Another Problem Solver: 3M’s 2mm Hard Metric Connector

Another Problem Solver: 3M’s 2mm Hard Metric Connector
By Charles Staley, Product Marketing Manager, 3M Electronic Solutions Division

Until last year, system designers had no viable way to upgrade legacy CompactPCI systems to handle today’s high-speed serial applications, because they were limited by the connector. Standard unshielded 2mm Hard Metric (HM) connectors used in CompactPCI embedded computers can only enable transmission to 1.5 Gb/s at best, and cannot support the high-density pinout of high-speed differential signals demanded by many new applications. No known connector on the market that could handle higher speeds was also compatible with legacy CompactPCI systems. It appeared that in order to gain speed, the old system would have to be scrapped and an entirely new architecture would need to be developed.

But then, two years ago, a solution appeared in the form of a customer with a problem. The customer had invested in a new backplane that was designed for high-speed applications. However, in the real world, the system was not processing at near the speed it was capable of. The problem, we discovered, was the connector. To address the problem, 3M retooled an existing high-speed hard-metric connector into what was globally introduced in 2009 as the Ultra Hard Metric (UHM) Socket Connector.

The UHM socket connector provides the improved signal integrity performance required to transmit high-speed digital signals. It provides full shielding, low crosstalk, and high signal density, while its controlled impedance characteristics offer increased performance. The UHM socket connector’s patented and patent-pending “virtual coaxial box” shielding technology dramatically reduces the severe crosstalk commonly experienced by 2mm HM connectors above 1 Gb/s speeds, and it can enable speeds greater than 7 Gb/s.

As it turned out, what was designed to help one customer trying to reach its system’s potential has ultimately helped many designers make cost-effective upgrades and extend the life of legacy hardware. The UHM socket connector mates to a standard 2mm HM backplane header and is compatible with both legacy and new equipment built to meet IEC 61076-4-101. The UHM socket connector installs on the circuit card and can plug into the current backplane. (However, system performance is limited by the backplane construction and whether the traces can accommodate intended data rates.)

The UHM socket connector enables the designer to build a board with high and low capability on the same pinouts. Maximum speed is based on the capability of the existing backplane, due to its construction and design. Replacement of the backplane is not trivial, but it is an option that would provide enhanced capability, while preserving the majority of the installation. This would also allow the designer to continue to use older yet still useful system cards.

The Ultra Hard Metric (UHM) Socket Connector by 3M quickly won industry acceptance. In late 2008, the PCI Industrial Computer Manufacturers Group (PICMG) specified the 3M UHM Socket Connector in the new draft PICMG 2.30 Compact PCI PlusIO standard. PICMG 2.30 is based on the PICMG 2.0 core specification and defines the migration path from parallel PCI to the serial PCI Express. The draft standard was approved in November 2008, and final approval is expected soon.

Since the 2.30 standard is based on the PICMG 2.0 CompactPCI core specification, it enables designers to make modular upgrades to incumbent systems and protect their investment in legacy hardware, and “future-proof” CompactPCI systems by creating a way to use both legacy processing cards and new advanced serial cards on the same backplane.

The new draft standard defines the pin assignment and the function of the user pins on the J2 connector for 32-bit system slots. The J2 pinout consists of 22 rows of six pins set in a 2mm x 2mm hard metric grid, where the outer rows are specified as grounds. The current pinout does not provide for high-speed signals such as PCI Express, SAS/SATA, USB, and Gigabit Ethernet, whereas the draft 2.30 standard does.

However, the new pin assignment defined by the PICMG 2.30 standard makes little difference to system performance without upgrading the connector as well. After intensive investigation of what was available on the market, PICMG found that the 3M UHM socket connector offered both the capability and the compatibility needed to implement the 2.30 standard.

Nevertheless, the designer has the option of replacing the component board connector with the UHM socket connector and continuing to utilize currently defined J2 pinouts for that system. In other words, the UHM socket connector can be used even if the PICMG 2.30 standard is not utilized.

The 3M UHM Socket Connector provides another valuable tool to help designers meet their Compact PCI clients’ perpetual need for higher speed at a lower cost.

Charlie Staley is a market development manager for the Electronics Solutions Division of 3M in Austin, Texas. Charlie is a connector veteran with more than 20 years in the industry. Before joining 3M, he spent five years with AMP (now Tyco) as an applications engineer, a development engineer, and in sales, supporting military markets. He also spent five years with Berg Electronics (now FCI) as a territory manager for tier 1 accounts focused on telecommunications markets. During his 11-year tenure with 3M, Charlie has worked in sales and marketing, supporting backplane, fiber optic, high speed, storage, and I/O products in the enterprise and network/communications markets.

Charlie can be reached at cstaley@mmm.com or 512.984.4731.