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Cleanroom Basics

Cleanroom Basics

Contaminants can cause a variety of defects when assembling or packaging sophisticated products such as medical devices. If the cleanliness of the product is important, increasingly they are assembled and packaged in cleanrooms. The environment is controlled where particulates in airflow are filtered and the particulates analyzed by size and number, thus controlling the airborne particles to meet predetermined limits.

Per ISO14644-1, a cleanroom is "a room in which the concentration of airborne particles is controlled, and which is constructed and used in a manner to minimize the introduction, generation, and retention of particles inside the room and in which other relevant parameters, e.g. temperature, humidity, and pressure, are controlled as necessary."

As the air is circulated through filters some amount of particulates are removed from the controlled environment. The level of cleanliness can be characterized by classifications in standards such as Federal Standard 209E.

Cleanroom manufacturing requires controls and discipline. Following the strict protocol most of time is not acceptable; it has to be a constant ongoing process. In addition, recordkeeping is required and it must be accurate and verified. In-house auditing and periodic auditing by independent agencies is the norm. The goal is to prevent contamination of the assemblies and their packaging.

Removing airborne particles requires controlling the airflow, including its volume, velocity, and direction. The clean assembly and packaging controlled environment will have temperature and relative humidity regulated. The cleanroom will be pressurized greater than outside the cleanroom to prevent dirty exterior air from entering the cleanroom. The filter will be specified, including size, media, and retention of a certain particle size. The filters will be High Efficiency Particulate Absorption air filters or HEPA.

The design of the cleanroom will depend upon the manufacturing to be performed. The work instructions will detail assembly procedures as well as the maintenance protocol that will be followed. Increasingly, cleanrooms are used for manufacturing medical devices and other sophisticated products including electronics, pharmaceutical, biopharmaceutical, and other high reliability products.

Airborne particles

Do you think the office worker works in a nice clean environment? Compare these typical numbers:

Environment

Particles per Cubic Foot

Particle Size

Office

750,000

0.5 microns or larger

Class 10,000 cleanroom

Less than 10,000

0.5 microns or larger

Class 1,000 cleanroom

Less than 1,000

0.5 microns or larger

Class 100 cleanroom

Less than 100

0.5 microns or larger

The diameter of a human hair is about two hundred times greater than a 0.5 micron particle. So cleanrooms do control its environment and removes most particles, even very small ones.

All employees, including maintenance personnel, must follow the procedures consistently. Training of all employees is essential. Training records should be kept. Non-compliance with required cleanroom protocols should be treated in the same manner of other impermissible actions that are handled through the company’s disciplinary process. This includes verbal warnings, re-training, written warnings, and eventually re-assignment or termination.

The cleanroom rules are for all personnel, not just operators. This includes management, engineers, and customers. Ideally, windows are installed to view what is happening in the cleanroom, and non-workers are kept outside the cleanroom. Every opportunity to prevent contaminants from entering the cleanroom should be seized. Strict procedures should be followed whenever entering or cleaning a cleanroom. Compromise is not acceptable when cleaning in a cleanroom.

Controlled environment contamination

Where does the contamination come from? Operators working in the controlled environment can be a big source of contamination. In addition, contaminants can be generated by the manufacturing process, facility materials, equipment, and even the product itself.

It is a little harsh to view operators as a source of contamination. But unfortunately it is a natural function for the human skin to be continually sloughing off particles and that the skin will have perspiration, oils, and acids. Then there is hair, shedding various particulates, and the operator may be wearing aftershave or perfume, and have clothing with fabrics that are not lint-free.

Every cleanroom has walls, a floor, and a ceiling. Care must be taken in their construction and particularly if painted or coated. Outgassing has to be evaluated. Superb maintenance is necessary to eliminate all leaks, spills, and extraneous materials.

Productivity is important in a cleanroom, so tools are provided. However, equipment often requires lubrication, and moving parts will wear. Even maintenance tools can be sources of contamination, including brooms and mops.

Chemicals can outgas, particularly plasticizers used in many commonly production items to improve flexibility. Cleaners and floor finish as well as bacteria and other organic materials can be sources of contamination.

It is a challenge when the cleanroom is manufacturing a product in which the product itself chips, flakes, or provides other particulation that itself contaminates the cleanroom. It can be particularly frustrating when there is electrostatic attraction, where a particle is charged and clings to a surface and is very difficult to remove. Trash can also be a challenge, either from the product or from supplies. A sufficient number of trash receptacles should be placed so the trash can be quickly collected. Then the trash receptacles should be emptied frequently.

Keys to control contamination

The cleanroom facility structure, its filtration, and periodic maintenance are the key areas to control contamination. The cleanroom should be designed producing uniform airflow throughout the room having about the same speed and similar parallel direction. The goal is a laminar flow avoiding turbulence. The most common filtration is using High Efficiency Particulate Absorption air filters, or HEPA. The “High Efficiency” enables removing most all 0.5 microns or larger particles from the airflow passing through the HEPA. In addition other mechanisms are employed to remove particles from the airflow.

Data collected will determine the frequency and intensity of the periodic maintenance necessary to maintain the standard of the cleanroom. It cannot be arbitrary; it must be driven by the data. In addition the protocol must be documented, and be precise. It is as important to train cleaning personnel as it is manufacturing operators in the cleanroom. Work instructions should specify the cleaning materials to be used and how to determine that the cleanroom has been adequately cleaned. The cleanroom structure, floors, walls, and ceiling, as well as all production equipment, should list the maintenance cleaning steps. Deviation from the work instructions should not be accepted. A detailed periodic maintenance schedule should be prepared for every cleanroom.

Operators - source of contamination

The operators and their behavior can greatly increase the contamination in the cleanroom. Moving around particularly rapidly can cause more particles to contaminate the cleanroom. An operator who is motionless not moving at all can contaminate the cleanroom with about 100,000 0.3 micron particles a minute. If walking, the rate can be five to ten times higher and be even a thousand times higher if running. That’s a lot of particulation but it is all normal. We all sneeze and cough, have skin that flakes with oils and perspiration. We all have hair that falls out.

Reduce contamination by covering up operators

See the photographs of the operators in a cleanroom and they sure look funny. The cleanroom garments such as “bunny suits” impair working on products reducing the operator’s dexterity, vision, and even the tactile feeling of the fingers handling small parts. Like an astronaut’s space suit, all these negatives are outweighed by a greater good. In the cleanroom case, the bunny suit is worn along with cleanroom gloves and hair covers to reduce the operator’s contamination of the cleanroom. Cleanroom operator garment requirements will vary, but may include facemasks. If not requiring a bunny suit, the cleanroom garment may be a smock with shoe covers.

Ideally the cleanroom garments are only worn inside the cleanroom and are not worn outside the cleanroom. Torn or soiled garments should be replaced. Cleanroom garments are not to be written on. When in the cleanroom removing an item from underneath the cleanroom garment should be prohibited. Regardless, operators should clean off the bottoms of their feet before entering the cleanroom; for example walking on a sticky mat when entering.

Ideally operators should be prohibited from wearing cosmetics including perfume or cologne. Cosmetics may contain calcium, iron, magnesium, potassium, silicon, sodium, etc. adding to the particles in the cleanroom.

Cleanroom supplies

The cleanroom manager should control the type and quantity of supplies stored or used in the cleanroom. Only items approved by the cleanroom manager should be purchased and allowed in the cleanroom. Specialty cleanroom supplies should be used. These may include cleaning and disinfecting solutions, and cleanroom wipers. Instead of normal janitorial items, cleanroom versions of mops, buckets, wringer, etc. should be required. A written list should be published by the cleanroom manager and updated from time to time.

Cleanroom specifications

The cleanroom manager needs to make measurements to ascertain if the cleanroom meets the required specifications. Equipment must be available to make accurate measurement. These would typically include:

•    Air flow and velocity
•    Particle count
•    Relative humidity
•    Surface cleanliness
•    Temperature

Cleanroom contract manufacturing

Many major high tech companies are subcontracting cleanroom manufacturing to contract manufacturers. SpecialTeam’s Class 1,000 facility in Yorba Linda, Calif. is certified ISO 13485:2003; ISO 9001:2008, and is FDA registered 2032092, and specializes in low volume projects and clinical trial production. The company offers assembly, packaging, sterilization, validation/testing; complete product manufacturing traceability (ISO, FDA, cGMP); quick turn-around of prototype and short run engineering device assemblies; and turnkey product development from inception to full production. The company’s product experience includes custom syringes, custom cannula assemblies, tubing sets, disposable respiratory devices, disposable filtration devices, custom needle/surgical knife packaging, disposable dental products, custom kit assembly and packaging, electro-surgical devices, and implants. Full-service capabilities include ultrasonic welding and cleaning, UV and solvent bonding, pouch/bag/tray sealing, shrink wrapping, repackaging, and kitting.

SpecialTeam has several certified Class 1,000 (ISO Class 6) cleanroom suites totaling 2,000 square feet. By segregating these suites into their own assembly areas, SpecialTeam is able to perform a variety of processes suited to specific client(s) requirements and maintain product separation. Full traceability of all phases of assembly/packaging is maintained with complete client communication during the production run.

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Cleanroom Industries Sdn. Bhd. was founded in 1999 as a pioneer manufacturer in Malaysia specializing in design and manufacture of a full range of cleanroom-related architectural products for cleanroom applications up to Class 1 cleanliness.

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