Cleanroom Testing and Certification

What is the difference between Cleanroom Performance Testing and Cleanroom Certification? Basically, cleanroom certification is to do performance testing of cleanrooms, but the certifier is fully responsible for the test results and must ensure that the test equipment and test procedures meet NEBB regulations. This is easy to say, but it is not easy to do, because the design of air-conditioning systems and cleanrooms varies a lot, and sometimes the requirements of owners are not the same. Under different design concepts and different owner requirements, the execution of the test is somewhat different. Therefore, the first thing to do for cleanroom certification is to be familiar with air-conditioning systems and Cleanroom designs. NEBB has four basic requirements for cleanroom certification personnel (called Cleanroom Performance Testing Supervisor):

• understanding of air-conditioning systems and modular cleanrooms,

• understanding of relevant specifications,

• understanding of test equipment and test procedures,

• personal experience and reputation.

These are the entry requirements. After passing the test and becoming a Supervisor, you must be under the jurisdiction of NEBB, and you must constantly review the regulations and standards and pay attention to the development of new technologies. You must report to NEBB at least once a year and re-examine your qualifications every two years. There are many requirements.

Therefore, anyone can do the clean room performance test, as long as they can operate the instrument; but to obtain rigorous and reliable test data, you must rely on qualified professionals. The following data is a description of the various performance tests of the clean room. First, there is a test introduction, which explains some basic concepts, followed by the test procedures and precautions. As for the bottom line of the test, the data cannot be changed or discarded. This is an unchanging iron rule.

Test Introduction

Before testing the clean room, if you can have some understanding of the test specifications, basic concepts of the clean room, and the terminology of the clean room, it will be helpful for the test. Here are some background information for readers' reference.

Regarding the international standards for the definition, construction, control, management, etc. of clean rooms, you can find a lot of relevant data by searching "contamination control" on the Internet. The definition of clean room first appeared in the US Federal Standard 209, and then became popular and widely accepted by the Semiconductor industry and pharmaceutical industry. In Europe and Japan, with the increasing development of industry, versions of various countries gradually appeared. In the late 1990s, the industry realized that economic globalization could not be achieved without common standards, so ISO-14644 was created. The following describes the various standards and specifications for clean rooms.

1.Federal Standard 209E (Fed-Std-209E): 

US Federal Standard 209E, 209 was published in the 1960s, and then it was continuously revised to respond to technological progress and industrial development. The versions ranged from the original 209, 209A, to the last version of 209E in 1992. On November 29, 2001, the United States officially announced the abolition of 209E and replaced it with ISO-14644, so 209E became history in writing. However, in the industry, except for some European companies, the United States, Japan, Taiwan, and mainland China still use 209E. Although particle counter manufacturers have launched new models that meet the metric counting method, it will probably take a long time for the old machines to be completely eliminated, so the new standard ISO-14644 has not yet replaced 209E.

2.ISO-14644 series; 

In order to promote economic globalization, the US government generously gave up its own 209E and instead promoted the international standard ISO-14644 that uses the metric system. The 14644 series has 8 sub-topics (Part), called 14644-1, 14644-2, and up to 14644-8. The entire series covers a wide range of level definitions, test and monitoring specifications, test procedures and methods, design and construction, operation, and other related equipment. Some topics have been finalized, such as Part 1 and Part 2. Some are only in draft form, and some are not even in draft form. Readers can order them on the ISO or IEST website.

3. JIS B9920 (1989): 

Japan's cleanliness standard, which specifies the method for measuring the concentration of suspended particles in clean rooms and the definition of cleanliness levels.

4. VDI 2083 (1993):

 Germany's cleanliness standard, which specifies the definition of cleanliness levels and the measurement technology of cleanliness.

5. Gost-R 50766 (1995): 

Russia's cleanliness standard, which defines the classification and general requirements of clean rooms.

The above are the clean room grade regulations and the relevant standards for cleanliness measurement.

Other Clean room Testing indicators

In addition, there are also some important test specifications for clean room pollution control (that is, cleanliness control) and environmental control (such as temperature, humidity, vibration and noise, etc.), because these environmental factors are all included in the scope of clean room performance testing.

1.IEST-RP-CC-006. 

This famous test specification is designed to make up for the shortcomings of 209. 209 only has particle measurement, 006 includes wind speed and volume, filter leakage, cleanliness, temperature and humidity, parallelism, recovery rate, particle sedimentation test, illumination, etc. The first edition of 006 is called 006-84-T, and 006.2 is the second edition. Now due to the rise of NEBB, 0062 has retired and gradually disappeared.

2. NEBB Clean Room Test Specification Second Edition: 

This is the most popular test specification at present. When it comes to Clean room Certification, NEBB is the only one. NEBB Clean Room Test Specification can be said to be an improved version of IEST-0062. Its test coverage is similar, but the test procedure is clearer and more rigorous, and the use of instruments is also detailed. Therefore, the emergence of NEBB Clean Room Test Specification has solved many test disputes, and therefore NEBB Clean Room Test Specification has successfully become an industry standard. For NEBB, please refer to NEBB on this website.

3. ISO-14698 series: 14698 has three sub-topics:

 Part 1, Part 2, and Part 3, which are about the control of biological contamination in clean rooms. Currently, there are only drafts.

Customized testing services

Every industry, even every company or factory, may have different requirements for modular clean rooms. Although the clean room definition and clean room test specifications listed above can meet the needs of most manufacturers, strictly speaking, these specifications are only a reference. When setting test specifications, each company should take out the applicable parts from the above specifications according to its own process requirements, and require suppliers and testing units to do so. If necessary, the test standards can be modified as appropriate to truly meet their own needs.

1.Clean room definition:

A clean room is a special closed building built to control particles in the air in the space. Generally speaking, clean rooms also control environmental factors such as temperature and humidity, airflow movement patterns, and vibration and noise.

2. Particle control: 

The first step in clean room particle control is to conduct a complete analysis of the degree of impact of indoor particles on the process, and then formulate appropriate particle control methods and clean room management models based on the analysis results to effectively control particle pollution. When analyzing the impact of particles, special attention must be paid to the quantification of data, that is, the impact of particle size and its number on the process is useful data.

3. External pollution sources: 

Pollution sources entering the system from outside the clean room. External pollution sources are mainly introduced by the air conditioning and ventilation system. In addition, doors, windows, wall cracks, etc. are also causes of external pollution sources.

4. Internal pollution sources: 

The sources of pollution inside the clean room are generally process machines and operating staff. The most serious internal pollution sources are generally operating staff.

5. Isolation:

Isolation is a concept of pollution control, that is, to isolate the pollution source outside the dust-free area. This concept is mostly used in high-cleanliness dust-free environments, such as Class 100, Class 10, Class 1 and other clean rooms with high filter coverage, or using mini clean rooms to cover the entire machine.

6. Dilution: 

Dilution is another concept of pollution control, which is mostly used in clean rooms with low cleanliness. For example, in a Class 10000 Clean room, because the ventilation volume is not large, the particles generated by the process and personnel will swirl in the room and take a long time to be discharged. Therefore, the new clean air can only dilute the particle concentration in the room to control the cleanliness of the room below a certain level. It is not required to separate the personnel from the process. When using the dilution method as particle control, special attention should be paid to the correctness of the second particle impact analysis in this section. Only when the particle generation rate is mastered can the particles be effectively diluted.

7. Airflow pattern: 

refers to the flow field pattern, airflow distribution, and airflow direction. Since the removal of particles is completely controlled by the airflow pattern, the cleaner the clean room or dust-free area, the more attention is paid to the control of the airflow pattern. Basically, the airflow pattern must be mastered first before the cleanliness can be mastered.

8. Single-flow airflow: 

The airflow moves in the same direction. This type of clean room is called a single-flow clean room. It was previously called a laminar clean room, and the definition has not changed much. High cleanliness cleanrooms require single-flow airflow.

9. Non-single-flow airflow: 

The airflow direction is not controlled, which is the so-called turbulent cleanroom. Cleanrooms with lower cleanliness use non-single-flow airflow to save costs.

10. As-built cleanroom: 

A cleanroom that has been completed and can be operated, and all related support facilities have been completed, but there are no equipment and personnel operating the equipment.

11. At-rest cleanroom: 

A cleanroom that has been completed and can be operated, and all related support facilities have been activated. The equipment has been loaded and can be operated or is already in operation, 1 as specified, but there are no personnel operating the equipment.

12. Operational cleanroom: 

A cleanroom that is already in normal operation, all related support facilities have been activated, equipment and personnel have been loaded, and the operating status can present and achieve its normal functions.

When users open the level of clean rooms to suppliers, there are several tips. First, the model of grade definition is as follows:

Class X (at Y μm )

Where X is the grade of the clean room, such as 100 or 10000, etc., and Y is the particle size such as 0.2μm, 0.5μm, etc., which can be selected. It means that the user stipulates that the particle content of the clean room must meet the limit of the grade at these particle sizes. This can reduce disputes. Here are a few examples:

• Class1 (0.1μm, 0.2μm, 0.5μm)

• Class 100(0.2μm, 0.5μm)

• Class 100(0.1μm, 0.2μm, 0.5μm)

In Classes 100 (M3.5) and Greater (Class 100, 1000, 10000....), generally one particle size is sufficient. In Classes Less than 100 (M3.5) (Class 10, 1....), it is generally necessary to look at several more particle sizes.

The second trick is to specify the state of the clean room, for example:

Class X (at Y μm), At-rest

The supplier knows very well that the clean room must be accepted in the At-rest state.

The third trick is to customize the upper limit of particle concentration. Generally, the clean room is very clean when it is As-built, and it is not easy to test the particle control ability. At this time, you can simply lower the acceptance upper limit, for example:

• Class 10000 (0.3 μm <= 10000), As-built

• Class 10000 (0.5 μm <= 1000), As-built

The purpose of this is to ensure that the clean room still has sufficient particle control ability when it is in the Operational state.

The following two tables are the grade definitions of Fed-Std-209E and ISO-14644.

Comparing the above two tables, we can see that

• Although the metric and imperial standards of 209E are interchangeable, it is still difficult to see their relevance at a glance. Putting the two systems in the same table will only cause confusion.

• In both tables, 0.5 mm appears in almost every grade definition, indicating that particles with a particle size of 0.5 mm are very representative.

• In the classification of cleanliness, whether it is high cleanliness or low cleanliness, the scope of ISO-14644 is wider than 209E, so it has future potential.

Clean room test scope

All factors related to modular clean room environmental control are within the scope of clean room certification. Before the clean room is completed, the owner, construction unit, and testing unit should discuss and reach an agreement on the following topics in detail to facilitate testing.

• The scope, grade, area, filter location, and number of the clean room to be tested

• The purpose of the test

• Test procedure

• Instruments used

• Test report writing method and content

• Construction period

Before the test, clearly define the above items, so that the test can proceed smoothly, and when problems are found, they can be eliminated as soon as possible, which is beneficial to both the owner and the construction unit.

IEST-0062 has a table to explain the test items and applicable conditions, which is of considerable reference value and is listed below.

As can be seen from the above table, the wind measurement test (using an air hood) is applicable to any state because it is not easily disturbed. Wind speed measurement is not recommended in non-single flow type (turbulent type) clean rooms because it is easily disturbed. Of course, this is the recommendation of IEST, and we can decide for ourselves.

As for the selection of test items, NEBB recommends: divided into three levels according to importance, as follows.

Level I: Level I test is the so-called main test. Tests directly related to cleanliness belong to Level I, and every clean room should at least do the test. The first level test items include:

• Wind speed measurement

• Wind measurement

• Uniformity analysis of the first two items

• Filter leakage test

• Cleanliness test

• Pressure measurement

Level II: Although the second level test is also related to cleanliness and airflow, it is only required in special circumstances.

• Airflow parallelism measurement (only applicable to laminar cleanrooms)

• Space leakage test (almost replaced by differential pressure test)

• Recovery rate test (only applicable to turbulent cleanrooms according to recommendations)

• Particle deposition test (rarely done in recent years)