The role of particle counters in the field of clean rooms

The term cleanroom is derived from European medicine in the 1860s. At that time, the understanding was limited to treatment rooms and operating rooms that could control the infection rate of the wound after spraying and disinfection. The working environment of the bacteria treatment. Although the modern clean room has extended the term, it is fundamentally different in definition and connotation from the original concept. The modern clean room forms a specialized technology, but its history is only half a century. With the development of technology, cleanroom is an emerging technology that is adapted to the requirements of precision, miniaturization, high purity, high quality and high reliability of experimental research and product processing. This paper mainly describes the detection function of the particle counter in the clean room from several aspects of the clean room’s grade standard, field division and grade requirements.

particle counter in the clean room area Detection function

Clean room

Clean room level standard

The cleanroom level standard, like the international standard ISO 14644, is based on the unique indicator of suspended particle concentration to classify the cleanliness of the clean room (zone) and related controlled environments, and Only particle groups with a cumulative distribution of particle size limits (lower limits) in the range of 0.1 um to 5.0 um are considered. According to the particle diameter, it can be divided into conventional particles (0.1um to 5.0um), ultrafine particles (<0.1um), and macro particles (>5.0um).

ISO/DIS 14644-1 Classification of suspended particulates in air in clean rooms and clean areas

Detection of particle counters in the clean room area

ISO Rating

Hanging Cleanliness Level in Cleanroom and Clean Area Air

Detection of particle counters in the clean room area

Air cleanliness level

Field division of cleanroom

The clean room is divided into units The number of dust contained in the volume is calculated. The smaller the number, the higher the cleanliness level. Generally, the division of each level has different requirements for the number of dusts in different diameters, such as general pharmaceutical factories, automobile 4s stores, 100,000 or 10,000 grades. Enough, but this is only the minimum requirement for the electronics industry (especially the microelectronics industry). For example, the test room with the lowest level requirement in the semiconductor industry can’t be higher than 10,000. Let’s take a closer look through the industrial clean room.

According to the standards promulgated by the US federal government, the clean room can be divided into six levels. They are Level 1, 10, 100, 1000, 10000, and 100000. If the level of the clean room is only described by the number of dust particles, the size of the dust particles can be assumed to be 0.5 μm, for example, level 1, The maximum number of dust particles in the Class 10 and Class 100 clean rooms is less than or equal to 1, 10, and 100, respectively. And by the FS209E standard, the maximum number of 0.5 micron dust particles allowed per cubic foot is the clean room grade. For example, if you want to contain up to 1000 0.5 micron per cubic foot, then this clean room is a thousand, if 10,000 particles are 10,000 grades, totaling from first grade, ten grade, hundred grades, thousand grades, ten thousand grades to one million grades; industrial clean room mainly controls the pollution of non-living particles to working objects, and the inside thereof generally maintains positive pressure. It is suitable for the precision industry, electronics industry, aerospace industry, chemical industry, printing industry and other departments. Industrial dust-free workshops as long as the control parameters are temperature, humidity, wind speed, flow field, cleanliness. Therefore, in order to meet the cleanliness and heat and moisture balance in the purification workshop, a large air supply volume is required. The workshop of 300 square meters has a height of 2.5 meters. If it is 10,000 grades, it needs 300×2.5×30=22500 m3/h. Air supply volume (the number of air changes is ≥25 times/h); if it is 100,000, the air supply volume needs 300×2.5×20=15000m3/h (the number of air changes is ≥15 times/h). In addition, in order to maintain the cleanliness of the clean room, the entry and exit personnel have certain wearing regulations; 10000 and 100000 grades must wear robes, dust-free clothes, dust-free shoes, hats and masks; 1000 or more, special wear is required. The clean jumpsuit and dust-free shoes will be wrapped around the body with gloves and a face mask. Therefore, each clean room is equipped with a high efficiency air particulate (HEPA) filter to prevent the spread of airborne organisms and viral organisms. The filter also features a positive pressure design that isolates unfiltered air from the outside of the room, while the air shower removes contaminated particles before the worker and product enter the room. The clean room audit maintenance process includes counting microorganisms to ensure compliance with cleanliness and bioburden levels.

Cleanhouse Level Requirements

To ensure that cleanrooms and related environments meet controlled standards, basic air-heat treatment equipment and air purification equipment , aerodynamic equipment, air distribution system, cold and heat source equipment, high efficiency air supply, purification workbench, clean unit, air shower, transfer window and micro-environment, as well as clean clothes, clean gloves, masks, cleaning supplies, etc. also have special requirements. However, the physical properties, chemical properties, radiation characteristics or characteristics of suspended particles of the clean room are not stated in terms of cleanliness standards.

It is well known that both the dust detector and the particle counter can use the principle of light scattering, but the particle counter is used in the clean room, and the dust meter is mainly used to measure the atmospheric environment. Why is this so? We can judge by the principle of two kinds of light scattering. The dust detector sucks the aerosol to be tested into the detection chamber through the gas pump, and the aerosol to be tested is divided into two parts at the branch, and a part is filtered through a high-efficiency filter and filtered into clean air to protect the sensor chamber as a sheath gas. The components are not contaminated by the gas to be tested. Another part of the aerosol enters the sensor chamber directly as a sample to be tested. In the sensor room, the main components are laser diodes, lens groups and photodetectors. In the detection, the laser light emitted by the laser diode is first formed into a thin-layer light source through the lens group. When a thin layer of light is irradiated through the aerosol to be tested flowing through the sensor chamber, scattering occurs, and the scattered light intensity of the light is detected by the photodetector. The photodetector produces an electrical signal after exposure to light, proportional to the mass concentration of the aerosol. It is then multiplied by a voltage calibration factor that is obtained by measuring a specific concentration of aerosol. The test aerosol commonly used for calibration is Arizona test dust (or ISO 12103-1, A1 test dust).

Particle counter principle: The particle counter extracts the sample gas through the sampling pump. In the laser chamber, the sampled gas is irradiated by the laser. The frequency of the flash reflected by the particles represents the number of particles and the reflected light intensity. The particle size of the particles, the components in the laser chamber, without sheath gas protection.

particle counter in the clean room area Detection function

Handheld particle counter

In order to better detect the suspended particle processing network in the clean room The US AIRY Handheld Particle Counter is available – Model P611 is used to measure particles with a flow rate of 0.1 CFM (2.83 LPM) and a particle size of 0.3 to 10 μm. The handheld particle counter weighs only 1.26 lb (0.57 kg) and is user-friendly and easy to set up. It can display data of 6 size channels at the same time in its 3.5” LCD color screen к, and can also display temperature and relative humidity (optional). At the same time, P611 can store up to 10,000 sample records, which can be used in this device or through USB data cable. View data records on the computer. P611 is ISO 21501-4, 2 years warranty. P611 is of high quality and reliable performance. It is the best product solution for professionals to verify ISO clean room (level 5~9) and investigate indoor air quality problems. .