A method for measuring the airtightness of a clean room

Abstract

The present invention relates to the field of indoor pollution control technology and discloses a method for determining the airtightness of a cleanroom. This method calculates the infiltration air volume into the cleanroom by measuring the air volume and particle concentration in the upper and lower technical mezzanines and fresh air handling units of the cleanroom system, as well as the particle concentration outside the cleanroom system. This method reduces workload while accurately and conveniently determining the airtightness of the cleanroom.

Description

Technical Field

[0001] The invention relates to the technical field of indoor pollution control, in particular to a method for measuring the airtightness of a clean room. Background Art

[0002] With the development of science and technology, more and more technical fields have higher requirements for the environment, requiring parameters such as cleanliness and indoor pressure to be controlled within a specified range. This led to the invention of clean rooms. Usually, a clean room enclosure is built around the clean room, and a clean room purification and air conditioning system is installed. The clean room enclosure system and the purification and air conditioning system work together to remove and purify pollutants such as particulates, harmful air, and microorganisms in a certain space environment, so that the cleanliness level, pressure, microbial limit, etc. in the specified space environment can meet the specified requirements.

[0003] To ensure the cleanroom's cleanliness level, a certain pressure differential is typically maintained between the cleanroom and its surroundings. This prevents ambient air from entering the cleanroom through the cleanroom enclosure and affecting the cleanroom's cleanliness level. If dirty air from the surrounding environment enters the cleanroom through the enclosure, it will not only affect the cleanroom's cleanliness level but also shorten the service life of high-efficiency air filters (HEATs) and ultra-high-efficiency air filters. Therefore, it is crucial to ensure that the enclosure surrounding the cleanroom is airtight, thereby ensuring the cleanroom's airtightness and maintaining the cleanroom's cleanliness level and extending the service life of high-efficiency air filters (HEATs). In the prior art, if a cleanroom's airtightness is poor, the airflow of the fresh air handling unit (FAH) is increased to maintain the required pressure differential. However, this solution is not energy-efficient. Furthermore, if the cleanroom enclosure is poorly airtight, the FHU may not have sufficient excess capacity to compensate for air leakage. Therefore, after cleanroom construction is completed, the cleanroom's airtightness is typically tested to assess whether it meets the requirements.

[0004] Existing techniques for testing cleanroom airtightness typically employ methods such as light leakage, particle counter scanning, and air leakage. The light leakage method involves introducing a light source into the joints of the cleanroom enclosure to observe whether light passes through the gaps, thereby determining the airtightness of the cleanroom enclosure. However, this method can only provide a qualitative assessment of cleanroom airtightness, failing to generate quantitative data. Furthermore, it cannot detect non-through gaps.

[0005] The particle counter scanning method uses a particle counter to scan the joints of the cleanroom enclosure and determine if there are air leaks based on the particle counter readings. While this method can pinpoint air leaks within the cleanroom enclosure, it requires excessive effort for large cleanrooms like those in current flat-panel display and semiconductor fabs. Furthermore, due to cleanroom construction, some joints are inaccessible to both personnel and equipment, making it rarely used in actual projects.

[0006] The air leakage method involves first sealing the cleanroom to be tested. This involves blocking all openings, such as the supply / return air vents and exhaust vents. Air is then supplied to the cleanroom using an air filter unit or blower to maintain a constant pressure. The air volume entering the cleanroom at this point represents the air leakage rate of the cleanroom enclosure. This method is effective for relatively small cleanrooms, but similarly, it is impractical for large cleanrooms, such as those used in current flat panel display and semiconductor fabs, due to the large number of openings that need to be sealed prior to testing.

[0007] Therefore, for existing technologies, how to accurately measure the airtightness of a clean room while reducing workload remains a difficult problem. Summary of the Invention

[0008] The invention discloses a method for measuring the airtightness of a clean room. The method can calculate the infiltration air volume of the clean room by measuring the air volume and particle concentration of each part of the clean room, thereby accurately measuring the airtightness of the clean room while reducing the workload.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A method for measuring the airtightness of a clean room, the method being used to measure the airtightness of a clean room in a clean room system; the clean room system comprising a clean room, a clean room enclosure structure, and a clean room purification and air conditioning system; the clean room enclosure structure comprising an upper technical interlayer located at the top of the clean room, a lower technical interlayer located at the bottom of the clean room, and a return air duct connected between the upper and lower technical interlayers; the clean room purification and air conditioning system comprising a fresh air handling unit, a fan filter unit disposed at the top of the clean room, and a dry cooling coil disposed in the lower technical interlayer; the method comprising:

[0011] Obtain the clean room supply air volume of the upper technical mezzanine, the clean room return air volume of the lower technical mezzanine, and the fresh air volume of the fresh air handling unit;

[0012] Obtaining the particle concentration of the upper technical interlayer, the particle concentration of the lower technical interlayer, the particle concentration at the air outlet of the fresh air handling unit, and the particle concentration outside the clean room;

[0013] The infiltration air volume of the clean room enclosure is calculated based on the clean room supply air volume of the upper technical mezzanine, the clean room return air volume of the lower technical mezzanine, the fresh air volume of the fresh air handling unit, the particle concentration of the upper technical mezzanine, the particle concentration of the lower technical mezzanine, the particle concentration of the air supply port of the fresh air handling unit, and the particle concentration outside the clean room;

[0014] The air infiltration volume of the clean room enclosure structure is compared with the standard value of the air infiltration volume of the clean room to evaluate the airtightness of the clean room.

[0015] Optionally, the infiltration air volume of the clean room enclosure is calculated based on the clean room supply air volume of the upper technical interlayer, the clean room return air volume of the lower technical interlayer, the fresh air volume of the fresh air handling unit, the particle concentration of the upper technical interlayer, the particle concentration of the lower technical interlayer, the particle concentration at the air supply port of the fresh air handling unit, and the particle concentration outside the clean room, including:

[0016] The infiltration air volume of the clean room enclosure is calculated using the following formula:

[0017] Ls=(Lt·Ct-Lr·Cr-Lx·Cx) / Cs;

[0018] Among them, the Ls is the infiltration air volume of the clean room enclosure structure, the Lt is the clean room supply air volume of the upper technical interlayer, the Ct is the particle concentration of the upper technical interlayer, the Lr is the clean room return air volume of the lower technical interlayer, the Cr is the particle concentration of the lower technical interlayer, the Lx is the fresh air volume of the fresh air handling unit, the Cx is the particle concentration at the air supply port of the fresh air handling unit, and the Cs is the particle concentration outside the clean room.

[0019] Optionally, obtaining the particle concentration of the upper technical interlayer includes:

[0020] Determine the primary particle concentration at the inlet of the fan filter unit.

[0021] Optionally, obtaining the particle concentration of the lower technical interlayer includes:

[0022] Determine the secondary particle concentration at the dry cooling coil.

[0023] Optionally, determining the second particle concentration at the dry cooling coil comprises:

[0024] Measure the particle concentration at the air inlet of the dry cooling coil or the particle concentration at the air outlet of the dry cooling coil.

[0025] Optionally, obtaining the clean room air supply volume of the upper technical mezzanine includes:

[0026] The air supply volume of the clean room is obtained according to the commissioning acceptance result of the clean room.

[0027] Optionally, obtaining the clean room return air volume of the lower technical mezzanine includes:

[0028] The air volume passing through the dry cooling coil was measured.

[0029] Optionally, measuring the air volume passing through the dry cooling coil includes:

[0030] Measure the wind speed at the air inlet of the dry cooling coil or the wind speed at the air outlet of the dry cooling coil, as well as the area of ​​the dry cooling coil. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A simple schematic diagram of a clean room system provided by an embodiment of the present invention;

[0032] Figure 2 A schematic flow chart of a method for determining the airtightness of a clean room provided in an embodiment of the present invention.

[0033] Reference numerals:

[0034] 1-clean room; 2-upper technical mezzanine; 3-lower technical mezzanine; 4-return air duct;

[0035] 5-Fan filter unit; 6-Dry cooling coil; 7-Waffle plate; 8-Raised floor;

[0036] 9-Fresh air handling unit. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] The present invention provides a method for measuring the airtightness of a clean room, which is used to measure the airtightness of a clean room in a clean room system. The clean room system includes a clean room 1, a clean room enclosure structure, and a clean room purification and air conditioning system. Figure 1As shown, the clean room enclosure structure includes an upper technical interlayer 2 located at the top of the clean room 1, a lower technical interlayer 3 located at the bottom of the clean room 1, and a return air duct 4 connected between the upper technical interlayer 2 and the lower technical interlayer 3. The clean room purification air conditioning system includes a fresh air handling unit (MAU) 9, a fan filter unit (FFU) 5 arranged at the top of the clean room 1, and a dry cooling coil (DCC) 6 arranged in the lower technical interlayer 3. It should be understood that the fresh air handling unit 9 is connected to the clean room through a pipe, but the pipe is omitted here in the figure. In addition, in order to facilitate the air from the clean room to enter the lower technical interlayer 3, an open raised floor 8 and a waffle plate 7 are also provided between the lower technical interlayer 3 and the clean room 1.

[0039] However, in actual operation, since cleanroom 1 typically experiences a positive pressure of 10 to 20 Pa relative to the surrounding environment, air entering the lower technical mezzanine 3 through the perforated raised floor 8 and waffle plate 7 inherently exerts an air resistance of 3 to 5 Pa. Therefore, the lower technical mezzanine 3 typically experiences a positive pressure of 5 to 17 Pa relative to the surrounding environment. The air in the lower technical mezzanine 3 then passes through the dry cooling coil 6 and enters the return air duct 4. Since the dry cooling coil 6 typically exerts an air resistance of approximately 40 Pa, the return air duct 4 typically experiences a negative pressure of -35 to -23 Pa relative to the surrounding environment. The pressure in the upper technical mezzanine 2, connected to the return air duct 4, is also lower than that in the return air duct 4. Therefore, the cleanroom system can be divided into a positive pressure zone and a negative pressure zone. The cleanroom 1 and lower technical mezzanine 3 constitute the positive pressure zone, while the return air duct 4 and upper technical mezzanine 2 constitute the negative pressure zone. Near negative pressure zones, due to the pressure differential, dirty air surrounding the cleanroom system will infiltrate the return air duct 4 and upper technical mezzanine 2 through gaps in the cleanroom enclosure. This dirty air, unfiltered, directly mixes with the circulating clean air and enters the fan-filter unit 5. This not only affects the cleanroom system's cleanliness level, but also shortens the service life of the filters in the fan-filter unit 5. Therefore, cleanroom density is crucial for cleanroom systems.

[0040] The method for determining the airtightness of a clean room provided by the present invention is used to accurately measure the air volume infiltrating into the clean room system and thus accurately determine the airtightness of the clean room. Figure 2 As shown, the method for determining the airtightness of a clean room includes the following steps:

[0041] S1: Obtain the clean room supply air volume of the upper technical mezzanine, the clean room return air volume of the lower technical mezzanine, and the fresh air volume of the fresh air handling unit;

[0042] S2: Obtain the particle concentration of the upper technical mezzanine, the particle concentration of the lower technical mezzanine, the particle concentration at the air outlet of the fresh air handling unit, and the particle concentration outside the clean room;

[0043] S3: The infiltration air volume into the cleanroom enclosure is calculated based on the cleanroom supply air volume of the upper technical mezzanine, the cleanroom return air volume of the lower technical mezzanine, the fresh air volume of the fresh air handling unit, the particle concentration of the upper technical mezzanine, the particle concentration of the lower technical mezzanine, the particle concentration of the fresh air handling unit air outlet, and the particle concentration outside the cleanroom;

[0044] S4: Compare the infiltration air volume of the clean room enclosure structure with the standard value of the infiltration air volume of the clean room enclosure to assess the airtightness of the clean room.

[0045] Since the entire cleanroom system is a closed environment, circulating air enters the return air duct 4 from the lower technical interlayer 3, then mixes with the infiltrated air and the air supplied by the fresh air handling unit 9, and finally mixes into the upper technical interlayer 2, entering the cleanroom 1 via the fan filter unit 5. Therefore, it can be concluded that the sum of the number of particles in the lower technical interlayer 3, the number of particles supplied by the fresh air handling unit 9, and the number of particles in the infiltrated air is the number of particles in the upper technical duct. Furthermore, the cleanroom air supply volume of the upper technical interlayer 2 corresponds to the particle concentration in the upper technical interlayer 2, the cleanroom air volume of the lower technical interlayer 3 corresponds to the particle concentration in the lower technical interlayer 3, and the air volume at the fresh air handling unit 9 corresponds to the particle concentration at the fresh air handling unit air outlet. Therefore, the air volume at the infiltration point of the cleanroom enclosure should also correspond to the particle concentration outside the cleanroom. When several other parameters are measured, the infiltrated air volume can then be accurately calculated. In specific applications, the order of steps S1 and S2 can be reversed and is not limited. Furthermore, the order of obtaining the air volume parameters at different locations in the clean room in step S1 is not limited, and the order of obtaining the particle concentration parameters at different locations in the clean room in step S3 is also not limited.

[0046] At the same time, since the value of the infiltration air volume can be accurately calculated, the calculated value can be compared with the required standard value, and then the airtightness of the clean room can be obtained and a more accurate evaluation can be made.

[0047] Specifically, the air volume and particle concentration at various locations in the clean room system follow the following patterns:

[0048] Lr·Cr+Lx·Cx+Ls·Cs=Lt·Ct;

[0049] Among them, Ls is the infiltration air volume of the clean room enclosure structure, Lt is the clean room supply air volume of the upper technical mezzanine 2, Ct is the particle concentration of the upper technical mezzanine 2, Lr is the clean room return air volume of the lower technical mezzanine 3, Cr is the particle concentration of the lower technical mezzanine 3, Lx is the fresh air volume of the fresh air handling unit 9, Cx is the particle concentration at the air supply port of the fresh air handling unit 9, and Cs is the particle concentration outside the clean room.

[0050] Therefore, the infiltration air volume of the clean room can be calculated using the following formula:

[0051] Ls=(Lt·Ct-Lr·Cr-Lx·Cx) / Cs;

[0052] That is, the method for calculating the air volume infiltrating the cleanroom enclosure is to divide the total number of infiltrated particles by the particle concentration at the infiltration point. The particle concentration at the infiltration point is also the particle concentration outside the cleanroom system. The method for calculating the total number of infiltrated particles is to subtract the number of particles at the lower technical mezzanine 3 from the number of particles delivered by the fresh air handling unit 9 from the number of particles at the upper technical mezzanine 2. Among them, the method for calculating the number of particles at the upper technical mezzanine 2 is to multiply the cleanroom supply air volume at the upper technical mezzanine 2 by the particle concentration, the method for calculating the number of particles at the lower technical mezzanine 3 is to multiply the cleanroom return air volume at the lower technical mezzanine 3 by the particle concentration, and the method for calculating the number of particles delivered by the fresh air handling unit 9 is to multiply the fresh air volume by the particle concentration at the fresh air handling unit supply port.

[0053] Specifically, since the air in the upper technical interlayer 2 will eventually pass through the fan filter unit 5 and enter the clean room, the particle concentration at the upper technical interlayer 2 and the clean room air supply volume can be obtained by measuring the particle concentration and air supply volume at the inlet of the fan filter unit 5. Similarly, since the air in the lower technical interlayer 3 will eventually pass through the dry cooling coil 6 and then enter the return air duct 4, the particle concentration at the lower technical interlayer 3 and the clean room return air volume can be obtained by measuring the particle concentration and air volume at the dry cooling coil 6. At the same time, due to the different specific structures of different clean rooms, the particle concentration and air volume of other structures of the upper technical interlayer 2 can be measured according to actual conditions, and the results obtained can be regarded as the particle concentration of the upper technical interlayer 2 and the clean room air supply volume. Similarly, the particle concentration and air volume of other structures of the lower technical interlayer 3 can be measured according to actual conditions, and the results obtained can be regarded as the particle concentration of the lower technical interlayer 3 and the clean room return air volume.

[0054] Specifically, the particle concentration and air volume of the dry cooling coil 6 can be measured at the air inlet of the dry cooling coil 6, at the air outlet of the dry cooling coil 6, or at both the air inlet and the air outlet of the dry cooling coil 6. While measuring at the air outlet of the dry cooling coil 6 provides more accurate data, for ease of operation, measurement can also be performed at the air inlet of the dry cooling coil 6.

[0055] In addition, since the amount of fresh air delivered by the fresh air handling unit 9 in the clean room purification and air conditioning system and the amount of air delivered by the fan filter unit 5 are basically fixed within a certain period of time, that is, after the clean room system is completed, these two values ​​are basically fixed within a certain period of time. Therefore, they can be directly obtained through the commissioning and acceptance results of the clean room system and applied to subsequent calculations.

[0056] The present invention can adopt a measuring device for clean room airtightness, which is used to perform the above-mentioned measuring method to measure the clean room airtightness of the clean room system. The measuring device includes a clean room system, a particle counter and an anemometer. The anemometer is used to detect the air volume at the location to be measured, and the particle counter is used to measure the particle concentration at the location to be measured. The infiltration air volume of the clean room enclosure structure is calculated by measuring the air volume and particle concentration, and then compared with the standard parameters of the clean room air leakage to obtain the final clean room airtightness result. During the measurement process, the particle counters are placed successively at the fan filter unit 5, the air inlet or air outlet of the dry cooling coil 6, the fresh air handling unit 9, and the return air duct 4 and the outside of the upper technical interlayer 2. It should be noted that the order of measurement here is not specified and can be changed according to actual conditions.

[0057] Obviously, those skilled in the art may make various changes and modifications to the embodiments of the present invention without departing from the spirit and scope of the present invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims and their equivalents, the present invention is intended to include such modifications and variations.

Claims

1. A method for determining the airtightness of a clean room, characterized in that: The measuring method is used to measure the airtightness of a clean room in a clean room system; the clean room system includes a clean room, a clean room enclosure structure, and a clean room purification and air conditioning system; The clean room enclosure structure includes an upper technical interlayer located at the top of the clean room, a lower technical interlayer located at the bottom of the clean room, and a return air duct connected between the upper technical interlayer and the lower technical interlayer; The clean room purification air conditioning system includes a fresh air handling unit, a fan filter unit arranged at the top of the clean room, and a dry cooling coil arranged in the lower technical interlayer; The determination method comprises: Obtain the clean room supply air volume of the upper technical mezzanine, the clean room return air volume of the lower technical mezzanine, and the fresh air volume of the fresh air handling unit; Obtaining the particle concentration of the upper technical interlayer, the particle concentration of the lower technical interlayer, the particle concentration at the air outlet of the fresh air handling unit, and the particle concentration outside the clean room; The infiltration air volume of the clean room enclosure is calculated based on the clean room supply air volume of the upper technical interlayer, the clean room return air volume of the lower technical interlayer, the fresh air volume of the fresh air handling unit, the particle concentration of the upper technical interlayer, the particle concentration of the lower technical interlayer, the particle concentration of the air supply port of the fresh air handling unit, and the particle concentration outside the clean room; Comparing the infiltration air volume of the clean room enclosure with the standard value of the infiltration air volume of the clean room to assess the airtightness of the clean room; The infiltration air volume of the clean room enclosure structure is calculated based on the clean room supply air volume of the upper technical interlayer, the clean room return air volume of the lower technical interlayer, the fresh air volume of the fresh air handling unit, the particle concentration of the upper technical interlayer, the particle concentration of the lower technical interlayer, the particle concentration of the air supply port of the fresh air handling unit, and the particle concentration outside the clean room, including: The infiltration air volume of the clean room enclosure is calculated using the following formula: Ls=(Lt·Ct-Lr·Cr-Lx·Cx) / Cs; Among them, the Ls is the infiltration air volume of the clean room enclosure structure, the Lt is the clean room supply air volume of the upper technical interlayer, the Ct is the particle concentration of the upper technical interlayer, the Lr is the clean room return air volume of the lower technical interlayer, the Cr is the particle concentration of the lower technical interlayer, the Lx is the fresh air volume of the fresh air handling unit, the Cx is the particle concentration at the air supply port of the fresh air handling unit, and the Cs is the particle concentration outside the clean room.

2. The method for measuring the airtightness of a clean room according to claim 1, wherein: Obtaining the particle concentration of the upper technical interlayer includes: The particle concentration at the inlet of the fan filter unit is measured.

3. The method for measuring the airtightness of a clean room according to claim 1, wherein: Obtaining the particle concentration of the lower technical sandwich includes: The particle concentration at the air inlet of the dry cooling coil or the particle concentration at the air outlet of the dry cooling coil is measured.

4. The method for measuring the airtightness of a clean room according to claim 1, wherein: Obtaining the air volume of the upper technical mezzanine includes: The air supply volume of the clean room is obtained according to the commissioning acceptance result of the clean room.

5. The method for measuring the airtightness of a clean room according to claim 1, wherein: Obtaining the fresh air volume of the fresh air handling unit includes: The fresh air volume of the fresh air handling unit is obtained according to the commissioning acceptance result of the clean room.

6. The method for measuring the airtightness of a clean room according to claim 1, wherein: Obtaining the clean room return air volume of the lower technical mezzanine includes: The air volume passing through the dry cooling coil was measured.

7. The method for measuring the airtightness of a clean room according to claim 6, wherein: Determining the air volume through the dry cooling coil includes: The wind speed at the air inlet of the dry cooling coil or the wind speed at the air outlet of the dry cooling coil, and the area of ​​the dry cooling coil are measured.

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