It is recommended that when comparing cleanroom consumable products manufactured by several vendors that all products be tested at the same lab, with the same test method, and by the same technician. What test methods are recommended for cleanroom consumable products?
Disposable gloves, wipers, swabs, bouffant, and garments are used in cleanrooms and controlled environments throughout the world. They are tested by contract testing labs and or by the consumable manufacturer during product development for product literature information, compliance to customer specifications, and during root cause investigation for product failure or contamination. The customer may also perform similar tests to confirm the consumable item is per contracted specifications.
There are a variety of tests to determine contamination, functionality of the cleanroom consumable item, and its physical characteristics. The test methods are described in standards from the ASTM (American Society for Testing and Materials), ANSI (American National Standards Institute), ISO (International Organization for Standardization), IEST (Institute of Environmental Sciences and Technology), and military specifications. I recommend consulting the IEST recommended practices for gloves, wipers, and swabs for performance of specific test methods.
Some countries and industries have specific standard methods, such as the Gelbo flex test used in Germany and the U.S. to determine the number of particles on wipers and garments, and the standard methods established by IDEMA for the disk drive industry and SEMI for the semiconductor industry.
The company requesting the tests specifies the testing to be fast, inexpensive, a direct sampling of their product, quantitative, and robust. Therefore the testing lab delivers a standard test method that is repeatable and reproducible, can test a variety of products, delivers relevant information at the lowest possible detection limit, and value for the price of the testing.
The most common elements that are evaluated when testing cleanroom consumable products are organic and inorganic particles, dissolved materials or films, and gases. If the method is not direct, then the sample must undergo extraction using air, liquid, or surface-to-surface extraction methods. After extraction, the following tests can be performed:
- liquid particle counting
- airborne particle counting
- optical microscopy
- scanning electron microscopy (SEM) with energydispersive X-ray analyzer (EDX or EDS)
- Fourier transform infrared spectroscopy (FTIR)
- gas chromatography/mass spectrometry (GC/MS)
- ion chromatography (IC)
- inductively coupled plasma (ICP)
- atomic emission spectrometer (AES)
- mass spectrometer (MS)
- X-ray fluorescence (XRF)
The selection of what test to be performed is based on the analyte listed above that is requested to be analyzed correlated with the detection limits, repeatability and reproducibility of the test method, and the calibration of the instrumentation used.
Increasingly, the types of analytes being requested changes with the cleanroom application. However, typical laboratory tests performed on cleanroom consumable products are:
- Viable particle enumeration and identification (microorganisms)
- Non-viable particle enumeration using either liquid particle counter or air particle counter test methods
- Microscopic fiber enumeration and analysis
- Non-volatile residue
- Ion content (Sodium, Lithium, Ammonia, Potassium, Magnesium, Calcium, Fluoride, Chloride, Nitrate, Phosphate, Sulfate, etc.)
- Presence of silicone
At the conclusion of the testing of the cleanroom consumable item, a summary report of the analysis is generated. This report should include the following information:
- Date of sampling, analysis, and reporting
- Name of analyst for sample preparation, analysis, and report writing
- Lot number or other sample traceability information
- Measurement type
- Equipment specifics, such as serial number, model number, and calibration status
- Sample preparation specifics, such as whole sample, extract, or SIP (sample item portion)
- System blank and control values
- Test values
- Detection limits
- Numerical analysis
- Comments regarding unusual results
- Second party verification and review of the test results
When the recommended criteria for the specific test method is followed, the sources of variation (i.e. sample differences, test method differences in preparation and/or analysis, equipment differences, operator technique differences, and environmental conditions of the laboratory) are reduced. Therefore, achieving the recommendation that the testing of the cleanroom consumable items be performed by the same test lab, using the same test method and equipment, and performed by the same technician. All test results can be trended and monitored to assure the consistent quality of the cleanroom consumable product.
Testing cleanroom consumable products reduces the risk of unfortunate “surprises” in the manufactured product and protects the R&D investment of both current and new developed products