Its flexibility, small form factor, scaleable architecture with high function density and high data transfer rates on the backplane gives the MicroTCA standard the potential to offer the advantages of today's industrial PCs while compensating for their shortcomings. MicroTCA is already also finding its first applications in several industrial branches outside of telecommunications. Yet there are areas in which, on account of higher demands, the boundary conditions set out in the specification for shock and vibration are insufficient. Such areas include railway and transport technology, traffic systems, mechanical engineering, safety engineering and defence technology (Fig. 1).

Since the start of 2007 the PICMG working group "Rugged MicroTCA" has been engaged on solutions for more demanding requirements in the ruggedized sector on the one hand, particularly in regard to shock and vibration resistance, and on the other with effective heat removal in a situation of increasing demand as chips continue to increase in power. Appropriate specifications have been created in three steps.

1. MicroTCA.1: Air-cooled ruggedized AdvancedMC modules and MicroTCA systems: solutions for air-cooled AMC.0 modules with higher mechanical and thermal requirements
2. MicroTCA.2: Conduction cooled ruggedized AMC modules and MicroTCA systems: solutions for 'contact-cooled' AMC modules where requirements are higher, e.g. by bringing 'cold plates' into contact with hot spots.
3. Market-specific layered dot specifications: other requirements

Like MicroTCA.0, the MicroTCA.1 specification is divided into the following sections: Introduction, Mechanics, Management, Power, Thermal, Interconnect, Connectors and Regulatory. MicroTCA.1 additionally contains sections titled Area of Validity, Requirements and Test Methods. In the Test Methods section, testing systems and procedures for the various MicroTCA components are described on the basis of existing test specifications, thus enabling an objective comparison of the products of different manufacturers. The specification is expected to be published in September 2008, so making specified ruggedized solutions based on AdvancedMC modules and MicroTCA systems available to the above-mentioned industry sectors as quickly as possible. Implementation of step 2, MicroTCA.2, Conduction cooled ruggedized AdvancedMC modules and MicroTCA systems, is more complex and is therefore being developed by a separate working group.

Cases, subracks and systems as set out in the MicroTCA.0 basic specification must pass the shock and vibration tests of IEC 61587-1 performance grade DL1, i.e. they must withstand accelerations of 7 g in the shock test and a vibration load of 0.5 g acceleration amplitude. The DL1 grade is designed for general industrial applications. The IEC standard defines this with examples such as use in power stations or situations in which low-energy impacts such as localised explosions may occur. The minimum thermal requirement was declared to be the temperature range -5 °C to +45 °C as per ETSI EN 300 019-1-3. When tested to this specification in an external test laboratory, Schroff's MicroTCA and AdvancedMC products passed all the tests.

Peak accelerations of 25 g in the shock and 3 g in the vibration test, an increased demand over that of MicroTCA.0 of factors of 4 and 6 respectively, covers IEC 61587-1 grade DL3. This is the minimum mechanical requirement of the MicroTCA.1 specification. Typical uses for such systems include situations with very high vibration levels, such as on rotating machines (offset printing) and in railway and marine applications. Thermal requirements under IEC 61587-1 level C3 assume ambient temperatures in the range -40 °C to +85 °C. These increased mechanical requirements of the ruggedized sector cover some 85 % of applications. Many of the measures by which mechanical robustness can be enhanced, such as plate thickness, stiffening beads or strutting, are given sufficient scope by the 'normal' MicroTCA.0 standard. The MicroTCA subracks and chassis now available can thus simply be upgraded accordingly. Of particular importance are the interfaces to the modules and the robustness of mechanical connections.

The first mechanical tests, using standard AdvancedMC.0 modules, were performed in February 2008. Observing the 'worst-case' test specification for MicroTCA.1, AdvancedMC modules must be used with the maximum permitted weight of 700 grammes per module. This requirement, however, cannot be met with the standard AdvancedMC module locking system. Only standard AdvancedMC modules carrying up to 525 grammes were able to withstand the loading. This is unsurprising, since the module mechanics were in fact designed for AdvancedMC.0 and no provision was made for such high physical demands.

The very stringent mechanical requirements of MicroTCA.1 can only be satisfied with the necessary additional locking mechanism fitted to the AdvancedMC modules. For the front panels of the AdvancedMC module this means that the locking mechanism must be extended in both vertical directions and fixed to the MicroTCA systems. It is particularly important that the locking is effected without any force being applied to the MicroTCA backplane connector. An 'ordinary' bolt would, when turned, press the AdvancedMC subassembly board generally in the direction of the backplane and so apply a force onto the connector. The use of a conventional bolt is therefore excluded.

All manufacturers of 19" mechanical and locking elements were therefore asked by the PICMG standardising committee to develop appropriate solutions. In early March 2008 Schroff presented, as the sole manufacturer, a functioning AdvancedMC module fixing (Fig. 2), electrically and mechanically tested and fully meeting the requirements of the MicroTCA.1 specification, allowing locking without applying pressure on the connector.

This solution, for which Schroff has registered a patent, will be an element of the MicroTCA.1 specification. One of the bushings fitted to the front panel (blue) serves to receive an expansion plug (green) with an inner funnel. The bolt (grey) has a geometry that corresponds to the funnel of the plug. When the bolt is screwed in, the plug splays out and jams with a positive fit against the bushing fixed to the front panel. No resultant force (pressure) occurs in the direction of the backplane connector. This solution - as the only one tested to date - will be documented visually with its Schroff order number in the appendix to the specification.

The connectors to be used with ruggedized MicroTCA must also satisfy the higher requirements concerning shock and vibration resistance. In response to this, HARTING and ept together developed the MicroTCA con:card+ connector (Fig. 3). The guide spring in the upper section of the con:card+ connector equalises the tolerance deviations of the AdvancedMC modules by constantly pressing the module against the opposite wall. Since this wall is displaced a little towards the centre, the mating area is optimally matched to the AdvancedMC module and connection reliability is thus enhanced. The guide spring also secures the position of the module under shock and vibration. By this means, contact interruptions are avoided and wear to the surfaces obviated. In addition, a palladium/nickel surface (Pd/Ni) with additional gold flash is used for these connectors. For the con:card+ connector HARTING also uses a special alloy with very little relaxation as the contact material. When the connector is inserted a high-grade mechanical connection that is gas-proof, corrosion-resistant and low in ohmic resistance is created between the pin and the through contact of the board. This remains secure and stable even under high mechanical and thermal stresses such as vibration, bending and frequent temperature changes. This design has achieved an improvement in wear resistance of some 30 %. Pd/Ni surfaces offer a qualitatively high-grade and corrosion-resistant coating even where only thin, and meets the high demands of the connector far more effectively than pure gold.

Tests performed in accordance with the guidelines of the MicroTCA.1 specification have demonstrated the reliability and contact security of the con:card+ connector. In the vibration and shock resistance test using AdvancedMC type 2 modules, fitted into a test chassis with ESD contacts and Schroff locking systems, no contact interruption of more than 10 Ω/10 ns was detected. The visual inspection of all mechanical parts that followed likewise indicated no damage that would impair the normal functioning of the connector. The locking system of the AdvancedMC modules also withstood the test loading. No loosening of the retention screws occurred during the test. The contact resistance measurement also showed a maximum increase of 2.2 mΩ.

Kontron is already offering MicroTCA system solutions for non-telecommunications uses, e.g. for industrial automation, medical technology, transport and military applications. Here, AdvancedMC modules offer ideal conditions for the implementation of multiprocessor systems with high data rates and short latency times. The MicroTCA specification indeed defines a comprehensive shelf management to fulfil the high demands of the telecommunications networks, in particular with regard to the redundancy necessary in order to achieve an availability of 99.999 %. Outside the telecommunications sector such a powerful management is often not required and can thus be reduced to a minimum to optimise cost. On the other hand, however, it is necessary to respond to the increased mechanical stressing.

The possibilities for the application of MicroTCA systems (Fig. 4) in industrial automation indicate two main tendencies: image processing and networking via Ethernet. Image processing generally requires multiprocessor systems with high data rates. Here MicroTCA systems are considerably ahead of traditional parallel-bus systems. As an established platform, CompactPCI is sufficient in many cases and under the PICMG 2.16 standard also offers the possibility of Ethernet networking, though only with 6 U board size. For transport capacities of 10 Gb per second over 10 GbE or SRIO, MicroTCA systems are the better choice. Even the serial version of PCI, PCI Express, can be advantageous for software support, as the same operating system and applications software can be used here.

A further possible industrial use is the controlling of complex motion sequences under real-time conditions. Where the analysis of measured values and parameters for actuators requires multiple processors, MicroTCA systems are a suitable candidate. Under the MicroTCA standard the clock cycles of systems can be synchronised - a further benefit of this architecture. In terms of vibration, however, the operating conditions of such systems are as a rule more demanding than those of a telecommunications system.

A basic advantage of systems designed to the MicroTCA standard is their system management. The system configuration is documented in the system. The systems contain an inbuilt management that monitors and secures the hardware. In conjunction with networking, these systems also offer the possibility of monitoring and remote maintenance via central system management.

One trend in medical applications is the growth in image-based systems. Modern diagnosis equipment for ultrasound, computer tomography, magnetic resonance imaging and digital radiography systems generates raw images that require further processing. The processing power required may be realised by a multiprocessor system. Embedded systems such as MicroTCA systems have the advantage over regular IT servers of better system integration (a complete system, no separate boxes) and a better performance balance (computing cycles per watt). In this area MicroTCA systems are an outstanding choice, partly because the manufacturer's ecosystem permits upgrading to the latest processor generation at any time.

In transport, trains are increasingly being equipped with video monitoring systems and trains and aircraft fitted with information systems for passengers that also function as entertainment systems. Telecommunications applications such as WLAN and telephone can also be integrated into such systems. MicroTCA systems form a suitable basis for such systems since they are very compact (small form factor) and have extremely high capacity. Here again the mechanical demands made upon such systems play a decisive role.

Military applications are very close to those of telecommunications out of which MicroTCA was developed. In this sector, redundancy is a requirement: no singular sources of failure, everything doubled - i.e. doubled power supply, doubled system management, doubled networking and multiple redundant processors. The MicroTCA standard offers all of this, and MicroTCA.1 and 2 add to it the prerequisites and aptitude for heightened mechanical demands.

In March 2008 the 'kick-off' event for a further working group took place: MicroTCA.2. This group is occupied with the use of AdvancedMC modules and MicroTCA mechanics in the area of defence. Products used here are subjected to the highest extremes of shock, vibration and temperature. The requirements for this go beyond those of the DL3 performance class described by MicroTCA.1. This working group is also engaged in the specification for "Conduction cooled ruggedized AdvancedMC modules and MicroTCA systems".

The 2008 MicroTCA Interoperability Workshop, hosted for the first time in Europe in September 2007 by Schroff GmbH in Straubenhardt, Germany, is planned for 22-25 September in the training centre of Schroff GmbH. In 2007 more than 55 developers from 18 companies in Europe, the USA and Asia met here for a four-day testing marathon and exchange of ideas. The participants rated it consistently "the most successful MicroTCA interoperability workshop yet".