A cleanroom is a room with a controlled atmosphere where temperature, humidity, internal pressure, flow and particles in the air are the elements that determine the level of contamination.
The objective of a Cleanroom Certification is to minimize the level of contamination. The classification of that room is evaluated based on the average level of concentration in the air of particles of a certain size.
The use of cleanrooms is widespread in many sectors, such as:
- Chemistry.
- Pharmacy.
- Food.
- Biology.
- Cosmetics.
- Microelectronics.
The airflow that enters a cleanroom can be unidirectional (laminar flow) or non-directional (turbulent), but in any case, it must pass through special filters called HEPA or ULPA.
The goal of using these filters is to eliminate suspended particles and microorganisms so that the air is as sterile as possible and is periodically renewed to avoid dust accumulation.
HEPA filters are composed of a mesh of glass fibers arranged randomly and a diameter of between 0.5 and 2 µm. And space between the fibers greater than 0.3 μm.
Particles are trapped (stick to a fiber) by a combination of these mechanisms:
Interception: Where the particles that follow airflow graze a fiber and stick to it.
Impact: Where big constituent parts are not capable of avoiding the fibers while following the airflow and are strained to directly crash one of them. This effect increases with the decrease in the separation between fibers and the increase in airflow speed.
Diffusion: The smallest particles, especially those smaller than 0.1 µm, collide with the gas molecules, preventing and delaying their passage through the filter.
The Cleanroom Hepa Filter is also used in autonomous extraction equipment for welding fumes. The size of the particles and their typology (hydrochloric acid, benzene, toluene), make these fumes a highly harmful element to the operator. For this reason, where a manual welding station is available, these smoke extraction equipment should be required.
The air pressure in the cleanroom is a factor to be controlled, being slightly higher than the outside to prevent or hinder the entry of outside air into the room. Some locks or doors maintain the pressure differences between the rooms and isolate them from the outside. The laboratory should have a Fume Hood Certification.
The pre-rooms are the spaces where the operators will dress in special suits to avoid contaminants or generate dust particles. The fabrics used to avoid the generation of microfibers and consequently, contamination.
An aspect to consider in a clean room where we manipulate electronic circuits or cleanrooms for microelectronics is that they must also be EPA areas. The cleanroom laboratory should have Clean Room Certifications.
Regarding the clothing of the operators
They need ESD gowns or ESD overalls with specifications for a clean room and hats or executioners.
A particularly noteworthy point in clean rooms - EPA areas is the use of bootees or gaiters that do not have a direct connection with the operator. Therefore is not the main landing element for the operator's loads (pavement/footwear assembly). There are some specific rules for Cleanroom Testing And Certification.
In these cases, when the operator moves an ESD sensitive device (ESDS) through the cleanroom. They must be screened using conductive trays with a lid or shielded bag.
Comments