chip 20 is attached to the die pad 14 using a conductive adhesive 22 e g a silver filled epoxy or a silver filled glass adhesive the semiconductor chip 14 and the metal wiring 16 are electrically interconnected by a conductive wire e g metal wire 24 the wiring pattern 16 on the chip mounting surface may extend to the bottom surface through via holes 28 heat generated from the chip 20 can be dissipated through thermal via holes 17 the ball land 18 is surrounded by the solder mask 19 by placing the solder balls 25 onto the ball land is and then performing reflow soldering the solder balls 25 are soldered to the land 18 at this time a solder ball joint 27 is formed by the joint e g metal to metal between the solder ball 25 and the ball land 18 the semiconductor chip 20 and metal wiring 16 are protected by an encapsulant such as a plastic resin 26 to form a package body the bga package 10 is mounted onto a circuit board 30 for example a module board consisting of a memory module by surface mounting the package so that the solder ball 25 is soldered to the conductive pad 32 the reliability of the solder ball joint 27 is affected by the design of the conductive pad 32 however the.