Understanding Cleanrooms: Definition, Types, Applications, and Technology

Figure 1. A cleanroom with personnel wearing special cleanroom clothing

I. What's a Cleanroom, Then?  

As the name hints, a cleanroom is indeed a spick-and-span space. However, it has a rather posh definition in the ISO 14644-1 standard: 

A room in which the concentration of airborne particles is controlled, and which is constructed and used in a manner to minimise 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.

First off, pumping in vast amounts of air filtered through high-efficiency filters—think of it as a fancy air freshener for cleanliness. This air helps to:  

1. Dilute and whisk away particles and bacteria from staff and machinery  

2. Keep the room under pressure, ensuring no filthy air sneaks in uninvited  

Next, these rooms are crafted from materials that are as clean as a whistle and easy to tidy up. And let's not forget, the folks inside wear full-body suits—after all, we can't have them shedding particles like confetti at a wedding! Cleanrooms also keep an eye on temperature, humidity, noise, lighting, and vibration—though these aren't exactly their exclusive domain.  

Cleanrooms are a modern marvel. While their roots can be traced back over a century to infection control in hospitals, the industrial need for pristine environments is a contemporary affair. Why the fuss? Because humans and machines can churn out millions of particles, and regular building materials are prone to fall apart like a biscuit in tea. Cleanrooms keep this chaos in check, offering a tidy environment for manufacturing.  

II. Why We Need Cleanrooms  

Cleanrooms aren't just for show; they have a variety of uses. Take a gander at Table 1 for some current cleanroom creations.  

Table 1. Applications of Cleanrooms

Figure 2. The possible surface contaminants on a silicon wafer

Using the semiconductor manufacturing industry as an example, processors used in computers, cars, and other machinery are produced. Figure 2 shows a microscopic image of a particle on a semiconductor. Such particles can cause circuit shorts and damage the semiconductor. To mitigate contamination issues, semiconductors must be manufactured in cleanrooms that meet very high cleanliness standards.

The red section of Table 1 highlights manufacturers requiring microbial control, as the growth of microorganisms in products (or in hospital patients) can lead to human infection. In the medical field, hospitals use cleanroom technology in operating rooms to minimise wound infections, as it is essential to prevent microbes or dirt from being injected or infused into patients (see Figure 3).

Figure 3. Unidirectional flow system in an operating room

Moreover, Table 1 indicates that many of these industries are modern, and this list will undoubtedly continue to expand, driving ongoing demand for cleanrooms.

III. Types of Cleanrooms

Cleanrooms have evolved into two main types, distinguished by their ventilation methods: turbulent airflow cleanrooms and laminar airflow cleanrooms. Turbulent airflow cleanrooms are also known as "non-unidirectional airflow cleanrooms", while laminar airflow cleanrooms are referred to as "unidirectional airflow cleanrooms". Unidirectional airflow cleanrooms use significantly more air than non-unidirectional types, providing higher cleanliness levels.

Figures 4 and 5 illustrate the basic principles of these two main types of cleanrooms. Figure 4 depicts a turbulent airflow cleanroom, which receives clean, filtered air through ceiling-mounted diffusers. This air mixes with the room air and is expelled through outlets at the bottom of the walls to remove airborne contaminants.

Figure 4. Turbulently ventilated type of cleanroom

Air changes per hour typically equal or exceed 20 times, which is significantly more than in ordinary rooms (like offices). In this type of cleanroom, pollutants generated by personnel and machinery mix with the supplied air, diluting it before removal.

Figure 5. Laminar flow type of cleanroom

Figure 5 illustrates the fundamental principle of a laminar airflow cleanroom. High-efficiency filters are installed throughout the ceiling (or walls) to supply air. This air flows in a unidirectional manner at approximately 0.4 m/s (80 ft/min) across the room and is expelled through the floor, thereby removing airborne contaminants. This system uses more air than a turbulent airflow cleanroom but minimises the spread of pollutants within the room due to the directional airflow, sweeping them out through the floor.

Clean air devices, such as unidirectional workstations or isolators, are used in both turbulent and laminar airflow cleanrooms, providing locally enhanced filtered air where necessary, such as in areas where products are exposed to contamination.

IV. What's the Deal with Cleanroom Technology?  

As illustrated in Figure 6, cleanroom technology can be divided into three realms, working together as users move from the decision to acquire a cleanroom to its final operation.  

Figure 6. Various parts of cleanroom technology and their interconnections

First off, designing and constructing the room involves considering:  

1. Which design standards to follow?  

2. What layouts and materials to use?  

3. How to service the cleanroom?  

Once the cleanroom is up and running, testing is essential to ensure it meets design specs. And throughout its life, ongoing monitoring is necessary to keep standards in check. Finally, to ensure products remain as clean as a whistle, cleanrooms must be operated properly—managing personnel and materials, garment choices, discipline, and cleanliness within the room, like a well-oiled machine.

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Tags：Cleanroom Technology   Cleanrooms