Ultrasonic wire bonding tool and method for self-threading same

Abstract

An improved tool for ultrasonic wire bonding, and a novel method by which the tool may be semi-automatically threaded with bonding wire are disclosed. The overall exterior shape of the tool is that of an elongated rectangular cross-section bar having at the lower end thereof a tapered, smaller cross-section tip. The tip includes a flattened front toe section for applying ultrasonic energy to wire and a bonding pad, and an upawardly angled oblique lower face rearward of the toe section. A wire guide hole through the tip that has a longitudinal axis that slopes upward at a steeper angle than the oblique lower face has an exit opening in the lower oblique face, just rearward of the front toe section. The guide hole has an enlarged opening in the rear face of the tip. An elongated straight shallow groove formed in a side wall of the tip extends obliquely downwards from the rear face to front face of the tip. To semi-automatically thread bonding wire into the guide hole of the tool, a length of bonding wire is laid in the groove and severed at a ledge formed by the intersection of the groove with the front face of the tool. Microprocessor controlled clamp means are then used to retract the wire from the tool to a pre-set Retracted position. The wire end is then moved under microprocessor control forward towards the tool to a pre-set Home position, inserting the wire into the guide hole entrance.