Lead wire bonding with increased bonding surface area

Abstract

An improved lead wire ball bonding machine for bonding wire leads between an integrated circuit chip and the lead frame on which the chip is mounted is provided with a bonding tool position sensor coupled to receive the Z-motion velocity waveform signal to the servo motor which drives the bonding head and bonding tool. This sensor detects the signal level and direction of change or polarity of the Z-motion velocity waveform signal for determining the location of the bonding head and bonding tool. The bonding tool position sensor is coupled and adjusted for generating a first output signal corresponding to a first location of the bonding head and bonding tool during motion downward to the die pad of an integrated circuit chip prior to contact by the bonding tool and lead wire for ball bonding. The position sensor also provides a second output signal corresponding to a second location of the bonding head and bonding tool during motion downward toward a lead frame finger prior to contact of the bonding tool and lead wire for wedge bonding. The first and second output signals from the sensor are coupled to the ultrasonic generator of the bonding machine for application of ultrasonic bonding energy to the bonding tool prior to contact thereby increasing the bonding surface area between the lead wire and substrate. According to an alternative embodiment, an electrical sensor is provided for electrically sensing initial contact of the bonding tool and lead wire with the die pad or lead frame finger for actuating the ultrasonic generator and applying ultrasonic bonding energy to the bonding tool substantially upon initial contact with minimal delay thereby also optimizing the bonding surface area of the ball bond and wedge bond. Both the apparatus and method for lead wire bonding with increased bonding surface area are described.