Molex Boosts Xeon Connector Contacts, Speed
Oct 02, 1998 (Tech Web - CMP via COMTEX) -- The Slot 2 connectors Molex
will roll out next week for Intel's Pentium II Xeon processor will
employ novel techniques to satisfy requirements set by Intel and Molex
when they began working together in 1994. The connectors borrow
circuit-board techniques to handle higher speeds while increasing
contact density.
The HiSpec card edge connectors are designed for servers and other
high-end applications that require Xeon, which was introduced in June.
The connector itself is only slightly larger than the Slot 1 connector
found on many desktop systems, but it has 110 extra contacts and can
handle signals that are more than twice as fast. Some of the techniques
implemented on the Slot 2 connector are already being employed in other
Molex connectors.
Molex and Intel worked for four years to get more lines running at
higher frequencies. The challenge was heightened because the
characteristics were to be achieved without making manufacturing more
complex for Molex or for the system houses and contract manufacturers
that will use it.
Lofty Goals "We had plenty of goals: We had to hit Intel's speed and
density requirements, and we had to carry enough power for future
generations of the chip, which will draw more power and have more
simultaneous switching," said Jim McGrath, strategic product manager at
the Computer Strategic Business unit of Molex, in Lisle, Ill. "This
couldn't use new manufacturing techniques. It had to hit the
manufacturing floors at our plants and our customers and be running
right away."
It took an international team of Molex designers to come up with the
complete system for the interconnection system. Although Santa Clara,
Calif.-based Intel was setting the guidelines, Molex was able to adjust
them so installed costs for the connector could be decreased.
"Intel originally wanted a 0.025-inch pinch, but we ended up with a
0.030-inch pitch," McGrath said. "We said 0.025 would be difficult at
our end, but it would be a nightmare at theirs. In the module, there
would be a much greater chance of solder-bridging, and the ability to
route to the contacts would be much harder at the finer pitch. They
might have had to add substrate layers to route at that density, and
that would add to costs."
The connector has several more pins than its desktop counterpart. The
Slot 2 connector puts 330 card edge contacts in a housing that is 5.66
inches long, while the Slot 1 connectors found on desktops have 242
contacts in 5.23 inches, with a pin pitch of 1 millimeter.
Molex's Goal-Reaching Strategy To meet the goal, Molex came up with the
idea of staggering the pads. That allows a 0.030-inch pitch for the
edge contacts while providing pad widths of 0.032 inches. That matches
the tolerances of conventional PCI connections, which helps the
connectors to fit existing production techniques.
The combination of density and high performance forced Molex to come up
with a novel concept it calls complementary contacts. Metal contacts
are the same size in most connectors, but Molex has made the power and
ground contacts much larger than those that carry signals.
The larger surfaces look and act more like ground planes. Use of the
smaller contacts for signals lets Molex put more contacts in a given
amount of space. The signal lines employ microstrip and stripline
techniques like those used on circuit boards to provide high speeds.
The microstrip and stripline techniques are complemented by a number of
power/ground contacts. Many high-speed connectors employ a 1-to-1 ratio
of ground and signal lines to minimize crosstalk, but Molex and Intel
couldn't afford the space required for that many contacts.
Instead, they employed larger contacts for power and ground signals,
and placed two smaller ones between each pair of ground connectors.
While grounding is important, power-handling is equally critical for
future products.
"As we see continued drops in voltage, wattage doesn't change, so
current goes up," McGrath said. "In processor applications, it's not
just the processor, but the Level 2 cache runs as fast as the chip, so
you need more current."
Although Molex is prepared to license the technology to other connector
makers, it is a sole source supplier for Intel, and no other
manufacturer has signed on as yet. The company said it does not expect
that to be a problem, however.
"We have 50 percent more capacity than the highest-demand estimate,"
McGrath said. "We're probably OK for three years."
Other Molex groups are already adopting the complementary contacts
technology. Molex is also preparing to introduce connectors for Rambus
memory modules, and will use multisized contacts in that product. Other
Molex operations are also exploring possible uses for the contacts.
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