Vacuum rotary feedthroughs

Paul Boughton

Ferrotec is announcing significant improvements to the standard ferrofluid magnetic liquids that provide the core sealing function in the company's Ferrofluidic vacuum rotary feedthroughs.

Ferrotec vacuum feedthroughs are used in semiconductor manufacturing equipment, vacuum chambers, and other clean and controlled process environments.

With changes to the ferrofluid that is used inside the feedthrough to form the rotational seal, users benefit from reduced operating torque, reduced vapour pressure and better thermal stability in demanding process environments.

Since their introduction nearly thirty years ago, Ferrotec's Ferrofluidic seals have been recognised by many within the semiconductor manufacturing industry as the 'gold standard' for introducing rotary motion into a vacuum environment.

A Ferrofluidic seal uses magnetic liquid and a permanent magnet to form a dynamic O-ring seal around a rotating shaft. This O-ring forms a barrier between the atmosphere and the process side of vacuum, ultra-clean, or aggressive gas environments.

Depending upon the application where the vacuum rotary feedthrough is being used, the quality and the attributes of the ferrofluid used inside the seal can affect the performance characteristics of the seal.

“Because we manufacture our own ferrofluid, we can work directly with our customers to optimise fluid and seal performance to meet unique or demanding performance requirements. These new ferrofluids leverage significant advances in our fluid material science, bringing a new level of performance to our standard seals,” says Jim Fraser, product manager for sealing solutions for Ferrotec. “While our existing customers are now benefiting from these new, enhanced performance fluids, the new fluids are a big 'plus' for new customers and applications with extended performance and exposure capabilities far beyond established limits.”

Ferrotec's enhanced performance ferrofluid is offered in two options for standard environments and for reactive gasses. Standard ferrofluid delivers optimal performance in most vacuum or non-reactive gas applications, while the reactive gas ferrofluid trades higher viscosity and increased seal torque for improved performance in more demanding environments, such as ultra-high vacuum (UHV) use, high temperatures, and applications that expose the seal to aggressive or reactive gasses.

With one-third less viscosity than the previous generation of standard ferrofluid, the improved standard ferrofluid offers vacuum feedthrough users reduced start-up torque, improved thermal stability, and reduced vapour pressure. For reactive gas applications, the improved reactive gas fluid offers dramatically increased thermal stability, and vapour pressure has been reduced by an order of magnitude.

Unless otherwise defined by a customer specification, Ferrotec's new ferrofluids are available in all standard Ferrotec vacuum rotary feedthroughs. Ferrotec's vacuum rotary feedthroughs and seals can be purchased directly from Ferrotec and through the company's network of sales representatives.

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