| 摘要 |
PROBLEM TO BE SOLVED: To prevent a ball formed at the tip part of wire from being hardened by quenching phenomenon until it is connected to a bonding part by supplying preheating discharge thermal energy lower than discharge heat energy for forming ball to the tip part of wire. SOLUTION: A control signal is sent from a first discharge time setting circuit 13 to a first discharge current supply circuit 15 for time T1 . The control signal is sent from a second discharge time setting circuit 14 to a second discharge current supply circuit 16 for time T1 +T2 , namely, discharge time containing ball forming time and preheating time. When discharge time T1 elapses, a discharge current automatic switch circuit 17 switches discharge current I1 to discharge current I2 . Current I2 is set to be smaller than current I1 , and preheating discharge energy which is set to be lower than discharge thermal energy for forming ball is supplied to wire 4 and an electrode 7. Since preheating discharge thermal energy is reduced with the lapse of time, the quenching phenomenon of the ball 4A can he prevented. |
