Incorporating cleanroom practices in a management program
BY JAN EUDY
The cleanroom industry turns to three main sources for standards and best practices in cleanroom management: the International Organization for Standardization (ISO), the American National Standards Institute (ANSI) and the Institute of Environmental Sciences and Technology (IEST).
The ISO has had a decade-long program to develop cleanroom standards for the world. Seventeen member nations have sent delegates to nine different working groups to develop these standards. At press time, ISO 14644-1, 2, and 4 have been published as both ISO and ANSI standards. Additional standards will be released over the course of the next two years.
The IEST is a volunteer professional organization that develops recommended practices for the contamination-control, design, test and evaluation, and product reliability industries. For more than 50 years, this society of voluntary commitment by industry professionals has developed these recommended practices based on their industries' best practices. Many of the same professionals assist in the development of the ISO standards.
The three ISO documents that have been approved by the international community have also been approved by ANSI. Together, these non-profit organizations contribute a vast amount of knowledge and resources to the cleanroom industry.
There are several IEST recommended practices that enable end users to meet the requirements of the worldwide cleanroom standard, ISO 14644:
- IEST-RP-CC001: HEPA and ULPA Filters—This recommended practice should be used as a reference before selecting cleanroom air filters. The IEST-RP-CC007 and IEST-RP-CC021 documents should be referenced to test the filters installed and in-use.
- IEST-RP-CC002: Unidirectional Flow Clean-Air Devices—Reviews various products and systems available for directing the cleanroom airflow.
- IEST-RP-CC006: Testing Cleanrooms—Reviews how to perform particle testing and associated testing to achieve the desired cleanliness classifications of the ISO documents.
- IEST-RP-CC007: Testing ULPA Filters—This recommended practice should be used to evaluate the ULPA filters used in the cleanroom.
- IEST-RP-CC019: Qualifications for Agencies and Personnel Engaged in the Testing and Certification of Cleanrooms and Clean-Air Devices—Provides guidelines for evaluating and selecting subcontractors to test and certify cleanrooms.
- IEST-RP-CC021: Testing of HEPA and ULPA Filter Media—Describes test methods for physical and filtration properties (i.e., resistance to airflow, penetration test, particle count test, basic weight test, thickness test, tensile strength test, and elongation test). This document also includes a table providing guidelines on the frequency of filter-testing frequency.
IEST technical guides
Additionally, the IEST publishes four technical guides to assist cleanroom operators when testing for particles:
- IEST-G-CC1001: Counting Airborne Particles for Classification and Monitoring of Cleanrooms and Clean Zones;
- IEST-G-CC1002: Determination of the Concentration of Airborne Ultra fine Particles;
- IEST-G-CC1003: Measurement of Airborne Macroparticles;
- IEST-G-CC1004: Sequential-Sampling Plan for use in Classification of the Particulate Cleanliness of Air in Cleanrooms and Clean Zones.
In 2000, ISO 14698 1 and 2 was published. Part 1 reviews general principles in biocontamination control inside the cleanroom, while Part 2 provides methods for evaluating and interpreting biocontamination data. The associated IEST recommended practices that assist cleanroom operators in achieving the principles in these ISO standards are:
- IEST-RP-CC013: Procedures for the Calibration or Validation of Equipment;
- IEST-RP-CC023: Microorganisms in Cleanrooms.
Both of these IEST documents are in the final phases of revision to comply with the ISO 14698 standards.
Metrology and test methods
The ISO standard on metrology and test methods is in the FDIS (final draft international standard) stage. IEST recommended practices that provide guidelines are the same as for ISO 14644-1 and 2. Additionally, IEST-RP-CC01: Procedures for the Calibration of Particle Counters, and IEST-RP-CC034: HEPA and ULPA Filter Leak Tests, provide test methods to use for compliance to ISO 14644-3.
The ISO 14644 series document provides guidance on facilities design, construction, and start-up. Architects and cleanroom contractors desiring to achieve the construction results of ISO 14644-4: Cleanrooms and Associated Controlled Environments-Part 4, should refer to the IEST recommended practices used to classify cleanroom cleanliness. In addition, IEST-RP-CC012: Considerations in Cleanroom Design, ensures that the design and installation of cleanroom production equipment is carried out in the best possible manner. This document includes a table describing cleanroom classifications, airflow velocities, and recommended number of air changes per hour for cleanroom classifications.
Both IEST-RP-CC024: Measuring and Reporting Vibration in Microelectronics Facilities and IEST-RP-CC030: Cleanroom Electrical Systems, provide guidance for cleanroom construction companies regarding special electrical and vibration considerations for equipment.
The IEST recently published a new revision of IEST-RP-CC022, Electrostatic Charge in Cleanrooms and Other Controlled Environments, that addresses many aspects of design to enable control of static electricity in cleanrooms. Other recently revised IEST recommended practices support the guidelines of the ISO 14644-5 document, including:
- IEST-RP-CC003: Garment System Considerations for Cleanrooms and Other Controlled Environments—Used to select garments that will ensure that both the product and personnel are protected from contaminants.
- IEST-RP-CC004: Evaluating Wiping Materials Used in Cleanrooms and Other Controlled Environments—Used to evaluate the wipers used to clean surfaces of the product and the cleanroom. Wipers should be selected based on their intended usage in the cleanroom. This document describes test methods used to evaluate wipers.
- IEST-RP-CC005: Gloves and Finger Cots Used in Cleanrooms and Other Controlled Environments—Used to select gloves that will ensure that both the product and the personnel are protected from contaminants or hazardous materials. (It should be noted that it is impossible to design and manufacture gloves to meet all applications; therefore, it is incumbent upon the user to select appropriate gloves based on requirements of the process. Gloves should be selected for their mechanical, structural and thermal properties.) This IEST document describes methods to test glove properties, and provides guidance on donning and doffing the glove.
- IEST-RP-CC018: Cleanroom Housekeeping-Operating and Monitoring Procedures—Provides practical information regarding cleaning techniques, equipment, cleaning compounds, housekeeping checklists, and methods for auditing of housekeeping.
- IEST-RP-CC026: Cleanroom Operations—Provides guidance to maintain the integrity of the cleanroom during operation.
- IEST-RP-CC027: Personnel Practices and Procedures in Cleanrooms and Controlled Environments—Reviews behavior requirements for personnel working inside the cleanroom; includes gowning requirements.
To facilitate compliance with ISO 14644-5, the IEST working groups are also diligently striving to release revised versions of RP-20, Substrates and Forms for Documentation in Cleanrooms; RP-25, Evaluation of Swabs Used in Cleanrooms; and RP-32, Packaging Materials for Cleanrooms.
The IEST also regularly updates IEST-RD-CC011: A Glossary of Terms and Definitions Related to Contamination Control, to keep everyone in the contamination-control industry apprised of common terms currently in use. Before publication of a recommended practice, all terms and definitions are carefully reviewed for consistency and accuracy.
An ISO 14644 working group specifically addresses separative enclosures, such as barrier isolator systems and minienvironments used inside cleanrooms. The IEST recently published IEST-RP-CC028: Minienvironments, which gives guidance specifically for minienvironments in the cleanrooms.
Molecular contamination, which has become a critical issue in the field of contamination control, is specifically addressed in the ISO 14644-8 "Classification of Airborne Molecular Contamination" document. The primary concern for any product produced in a cleanroom environment is its potential to be impacted by airborne molecular contamination (AMC), which can damage biological products as well as wafers. Geometries of wafers are now as small as bacteria, molds and yeasts, and may be affected by AMCs as well.
The IEST working group preparing IEST-RP-CC035: Airborne Molecular Contamination in Cleanrooms and Controlled Environments, is providing recommendations that affect decisions on the design of the HVAC system, selection of suitable filters, and material used to build the cleanroom.
Volatile, non-volatile substances
The IEST also recently published recommended practices to provide guidance on volatile and non-volatile substances:
- IEST-RP-CC016: The Rate of Deposition of Nonvolatile Residue in Cleanrooms—This document is the reference for cleanroom certification and monitoring of non-volatile residue. Recommendations affect decisions on the design of the HVAC system, selection of suitable filters, and material used to build the cleanroom.
- IEST-RP-CC031: Outgassing Performance Criteria for Cleanroom Materials—Provides guidance for selection of materials used in cleanrooms to assure cleanroom compatibility.
Recently, the IEST published IEST-MIL-STD 1246: Product Cleanliness Levels and Contamination Control Program, which describes testing surfaces for contaminants. This document provides guidance for the selection of the test methods of surfaces to demonstrate the cleanliness level required.
Another IEST working group is preparing the revised MIL-HDBK-406: Contamination Control Technology: Cleaning Materials for Precision Pre-Cleaning and Use in Cleanrooms and Clean workstations.
Volunteers on these ISO and IEST working groups have already spent many hours devoting time and talent to publish the ISO standards and IEST recommended practices. But there is more work ahead for these dedicated professionals, who must complete the work in progress, regularly review existing documents, and make the changes required to keep the contamination-control industry informed.
JAN EUDY is corporate Q. A. manager for Cintas Cleanroom Resources and president-elect of the Institute of Environmental Sciences and Technology (IEST).