Packaged semiconductor dies, including memory chips, microprocessor chips, and imager chips, can include semiconductor dies mounted on a package substrate. The semiconductor dies are encased in a plastic protective covering, and each die includes functional features, such as memory cells, processor circuits, and imager devices. Bond pads on the dies are electrically connected between the functional features and terminals on the package substrate that allow the dies to be connected to external circuitry.
To increase the density of dies within a package, the dies can be stacked upon one another within the casing. One challenge with vertically stacked dies, however, is that the dies can have different sizes or footprints. For example, in a memory package, a memory controller die can have a smaller footprint than the memory dies within the package. The memory controller die can be more difficult to wirebond because it is offset from the memory dies. Also, the memory dies can sometimes tilt when stacked upon the smaller memory controller die.