A stackable semiconductor package is described which has external contact points (pins, pads, solder-bumps, etc.), which are arranged in arrays on the top and bottom surfaces of the package. This package also has internal contact points (bond pads) for connection to an integrated circuit die. The external and internal connection points are connected by a programmable interconnection matrix, which may be manufactured separately from the package body and then assembled within the package. The internal contact points can each be selectively connected to the external contact points, and selective connections can also be made linking pairs of the external contact points. Stacks of such packages, containing different dice, may be formed, creating large, tightly-coupled circuit blocks. A presently-preferred embodiment of the programmable package is described in which the package body and programmable matrix are manufactured as a unit. The described embodiment comprises a package body (12) with a formed recess (14) for receiving a package lid (50) surrounding a deeper die cavity (16), both on the package's top surface. After mounting, an integrated circuit die (20) is connected through internal contact points (24) to a first metal trace layer (28) formed on the package's bottom surface. A second metal trace layer (30) is connected to the package external contact points, consisting of a horseshoe-shaped array of solder bumps (38) on the package bottom, a matching array of solder-contacts (42) on the top, a linear array of solder bumps (34) along one edge of the package, and a matching linear array of solder-contacts (36) along the opposite edge of the package. A flange on lid (50) is bonded to lid recess (14), and the lid body is bonded to the surface of IC die (20) with a material which is thermally conductive, but electrically insulating. The lid conducts heat away from the IC die, and extends beyond the package body to act as a cooling fin for the package. If further cooling is required, a hole (52) bored through the lid beyond the package body may be used to bolt the lid to a heat sink. Alternatively, a heat sink or heat dissipation device might be connected to the lid using a conductive epoxy.