Dale Ashby
VP of Technology
Parker Seal Group

Dale Ashby is the vice president of technology and innovation for the Seal Group at Parker Hannifin Corporation. In this role, he serves as the key representative for advanced technology research. Currently, Mr. Ashby”s research interests are in the areas of finite element modeling, practical application of seal life prediction models, and fluorinated elastomer material. He is active in numerous technical committees and industry organizations including SAE, NACE, AIChE, ACS, and ASTM. Mr. Ashby can be reached at dashby@parker.com or 216 896-2603.

Q: For semiconductor applications specifically, what are the key issues users need to be aware of when specifying seal & gasket technologies?

A: The biggest challenge for seal suppliers is anticipating the needs of the user community. Users are typically not very familiar with the vast array of sealing solutions available today and typically don”t know exactly what information is critical to the seal supplier. The rule of thumb that we subscribe to with our customers is that there can never be too much information provided about the application.

Another big issue for the semiconductor seal designer is determining the relative importance of sometimes conflicting design goals. All design scenarios are usually a compromise between a wide variety of design constraints. With this in mind, the challenge for the user is to think about the relative “weighting” of design variables and articulate a “ranked” list to the seal supplier as early as possible in the design schedule. If done early enough, the seal supplier can usually develop a robust engineering solution.

Finally, there are the typical design questions that need to be answered for all seal configurations independent of material, including time, temperature, pressure, media, type of installation (static, dynamic, or both), etc. etc. etc.

Q: What are the most common materials used for semiconductor applications? What are the advantages/disadvantages of each material?

A: In the sealing industry there are literally hundreds of materials that have been used successfully, ranging from elastomers to thermoplastics to composites to metals and many hybrids in between. In the area of elastomers alone, there are over 12 polymer families available to seal suppliers. For semiconductor applications specifically, the choices are limited to six or seven polymers that include nitrile, ethylene propylene, polychloroprene (more commonly called neoprene), fluorosilicone, fluorocarbon, and perfluorinated elastomers. The most common elastomers used currently are of the fluorinated variety — i.e., fluorosilicone, fluorocarbon, and perfluorinated — due to their excellent ability to resist both high temperatures and a host of aggressive media.

The advantages and disadvantages of these materials are well documented on various seal supplier Web sites and in popular design handbooks. The key point for users to keep in mind is what I mentioned before — i.e., what is the “ranked order” of fluid or gas or plasma exposures that the seals will be subjected to, including any cleaning operations that the seals might come in contact with. In my experience, seal failures are often attributed to the innocent omission of information relative to the “complete” sealing environment.

Q: How does seal and gasket maintenance differ in a semicon process as compared to a general industrial environment? Do seals and gasket require more care and attention given the high-purity/high-temperature/highly aggressive nature of semicon applications?

A: There are many differences between the semicon industry and general industry as it relates to seals and sealing. You have mentioned the most salient ones: very high temperatures, ultra-clean environments, and very aggressive chemistries. Because the environment is so aggressive, special care must be taken when choosing, installing, and performing prediction models on seals. In industrial applications, leakage is usually defined by weepage of the fluid being sealed, which progressively leads to gross leakage of the fluid, both of which are usually visually detectable. In the semicon industry, leakage is defined much differently. Phrases like loss of vacuum, high particle counts, molecular contamination, outgassing contamination, and reductions in wafer yields come to mind. The big challenge here is that these types of leakage are usually not detectable visually with the unaided eye.

As a result, much care is needed in selecting, installing, and monitoring seals for this industry. The key here is to rely on the expertise of the seal supplier to help in diagnosing seal failures in real-time.

Q: What are some of the common pitfalls users in the semicon industry fall into when specifying seal and gasket technology?

A: The most common pitfall that users fall into is making the assumption that all seals are created equal, so to speak. What I mean by this is that in many instances, there is the impression that a 75 durometer fluorocarbon seal from one seal supplier will function identically to all other 75 durometer fluorocarbon seals manufactured by other suppliers. While this may be true in some applications, the severity of the environments in semicon applications really would preclude this type of generalization. The root cause of failure really boils down to under-specifying the sealing requirements for the given application.

Another common pitfall that users fall into is that they fail to fully engage the seal supplier”s design engineering department. Some semicon companies have changed this dramatically in recent years, as the overall expectations for the industry have increased. However, there are still many instances where engaging the sealing supplier”s engineers and R&D technologists earlier in the process could minimize or even eliminate leakage due to sealing elements.

Q: In evaluating seal and gasket providers, what characteristics/capabilities should semicon users be looking for?

A: As would be the case in any industry, competitive prices, excellent delivery, and impeccable quality are the three attributes that all users should use as the initial screening test for potential suppliers. Since these things are really the foundation for all seal suppliers in today”s global economy, there are a number of additional differentiators that should be considered when choosing a seal supplier partner. First of all, does the supplier have a market focus dedicated to the semicon industry? Second, is the supplier well positioned in the sealing industry in terms of the competitive landscape? Third, is the supplier well positioned in terms of financial stability? Fourth, does the supplier have a technically competent R&D organization that is aware of and conversant in the technological needs of the semicon industry, both now and in the future? Finally, is the supplier capable of consistently providing rapid technical assistance?

There are a number of additional things such as laboratory capabilities, breadth of product portfolio, and supply chain management philosophy that are also important.

In the final analysis, the seal supplier must be able to provide value to the user via one or more of these attributes if they are to be successful in the semicon market.

Q: How has seal and gasket technology for semicon applications changed over the past 5-10 years? How has the technology improved?

A: Sealing technology for the semicon industry has changed dramatically in just the last 5 years, much less the last 10 years. There are a couple of general improvements that are common to the industry as a whole, for example, the more widespread use of perfluorinated elastomers due to higher temperatures and more aggressive chemistries. Another improvement is in the relative cleanliness of seals. An intent focus on reducing the number, size, and concentration of contaminants in seal material has become common among semicon users. Another change in sealing technology relates to embracing differ sealing solutions including bonded seals, composites, and metal solutions where in the past o-rings were the default standard for most sealing applications.

Seal suppliers have been challenged to innovate new and novel solutions for the semicon market both in terms of design solutions and advanced materials technologies. Hopefully this trend will continue with the one caveat mentioned before; engage the seal supplier as early as possible as a true “partner” so the sealing solution becomes a fully integrated part of the overall system design.

Q: Where can the technology go from here? How can seals and gaskets be more valuable to semiconductor users?

A: Sealing technology can go wherever the imaginations of the semicon design engineers, seal designers, and materials scientists can go. The world of advanced materials technology is the foundation of both the sealing industry and the semiconductor industry. Working together to address the challenges presented in the semiconductor roadmap, seals and sealing can become an integral part of a system solution going forward. These are exciting times in terms of new polymer architectures, new material chemistries, and unprecedented analysis and material characterization tools. The sealing industry is poised to add value to the semicon industry by offering new materials and design solutions not previously considered.

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