Design Tips - Page 2

Design Tip For RapidIO Product Development- Addressing Electromechanical Implementation Challenges

By Robert Applebaum, President, Silicon Turnkey Express

Mechanical complexity, pervasive today in high-speed interconnects, required careful and often meticulous design. Serial RapidIO uses several variants of a standard compression connector available in permutations of 85 pins (170 and 340), which supports speeds of up to 12.5 Gbps.

In manufacturing Serial RapidIO carrier and switch cards, Silicon Turnkey Express (STx) uses Yamaichi Electronics’ connector series CN074-170-0005. In doing so, caution must be taken when installing the connectors on a board as they make contact through compression force versus a “soldered connection.” The proper torque (30-40 cN - M) must be applied to the mounting screws to ensure that proper contact is made.

The mounting screws can only be tightened and loosened a maximum of three times; otherwise the spring force of the contacts is compromised. The connector insulators on the secondary side of the board must be installed properly to prevent shorting of the connector. No passive components can be placed under the insulator. Finally, the connectors are only rated for a maximum of 200 insertions and extractions; therefore they must be replaced if the limits are exceeded. One example of board that uses these connectors is the STx SSRP, which is currently used by the RIOLAB™ for interoperability testing between vendors.

Parallel RapidIO uses a “HIP” or Tyco HM-ZD connector such as the AMP_1469002-1. A special press fit tooling from Tyco must be used and adapted by the OEM into a custom fixture than can apply at least one ton of force. Care must be taken to align the connector onto the board, prior to press fitting, and uniform constant pressure must be applied or the connector will be destroyed. An example of a product that uses this connector is the STx GP3 PowerPC processor board, which is part of the Tundra Semiconductor HIP development system.

AMC card mechanical support is required in carrier and switch cards so that the insertion of the AMC cards does not destroy their hosts. Customized top and bottom covers, guiderails, and backstops need to be modified (i.e. sheared/drilled out) to allow for proper clearance and installation to meet AMC standards specification. Guide pins such as Tyco’s 223985-5 must be ordered in the proper size to ensure the screws do not “bottom” before they attach the guide posts, which can cause damage. Finally, proper standoffs are required to make sure the PCB is not in contact with any surface, in order to prevent shorting. STx’s SRDP and SSRP cards provide both the lateral and longitudinal reinforcement to safely allow AMC cards to be inserted by a novice user without the possibility of damage.

Printed circuit boards for Serial RapidIO must be unusually thick to provide sufficient mechanical rigidity. The thickness of the PCB should be a minimum of .093 to minimize flex of the board and ensure full contact of Yamaichi connectors. The STx SRDP board, which is a reference system for the Tundra Semiconductor’s Tsi568a switch, meets these requirements.

AMC cards (the blades) for both ATCA and microTCA systems, have special mechanical requirements of their own. Standard faceplates (half and full height) need to have specific cutouts added in order to provide access for serial, Ehternet and other IO. AMC standard ejection switches must be used and component height must be watched carefully per specificaion to ensure the AMC card doesn’t bump into something inside the chassis. For EMI sensitive AMC cards, shields and RF gaskets need to be applied. The biggest AMC card challenge is thermal management; today’s devices produce more current draw and heat than ever before. STx has developed specialized knowledge in thermal management for PICMIG standard systems to address the needs of leading edge semiconductor manufacturers.

These Serial RapidIO products and many others soon to be announced, are fully industry standard, PICMIG compliant, and commercially available from Silicon Tunrkey Express. For information, visit www.SiliconTKx.com.