What is the acceptance criterion for HEPA filters?    Most test standards regarding the acceptance criterion for HEPA filter leak rates state that the acceptable leak limit is ultimately determined by the customer and supplier. However, for many applications using HEPA filters or different levels of cleanroom, most adopt a scan test leak criterion of ≤0.01%. Although 0.01% leak rates have been used historically and their origins are related to the accuracy of early photometer test equipment, using a 0.01% leak rate criterion as the acceptance criterion without a scientific and risk-based assessment will lead to problems associated with leak testing and may result in significant operating costs if an over-limit or failure is found in a low-risk area. Filters are not 100% retaining and particles near the MPPS are expected to penetrate the filter partially or entirely. When using lower-level HEPA filters, the factory-performed acceptable leak rate criterion for particles at or near the MPPS may be equal to or greater than the acceptance criterion for field leak rate testing, and testing acceptance criteria becomes more controversial and difficult. This is especially true in areas where leaks may occur. Therefore, when purchasing filters, it is important to consider the filter rating and how it will be tested after installation to avoid unnecessary field test failures.   ISO 14644-3 [33] provides guidance on how to implement alternative leakage criteria. In a risk-based approach, the ideal acceptance criterion is one that reflects the efficiency of the filter used or the cleanliness of the room being tested. ISO 14644-3 uses the factory filter efficiency rating as the basis for negotiating the acceptance criterion. The leakage acceptance criteria for photometric leak testing and particle counter-based leak testing should be the same because the theory and methodology behind both methods are the same. If performed properly, leak tests using a photometer and a particle counter will give the same leak rate results (Meek et al., 2011 [121]).     If the detected leakage exceeds 0.01% of the upstream concentration, it is generally considered that the leakage rate exceeds the maximum permissible standard. However, for filter systems with an overall efficiency MPPS ≥ 99.95% and less than 99,995% (such as H13 filters), the acceptance standard is 0.1%. If a filter system with an overall efficiency of less than 99.95% MPPS is to be tested, a different acceptance standard is required, depending on the agreement between the customer and the supplier.   Importance of High Efficiency Particulate Air Filters (HEPA) and Leak Detection Methods and Standards   Cleanrooms require air filters to prevent contaminants from entering the cleanroom through their HVAC systems. Cleanrooms are controlled environments where the control of temperature/humidity, pressure, and particulate matter is critical for optimal operational performance. Cleanrooms are designed based on the cleanliness required for a specific process. In the semiconductor industry where microchip manufacturing is performed, air filtration has a higher efficiency because microchips are very sensitive to particles, especially small particles that get wedged between the conductive circuits on the wafers when the wafers are handled.   High Efficiency Particulate Air Filters (HEPA), these filters are very effective in contamination control. They filter particles as small as 0.3 microns and are widely used in pharmaceutical facilities. ULPA (Ultra High Particulate Air Filters) filter particles below 0.12 microns and are widely used in semiconductor equipment.    Importance of Filters in Cleanrooms  Managing Contamination Control in Cleanrooms through Several Activities High Efficiency Particulate Air Filters or UPLA Filters play a vital role in cleanrooms. High Efficiency Particulate Air (HEPA) filters must be as efficient as 99.97% penetrating particles, 0.3 microns. This efficiency rating is given by the U.S. Department of Energy to qualify as a true HEPA filter.      HEPA Filter Specifications    As defined by the U.S. Department of Energy (DOE) standards adopted by most U.S. industries, the minimum resistance or pressure drop a HEPA filter presents to airflow is usually specified at 300 Pascals (0.044 psi) across the filter diameter. Specifications used by the European Union: European Standard EN 1822-1:2009 defines categories of HEPA filters by their retention at a given most penetrating particle size (MPPS).   According to GMP, filters must be leak-free. This is verified by qualification and periodic leak testing according to ISO 14644-3. Recommended Practices for HEPA Filter Construction, Performance, Labeling, and Certification are maintained by the Institute of Environmental Sciences and Underwriters Laboratories (UL). Key requirements include: ■ IEST-RP-C021 “Testing HEPA and ULPA Media, which governs requirements for filter media ■ IEST-RP-CC001 “High Efficiency Particulate Air Filters and Ultraparticulate Air Filters”, governs overall filter construction and labeling requirements ■ IEST-RP-C034 “HEPA and ULPA Filter Leak Testing, for HEPA and UL PA filter penetration (leakage) testing ■ Testing and certification to UL900 flammability requirements ■ American Standard MIL-STD-282 Other testing standards include: ■ ISO 14644-3 Test Method – Qualified Persons Used During Installed Filter Leakage Testing ■ ISO 29463 (2017) – High Efficiency Filters and Filter Media for Removal of Airborne Particles ■ ISO 16890 (2017) – Air Filters for General Ventilation ■ PIC/s PI 032-2 GMP Guide ■ EN1822 used by HEPA/UPA filter manufacturers   High efficiency filter testing is a key technology and an important step to ensure a safe working environment and improve air quality. Filter test data is more effective in formulating a more scientific maintenance and replacement plan for customers.    KLC high efficiency filter testing program:     1. Smoke test    During the testing process, we use advanced instruments and technology to accurately measure the filter's capture rate of particles of different sizes and control a variety of environmental variables.      2.MPPS test    Comprehensively analyze the filter's performance under high flow conditions to ensure it can effectively maintain good air quality and system efficiency in actual use.      3.DOP Test  Used to verify the performance of filters in capturing fine particles of dirt, especially in fields such as pharmaceuticals, electronics and aviation where air quality is extremely high. This test uses DOP aerosol to accurately simulate the filtering effect of fine particles in actual working environments.  

 1. Cleanroom grade standards  The grades of cleanrooms are usually divided according to the number and size of particles allowed in the air. Internationally, ISO 14644 is usually used for grade classification. According to this standard, the grades of cleanrooms are from high to low: ISO 1-9. It should be noted that cleanroom standards can vary depending on the specific industry and application. In semiconductor chip production, cleanroom standards are usually more stringent to ensure that the quality and performance of the chips produced meet expectations. Cleanroom levels can be divided into: Class 1 > Class 10 > Class 100 > Class 1000 > Class 10000 > Class 100000 > Class 300000. Class 1 cleanrooms are mainly used in the microelectronics industry for manufacturing integrated circuits, and the precision requirements for integrated circuits are submicron. Class 10 cleanrooms are mainly used in the semiconductor industry with a bandwidth of less than 2 microns. Class 100 cleanliness is widely applicable and can meet the cleanliness needs of most industries. It can be used for aseptic manufacturing technology in the pharmaceutical industry. This cleanroom can be used for surgery for the manufacture of transplants and integrators, as well as isolation treatment of patients who are particularly sensitive to bacterial infections. Class 1000 cleanrooms are mainly used for the production of fine optical products, and are also used for testing, assembly of aircraft gyroscopes, assembly of fine micro bearings, etc. Class 10000 cleanrooms can be used for the assembly of hydraulic equipment or pneumatic equipment, and in some cases are also used in the food and beverage industry. In addition, Class 10000 cleanrooms are also widely used in the medical industry.     The permissible particle concentration of 0.5um in a Class 1000 clean room is less than 35200 (pc/m3), and the permissible particle concentration of 5um is less than 293 (pc/m3). 2. The permissible particle concentration of 0.5um in a Class 10,000 clean room is less than 352000 (pc/m3), and the permissible particle concentration of 5um is less than 2930 (pc/m3).    Safety considerations    The decoration of semiconductor cleanrooms must meet safety requirements. Generally speaking, there are a large number of flammable and explosive substances in semiconductor cleanrooms, so the relevant national safety regulations, such as fire prevention and explosion prevention, should be followed during decoration. In addition, environmental pollution and the health and safety of staff should also be considered to ensure that the decoration materials meet national standards and will not cause harm to human health.    Cleanroom air treatment system    Semiconductor cleanrooms require air treatment systems to ensure the cleanliness of the air in the workshop. The air treatment system is mainly composed of air filters, air supply systems, return air systems and exhaust systems. Among them, air filters are an important component that can effectively remove particulate matter and microorganisms in the air.    Floor, wall and ceiling decoration    In the decoration of semiconductor cleanrooms, the decoration of floors, walls and ceilings is very important because these areas are susceptible to pollution. The floor should be made of wear-resistant, anti-static and easy-to-clean materials, such as Epoxy self-leveling floor or PVC plastic floor; the walls and ceilings should be made of corrosion-resistant, anti-static and easy-to-clean materials, such as aluminum plates, stainless steel plates, glass curtain walls, etc.    Layout of electrical equipment such as lamps and sockets    In the decoration of semiconductor cleanrooms, the layout of lamps and sockets is also very important. In order to prevent pollutants such as dust and microorganisms from entering the workshop, these devices should be installed on the ceiling or above the wall height, and anti-static and non-powder-shedding materials should be selected.    Doors, windows, clean workbenches and other facilities    In the decoration of semiconductor cleanrooms, doors, windows, clean workbenches and other facilities also need special consideration. Doors and windows must be made of materials with good sealing performance and easy to clean, such as stainless steel doors and windows; clean workbenches should be made of materials that do not shed powder, slag particles, are corrosion-resistant and easy to clean, such as stainless steel workbenches.

The filtration system of the semiconductor clean room is a key equipment to keep the internal environment of the workshop clean and dust-free. In order to ensure the effective operation of the filtration system and extend its service life, we need to take a series of maintenance and care measures.   Clean the filter regularly: The filter in the semiconductor clean room is the core component to ensure air cleanliness. Therefore, the filter should be cleaned or replaced regularly to prevent dust and particles from clogging the filter material and affecting its filtering effect. When cleaning the filter, special cleaning agents and tools should be used to avoid damage to the filter material.    Check the exhaust system regularly:  The operating status of the exhaust system directly affects the air quality in the clean room. The exhaust system should be checked regularly to ensure its normal operation and smooth ventilation. The inspection content includes components such as fans, air ducts, and exhaust ports. If damage or failure is found, they should be repaired or replaced in time.        Monitor air quality:  By installing air quality monitoring equipment, the air quality in the semiconductor clean room can be monitored in real time, air quality problems can be discovered in time, and corresponding measures can be taken. For example, when the concentration of particles in the air exceeds the set value, the standby filter can be started or the number of cleanings can be increased to reduce the concentration of particles.    Regularly replace consumables and accessories:  Consumables and accessories in semiconductor clean rooms, such as surgical caps and gloves, should be replaced regularly to ensure their cleanliness and filtering effect. When replacing consumables and accessories, you should pay attention to selecting products that meet the requirements and replace them according to the prescribed operating procedures.        Train operators:  Operators in semiconductor clean rooms should receive systematic training to understand the principles, operation and maintenance methods of the filtration system and improve their operating skills and safety awareness. Through training, operators can better understand the operating status of the filtration system and find and solve problems in a timely manner.    Develop a maintenance plan:  According to the actual situation of the semiconductor clean room, develop a detailed maintenance plan for the filtration system, including cleaning cycle, inspection cycle, replacement cycle, etc. Maintenance according to the plan can ensure the long-term stable operation and filtering effect of the filtration system.    Records and maintenance logs:  Establish maintenance records and maintenance logs for the filtration system, and record the time, content, personnel and other information of each maintenance. By analyzing the maintenance records and maintenance logs, you can understand the operating status and existing problems of the filtration system, and provide a reference for subsequent maintenance and improvement.       In short, effective maintenance of the filtration system of the semiconductor clean room requires comprehensive consideration of multiple aspects, including cleaning, inspection, monitoring, replacement, training, planning and record keeping. Through comprehensive maintenance measures, the long-term stable operation and filtration effect of the filtration system can be ensured, thereby ensuring the air quality and cleanliness in the clean room.

From May 28th to 30th, the three-day SEMICON Southeast Asia 2024 was held in the Malaysia International Trade and Exhibition Center (MITEC)! KLC has been deeply involved in the clean industry for more than ten years. It appeared at SEMICON Southeast Asia 2024 to explore new trends and opportunities in the semiconductor industry with colleagues from the global industry.    2024 SEMICON Malaysia International Semiconductor Exhibition  SEMICON Southeast Asia is the largest semiconductor equipment exhibition in Southeast Asia. Attendees are offered the opportunity to discover new technology trends and markets, with a focus on key technologies and regional markets, where exhibitors can collaborate with new suppliers and discover new solutions. The purpose of this exhibition is to promote semiconductor technology through technology, innovation, and design.   At this event, KLC displayed brand-new filters, transfer windows and other equipment products. Visitors stopped at the booth to learn more about KLC clean systems. At the same time, KLC had in-depth exchanges with industry experts and companies from all over the world, and jointly discussed the needs and trends of clean rooms in the semiconductor industry, helping us to continuously improve and innovate products and services.     This exhibition was a very meaningful and valuable experience. We thank all participants and organizers for giving us the opportunity to demonstrate our expertise and technical strength. We hope to work with you in the future to jointly promote the development and progress of semiconductor clean production space and create a better production environment!