Wire Bonding - Gold Ball Bumping

Gold-ball bumping - or stud bumping - can be accomplished with commercially available gold wire bonders using a 1-mil gold wire. In fact, gold ball bumping is an evolution of the 50-year-old wire bonding process.

Forming the First Connection

In wire bonding, a gold ball is forced down and thermosonically bonded to a die-bond pad forming the first connection of an integrated circuit (IC) and substrate. With the ball connected, the wire is fed out and attached to a second surface, and then torn off to complete the connection.

Ball Bumping Instead of Wire Loops

In the ball-bumping process, instead of making the second connection with a wire loop and stitch, the wire is removed after the ball is connected to the die. A new ball is formed and the process repeats as necessary on all the die bond pads.Gold-ball bumping can be a one-step process, but can involve two steps if a coining process is needed to planarize the ball bumps.

Flip Chip Attach to the Substrate

Once the die is completely bumped, it is flipped and attached to the substrate, providing the first-level interconnect as well as protection for the active die surface.