IEST standard shows difference between minienvironments, isolators
10/01/2002
By Mark A. DeSorbo
ROLLING MEADOWS, IL—Right around the time the now retired Federal Standard 209 debuted, gloveboxes were being used by the pharmaceutical and microelectronics industries in similar fashions.
The glovebox is indeed a steadfast genesis, but over time philosophies in both camps changed dramatically, creating two technologies: One drug makers now call "isolation," or containment technology, and the other is referred to by the chip and microelectronics industries as simply "minienvironments."
"An isolator isolates the process from the surrounding area. That means there is something evil in the isolator and you're trying to protect the environment around it," says Michael A. Fitzpatrick, program director of microelectronics for Lockwood Green Engineers (Spartanburg, SC). "In the microelectronics industry, it's the flip side. You are trying to protect product from contaminants in the environment around it."
Fitzpatrick, who also chairs Working Group 28 Minienvironments (WG028) for the Institute of Environmental Sciences and Technology (IEST), says the writing arm tried to pen one recommended practice to fit both industries, but the diversities of technologies just would not allow it.
The working group's efforts recently produced a new recommended practice (RP)—IEST-RP-CC028.1, Minienvironments, which provides a framework for describing minienvironments for microelectronics and similar applications, including medical devices.
"This new RP discusses applications, planning, design and evaluation in detail," according to the IEST.
Fitzpatrick elaborates, saying the document describes types of minienvironments, discusses advantages and disadvantages and includes a testing and qualifying procedure. "Along with microelectronics, any number of industries that want to employ minienvironments can use this document, including medical devices and optics," he adds.
Fitzpatrick, who chairs the working group with Ken Goldstein, principal of Cleanroom Consultants Inc. (Phoenix, AZ) and a member of the CleanRooms Editorial Advisory Board, says two factors are fueling minienvironment popularity: the move toward 300 mm fabs and tighter air cleanliness requirements.
Back in the late 1980s and early 1990s, Fitzpatrick says the micro-device and chip industries were so enthralled with minienvironments; many believed fabs would be no more. That train of thought shifted, he adds, saying now these tools greatly enhance the manufacturing process and even allow the cleanrooms that house them to be degraded in cleanliness.
"The shrinking of the geometries has forced the need for cleaner air; cleaner air that can be provided by cleanrooms. Because of minienvironments, the quality of the cleanroom can be degraded," he says. "All 300 mm fabs are, or will be, equipped with minienvironments, and if there were a typical facility, it would most likely have an ISO Class 6 background and better than ISO Class 3 at the tool."
For more information on the new IEST recommended practice on minienvironments, contact the IEST (www.iest.org) at (847) 255-1561.