Sources of Contamination in the Cleanroom
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A controlled environment is designed to provide a clean space, free of contaminants that can potentially damage products or compromise a process. Classifications range from ISO 3/Class 1 to ISO 8/Class 100,000 and are determined by the number of particles allowed per volume of air.
The highest level, most stringent controlled environments are those that house the manufacturing and production of semiconductors, medical devices, and pharmaceutical products. These cleanrooms have strict regulations and guidelines that must be closely followed to preserve and maintain product quality.
The causes of cleanroom contamination can vary, and if we look closely, it’s often traced back to unsuspecting sources. Supplies, materials, and equipment used in the cleanroom are common sources. People and their behaviors are another cause of contamination. Unsuspecting products that are needed in the cleanroom such as tape are a major concern because non-cleanroom rated product are typically used. Read on to see a variety of hidden causes of contamination within a controlled environment.
There is a lot of focus on protecting a cleanroom from outside contaminants. Often the number one cause of cleanroom contamination can be generated from people within the environment. There are well known measures taken to protect the environment such using the proper garments, cleaning supplies, and equipment. The less known culprits can be in the actions of people. Rapid movement within the cleanroom is a significant source of particle generation. Furthermore, not following gowning procedures, such as wearing garments for too long between changes can also increase particle levels.
Not being aware of cleaning procedures can also be problematic. For example, a defective or torn garment can be a source of cleanroom contamination. So can wearing jewelry or wearing a garment improperly. Cuffs that are too loose can be optimized with sealing tape to lessen chances for cleanroom contamination.
Labels and Tapes
Sometimes, it’s the small things that are overlooked – especially when outfitting a cleanroom with supplies. Common office supplies such as labels and cleanroom tape can be an unforeseen source of cleanroom contamination. These products are often made of or with paper, have paper cores as well as adhesives that outgas unwanted VOC’s. these products can also leave behind unwanted residue.
Let’s take a look at each one of the various components of these products.
Cores: Many traditional tape products are made with cardboard cores. This is problematic because cardboard is often a prohibited material in a cleanroom. Using tape rolls that have plastic cores with smooth finishes is one way to prevent shedding. Plastic with burrs and sharp edges pose a risk to gloves and bags – highlighting the importance of smooth edges.
Backing and Liners: Tapes that have paper backing/release liners should not be used within the cleanroom. Instead, opt for synthetic materials to reduce the risk of cleanroom contamination.
Packaging: It’s important to not overlook the packaging that these supplies come in. We discussed avoiding paper materials because of their potential for cleanroom contamination. Printed bags, single bagged items, or packaging that has the potential for electrostatic discharge should be avoided.
For the highest safeguard, items should be double-bagged and correctly de-bagged inside the cleanroom outside cleanroom contamination from packaging.
Adhesives: Another source of cleanroom contamination related to tapes and labels comes from adhesives that can leave sticky residue that can outgas, leaving and invisible layer of contamination in the cleanroom. Chemical contamination is a major concern in both semiconductor and medical/pharmaceutical manufacturing; therefore, eliminating any source of outgassing or adhesive residue is vital. Organic contaminants adhering to silicon wafer surfaces, as well as the lenses used in lithographic processes, have become a serious problem for chip, medical device, and pharmaceutical manufacturers.
All the above-cited label and tape generated sources of cleanroom contamination can easily be eliminated by using residue-free and cleanroom certified tapes, release liners and packages from a certified cleanroom consumable supplier.
A necessary evil in terms of cleanroom contamination sources, all equipment to be used in a cleanroom must be inspected and cleaned prior to installation and before each use. While this requirement seems obvious, its importance can’t be overemphasized, as examining process tools thoroughly can reveal hidden sources of potential contamination that could otherwise be overlooked.
Monitoring should take place before, during and after use since tolls typically generate gases, volatiles and solid airborne particulates in all stages of operation. Consistently evaluating a facility’s equipment and having a plan in place to minimize the impact of the known sources of cleanroom contamination will have major positive impact on the cleanliness of your environment.
Raw material and consumables
Before and raw material or manufacturing product is brought into a cleanroom, it must itself be cleaned thoroughly. Contaminants can lurk on packaging or arise if materials and consumables (e.g., face masks, gloves, mats, etc.) and not handled properly. The extent of cleaning required varies depending upon the class of cleanroom, the destination of the raw material and the possibility of any cross cleanroom contamination to other processes.
Cleanliness standards for cleanroom maintenance are much higher than for other environments, meaning that household and even industrial cleaning products are not sufficient. In addition to requiring dedicated cleanroom supplies the cleaning solutions themselves are also purpose-specific (e.g. products that can only be used to clean the floor and not counters). Examples of proper cleaning products include nonparticipating wipes and mops, as well as solution that minimize off-gassing. Additionally, vacuums must have a classification rating equal to or better than the cleanroom in which they are to be used.
Cleanroom Contamination can derive from a range of hidden sources, from the people occupying and working in a cleanroom, to the process equipment and materials used, even down to consumable such as tapes and labels. By taking proper steps to minimize the impact of these seemingly benign but potentially harmful sources, you can ensure the level of foreign object debris in your cleanroom meeting or exceeds the specific rating. Simple but crucial actions, such as securing particulate-free materials and consistently implementing proper protocols, will help maximize manufacturing yields and shorten your time to market.
Kwang Cleanroom is proud to offer examples of a variety of our cleanroom projects below. Electronics Assembly Cleanrooms, Cosmetic Production Cleanrooms, Automotive Cleanrooms, Aerospace Cleanrooms, Medical Device Cleanrooms, Pharmaceutical & Biotechnology Cleanrooms Powder Coating Cleanrooms.