Recently, our cleanroom became contaminated with silicone. Contamination with silicone is a very serious problem in our industry. Please help us determine the source of the silicone contamination.
Silicone contamination is a serious problem in the semiconductor, microelectronics, defense and automotive industries internationally. Silicone becomes aerosolized inside the cleanroom and as an airborne molecular contaminant can redeposit on the manufactured product causing a variety of defects and rejection of a high percentage of the manufactured lot of product. In the paint spray industries, the redeposited silicone causes craters and/or fish-eyes on the painted surface. In the optics and wafer industries, the re-deposited silicone creates a thin film on surfaces. Obviously silicone contamination negatively impacts the bottom line of these industries and must be controlled and prevented.
The quality assurance departments of these companies have learned through many FMEA (failure mode evaluation and analysis) investigations to position the risk management programs to aggressively prevent silicone from contaminating the cleanroom operations. The information accumulated over the years provides training materials for cleanroom operators and supervisors.
Silicone contamination can come from a variety of sources. Traditionally textiles have been manufactured using silicone as a lubricant in the manufacturing process. Some components such as Velcro and embroidered emblems also can contain silicone. Many deodorants, hair sprays, styling gels and mousses, body lotions, hand cleaners and creams, perfumes and colognes, when worn by cleanroom operators and supervisors into the cleanroom, can cause silicone contamination of the product manufactured in the cleanroom. Food that is consumed by the cleanroom operators during breaks and meals during the day may contain silicone. Therefore, rigorous and regularly positively reinforced training in cleanroom operations and behavior per IEST-RP-CC026, “Cleanroom Operations”, IEST-RP-CC027, “Personnel, Practices and Procedures in Cleanrooms and Other Controlled Environments” and ISO 14644-5, “Cleanrooms and Associated Controlled Environments – Operations” should be performed. Additionally, production in-coming components and preventive and corrective maintenance materials can contain silicone and therefore should be pre-screened by the purchasing department in the product specification and vendor verification process.
Once the silicone contamination is discovered, a corrective and preventive action plan is initiated. The CAPA team must be aware that there also are many cleaning agents that contain silicone.
The following lists of materials have been tested and are believed to contain potential contamination causing materials. The contaminating substance may be silicone, aluminum, magnesium, manganese, iron or other anions and cations that interferes with the products and/or processes in cleanrooms. This list is by no means all inclusive of materials which may be used or present at each individual plant nor does it necessarily indicate silicone contamination problems will result if the material is being used and present in the plant environment. Many materials if used properly and controlled in the process will not result in silicone contamination even though it may test as a potential contamination causing substance. The material must be present and in the right environmental conditions during the manufacturing process to cause silicone contamination.
The purpose of this list is to inform cleanroom operations as to potential silicone contamination causing materials and can be used as a guide should a contamination problem occur. This list is continuously updated as additional materials are identified and tested for presence of silicone.
If cleanroom garments become contaminated with silicone during cleanroom manufacturing, the contaminated garments should be segregated, placed in water soluble plastic bags and sent separately to the cleanroom garment laundry for remediation. Remediation of cleanroom garments uses aggressive wash chemicals and therefore shortens the life span of the cleanroom garment. Therefore, prevention of contamination through rigorous enforcement of cleanroom protocol is recommended.
Jan Eudy is Corporate Q.A. Manager for Cintas Corporation and President-Emeritus and Fellow of the Institute of Environmental Sciences and Technology.