Specifications for the Evaluation and Application of High-Efficiency Filters in High-Tech Cleanrooms
1. Purpose
These specifications are formulated to standardize the selection, evaluation, testing, installation, monitoring, and replacement processes of High-Efficiency Particulate Air (HEPA) and Ultra-Low Penetration Air (ULPA) filters. The goal is to ensure their performance continuously meets the stringent air cleanliness requirements of high-tech cleanrooms, safeguarding the stability and reliability of the production process environment.
2. Scope
These specifications apply to all HEPA and ULPA filters used at the terminals of ventilation and air conditioning (HVAC) systems in cleanrooms of semiconductor high-tech factories. They cover the entire lifecycle management of filters, from initial selection and evaluation to disposal and replacement. All departments and personnel involved in facility operation and maintenance, quality control, and engineering management must comply with these requirements.
3. Basic Understanding and Selection Evaluation of High-Efficiency Filters
3.1 Filter Types and Definitions
HEPA Filter: High-Efficiency Particulate Air Filter, with a minimum collection efficiency of 99.97% for particles of 0.3μm in size.
ULPA Filter: Ultra-Low Penetration Air Filter, typically with a minimum collection efficiency of 99.999% for particles of 0.12μm or smaller specified sizes.
3.2 Key Performance Parameters and Selection Criteria
Selection and evaluation must be based on the following core parameters, ensuring compliance with cleanroom design grades (e.g., ISO 14644 classes) and process requirements:
Filtration Efficiency: Select the filter grade meeting the minimum efficiency requirement based on the particle size to be controlled (e.g., 0.3μm, 0.1μm) and target cleanliness class.
Initial Pressure Drop: Airflow resistance of a new filter at rated air volume. This value affects system energy consumption and shall serve as the basis for fan selection and energy efficiency evaluation.
Rated Air Volume: Optimal airflow range designed for the filter. Selection must match the actual operating air volume of the system.
Dust Holding Capacity: Total amount of dust a filter can hold before reaching final resistance. High dust holding capacity extends service life.
Material and Structure: Evaluate filter media (e.g., glass fiber), separator structure, sealant, and frame material (e.g., aluminum alloy, stainless steel) for corrosion resistance, strength, and compatibility with facility environments (temperature, humidity, potential chemical exposure).
4. Filter Performance Testing and Verification
To ensure filter performance meets standards, the following tests must be conducted:
4.1 Factory Acceptance Testing (FAT)
Suppliers must provide a test report for each filter complying with relevant standards (e.g., EN 1822, IEST-RP-CC001), including at minimum:
Efficiency Test: Determine the minimum efficiency of the filter at its Most Penetrating Particle Size (MPPS) using the particle counting method.
Resistance Test: Initial pressure drop at rated air volume.
Integrity Test: Scan test to ensure no leakage in filter media or seals.
4.2 On-Site Post-Installation Testing
After filter installation in cleanrooms, on-site verification testing is mandatory as a core part of system acceptance:
Leakage Test: Generate aerosol (e.g., PAO, DOP, DOS) upstream, and scan the filter media, frames, and seals between filters and mounting frames using a photometer or particle counter downstream. Any leakage exceeding the limit (e.g., leakage point reading exceeding 0.01% of upstream concentration) must be recorded and addressed until re-testing passes after remediation.
Air Velocity Uniformity Test: For unidirectional flow cleanrooms (e.g., tunnels, FFU systems), measure the air velocity at the filter air outlet surface. Uniformity must meet design requirements (typically within ±20% of the average value).
Air Volume Test: Verify that the total supply air volume of the installed filter meets the system design value.
5. Application and Management in Cleanrooms
5.1 Installation Management
Installation must be performed after completion of all civil engineering and decoration work, followed by thorough cleaning.
Installers must receive professional training and strictly adhere to installation procedures to prevent damage during transportation and handling.
Sealing between filters and mounting frames must be reliable. Appropriate sealing materials (e.g., liquid sealant, closed-cell foam rubber gaskets, gel pads) and methods shall be used to prevent bypass leakage.
5.2 Operation Monitoring and Maintenance
Pressure Drop Monitoring: Install differential pressure gauges upstream and downstream of filters for continuous or periodic monitoring. Record initial pressure drop and operating pressure drop as baselines.
Replacement Criteria: Filters must be scheduled for replacement if any of the following conditions are met:
a) Operating pressure drop reaches 1.5 to 2 times the initial pressure drop, or exceeds the fan's capacity limit, affecting system air volume.
b) Periodic leakage test fails and cannot be remediated to meet requirements.
c) Service life exceeds the manufacturer's recommended cycle (assessed in conjunction with ambient air quality), even if final resistance is not reached.
d) Filters fail due to irreversible physical damage, contamination (e.g., chemical corrosion, heavy oil contamination), or system modifications.
Periodic Testing: Based on cleanroom class and regulatory requirements, develop and implement a regular filter integrity leakage test plan (typically once every 12 months; shortened to 6 months for critical areas).
5.3 Documentation and Traceability
Establish an independent file for each HEPA/ULPA filter in critical areas, recording the following information:
Filter model, serial number, and production date.
Key performance parameters (efficiency, initial pressure drop, rated air volume).
Supplier information and factory test report.
Installation location, installation date, and post-installation test report.
Records of periodic inspection pressure drops and leakage test reports.
Replacement date, replacement reason, and disposal records.
Suzhou Pharma Machinery Co.,Ltd.
2026/02/09
Gino
