Cleanroom applications determine lighting options
Advances in manufacturing processes fuel product improvements
by Tammy Wright
Teardrops and troffers may not be words that conjure cleanroom images. But they happen to be two kinds of lighting for controlled environments.
“In Class 1 rooms, there has to be 100-percent filter coverage in the ceiling. There`s no space for lights so you have to attach fixtures to the grid or use ceiling systems with lights incorporated into the grid,” explains Steve Pitts, cleanroom consultant and project manager at Ledgewood Inc.–a construction company in Portland, ME.
According to Pitts, drop-in fixtures are typically used in cleanrooms up to Class 100. Teardrop fixtures are suited for cleaner environments.
Other factors that must be considered, he says, include the light sensitivity of the product being manufactured; foot candles per square foot (the level or intensity of lighting); and maintenance.
For example, he notes that integrated circuits are vulnerable to light so the environment in which they are produced requires yellow illumination or some type of UV control. Because some yellow lights are reportedly not user-friendly, cleanroom owners have a couple of options, including colored sleeves that go over regular fluorescent tube lights and shrink-wrapped bulbs.
“There`s a debate going on now about which [option] is better,” Pitts claims, adding that sleeves are probably better suited to less clean environments because their change-out could cause contamination — a serious yield inhibitor for some industries.
With more companies starting to manufacture in clean environments, many believe cleanroom lighting will follow general office trends like providing for worker comfort. Paul Burch, national sales manager at CD Lighting Inc. in Orland Park, IL, says a problem often cited in cleanrooms is glare, which makes it difficult for operators to view computer monitors and other video or imaging equipment. The dilemma, however, can be addressed with louvered fixtures that direct light to reduce veiling reflections.
As technology advances in this category, less is becoming more. Manufacturers are reducing the size of cleanroom lights to better maintain room integrity and to enhance energy efficiency. Some of the latest product developments are based on T-5 linear technologies, which run cooler and brighter for longer periods of time than comparable units. The latest T-5 lamps are fluorescent products with more compact dimensions. They are available in different wattages and have a 5/8-inch diameter versus conventional T-8 lamps, which have a 1-inch diameter, or older T-12 lamps, which have a 1.5-inch diameter.
According to Duane Paehlig at Paramount Industries Inc. in Croswell, MI, the average rated life of T-5 high performance and T-5 high output high performance lamps is 16,000 hours–33 percent longer than T-12/HO lamps; the T-5/HO lamp can also generate 75 percent more lumens than T-8 lamps.
Terri Thornton, Paramount`s manager of engineering applications, says another benefit of the smaller T-5 lamps is that they allow the design of smaller fixtures. “Because of the small diameter of the lamp, it`s easier for us to control or direct light,” she notes.
Changes in manufacturing processes are also fueling improvements in cleanroom lighting products. One catalyst is the semiconductor industry`s shift to 300- mm technology. Bob Catone, general manager at Guth Lighting in St. Louis, says stronger and more focused light beams will be needed as cleanroom heights are increased to accommodate next-generation fabrication.
“We have to change the photometry of the instruments to get the light on the work plane,” he explains. “Otherwise it`ll just get eaten up and scattered.”
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above: Simple Seal sealed enclosure. (Kenall)
middle: Sentry Series gasketed enclosure. (A.L.P.Lighting)
bottom: Flow-through troffers (Laminaire)
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