CleanroomsUSA

Cleanroom Construction and Design Part 2

Stick-Built Cleanrooms

Stick-built cleanrooms offer an alternative to modular cleanrooms, characterized by a metal frame (referred to as "sticks") covered with gypsum wallboard. These cleanrooms are affordable and straightforward, known for their flexibility in shaping and fitting into various workspaces. The construction process involves a customized floor plan, wall and ceiling installation, a high-efficiency HVAC system, and other components tailored to the cleanroom's specific needs.

Ceiling options for stick-built cleanrooms range from ceiling grid systems to hard ceilings made of gypsum wallboard. Both walls and ceilings are typically coated with epoxy or PVC for added protection. The flexibility of stick-built cleanrooms makes them a popular choice for businesses undergoing expansion and redesign, as they can be adapted to fit any available space.

However, stick-built cleanrooms do have some drawbacks, primarily related to durability. While they are less expensive to construct, their lower cost is offset by a shorter useful life and the need for regular maintenance, which can reduce the initial cost savings.

Standard Cleanrooms

A standard cleanroom is designed to protect against particulate matter that can negatively impact product quality or processes. The specific type of standard cleanroom is determined by its ISO classification, and they are commonly used in industries such as semiconductor manufacturing, pharmaceuticals, biotech, and medical devices.

Cleanrooms are constructed and designed to meet the specific conditions required for their use. For instance, there is a distinct standard cleanroom for microelectronics and another for pharmaceuticals. Factors such as the type of product, regulatory standards, and available space influence the design and specifications of a cleanroom.

The primary goal of a cleanroom is to minimize the size and number of particles in its atmosphere, controlling contaminants, temperature, humidity, and pressure. HEPA filters are crucial components, as all incoming air is filtered to achieve the desired level of cleanliness.

Personnel using cleanrooms must adhere to strict attire requirements, which vary depending on the cleanroom's ISO rating. Higher ISO ratings demand more rigorous protective clothing, ranging from hair nets, masks, gloves, and lab coats to full-body coverings known as bunny suits.

It is essential to understand that cleanrooms are controlled environments with stringent requirements to protect both personnel and the integrity of the products handled. Workers are trained to adhere to these standards to maintain the cleanroom's conditions.

Turbulently Ventilated Cleanrooms

Turbulently ventilated cleanrooms feature non-unidirectional airflow, where air is mixed with filtered air to remove lingering contaminants. These systems use complex methods to eliminate particulate matter, including laminar filters and random velocity filters. The turbulent airflow pattern makes it challenging to separate particle-laden air from clean air, but the random movement helps direct particles through the filtration system.

In these cleanrooms, air moves in all directions, with air quality maintained by directing and circulating air towards strategically placed filters. Despite the term "turbulent," the airflow is planned, circulating around tools, booths, objects, and equipment to maintain air quality by continuously moving air through filters.

The vortex-shaped airflow dilutes particle concentration, making it easier for HEPA filters to remove contaminants. This constant air movement ensures that the particulate count and size remain within acceptable limits.

Unidirectional Cleanrooms

Unidirectional cleanrooms, the most common type, feature airflow in a single direction, either horizontally or vertically. These cleanrooms can achieve ISO classifications of ISO 5 or lower. Filtered air enters from the top, sweeps down, and removes contaminants through vents at the bottom or sides. The air exchange rate typically ranges from 0.3 to 0.5 meters per second.

The architecture of unidirectional cleanrooms prevents turbulence, ensuring that only clean, filtered air enters. This airflow design effectively removes particles from personnel and equipment, with air moving at a steady velocity in parallel streamlines, directed by laminar flow hoods.

Used Cleanrooms

As cleanroom technology evolves, older cleanrooms may be replaced by newer versions. However, used cleanrooms can still provide much of the same functionality, though they may lack advanced features. Purchasing a used cleanroom can be a cost-effective option for applications that do not require the latest technology.

While used cleanrooms offer reduced upfront costs, it's important to ensure they meet the required specifications and to be aware of potential issues from prolonged usage.

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