Chip Packaging Technology

Chip packaging is the stage that turns a fragile silicon die into a finished component that can be handled, mounted on a circuit board, and connected to other parts. The bare die that comes from the fabrication process is tiny and easily damaged, and its electrical contacts are far too small to wire directly. The package protects the die from moisture, dust and mechanical stress, carries the heat it produces away to the surroundings, and provides robust connections of a practical size.

Inside a typical package the die is attached to a base or substrate, and its contact pads are joined to the package’s leads. This connection is made either with fine bond wires running from the pad to each lead, or, in flip-chip designs, by turning the die over and joining it through small solder bumps directly to the substrate. The assembly is then sealed in plastic or ceramic to form the body of the component.

Many package styles exist to suit different needs. Through-hole packages have leads that pass through holes in the board, while surface-mount packages such as the quad flat package (QFP) and small-outline package (SOP) have leads that solder to pads on the surface. Ball grid array (BGA) packages place an array of solder balls under the body, allowing far more connections in a small area. Chip-scale packages (CSP) are barely larger than the die itself, helping to shrink modern electronics.

Frequently asked questions

Why does a chip need a package?

The bare silicon die is fragile and its contacts are far too small to use directly. The package protects it, removes heat, and provides connections of a practical size for mounting on a board.

What is a ball grid array?

A BGA is a package with an array of solder balls on its underside instead of leads around the edge, allowing many more connections to fit in a small footprint.

What is flip-chip bonding?

In flip-chip bonding the die is turned upside down and joined to the substrate through small solder bumps, rather than with bond wires, which shortens the connections.