PURPOSE: To form a uniform bump using an Au-Sn alloy wire, having relatively high degree of hardness, which is not used as the wire for conventional bump, by a method wherein the ball formed on the wire is pressure-connected to the part to be connected, and the strength-reduced part is cut by giving ultrasonic vibration.

CONSTITUTION: Non-oxidizing atmospheric gas 8 is blown against the tip part 20a of an Au-Sn alloy wire 20, and a bump ball is formed by arc-discharge. Then, a capillary 1 is lowered, load is added to the ball, and the ball is pressed and jointed to the part. At the same time, ultrasonic wave vibration is given to the capillary 1, and the strength of the cutting part of the wire 20 is lowered. Then, the load to the ball is reduced by slightly moving up the capillary 1, ultrasonic wave output is increased, and the strength of the cutting part of the wire 20 is lowered furthermore. Then, after the wire 20 has been cut at the cutting point by pulling the wire, a bump 41 is formed by heat-melting the ball connected to the point to be junctioned.