Detection of welding condition and welding characteristics of ultrasonic wire bonding using a complex vibration welding tip

The vibration locus-shape of the welding tip undergoes a change from linear to elliptical to circular or from linear to rectangular to square using complex vibration systems. Thin aluminum- or copper-wire specimens of 0.025- to 0.1-mm diameter were welded successfully using the complex vibration systems. The required vibration amplitude and weld times are about one-half to one-third those of conventional wire-bonding systems. The weld strength was independent of the direction of wire length with this method. To detect the weldment condition during the welding process, the welding-tip vibration signal through the weldment and the acoustic emissions from the weldment are measured by a PZT detector under a lower welding specimen or an anvil. These detected signal changes correspond to weldment conditions