MANUFACTURE OF SEMICONDUCTOR DEVICES

摘要

1468974 Welding by pressure; spark erosion machines FERRANTI Ltd 24 May 1975 [20 July 1974] 32269/74 Headings B3R and B3V [Also in Division H1] In a method of wire bonding including bonding a wire 17, usually Au or Al, to a semiconductor device contact (e.g. of a transistor 10) and to another terminal (e.g. a conductor terminal 19), in either order, the wire is severed, either before or after the second bonding action, but after the bonding to the semi-conductor device, by an electric spark between two electrodes 30, 31 (Fig. 6), e.g. of tungsten wire, raised to the same potential but of opposite polarity such that at the point of severing, i.e. the centre of the spark the potential is zero, resulting in a negligible inadvertent current flow back into the semi-conductor. In operation, a ball 26 on the wire 17 is thermooompression bonded to a contact on the transistor 10, e.g. with ultrasonic vibrations, by a tungsten carbide nozzle 25 at 180‹ C. The nozzle is then indexed to a position above a Ag coating 28 of a terminal 19 of a conductor (15, Fig. 1, not shown) whereupon a second thermocompression bond is completed. The wire is then severed by the electric spark to produce two ball ends (261, 33, Fig. 7, not shown) on the wire. The ball end (261) adjacent the nozzle 25 may be used to restart the sequence. An electric circuit to produce the electric spark (Fig. 8, not shown) comprises a capacitor (36) and an pulse transformer.