| 摘要 |
PURPOSE:To obtain a ball having high sphericity and appropriate softness from even a thin metal wire on which an insulating film such as oxide film is existing, by a method wherein the controller is arranged to enable sequence control so that the electric energy not higher than the melting point of the thin metal wire can be applied in the first half of the formation of the ball and an electric energy not lower than the melting point of the thin metal wire can be applied in the latter half. CONSTITUTION:After the tip of an Al wire 14 in a shielded cylinder 21 is maintained in the atmosphere of Ar+H2 gas, a controller 26 controls a power supply 25 to provide negative polarity to the Al wire 14 side and positive polarity to the electrode 19 side, applies a d.c. voltage of about 1,000V between the two to cause electric discharge, an once the electric discharge occurs, the controller 26 lowers the voltage to about 500V and maintains it. At the same time, about 0.5A of electric current is applied between the two to peel the oxide film on the surface of the Al wire 14, exposing the clean Al surface. Then, the controller 26 again controls the power supply 25 to reverse the polarities of the Al wire 14 and the electrode 19 to - and +, respectively, and after first increasing the voltage to restart the electric discharge, the controller 26 changes the voltage to -20V and allows the electric discharge to continue, while it causes 3-6A of electric current to flow, thereby forming an Al ball. |
