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Staubli connectors for thermal management of electronics

Stäubli’s range of high integrity products provides the ideal connection solution for many thermal management applications.Traditionally, most electronics used in the military sector have been air cooled, using natural convection through metal heat sinks. This passive solution can successfully accommodate the cooling requirements of fairly simple electronics, but proves inadequate where greater power densities or reduced available space are encountered, often associated with faster operating speed or there is a requirement to maintain the thermal environment within a close temperature range.

Recent significant increases in data processing speed, moving from parallel to very high speed serial bus technology in the CPCI, VME, VPX, VXS, and µTCA architecture, have created an opportunity for new and innovative high power enclosures. High speed requires high power, increasing junction temperatures and therefore higher cooling requirements.

There are several other cooling techniques that can be applied. The first is forced convection, using fans alongside the heat sinks to increase air flow and the cooling rate. The second is the fluid phase change system, where closed loop heat pipes allow the rapid exchange of heat through evaporation and condensation of the piped refrigerant. Ultimately, there are liquid cooled systems where coolant is pumped through cold plates which, with an associated heat exchanger, cool the system. Generally liquid cooled technology is reserved for applications where high heat density results in forced convection or phase change systems being unable to dissipate the power demands. Managing and connecting, quickly and securely, the fluids required in these systems are the applications where Stäubli’s expertise in connection solutions is an advantage, resulting in a reliable and efficient thermal management system.

Small diameter heat pipe assemblies provide greater thermal efficiency by embedding heat pipes into an assembly that transports heat away from the concentrated force. Heat pipes passively facilitate this transfer by employing an evaporator and condenser in a closed loop mechanism, spreading heat evenly within a unit base or transporting it to peripheral fins. Large diameter heat pipe assemblies function in the same manner, but are capable of transferring much greater thermal loads because of the increased volume of refrigerant and the circumferential surface area of the pipe. Liquid cold plate heat sinks provide the best thermal performance per unit volume and counter nearly every drawback associated with air cooling by dissipating more heat with considerably less flow, better thermal performance and less local acoustic noise. Cold plates take advantage of the increased thermal conduction properties of liquid by actively circulating fluids past a heat source through a closed loop system. These liquid passageways are formed by sealing machined channels or adding copper or other tubing to a metal base plate. Micro channel cold plates provide the superior performance of traditional liquid cooling in a much smaller footprint by forcing fluid through a network of miniature passageways in a cold plate, mounted directly above the heat source.

These compact active solutions are suitable for high performance microprocessors and other high heat flux density applications. The major advantage of micro channel heat sinks is the high heat transfer coefficients, up to 60 times higher than conventional heat exchangers. Micro channel heat sink technology will have a major impact on the future of electronic packaging and design. However, due to the construction and size of micro bore the associated fluid pressures are extremely high and so high pressure pumps are required. The management of these connections will be a concern in the future, with multiple small diameter, high pressure lines needing to be connected safely.

The technology of spray cooling is now being developed further, using a non conductive dielectric, sprayed in a fine mist over the hot areas. The phase change associated with evaporation of the fluid on contact with the hot surface provides a very efficient direct cooling system. The evaporated liquid is then cooled via heat exchanger and returned to the circuit in a closed loop. Again there are high integrity fluid connections for each spray and receive device and to the main pump and heat exchanger system. All these connections require effective management. With all fluid thermal management systems there is increasing complexity with pump and external heat exchangers, all of these have specific fluid connection challenges, such as micro couplings for board mounting or large connectors for main feed. The environmental and operating conditions of military vehicles and aircraft demand high integrity quick release connections that introduce nothing to a closed loop circuit and do not spill fluid on disconnection.

Vibration and temperature effects have a large effect on the overall success of the connection systems. Care must be taken when designing and specifying components for such arduous and exacting conditions. Stäubli has wide experience in providing reliable and efficient connection systems for the most demanding applications. Their knowledgeable technical specialists work alongside project development teams to ensure that the most suitable connection solution in achieved and supported by Stäubli, wherever in the world it is required.

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