Importance

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Abstract

The following specification discloses a touchdown sensor for ultrasonic wire bonding devices. Such ultrasonic wire bonding devices are used for purposes of bonding wires to integrated circuits, package terminations, hybrids, and discrete semiconductor devices. The devices entail the utilization of a transducer that operates in a series resonant mode. The means of exciting the resonant mode is through an electrical signal imparted thereto, so that a tool attached to the transducer can then impart an ultrasonic bond to a wire with which it is placed in contact. The tool attached to the transducer is lowered by the device to a discrete location. The point of contact is monitored by sensing an increased impedance by contact of the tool and dampening of the transducer's resonant mode. This increased impedance is read by means of producing a voltage proportional to transducer current and determining when it has decreased below a previously set reference voltage. A comparator then makes a comparison of the reference voltage with respect to the decreased voltage and signals a control microprocessor to stop the device. This is done by preventing a motor from carrying the tool farther after it has made contact with the work.

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First Claim