PURPOSE: To inhibit the age sofening of Ag in a mounting state subsequent to bonding to improve its mechanical characteristics and also, to contrive to stabilize the hardness of a ball by a method wherein a prescribed amount of Ca is added to the high-purity Ag.

CONSTITUTION: Ca, 0.0005W0.02wt.%, is added to high-purity Ag. According to such a way, as the recrystallization temperature of a core material is enhanced and the age softening of the Ag can be inhibited to hold a high tensile strength, the mechanical nature of the Ag can be improved. Moreover, as the upper limit of the amount of added Ca is regulated, a ball, which is formed at the time of bonding, is sufficiently soft and also, becomes one near a true sphere. As a result, a failure of an Si chip can be prevented and the reliability of a bonding work can be improved.