Changes on the horizon. FM Global Research has been concerned about the number and size of losses associated with semiconductor fabs and has done extensive research to make future semiconductor fabs safer and less expensive to protect from fire.

A few years ago, FM Global Research took on the challenge of testing a range of polymers to see if they were a viable option to combustible plastics. They turned to the Fire Propagation Apparatus (FPA) to determine which plastic materials can best limit property loss potential in the event of a fire. The FPA has become invaluable in developing loss prevention standards, as well as saving money for both FM Global and manufacturers. Since the 1980s, FM Global Research has been using the FPA to perform small-scale tests for some products, at a fraction of the cost of running the large-scale test.

The original concept for using the apparatus to test semiconductor fab materials stemmed from research on electrical cables performed in the late 1980s. “We realized that use of the FPA to determine fire propagation of other materials could quickly be developed into a cleanroom protocol. A testing method for smoke generation rates was the only upgrade we needed to add,” said Bob Bill, director of FM Global Research’s materials research area.

The FPA was upgraded to test the ability of polymers to resist fire propagation and to emit little or no smoke. This means polymers will not propagate fire beyond its point of origin or release significant quantities of smoke contamination.

As a result of the research, semiconductor and plastics manufacturing industries have experienced cost savings by eliminating special protection and by using small-scale testing.

According to George Smith, FM Approvals materials section manager, “It’s more efficient and much less expensive to design materials that meet testing protocols than to provide fire protection systems to protect wet benches—and there is much less risk of fire using FM-Listed materials.”

Since 1997, the FPA has been available to test products for the semiconductor fab environment, a development that has been welcomed by the high-tech industries because of the increase in the size, complexity and dollar values of cleanrooms. As their size, complexity and dollar values grew, so did their hazards. “Over time, we became acutely aware of the loss potential,” said George, “so our research gave us a better understanding of what steps a manufacturer of polymers might take to reduce their fire, smoke and corrosive characteristics. The FPA determines which plastic materials can best limit property loss potential in the event of a fire.”

The FPA works this way: a product sample sits on a pedestal, where it’s preheated by quartz heaters. Extra oxygen is added to the area around the sample during the procedure (one way to simulate the flame heat flux of large-scale fires is to enhance the oxygen of the air). At the top of the FPA is a “collector” or hood that collects the burned particles, soot, smoke and gases. These fire by-products are sent up stainless steel ducts to the flue, where they are analyzed by sophisticated instrumentation.

Not all products can be tested with this equipment: to qualify, when they burn they have to stay in one place. Thermoplastic products such as polystyrene and polypropylene are not appropriate because they run, drip and burn on the floor.

The equipment was upgraded to test the ability of polymers to resist fire propagation and emit little or no smoke. This means they will not propagate fire beyond its point of origin and will not release smoke contamination.

While FM Global Research’s small-scale testing is typically all that is required, full-scale testing for “borderline” materials is available if needed. FM Global has produced a simulated cleanroom testing environment for evaluating fire protection. Testing within the simulated wet bench environment shows fine-water spray, FM-200, and CO2 systems are effective for today’s cleanroom where fire-retardant polypropylene is the common material of wet bench construction. Since the cleanroom testing protocol for small-scale tests has been established, non-metallic ducts have been FM-Approved for cleanroom application.

Global Effort

FM Global Research has shared with participating laboratories the method for conducting its cleanroom protocol now that suitable agreements have been obtained to protect its technology and devices. The first commercial FPAs also have been produced. Of course, the transfer of technology will require that participating laboratories train personnel and correlate their test results with FM Global Research to ensure the proper use and accurate interpretation of the data.

FM Global Research’s FPA also has been accepted by the American Society for Testing Materials (ASTM), and the National Fire Prevention Association’s (NFPA) Fire Test Committee, as well as NFPA’s Committee on Protection of Cleanrooms that materials complying with the FM Approvals Protocol are accepted for use in cleanrooms.

4910 Cleanroom Protocol

According to Vinnie DeGiorgio, FM Global semiconductor industry leader, the purpose of a test standard is to present the procedures and testing criteria that are required as a part of the evaluation of any products and services. They provide guidance for manufacturers, users and authorities using the product or services.

The FM Approvals test standard, “Cleanroom Materials Flammability Test Protocol, Class Number 4910” (more commonly known as the 4910 Protocol), specifically states test requirements and procedures for the evaluation of materials used in semiconductor cleanroom occupancies. The test evaluates the materials’ fire propagation behavior and potential for smoke contamination. It also describes minimum performance requirements for materials that are intended for use in cleanroom facilities, and verifies that the product will not propagate fire beyond the zone of ignition and will evolve minimal amounts of smoke. All requirements in the standard must be met for materials to be listed for use in the fabrication of cleanroom tools.

Once the materials have been evaluated, they are listed in the “Specification Tested Products” section of the FM Approvals Approval Guide (see section for specific materials and/or products). These products are not necessarily end-use products. Some may be a single component in a factory-produced, finished product for use in cleanrooms.

4910-Listed products are highly resistant to fire but, in the event they do ignite, they do not allow the fire to spread beyond the ignition zone. They also produce less smoke than traditional plastics. According to George, cleanroom manufacturers who use 4910-Listed products are less likely to have a fire and less likely to endure expensive downtime should a fire occur. “In addition,” said George, “equipment made from 4910-Listed plastics do not require supplemental fire protection systems such as fine-water spray, FM-200 or CO2.

FM Global’s Fab Team

Because loss experiences in the semiconductor fabrication occupancies are significantly higher than in other industries, FM Global has established a team of engineers with expertise in this occupancy. According to Richard French, Norwood, Massachusetts and Harry Yonemoto, San Francisco, California, semiconductor field engineering group managers, the fab team is a dedicated group of engineers who work together as a team to help our customers understand their hazards and to provide them with solutions for those they fear. “Changes in the semiconductor industry occur so rapidly, we felt the need to have a way of communicating these changes among our industry experts,” said French. “Working as a team is one way to ensure that this information is shared quickly.”

The team, which services more than 160 locations worldwide, assists with project management, construction reviews, consultations on human element programs, risk management services, and provides tailored solutions to recommendations. The team also will work with insureds to review tools, both onsite and at the manufacturer, even before the tool is shipped.

“By providing such timely service, the team can identify site exposures, help reduce loss severity and frequency, provide business contingency planning, and protect your value and profitability,” said French. “Our prime responsibilities are to service these sites so that we can better identify and understand exposures, and collaborate with onsite customers to measure the related risk and to develop potential solutions for them.”

According to Yonemoto, FM Global has learned several things from our work with semiconductor fabrication facilities. “One of the most critical aspects of a fab is the design of site electrical systems. Also important is the design and maintenance of site liquid process lines and waste lines,” said Yonemoto.

Have they been successful? It seems so. During the first quarter of 2000, team engineers achieved more than US$4 billion in risk mitigation. That means customers implemented fab team loss prevention recommendations that had an aggregate loss expectancy of that amount. Of course, the fab team does not work alone. Their expertise is enhanced by interacting with groups from FM Global Research who provide risk service testing, develop the protection alternatives and interface with appropriate codes and industry, and approve product performance.