Typically, “ball bonding” applications are associated with thermocompression (T/C) and thermosonic (T/S) joining methods. T/C utilizes pressure and temperature from about 150 degrees C (for most common applications) to create an intermetallic bond. T/S, on the other hand, adds ultrasonic energy from the previous process. With both methods, however, a “free air ball” is being created by a spark from an “electronic flame off” or EFO underneath the capillary before bonding takes place. This free air ball then gets deformed when the capillary touches the surface of the bond pad and applies force and ultrasonics with a given amount of time to deform the ball. Thus the inter-diffusion between the wire and the bond pad metallization occurs, which makes the intermetallic bond.

In general, “ball bonding” offers faster speeds of about 5-12+ wires per second. Types of wire used for this application include gold, palladium-coated and copper wires. Typical packages and applications for this process include BGA, QFP, SOP, MCM hybrids and wafer level bumping. The ball bonding process is suited for fine pitch applications down to 40 microns or less.

- https://www.palomartechnologies.com/blog/bid/206846/ball-bon...

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Ball Bumping

Ball bumping is an important process in flip-chip applications as it provides the necessary interconnects between chip and substrate. Ball bumping can be performed at the assembly or wafer level. - https://www.palomartechnologies.com/processes/wire-bonding-n...

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Note added at 6 hrs (2021-01-21 11:19:50 GMT)
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Ball bumping is an essential process in flip-chip applications as it provides the necessary interconnects between chip and substrate. Ball bumping can be performed at the assembly or wafer level, though it is most commonly done at the wafer level. - https://www.palomartechnologies.com/processes/wire-bonding/b...