Rough and Rugged:
New High-Speed Backplane Connectors Shake Up the Market
By Bob Hult, Bishop & Associates Inc.
 

We often think of high-performance computing systems based on backplane architectures as living in clean, climate-controlled environments. But not all applications have that luxury. Systems that must survive in military vehicles designed for bomb detection, shipboard radar, advanced jet fighter avionics, missile control, and satellite communications equipment must contend with incredible shock and vibration, extreme variations in temperature, as well as environmental contamination that ranges from salt spray to wind-driven dust. Heavy-handed personnel, whose first priority is to get equipment running again in a hurry, may be responsible for performing maintenance in the field. Performance and reliability under these adverse conditions is an absolute necessity.




On the commercial/industrial side, applications in mineral exploration and extraction, heavy equipment, and industrial control subject backplane connectors to environments that push way past the mechanical limits of conventional high-speed connectors.

Demand for multi-gigabit backplane connectors that can survive these environments has spawned the development of a new class of ruggedized connectors with proven reliability in the most difficult applications. They combine the attributes of high-speed, high-density, and design flexibility, and may be supported by an industry standard.



Starting in 1979, the VME connector—with its many upgrades—has served the embedded computing industry, as well as military, aerospace, transportation, medical, and telecom applications. This two-piece backplane interconnect has proven its reliability in a host of challenging environments over many years and remains a key interconnect in legacy systems. A full range of connector components and standard card racks are available from multiple sources.

Over the years, the development of ultra-reliable, two-piece contact systems has resulted in a variety of configurations. Most traditional commercial backplane connectors incorporate a dual-beam contact using either dual cantilever beams or a tuning fork design. Ruggedized backplane connectors typically incorporate a four-beam design that provides redundant parallel contact points, which results in greater shock and vibration resistance in multiple planes.

Tyco Electronics developed their High-Speed Ruggedized (HSR) connector to address performance requirements to 10 Gb/s. A machined metal shell qualifies it for aerospace and defense applications requiring line replaceable module (LRM) interconnects. These scalable connectors are based on common form factor modules, offering a choice of signal, power, coaxial, and fiber optic versions.

Tyco also introduced a four-beam box contact that makes contact with all four sides of the mating post. The dimensions of this contact were reduced and implemented into the Mini-Box Stacking Connector for challenging mezzanine card applications. One version is designed to support the ruggedized XMC-style architecture known as VITA 61.

Amphenol Aerospace took a different contact design approach using a brush contact that ensures multiple redundant points of contact with very low insertion forces.

Their high-performance replaceable module connector offers design flexibility, with one to three bays populated with signal, power, coaxial, and fiber optic contacts.


 






Amphenol also offers a ruggedized VME64X connector using the brush contact.

Hypertronics uses a unique hyperboloid contact design in their ruggedized connectors to ensure multiple low normal force points of contact on the mating round pin. They offer Compact PCI and VME64X backplane connectors that feature this interface for military and commercial applications that demand high reliability.

The advent of fabric-based systems using low voltage differential signaling operating at multi-gigabit speeds created demand for a new class of high-speed connectors featuring controlled impedance and high signal density.





The Tyco Electronics MULTIGIG RT-2 connector was adopted by the VITA 41(VXS) and 46 (VPX) standards. Rated at 10+ Gb/s, this connector adopted a unique PCB wafer design that eliminated the traditional pin and socket interface.








Moving to a pinless right-angle header and mating backplane edge connector offers mechanical stability, as well as design flexibility, as simple artwork can quickly create custom variations of signal, power, and ground contacts. The impedance of individual wafers can be adjusted and optimized for single-ended and differential signaling.

The MULTIGIG RT–2 connector has found applications in aerospace, mass storage, and telecom systems.

Although not presently part of the VPX standard, Tyco Electronics has also introduced a new product known as MULTIGIG RT Extreme. This “up-armored” MULTIGIG RT2 is a shell system meant to provide the designer with additional options for severe environment packaging. The shell comes in 3U and 6U configurations, provides supplemental impact protection, board stiffening, ESD/EMI benefits, and complies with the packaging requirements of VPX. Only the shell on the daughtercard has been modified, making it backward compatible with existing VPX backplanes.

Recently, Amphenol Backplane Systems introduced their VIPER backplane connector, which was defined under the VITA 60 specification. Although it is not intermateable with VITA 46 or 48 connectors, it is footprint compatible, giving users an alternative interface.

A dual fork-and-blade contact system and stainless steel frame and stiffener provide exceptional electrical and mechanical performance in high shock and vibration applications. Up to 63 differential signals per board inch with a rating of 6.5 Gb/s—scalable to 10 Gb/s—offers both speed and signal density. In addition to VITA applications, VIPER connectors are focused on equipment exposed to harsh environments in industrial and high-end computing systems. Offering both advanced backplanes with the connector allows Amphenol early access to new design opportunities as well as the capability to provide a complete package of engineering support, from early design through production of the final backplane assembly.



Hypertronics is also eyeing the expanding opportunities for VITA interfaces. A presentation to the VITA committee in March 2010 outlined a development effort for a VITA 46/48 footprint-compatible connector that utilizes their Hypertac® contact. It will feature wafer construction with a closed entry socket, and includes ESD protection. Designated VITA 63, the design will include single-ended, differential, and power modules, with anticipated bandwidth of 8 to 10 Gb/s.





The most recent entry into the market for ruggedized high-performance backplane connectors is the Fortis Zd Connector from Tyco Electronics. Named after the Latin word for strong, this new backplane connector was developed to address high-performance applications in most demanding environments. Although not designed to comply with a specific industry standard, it will likely be proposed for adoption by a VITA specification, as well as defense and space agency standards at some point in the future.

This modular connector incorporates the Mini-Box four-beam contact for reliability, and is offered in plastic, shielded, and machined-metal shell configurations. This flexibility allows the designer to chose the most cost -effective solution to provide the degree of ruggedness required by a specific application.

This connector has been characterized to provide signal integrity to >10 Gb/s based on a controlled differential impedance of 100 ohms.

Bishop & Associated Comments: 

• Growth in military, avionics, intelligence, and heavy industrial markets has stimulated the development of new high-performance, ruggedized backplane connectors from a select group of manufacturers.

• Leading connector manufacturers are applying high-speed expertise developed for the computing and telecom markets to connectors that can withstand extreme environments with exceptional reliability.

• Most of the connectors in this segment utilize four-point contact systems to ensure reliability in extreme shock and vibration environments. Many include metal shells for mechanical durability.

• Typical rated or scalable bandwidth is focused on 10 Gb/s.

• Many of these connectors are PCB footprint compatible with VITA standard interfaces, but often use unique contact designs that make them incapable of inter-mating between brands.

• The majority of these connectors use compliant pin termination to the PCB.

• VITA 65 (Open VPX) is a new system-level specification that will not define a specific backplane connector, allowing contractors to have several alternative choices that meet the electrical and mechanical requirements of the standard.

Robert Hult
Director of Product Technology, Bishop & Associates Inc.
Robert Hult has been in the connector industry for more than 36 years. Hult began his career as a sales engineer for Amphenol. He joined AMP in 1972 and served in several management positions through 1996. In 1997, Hult joined Foxconn as group marketing manager for Intel in Chandler, Arizona, U.S. Prior to joining Bishop & Associates, Hult was the regional application engineering manager for Tyco Electronics.

Hult graduated in 1968 from Bradley University with a bachelor of science degree in electronics technology and a minor in business.