Built to Spec: Existing building expanded and retrofitted into clean space

AlliedSignal's substrate technology and interconnects division shifts from printed circuit boards to multi-layer substrates

by Al Rogers

Converting one of two buildings at AlliedSignal Substrate Technology & Interconnects (Los Gatos, CA) into a laminate-package facility posed many engineering challenges.

The building slated for the retrofit and expansion was neither designed to accommodate long cleanrooms, nor was its ceiling able to support overhead loads. Rather than move to a new location, which would be time and cost consuming, AlliedSignal decided that retrofitting the facility would be more feasible.

A steel superstructure, which had to meet California's strict seismic code, was erected to provide the overhead support required within the existing building. The technology and interconnects division's two connected facilities encompass 100,000 square feet of space, with 45,000 square feet under some form of climate control. Together, they deploy a three-tier approach to contamination control from the warehouse, to the minienvironments, down to the smallest and most tightly controlled process tool environments.

Aluminum and steel cleanroom frames are powder coated with a white, baked-epoxy finish to reduce corrosion. Ceiling grids are constructed of heavy-duty aluminum, and each grid system utilizes double-gasket tape to create a contamination seal around the lights, vinyl tiles and self-powered HEPA filters. HVAC, mechanical and plumbing were also completed by Clean Rooms West, Inc.
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Starting at the manufacturing level, the plant is built with ballroom air conditioning, circulating approximately 70,000 cubic feet per minute (CFM). The air is controlled to meet or exceed Class 100,000 standards, forming a clean capsule to host the 10 cleanrooms inside. During the final stages of construction, the clean manufacturing area requires special attention not to compromise the environment. Clean Rooms West, Inc. (Tustin, CA), design-builder of the expansion project, took measures to ensure clean construction. All tools, equipment, and building supplies were cleaned prior to entrance, and periodic wipe downs were conducted to further reduce contamination.

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In the past, a typical printed circuit board (PCB) maker would produce products in batches.

The layout of the substrate technology and interconnects plant has tools and process equipment positioned in sequence according to their use on the manufacturing line. By designing a single-pass process, the substrate and interconnects division was able to realize short-term benefits and potential long-term benefits. Construction costs were reduced by 40 percent because cleanrooms were built tool- and process-specific, and a streamlined production line is the underpinning of gaining economies of scale—an imperative step to compete in the semiconductor world.

Tool- and process-specific cleanrooms

Building around the division's layout, Clean Rooms West, Inc. design-built 10 customized cleanrooms. “From laser to the sputter lines, photo to strip and etch, we designed each [clean space] precisely to match the tools and processes performed inside,” says Steve Alley, president of Clean Rooms West, Inc.

Separating workers from the critical tools played a determining role in the design of each cleanroom interior. Inside the laser cleanroom, the work area is on one side and the actual laser is in its own Class 100 bulkhead. Room temperature and humidity is controlled to a stable 68 degrees F, ± 1 percent and ± 1/2 percent RH, respectively. Eight self-powered HEPA filters, located in the ceiling above the laser, move 5,120 CFM. HEPA filters operate with 99.99 percent efficiency, removing particles 0.3 micron or larger; rated below NC45 at 50 dBA, measured 30 inches from filter set at 90 FPM. The cleaner laser room is a positive pressure plenum, which pushes out into the service area through two 18-inch x 25-inch return air grilles. The service area has two additional self-powered HEPA filters in the ceiling grid, which create a Class 1,000 cleanroom

Photo and sputtering cleanrooms are also designed with specific climate control features. During the critical process of photolithography, the imaging tool must be held to strict temperature and humidity control. “We custom-designed a dedicated blower and humidifier with an automated reheat process to ensure control over the imaging tool's environment,” Alley explains. The 26-foot imaging equipment, he adds, is boxed in a Class 10 environment from the manufacturer. Clean Rooms West constructed an additional barrier around the tool where temperature is held to 68 degrees F, ± 1 percent and humidity to 45 degrees F, ± 1/2 percent.

Along the 100-foot-long sputter lines, the Gold I, Gold II and Copper minienvironments are built with more than 30 doors. While protecting the sputtering process equipment from the Class 1,000 service area, the doors also provide access to each individual tool. In total, 70 storefront and sliding doors are used throughout the substrate technology and interconnects facility.

Access into the minienvironments is provided through a two-room gowning area. Workers are required to wear caps and shoe covers prior to entering the second gown room. In the second gown room, a HEPA filtered garment cabinet holds reusable Class 100 lab coats. In all of the substrate technology and interconnects facilities cleanroom environments, protective eyewear is mandatory. Other components installed by Clean Rooms West included bench seating, dressing mirrors, HEPA vacuum cleaner, portable eyewash center and a pair of wall-mounted material pass-through units.

Built to code

Designing and building a single-wall system to meet the varying demands of each minienvironment required Clean Rooms West to conduct extensive research. The wall system had to not only be modular, sound attenuating and chemical resistant, it also had to meet strict city building and fire codes. In response, four-inch and two-inch flex wall panels were customized with polystyrene cores, dual cement boards and Kydex outer skins. Unlike paper and aluminum core panels, foam cores would provide protection against corrosion. Cement board layered on both sides of the foam provided the fire-protecting barrier necessary to comply with city code. The outside Kydex is easy to clean and protects against chemical spills. “With equipment and tools constantly changing, the modular wall panels will provide access to move, update and add the next generation of equipment,” explains Roger Kersting, CRW's project supervisor in charge of the project's day-to-day construction.

The aluminum and steel frame members throughout each cleanroom are all powder coated with a white, baked-epoxy finish to reduce the threat of problematic corrosion. The ceiling grids are constructed of Power T-bar, a proprietary heavy-duty aluminum extrusion. Each grid system utilizes double-gasket tape to create a uniform contamination seal around the lights, vinyl tiles and self-powered HEPA filters. HVAC, mechanical and plumbing were also completed by Clean Rooms West, Inc.

The division has already begun full-scale production of laminate packages. “By year's end [1999], we will have the ability to produce tens of thousands of multi-layered substrates per month,” says Dick Pommer, vice president for research & development at AlliedSignal Substrate Technology & Interconnects.

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Researching and implementing new equipment, tools and cleanroom technology at the substrate technology and interconnects division will continue to evolve. With the development of higher input/output substrates, line sizes are headed below the once 0.25-micron level. Tighter geometry presented the need for more advanced tools and even greater control of sub-micron particles.

The new facility will not only act as the breeding ground for the next generation of substrates, but will also be used to develop the equipment, processes and cleanroom technology required for successful large-scale manufacturing. AlliedSignal's focus will be split on conducting research and design, and also low to mid-volume production. Technology and information acquired at this plant will be used to open another facility with ten times greater manufacturing capabilities.

“(We) are shifting away from the PCB industry and bonding us closer to the flat panel and integrated circuit industry. Unlike the PCB market, integrated circuit standards change every 18 months, which means our customers' flip chips will have higher inputs and outputs. We must be able to react quickly to accommodate the perpetually changing technologies,” Pommer says.

Al Rogers is production manager for Clean Rooms West Inc. (Tustin, CA)


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