Superconducting Technology Assessment - nitrd

The major issue to be addressed will be assuring a source of low-cost
packaging at affordable cost. Several approaches should be evaluated:
– Develop a superconducting MCM production capability.
– Find a vendor willing to customize its advanced MCM packaging
process to include superconducting wire layers.
– Procure MCMs with advanced normal metal layers for the bulk
of the MCM, then develop an internal process for adding
superconducting wiring.
MCMs
The design of MCMs for SCE chips is technically feasible and fairly well understood. However, the design for higher
speeds and interface issues needs further development. The panel expects that MCMs for processor elements of a
petaflops-scale system will be much more complex and require more layers of controlled impedance wiring than
those that have been built today, with stringent cross-talk and ground-bounce requirements. Although some of the
MCM interconnection can be accomplished with copper or other normal metal layers, some of the layers will have
to be superconducting for the low voltage RSFQ signals. Kyocera has produced limited numbers of such MCMs for
a crossbar switch prototype. These MCMs provide an example and base upon which to develop a suitable volume
production capability for MCMs.
Affordable Packaging a Concern
It is expected that the technology will be available for such packaging, but the major issue to be addressed will be
assuring a source of low-cost packaging at affordable cost. Several approaches should be evaluated:
■
■
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Develop a superconducting MCM production capability, similar to the chip production capability
(perhaps even sited with the chip facility to share facility and some staff costs). Although this is the
most expensive approach, it provides the most assured access.
Find a vendor willing to customize its advanced MCM packaging process to include superconducting
wire layers and procure packages from the vendor. Because of the relatively low volumes in the production
phase, the RSFQ development effort would have to provide most, if not all, of the Non-Recurring Engineering
(NRE) costs associated with this packaging. Smaller vendors would be more likely to support this than
large vendors.
Procure MCMs with advanced normal metal layers for the bulk of the MCM, then develop an internal
process for adding superconducting wiring. This is less expensive than approach 1, but it depends on
the vendor’s process, which may change without notice.
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