Superconducting Technology Assessment - nitrd

For this study, the readiness of the system integration technologies required by RSFQ was evaluated. The major
conclusions are:
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The design of secondary packaging technologies (e.g., boards, MCMs, 3-D packaging)
and interconnects (e.g., cables, connectors) for SCE chips is technically feasible and fairly
well understood.
The lack of a superconducting packaging foundry with matching design and fabrication
capabilities is a major issue.
The technology for the refrigeration plant needed to cool large systems, along with the
associated mechanical and civil infrastructure, is understood well enough to allow technical
and cost estimates to be made.
Testing of a superconducting supercomputer has not been fully addressed yet. Testing
mostly addressed modular approaches at cold temperatures by providing standard physical
interfaces and limited functional testing at high frequencies.
6.1 MULTI-CHIP MODULES AND BOARDS
In order to accommodate thousands of processor and other support chips for a SCE-based, petaflops-scale supercomputer,
a well-designed hierarchy of secondary packaging starting from RSFQ and memory chips and including
MCMs (with very dense substrates supporting these chips) and printed circuit boards housing MCMs is needed. In
addition, MCMs and boards are expected at an intermediate (40-77 K) for semiconductor electronics for data communications
and potentially for memory. Figure 6.2 illustrates such a packaging concept developed for the HTMT
design.
6.1.1 MULTI-CHIP MODULES AND BOARDS – STATUS
Demonstrations of RSFQ chip-to-chip data communication with low bit error rate (BER) at 60 Gbps were carried
out encouraging the notion that a petaflops MCM technology with inter-chip communication at the clock rate of
the chips is feasible (Figure 6.3). However, these demonstrations were carried out on very simple MCM-D packages
with superconducting inter-chip connections, fabricated in an R&D environment.
Figure 6-2. HTMT conceptual packaging for cryogenic processing and data communications.
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