Importance

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Abstract

A stackable fine ball grid array (FBGA) package is disclosed that allows the stacking of one array upon another. This stackable FBGA package is configured such that conductive elements are placed along the outside perimeter of an integrated circuit (IC) device mounted to the FBGA. The conductive elements also are of sufficient size so that they extend beyond the bottom or top surface of the IC device, including the wiring interconnect and encapsulate material, as the conductive elements make contact with the FBGA positioned below or above to form a stack. The IC device, such as a memory chip, is mounted upon a first surface of a printed circuit board substrate forming part of the FBGA. Lead wires are used to attach the IC device to the printed board substrate and encapsulant is used to contain the IC devices and wires within and below the matrix and profile of the conductive elements. Additionally, certain pins on the FBGA in the stack require an isolated connection to the PC board. Yet, this isolated connection should be able to be connected to an adjacent ball on a different FBGA stack above or below that particular isolated connection. This provides for a stair step connection from the bottom of the FBGA stacked array to the top. This allows IC devices to be stacked one upon the other while maintaining a unique pin out for each pin required in the stack.

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First Claim