Improving the Semiconductor Industry With Ultra-Pure Seals

Cliff • October 26, 2018

The semiconductor industry is a specialty market that requires seals to work in extreme chemical and temperature environments. 

Seals in the semiconductor industry must block seal materials from entering the fluid stream.

There are several different ways for seals to accomplish this task, but the first consideration is the operating characteristics.

Operating Characteristics of Seals for the Semiconductor Industry

For static seals where no relative motion exists, the use of perfluoro-elastomers, or FFKM rubber, is considered a first consideration.

Eclipse is a designated distributor of Dupont™Kalrez ®. Kalrez parts have excellent chemical and thermal stability, and have been specially formulated and processed to meet the unique requirements of wafer processing environments.

DuPont offers molded O-rings and custom seals using a series of specialty products and ultrapure processing for the semiconductor industry.

Ultrapure processing is standard for all semiconductor product grades and must be specified for Kalrez 6375UP and 7075UP.

Kalrez is a widely accepted choice as a supplier of Ultrapure compounds in the semiconductor industry and can be supplied by Eclipse.

The Role of PTFE in Semiconductor Seals

For dynamic seal applications where a consideration is wear and friction in these same operating conditions, Eclipse designs and manufactures spring and rubber energized seals made from materials such as Polytetrafluoroethylene PTFE , (Teflon®) or Ultra High Molecular Weight Polyethylene.

These seals are typically machined cross sections, and are energized by metallic springs or rubber elastomers.

PTFE is essentially inert to almost any chemical, and a metal spring can be selected from the accepted metals used in other areas of the equipment — typically a 300 series spring steel.

If the seal is rubber energized, the use of a Perfluoroelastomer such as Kalrez may be used for its excellent chemical and temperature compatibility.

The use of these polymers allows for dynamic motion to occur without abrading the mating surface. These polymers can resist contamination in the fluid stream, while keeping friction to a minimum and operating in varying temperatures to satisfy the application.

Dynamic seals can operate in reciprocating, oscillatory and rotary motion. Due to their relative coefficient of friction compared to elastomeric seals, these polymers can dramatically reduce the amount of heat induced by the dynamic motion into the system.

These materials are not limited to round shapes. They can be machined into virtually any profile to accommodate the application.

Specialty Design Elements for Semiconductor Seals

When pressures exceed the mechanical strength of these standard polymers, Eclipse can build backup ring combinations to handle pressures in excess of 100K PSI.

When pressures go negative or vacuum, Eclipse is capable of building sealing systems that are capable of sealing to extreme vacuum, and continue to function as dynamic seals.

This is accomplished with our super finish process for polymers, in combination with the application hardware and finishing of the mating surface for the dynamic application.

For boundary seals for electronic enclosures, Eclipse can design seals or protection devices to keep the outside environment out and retain fluids from getting out of the electronic device.

Eclipse has designed both Polymer enclosure seals that operate in severe glove box or electronic enclosures to insure product within the enclosure stays there, and the outside environment stays out.

When designing with the harshest of chemicals and operating at temperatures that can swing from -400 degrees Fahrenheit to an excess of 500 degrees, the use of a polymers such as PTFE and elastomeric materials such as FFKM (Kalrez) provide for long term solutions that will keep your production equipment up and running longer and your PM cycles to a minimum. This reduces overall downtime, improving run time and making your operation more profitable.

Eclipse has been in the seal business for over 20 years, supplying the world with sealing solutions used under, on and off our planet, operating in the harshest environments such as the semiconductor industry.

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Eclipse deals regularly with challenging sealing applications from all industries. High pressures and speeds create unique sets of conditions where seal design and material properties are pushed to the limit. While reciprocating applications can certainly test seals to the edge of capability, often times rotary applications can present the greatest challenge to seal integrity and wear life. Unlike reciprocating configurations where the seal is acting on a different part of the shaft or bore throughout it’s operating range, rotary seals must operate on the same sealing area continuously. This makes things like heat rejection much more difficult, especially in unlubricated or dry running applications. Extreme localized heating can have negative affect on both seal and hardware life. Rotary applications also pose sealing difficulties due to the simple fact that surface speeds can be much higher than in reciprocating systems. A simple electric motor can operate at very high rpm, while long stroke, high speed reciprocating machinery is a major piece of equipment that is far less common (though Eclipse also has sealing solutions in a number of these situations). A customer approached Eclipse with an application that was beyond the scope and capability of any standard, off-the-shelf rotary seal. This sealing system would require a combination of both wear resistance in high-speed rotary, as well as excellent leakage control and sealability. Two factors that, more often than not, work in opposition to each other. The Customer Issue The customer was developing a test system that required an electric motor shaft passed through the wall of a large vacuum chamber. The testing apparatus needed a sizable motor to meet the speed and torque requirements. Adapting the motor to operate inside the chamber would not be practical due to contamination and motor cooling concerns. Therefore, the motor would have to be placed outside the chamber and a driveshaft would have to go through the chamber wall. Which, of course, would need a seal. Operating Conditions:
 Rotary Shaft Seal
 Shaft Diameter: 2.5”
 RPM: 7,500 RPM - unlubricated
 Pressure: Vacuum internal side / 1 ATM external side Temperature: 40° - 90°F The customer knew any kind of off-the-shelf rotary seal with a rubber element would not last any amount of time in the combination of speed and a dry running condition. They also knew a single lip PTFE seal would likely not meet their leakage requirements. Therefore, they turned Eclipse for a custom sealing solution.