducing agent comprising a carboxyl group, and irradiating the semiconductor chip with a laser to bond the solder ball to the pad, wherein the bonding of the solder ball to the pad comprises changing a metal oxide layer formed on surfaces of the pad and the solder ball to a metal layer by heat generated by the laser.