IEST RP 028.1 takes mystery out of

11/01/2002

by Mike Fitzpatrick and Ken Goldstein, Ph.D.

Some people talked of mini-environments, others minienvironments and still others microenvironments and micro-environments. Young men, with shaved heads, dressed in saffron robes, sauntered outside the doors hoping to convert attendees to "Minienvironmentalism." Taking in this scene, one couldn't help but think back to "The Graduate" when Mr. Robinson whispered the word "plastic" into the ear of a young, unassuming Dustin Hoffman.

The exhibit hall only furthered the chaos. The rows of exhibits were packed with minienvironments of every shape, size and color. The first row displayed minienvironments consisting of plastic sheets hung from the ceiling, while the second row contained ordinary gloveboxes. Row by row the devices increased in complexity. There were minienvironments for microelectronics applications, minienvironments for pharmaceutical applications and minienvironments for people who had no application but wanted to have a minienvironment, just in case.

• We need to use minienvironments to reduce the cost of cleanrooms;
• Minienvironments will replace cleanrooms;
• We have just seen our last major microelectronics facility constructed.

All of this proved to be wrong.

Fortunately, in the intervening years since that meeting in Boston, things have sorted themselves out. Technology has advanced and concepts were developed that have allowed us to integrate minienvironments into our various industries.

Conventional wisdom now holds that:

• We need minienvironments to provide select areas of enhanced contamination control;
• Cleanrooms will be around for some time;
• Minienvironments will become an integral part of many cleanrooms;
• Minienvironments will increase facility costs but will provide significant offsetting benefits;
• 300 mm wafer facilities will make extensive use of minienvironments.

  Additionally, we have learned that one size does not fit all industries. Where we had previously referred to "microelectronics minienvironments" and "pharmaceutical minienvironments" we now talk of "minienvironments" and "isolators." Isolation technology has diverged from minienvironment technology and has taken its own path to better meet the needs of the pharmaceutical industry.

  In previous columns, we mentioned that a new standard on minienvironments would soon be released. That document, IEST Recommended Practice (RP) CC028.1 Minienvironments, is now available from the Institute of Environmental Sciences and Technology (IEST).

  This RP will prove to be essential reading for individuals in industries that might benefit from the use of localized, enhanced contamination control. RP 028.1 describes the various uses, configurations and benefits of minienvironments. It discusses their various design features and facility integration requirements. The document also provides a series of minienvironment testing and evaluation procedures.

  The IEST decision to develop an RP on minienvironments actually followed the CleanRooms East Show in Boston. Several members of Working Group 28 (WG028) attended the show and found that the lack of common terminology applied to minienvironments had left most potential users confused.

  No one had yet performed the tedious work of actually writing down what we collectively knew on the subject and, in turn, integrated that information with the contamination control and cleanroom concepts that we work with daily. The group realized that minienvironments cannot simply be installed within cleanrooms, but require integration with the entire cleanroom system, including the manufacturing tools and the materials-handling systems.

  Six years were spent developing the RP, a time interval driven by the evolutionary nature of the topic. Basic concepts, terminology and definitions were still being thrashed out in the industry, and it was difficult to find consensus until some time had passed and designers and users began to agree on some common principles.

  Difficulties also arose with initial attempts to produce a document that encompassed both minienvironments and isolators. The group eventually found the two topics sufficiently unique that a common document would serve neither adequately. While RP 028.1 does not cover biological applications of minienvironments (isolation technology), it will be of significant interest to those in the pharmaceutical industry who use minienvironments for enhanced contamination control.

  Several members of the group also were involved in the writing of IEST RP-012.1 Considerations In Cleanroom Design. Because of this overlap of membership of WG012 and WG028, the resulting documents share a common approach. Each is intended to be of use to both novices and experienced users. In each case, the RP does not actually tell the user how to design, build, install and operate cleanrooms or minienvironments. Rather, it provides a review of the design and operational criteria a user should carefully consider.

• Michael A. Fitzpatrick is program director of microelectronics for Lockwood Greene. A senior member of the IEST, he is chairman for WG012 (Considerations in Cleanroom Design) and WG028 (Minienvironments). Ken Goldstein is principal of Cleanroom Consultants Inc. in Phoenix, Arizona, and is a member of the CleanRooms Editorial Advisory Board.

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