The construction of wet benches from fire-safe plastics has been analyzed, discussed, debated, rebuked, and praised, sometimes in the same conversation. There are many opinions about this “new” generation of plastic materials used in wet bench construction, but the fact of the matter is that the acceptance of new materials continues to escalate. The evolution of standards, increased global awareness, and product availability have all contributed to the general acceptance of wet bench construction from fire-safe plastic materials.
With the current state of the semiconductor industry and the subsequent low book-to-bill ratio reports in recent months, there are not as many tools, either from fire-safe or fire-propagating materials, being constructed right now. All is not gloom and doom, however. New fab construction in China should create demand for tools.1 Japanese chipmakers are planning greater investments in facilities, thanks to restructuring plans and government tax incentives.2
Over the past year, new sheet products have been added to the list of materials that FM Global (FM) recognizes as listed FM4910 materials. As of this writing, at least 47 sheet products that have passed the 4910 test protocol are listed on FM Global’s website (www.fmglobal.com). Underwriters Laboratories (UL) also maintains a standard for semiconductor industry plastic materials (UL2360). In this standard, seven products are currently recognized. Within both standards, these recognized plastic products fall into three general families: polyolefins, vinyls and fluoropolymers.
A factor that has assisted in national recognition and greater acceptance of the FM and UL testing protocols is the adoption of FM4910 and UL2360 in the 2002 NFPA Standard 318, section A.10.5.1.2. NFPA also included a section in its standard relating to the welding of these materials and states that welders shall be qualified.3ÉRaw material manufacturers, sheet producers, and plastic welding equipment manufacturers have stepped up and offered assistance in developing a level of comfort with the fire-safe plastic materials.
Many classes have been conducted in group and private settings to offer an opportunity for users to weld these materials and provide feedback on the quality of welds being produced with the fire-safe plastics. A greater level of comfort in welding procedures for the plastics has also helped foster acceptance of the plastics at the tool fabricator as well as the semiconductor facility. In some instances, wet bench fabricators are now offering fire-safe plastic materials as the standard for shells and wet decks. Orders for tools constructed from non-fire safe plastics are considered custom orders.
Êhere are, however, some limitations in fire-safe material offerings. The availability of clear products is somewhat limited. Of the 47 materials listed under the FM4910 protocol, only four are clear.
What will 2003 and beyond hold for wet bench fire safety? Inevitably, more materials will be available to satisfy the needs of the industry. As the cost of cleanrooms and the subsequent revenue they produce continue to increase, the potential costs associated with downtime will rise as well. This will continue to make the use of fire-safe plastic materials in wet bench construction even more critical–and commonplace.
References1 International Wafer Fab News, November 2002
2 Wafer News, December 2002
3 Per David Quadrini, NFPA 318 chairperson, November 2002
