Far from being the passive containers for semiconductor devices of the past, the packages in today's high performance computers pose numerous challenges in interconnecting, powering, cooling and protecting devices. While semiconductor circuit performance measured in picoseconds continues to improve, computer performance is expected to be in nanoseconds for the rest of this century -a factor of 1000 difference between on-chip and off-chip performance which is attributable to losses associated with the package. Thus the package, which interconnects all the chips to form a particular function...