Cleanroom wipers help manage contamination in controlled environments in a number of ways, including wiping residues on hard surfaces and applying cleaning solutions.
One way to choose from cleanroom wipers of similar structural design is to compare test results across a variety of criteria using recommended practices set forth by IEST RP CC004.3.
Quality is typically evaluated across a range of performance characteristics that include:
- Fabric substrate and micro-structure,
- Sorption capacity and rate, and
- Particulate burden of various sizes, including bioburden, ions, metals and non-volatile residues (NVRs).
Methods to Assess Wiper Quality
The three major types of contamination are: particles and fibers, ions, and NCRs. These must be measured to control the amount of contamination carried into the cleanroom by the wiper.
1. Cleanliness Test
Fibers — A wiper is “washed” in water, using a biaxial shaker, for 5 minutes. Fibers released into the water are filtered onto a membrane and they are counted microscopically. Results are expressed as fibers ≥ 100µm per square cm of wiper. [IEST-RP.CC004.3, Section 220.127.116.11]
Particle Generation / Biaxial Shake Test — A wiper is “washed” in water, using a biaxial shaker, for 5 minutes. A liquid-borne particle counter then tallies the particles that are released into the water. Dividing the total number of particles that is released by the area of the wiper gives results expressed as particles ≥ 0.5µm per square cm of wiper. [IEST-RP.CC004.3, Section 6.1.3]
Airborne Particle / Helmke Drum Test — Under controlled conditions, 10 wipers are tumbled in a rotating drum to release any particles from the wiper fabric. An airborne particle counter is used to count released particles. These results are expressed as the number of particles per wiper per cubic ft of air sampled. [IEST-RP-CC003.4 Section B2.5]
Capacity — A sample of wiper material is saturated with as much fluid as it is able to hold. After a minute, the material is weighed. Results are expressed in milliliters of fluid per square meter. [IEST-RP.CC004.3, Section 8.1 (Modified)]
Efficiency — This calculates the rate at which a material absorbs relative to others. The results are expressed in milliliters of liquid per gram of material, assisting in comparing a raw material with another. [IEST-RP. CC004.3. Section 8.1 (Modified)]
Rate — This measures the time it takes a wiper to absorb half of the total liquid it can hold. These results are expressed in seconds. [IEST-RP. CC004.3. Section 8.2 (Modified)]
Non-Volatile Residue — Non-volatile residue data is generated using deionized water and 2-Propanol. The results are expressed in grams of extracted materials per square meter of wiper. This is a useful guide to relative purity of wipers. [IEST-RP.CC004.3, Section 7.1.2]
Metallic Ions — Ions are extracted in deionized water. They are quantitatively analyzed by Ion Chromatography. Results are expressed in parts per million (ppm). [IEST-RP.CC004.3, Section 7.2.2]
The selection of cleanroom wipers is a critical decision in any controlled environment. For more information or advice, get in touch with our friendly, knowledgeable, and professional staff today.