Technical Presentation by DuPont Performance Elastomers Demonstrates How Seal Selection Can Improve Photovoltaic Productivitiy And Lower Overall Cost
WILMINGTON, Del., May 18, 2009 – Solar cell manufacturers who require more stable process performance as well as increased equipment uptime to reduce cost will benefit from a presentation at InterSolar/SMET May 27, 2009 in Munich, Germany. In a presentation titled "Perfluoroelastomer and Fluoroelastomer Seals for Photovoltaic Cell Manufacturing Processes," Michele Vigliotti, DuPont Performance Elastomers (DPE), will present test results for various sealing materials used in demanding cell manufacturing processes. Results indicate that selecting the appropriate sealing materials can help improve seal performance and lower cost of ownership in both bulk crystalline silicon and thin film photovoltaic processes that use aggressive “wet” chemistries, high temperatures or reactive plasma/gas
According to Vigliotti, “Elastomer performance can vary dramatically, especially if more aggressive processing variants and technologies are used to help increase output and cell efficiency. Finding an elastomer that works in one environment, does not guarantee that it will work in all environments.” In his presentation, Vigliotti will review elastomer properties and the results of elastomer testing in various processes used in photovoltaic manufacturing.
In “wet” processes where aggressive acids and bases such as HF, HCl, HNO3, KOH and NaOH are used for etching and cleaning, Vigliotti will discuss how perfluoroelastomer parts (FFKM) tend to show better resistance to chemical attack, suggesting longer seal life. Seals also can leach contaminants into the process system and ultimately contaminate the finished product. Since ultrapure deionized (UPDI) water is used in many rinsing steps, maintaining purity is critical for success. Test results in UPDI water illustrate how FFKMs have considerably less metallic and total organic carbon (TOC) extractables than fluoroelastomer (FKM) parts. The comparison also demonstrates that performance variation can exist within the same elastomer category.
In addition to “wet” applications, Vigliotti also discusses test results in high-temperature applications like doping in crystalline silicon and diffusion in Cu (In, Ga) Se2 (CIGS). Exposure to high temperatures can cause seals to become hard and brittle, thereby losing their sealing functionality. Additionally, elastomeric seals can degrade under high temperatures causing outgassing to occur, thereby contaminating the process environment. Hydrofluoric acid (HF) is one of the gases evolved when FFKM and FKM begin to degrade. It can be harmful to process equipment, especially to quartz and stainless steel components. The outgassing performance of FFKM, FKM and silicone (VMQ) are compared in Figure 1.
Figure 1: Outgassing Comparison: FFKM Versus FKM And VMQ
In chemical vapor deposition and plasma etch processes, the plasmas used can be extremely aggressive and can cause seals to fail rapidly, thereby leading to problems during pump-down or causing toxic gasses to be released into the atmosphere. In order to better predict seal life, a more thorough understanding of plasma attack mode and chemistry is discussed. Test results will highlight the weight-loss properties of various fluorinated elastomers and silicone as result of exposure to both fluorine and oxygen containing plasma. Test results also indicate that “cleaner” elastomer formulations can help reduce particle generation, thus improving photovoltaic cell manufacturing processes.
As photovoltaic manufacturers improve productivity by using increasingly aggressive chemical, plasma and temperature environments, increased strain is placed on manufacturing systems. Vigliotti’s presentation will help cell manufacturers understand elastomer performance to help reduce unplanned maintenance as a result of incompatible sealing materials. “Seal selection is a science,” Vigliotti claims. “When manufacturers use the science for their benefit, productivity can improve beyond the added cost of purchasing a high-performance seal,” he added.
Vigliotti will be available for questions the three days of the SMET InterSolar Conference. If you wish to schedule an appointment, request a copy of his paper or have a question, please visit, http://www.dupontelastomers.com/pvintersolar.
DuPont Performance Elastomers, a global supplier of specialty elastomers with headquarters in Wilmington, Del., is a wholly owned subsidiary of DuPont. The company is an industry leader in chloroelastomers and fluorinated elastomers, serving the automotive, chemical, petrochemical, semiconductor, food and pharmaceutical processing construction, general rubber and wire and cable industries. DuPont Performance Elastomers has integrated manufacturing back to the polymer, enhancing quality control and product development. Kalrez® parts are manufactured in ISO 9000 registered facilities and are available in a wide variety of finished products from conventional seal shapes and bonded door seals to custom geometrics. Upon request, Kalrez® perfluorelastomer parts are specially cleaned and double packaged in Class 100 workstations to significantly reduce the potential for contamination. Each item is individually packaged in a bar-coded bag for full traceability. These products are available in the form of O-rings, sheets, and custom parts.
Kalrez® is part of a broad and growing portfolio of products represented by DuPont Photovoltaic Solutions, which connects science and technology from across the company on a global scale to help support the dramatic growth in the photovoltaic industry. For more information on DuPont Photovoltaic Solutions, visit http://www2.dupont.com/Photovoltaics/en_US/index.html.