Abstract: To permit ball-bonding of wires of aluminium or aluminium alloy to small electrical circuits or components, a spark discharge is created between the end of the wire and an electrode in a shielding atmosphere with a peak current density in the wire section which is from 40 to 450 times that used for ball-bonding gold wire. In this way oxidation of the ball is prevented.

Abstract: Difficulties in forming a ball on the end of a wire of aluminium or aluminium alloy for ball bonding are overcome by applying between the wire and an electrode a low voltage, typically 30 volts, and bringing the wire and electrode into temporary contact to fuse the wire and initiate a spark discharge which results in the formation of a ball on the wire end. The spark discharge takes place in a shielding gas to avoid oxidation of the ball.

Abstract: A method of controlling the duration of a resistance weld in which a preprogrammed AC current is fed to welding electrodes, the program including an abrupt increase in welding current after a predetermined number of cycles so that the weld duration can be extended into the high amplitude portion if the heat input has been insufficient. The voltage across the welding electrodes is monitored, the peak voltage detected, a reference voltage derived by dropping the peak voltage 2 - 20% and the weld terminated when the subsequent peaks fall to the reference voltage.