New guidelines for cleanrooms

After microelectronics, cleanrooms are also increasingly being used in board and component production. The VDI is expanding its range of support for industry and science with new guidelines to help successfully manage the constantly growing number of highly complex influencing factors in cleanrooms. The most recent example from August 2022 is VDI 2083, Sheet 3 with detailed specifications for metrological monitoring of cleanrooms.

Cleanrooms are workplaces where particularly high demands are placed on the working environment and employees. The air in a cleanroom should carry as few contaminating particles as possible. Particularly in semiconductor production, but increasingly also in the production of highly sensitive electronic assemblies, working in cleanrooms is necessary in order to avoid contamination and thus production damage or reduced product reliability. This ensures correct results and error-free delivery of electronic assemblies and devices. Due to the great diversity of technological manufacturing processes with regard to cleanliness requirements, standards have been established in which these differences are defined in the form of cleanroom classes.

High complexity of influencing variables in cleanrooms

In order to better understand the following explanations on the large scope of standardization work in the 'clean rooms' sector, we will first outline the wide range of factors influencing the construction and operation of clean rooms.

The cleanroom workplace is associated with strict rules of conduct as well as structural requirements. Air filtration and strict hygiene in the work area are not enough. The cleanroom is a closed area that may only be entered under certain conditions. In order to avoid influences from the outside air, it is cut off from the outside world and is only entered through airlocks wearing suitable clothing and clean shoes. All surfaces in the cleanroom are abrasion-resistant. This means that no dissolved particles can get into the air. It is equipped with an efficient ventilation system to constantly filter the air.

It is particularly important to wear special clothing in the cleanroom workplace in order to minimize the release of particles into the air. Synthetic fibers are best suited as they are more abrasion-resistant than natural fibers. Depending on the cleanroom class, employees wear complete suits or outerwear and underwear made of synthetic fibers. They also need shoes with abrasion-resistant soles and hair and mouth protection to keep the room free of hair, dander or microorganisms.

The furnishings and equipment must also be adapted to the requirements of the cleanroom. The furniture has smooth and closed surfaces. This makes them easy to clean and prevents particles from settling. Particular attention must be paid to upholstered cleanroom chairs. To ensure that particle emissions from the upholstery are particularly low, they are covered with plastic or artificial leather and specially back-foamed. The workplace in the cleanroom is linked to strict rules of conduct that are laid down in standards and guidelines. The requirements for the individual cleanroom classes can only be met if these regulations are strictly adhered to [1].

Definition of cleanroom classes

The international basis for working in and with cleanrooms is the ISO 14644 standard. This series of documents, which now comprises 18 parts, covers all the fundamental topics for the operation of cleanrooms. It covers the planning, operation and monitoring of cleanrooms, cleanroom areas and cleanroom technology as well as processes directly related to these. This international standard has been largely adopted into national standards by almost all countries.

Electronics production in the ISO 8 clean room for the space program at Hi-Tech Elettronica in ItalyParts 1 and 2 of ISO 14644 replaced the old US Federal Standard 209E. This had been used in previous years to determine a cleanroom classification. ISO 14644 was adopted in the EU as EN ISO 14644 and the cleanroom classifications are comparable to those of the Federal Standard. In Germany, the standard is published as DIN EN ISO 14644. DIN EN ISO 14644-1, i.e. Part 1 of the ISO series, defines the degree of air cleanliness. A distinction is made between the purity classes ISO 1 to ISO 9. The degree of purity is determined by setting limit values. The ISO classification is based on the particle concentration per m³. The highest purity is ISO class 1, while the lowest is ISO class 9. More information can be found at [1]. This standard for cleanroom classes is primarily used in cleanroom systems that are used for production in the semiconductor industry. However, it is also increasingly being used in PCB and assembly production.

VDI Guideline 2083

The above-mentioned international and national standards have been backed up by further national guidelines to ensure the uniform description of processes and specifications in cleanroom technology across industries and countries. In Germany, this is VDI 2083, which in more detail is a series of guidelines. It refers to ISO 14644-1 and also provides guidelines for practical aspects of cleanroom operation. The document is considered a recognized rule of technology, as it offers useful additions, for example on biocontamination or energy and cost efficiency, and constantly incorporates new research results. The VDI guideline thus contributes to a sustainable economy using the cleanroom classes. For this reason, its application in practice is a competitive advantage over mere compliance with the ISO classification, which should not go unmentioned here.

Differences in content between ISO 14644 and VDI 2083 [2]The comparative figure above shows the differences between ISO 14644 and VDI 2083. It is worth taking a look at VDI Guideline 2083 when planning a cleanroom. In addition to the ISO 14644 family of standards, the VDI 2083 series of guidelines is also frequently used in practice to describe the state of the art and to classify parameters and limit values. Both documents make an important contribution to quality assurance.

VDI 2083 distinguishes between the seven cleanroom classes 0 to 6, whereby class 0 places the highest demands on the cleanroom in terms of the number of particles per cubic meter. In a blog post entitled "ISO 14644 and VDI 2083: correlations and differences" [2], further correlations between the "umbrella document" and the German guideline are elaborated.

The most striking difference between the two sets of rules DIN EN ISO 14644 and VDI 2083 is their depth. While the ISO 14644 family of standards deals with cleanroom technology in just 16 parts, the VDI 2083 family is the world's most comprehensive set of regulations with over 21 individual sheets and sub-sheets on the various cleanroom aspects and areas.

Cleanroom monitoring

A stable, controlled climate is a prerequisite for the safe functioning of a cleanroom workplace. Temperature, pressure, humidity and the number of particles in the air must be constantly monitored. This is why high-performance cleanroom monitoring is an essential part of every cleanroom - regardless of its cleanroom class. Deviations from the required or legally stipulated standard can endanger human life or disrupt production.

Some areas of technology, such as microelectronics, precision mechanics and medical technology, have special requirements. This applies to the following aspects, among others:

• Air purity in the production area
• Equipment used
• Workplace
• Workers
• Process media

For this reason, the VDI Society for Construction and Building Technology (GBG), Technical Building Services Division, published the 71-page guideline VDI 2083 Sheet 3 'Cleanroom technology - Measurement technology' in August 2022 [3].

You should not be confused by the term 'Sheet 3' due to the large number of pages, as the six chapters and the two appendices A and B provide extensive information and instructions on the topics of measurement technology and procedures, which certainly justifies the price of € 158.10. Measurement methods for cleanrooms and associated cleanroom areas are described, which are used during handover, as part of the qualification of new facilities, routine checks and ongoing monitoring. The methods described in the guideline are specifically geared to the requirements of cleanrooms. The guideline applies to initial and one-off measurements as well as continuous or periodic monitoring. Continuous measurements for the purpose of monitoring are described in VDI 2083 Sheet 3.1. The specified methods are intended for the handover of cleanroom systems and for carrying out routine and monitoring measurements in accordance with DIN EN 12599, VDI 2083 Sheet 2 and DIN EN ISO 14644-4 and are intended to replace user-specific procedures wherever possible. The new guideline has been published in German and English (English title: 'Cleanroom technology - Metrology') and can be obtained from Beuth-Verlag [4]. For technical questions, please contact Dipl.-Phys. Thomas Wollstein, VDI-Gesellschaft Bauen und Gebäudetechnik (GBG), phone: +49 211 6214-500, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it..

References

[1] www.bimos.com
[2] https://blog.colandis.com/iso-14644-vdi-2083
[3] www.vdi.de/richtlinien/details/vdi-2083-blatt-3-reinraumtechnik-messtechnik
[4] www.beuth.de/en/publication/vdi-handbuch-reinraumtechnik/125065721