FC-PGA is an abbreviation for flip chip pin grid array. FC-PGA packages use chips that have been turned upside down and attached to the package or the board using solder balls instead of perimeter bonding wires. The solder balls are jointed directly to a set of solder balls on the substrate (the base layer of the chip and the electrical ground for the circuit). The exposed core rests on the actual package, and the chips make direct contact with the heat sink. This allows for more efficient cooling to take place. Since the chips are placed directly on the board, FC-PGA packages have a high I/O density and shorter electrical connections than other types of packaging.