Ball Bumping

Consistent, Planar Golf Bumps for Flip-Chip Assembly

Ball bumping is an essential process in flip-chip applications, providing the 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.

How Ball Bumps Are Formed and Controlled

Ball bumping shares many similarities with the first step of gold ball bonding: a ball is formed at the capillary and deposited onto the surface using force, ultrasonics, and heat. However, instead of forming a loop after the ball is attached, the wire is sheared off just above the ball to form a planar bump on the surface of the part.

Controlling ball size is vital because it determines the bump's overall size. That control depends on a reliable bonding process that produces a consistent wire tail length before each ball is formed. If every bump isn't executed consistently, bump sizes will vary significantly.

Why Bump Planarity Matters

Fine application of force is critical since it determines the shape and height of the bump. Precise control of the shearing step that separates the wire from the ball is then needed to form bumps of consistent height and planarity.

Consistent planar bumps across a wafer are imperative for the downstream assembly processes that use these components. Palomar's Tailless Smooth Bump software provides the controls needed to create bumps with highly consistent shape, size, and planarity. Combined with the Palomar 8100 Wire/Ball Bonder, it provides a reliable, capable solution for ball bumping applications.