A high performance integrated circuit chip package includes a support substrate having conductors extending from one face to the opposite face thereof and a multilayer wiring substrate on the opposite face of the support substrate for connecting chips mounted thereon to one another and to the conductors. A heat sink includes microchannels at one face thereof, with thermally conductive cushions connecting the one face of the heat sink with the exposed back sides of the chips, to provide a high density chip package with high heat dissipation. The support substrate and heat sink may be formed of blocks of material having thermal expansion matching silicon. The cushions are a low melting point solder, preferably pure indium, and are sufficiently thick to absorb thermal stresses, but sufficiently thin to efficiently conduct heat from the chips to the heat sink.