Advanced packaging for a 100-Mbps-per-port, 256-×256-port, auto-routing wideband packet switch

A prototype 100-Mb/s-per-port 256×256-port autorouting wideband packet switch using a novel three-dimensional circuit board packaging scheme is discussed. Chip-on-board mounting is used to attach the individual CMOS integrated circuits to both sides of small circuit boards. These small boards, called chip cards in the 3-D stack, are needed to meet the speed and data-rate requirements of the switch. However, their size and structure make the fabrication of the card subsystem very demanding. The fabrication techniques developed to meet these demands, including IC mounting, bonding, and encapsulation techniques and passive component surface mounting techniques, are described. As a result of this work, twenty working subsystems that met their physical, electrical, and thermal design goals were fabricated, permitting a small research version of the 3-D switch architecture to be demonstrated