ISO 5 and ISO 7 are cleanroom classifications defined by the International Organization for Standardization (ISO) that specify maximum allowable concentrations of airborne particles in a cleanroom environment. Cleanrooms are controlled environments used for critical manufacturing processes that require extremely low levels of contamination, such as semiconductor fabrication, pharmaceutical production, and medical device assembly. The lower the ISO class number, the cleaner the room is. So ISO 5 represents a cleaner environment than ISO 7.
What is an ISO 5 Cleanroom?
An ISO 5 cleanroom has stringent requirements for air quality. Specifically, ISO 5 allows no more than 3,520 particles per cubic meter that are 0.5 microns or larger in size. It also permits no more than 20 particles per cubic meter that are 5 microns or larger.
To achieve these low particle counts, ISO 5 cleanrooms use high-efficiency particulate air (HEPA) filters that remove at least 99.97% of particles 0.3 microns in size from recirculated air. The room must be constructed of smooth, impermeable materials that do not shed particles. Anyone entering an ISO 5 cleanroom must wear a bodysuit, headcover, gloves, mask, and shoes that cover their street clothes to prevent contamination. Strict procedures are followed for cleaning and disinfection.
ISO 5 cleanrooms provide an extremely clean environment for manufacturing and research involving highly sensitive processes and materials. The low particle counts help prevent defects and contamination. Common ISO 5 cleanroom applications include semiconductor wafer processing, hard disk manufacturing, pharmaceutical filling, and medical device assembly.
What is an ISO 7 Cleanroom?
ISO 7 cleanrooms allow higher concentrations of airborne particles than ISO 5 environments. Specifically, ISO 7 cleanrooms permit no more than 352,000 particles per cubic meter that are 0.5 microns or larger. They also allow no more than 2,930 particles per cubic meter that are 5 microns or larger.
To achieve ISO 7 air quality, these cleanrooms utilize HEPA filters just like ISO 5. However, the filtration and air exchanges may not be as stringent, allowing more particles to be present. The room construction and gowning procedures are similar but not quite as strict as ISO 5.
ISO 7 cleanrooms provide a clean environment for many critical manufacturing processes. The higher particle limits provide more flexibility for operators and processes that do not require the utmost in contamination control. Some common applications include pharmaceutical tabletting, medical device packaging, microscope assembly, and precision optics.
ISO 5 vs ISO 7 Particle Limits
| Particle Size | ISO 5 Particle Limit | ISO 7 Particle Limit |
|---|---|---|
| ≥0.1 μm | Not defined | Not defined |
| >=0.2 μm | Not defined | Not defined |
| >=0.3 μm | Not defined | Not defined |
| >=0.5 μm | 3,520 particles/m3 | 352,000 particles/m3 |
| >=1 μm | Not defined | 83,200 particles/m3 |
| >=5 μm | 20 particles/m3 | 2,930 particles/m3 |
This table summarizes the maximum allowable particle concentration levels for ISO 5 and ISO 7 at various sizes above 0.1 microns. It clearly shows how the concentration limits are much stricter for ISO 5 across the board.
Monitoring and Testing Methods
To ensure that the required air quality is maintained, ISO 5 and ISO 7 cleanrooms use a particle counter to continuously monitor particle concentrations. A small, automated instrument draws air samples and counts the number of particles at set sizes. Alarm systems alert personnel if counts exceed defined limits.
Cleanrooms are also tested and certified to verify compliance with ISO 5 or ISO 7 on initial qualification and then through routine re-certification, at least annually. Testing is performed using calibrated particle counters to measure airborne particle populations at designated sampling points and under operational process conditions. All measuring equipment used must be calibrated and traceable. Testing is performed by qualified technicians.
Differences in Construction and Gowning
While ISO 5 and ISO 7 cleanrooms utilize similar designs, materials, and gowning, there are some differences in stringency.
ISO 5 cleanroom walls, floors and ceilings require extremely smooth, non-shedding materials such as epoxy resin walls and conductive vinyl floors. ISO 7 allows for slightly more surface texture and permeability.
ISO 5 gowning procedures are also stricter. Personnel are required to pass through an air shower to dislodge particles from garments before donning a head-to-toe coverall, hood, boots, gloves, face mask and goggles. For ISO 7, an air shower may not be required and shoe covers are optional.
Due to the lower particle limits, cleaning and disinfection protocols for ISO 5 are more stringent than ISO 7. Surfaces are cleaned more frequently with stronger chemicals. Anything entering an ISO 5 room requires careful wiping and air showers.
Applications
ISO 5 cleanrooms are used when the highest levels of contamination control are needed. The ultra-low particle counts prevent defects in processes and materials highly vulnerable to microscopic particles. Some examples include:
– Semiconductor wafer fabrication – Photolithography processes require sub-micron control of particulate matter to prevent faults in circuits. A spec of dust could ruin an entire silicon wafer.
– Microelectronics manufacturing – Tiny airborne particles can destroy microprocessors, memory chips and other components. ISO 5 is essential for defect-free production and yields.
– Disk drive manufacturing – A particle landing on a hard disk platter can cause a crash or data loss. ISO 5 cleanrooms are used for media fabrication and assembly.
– Pharmaceutical filling – Parenteral drugs (injected medications) are filled and finished in ISO 5 conditions to ensure sterility and prevent particulate contamination.
– Medical device assembly – Implantable devices often require ISO 5 protocols to reduce bioburden and the risk of infection. Sterility is critical.
While ISO 7 cleanrooms maintain fairly strict air quality, the higher particle limits afford more flexibility for less contamination-sensitive processes including:
– Pharmaceutical secondary manufacturing – Tablet production, packaging and labeling may only require ISO 7 conditions.
– Medical device packaging – Protective packaging helps maintain sterility of finished devices, so ISO 7 standards may suffice.
– Precision optics – Lens, mirror and prism fabrication have tighter particle requirements than assembly and coating operations.
– Microscope manufacturing – Critical optics require ISO 5 or better, while assembling metal and optical components may need only ISO 7.
– Aerospace electronics – Certain avionics systems are packaged under ISO 7 conditions where ultra-high purity is not required.
So in determining ISO class, the product and process risks must be weighed against the costs of achieving and maintaining each cleanliness level.
Conclusion
ISO 5 cleanrooms clearly offer superior air quality over ISO 7 environments. The much lower particle concentration limits in ISO 5 rooms provide critical contamination control for sensitive semiconductor, pharmaceutical, biotech and medical processes where microscopic defects can have serious consequences. ISO 7 cleanrooms, while not as stringent, still offer a clean environment adequate for many manufacturing processes where product and economic requirements allow for higher particle levels. Determining the right cleanroom classification requires assessing process risks and needs. But when the highest air purity is paramount, ISO 5 is the clear choice.