In the processing and packaging of semiconductor devices, ultrasonic wire bonding (e.g., ball bonding, wedge bonding, ribbon bonding, etc.) continues to be a widely used method of providing electrical interconnection between two locations (e.g., between a die pad of a semiconductor die and a lead of a leadframe). An upper end of a bonding tool is, in many instances, configured to be engaged in a transducer (e.g., an ultrasonic transducer) of an ultrasonic bonding system which causes the bonding tool to vibrate during bonding. Ultrasonic bonding is a joining process that, for example, may use relative motion between the wire and an underlying surface to facilitate bonding to that underlying surface.
Wedge bonding is one well known type of wire bonding. Certain wedge bonding tools include a lower tip portion that defines a groove at the terminal end of the tip portion. For example, as illustrated in FIGS. 1A-1B, wire bonding tool 100 includes body portion 102 that terminates in tip portion 106. Tip portion 106 defines inverted V-shaped groove 108 (within circle “T”) which is defined by opposing walls (e.g., see FIGS. 2A-2C) and is adapted to receive a portion of a wire to be bonded.
FIGS. 2A-2C illustrate an enlarged view of tip portion 106/groove 108 of conventional wire bonding tool 100 shown in dashed circle “T” of FIG. 1A. Wire bonding tool 100 (including body portion 102) defines longitudinal axis 101 (e.g., along the Z-axis of a wire bonding machine). FIG. 2A illustrates tip portion 106 terminating in opposing walls 110 which define inverted V-shaped groove 108 with apex 112. FIG. 2B is a bottom-up view of FIG. 2A and illustrates walls 110 converging at apex 112 of groove 108. Groove 108 extends along a groove axis (the illustrated X-axis) with apex 112 defining a flat, or straight line, profile as illustrated in FIGS. 2A and 2C.
FIG. 2D illustrates conventional wire bonding tool 100 of FIG. 2C pressing engaged portion 118′ of wire 118 against substrate 116 (e.g., a bonding location to which wire 118 is being bonded). As shown in FIG. 2D, wire portion 118′ does not maintain complete contact with apex 112 of groove 108. That is, a gap G exists between apex 112 and wire portion 118′. Such a gap G tends to result in inefficient ultrasonic bonding of wire 118 to substrate 116 (e.g., wire portion 118′ may slip relative to groove 108). Weaker bonds may be formed between wire 118 and substrate 116. Further, the gap G (and associated slipping) may reduce the useful life of conventional bonding tools.
Thus, it would be desirable to provide improved wedge bonding tool designs.