| 摘要 |
A method and apparatus for confirming whether wire bonds are successfully made to sites on a workpiece by an ultrasonic bonding tool using wire supplied to an entrance bore through the tool from a despooling wire supply spool, and for providing a fault detection status signal if bonds are not successfully made, utilizes an automatic wire despooler which includes a spool drive motor for rotating a wire supply spool to thereby pay out wire from the supply spool to form a drooping catenary-shaped length of slack wire, located between the spool and an output wire guide having an aperture through which wire is supplied to a bonding machine head that supports an ultrasonic bonding tool. The apparatus includes a proximity-type feed sensor for detecting when the catenary straightens and shortens a predetermined amount in response to tension caused by moving the tool tip between successive bond sites, thereby drawing wire out through an exit opening of the bonding tool bore. Shortening the slack length a predetermined amount straightens and elevates the center part or vertex of the catenary upwardly towards the proximity sensor; when the slack length is sufficiently short, the catenary vertex is brought into the detection range of the proximity sensor, which then outputs an electrical signal that causes the drive motor to rotate a predetermined amount in a forward sense, paying out wire from the supply spool and increasing the length of the slack length catenary segment to a value which causes the catenary to droop below the detection range of the proximity sensor. After each wire interconnection made between a pair of bond sites of normal or greater length, or a small number of very short interconnections, the proximity sensor is interrogated by a computer logic means to determine that the despooler has been run to advance at least the minimum length of wire. If there has been no run, a bond fault alarm status signal is generated, halting further bonding operations.
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