Importance

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Abstract

A method for forming a bump by bonding a ball on an electrode of an electronic device comprises the steps of forming a ball at a bottom end of a metallic wire held by a capillary by discharging between the metallic wire and a discharge electrode, fixing the ball on an electrode of an electronic device, and cutting the metallic wire to form a bump on the electrode, wherein the ball is formed just under the capillary to touch the bottom end of the capillary. The heat of the ball transfer to the capillary and the metallic wire inside the capillary does not recrystallize, so that theinterface of recrystallization is positioned just above the ball, where endurance against the shearing stress is weak. As a result, the metallic wire is cut just above the ball, and a bump with no wire-shaped part is formed. An apparatus for forming a bump by bonding a ball on an electrode of an electronic device comprises a capillary for holding a metallic wire, a discharge electrode positioned face to face with the capillary, a power supply which constitutes together with the metallic wire and the electrode a circuit for discharging between the metallic wire and the discharge electrode to melt the metallic wire and form a ball at the bottom end of the metallic wire, a device for moving the capillary along the metallic wire to touch the ball at the bottom end of the capillary to make the heat of the ball transfer to the capillary, an instrument for fixing the ball on an electrode of an electronic device, and an instrument for cutting the metallic wire on just above the ball to form a bump with no wire-shaped part on the electrode.

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First Claim