Precision under vacuum: Cleanroom and vacuum technology as the key to new technologies

Factors influencing vacuum

The vacuum and cleanroom technology go hand in hand and form the foundation of many innovative technologies. Both cleanroom technology and vacuum technology create a controlled environment that eliminates unwanted influences, significantly increasing precision, purity, and efficiency in industrial and scientific applications. By generating a pure vacuum, unwanted particles, gases, and contaminants can be targeted and removed, thereby greatly improving product quality.

Streicher Maschinenbau GmbH & Co. KG combines vacuum and cleanroom technology to significantly improve the performance of their custom-made, fully automated vacuum systems.

A central aspect of ultra-high vacuum technology (UHV) is the control of various vacuum influence factors such as vaporization – the evaporation of film residues under vacuum. Residues from coolants, fats, or cleaning agents on vacuum surfaces can prevent the achievement of extremely low operating pressures, as vaporization increases the gas load within the vacuum system. To prevent irreversible contamination, water-based intermediate cleaning and visual cleanliness checks – Water Break Test, Wipe Test, UV and White Light Inspection – are already used during the manufacturing process. They serve to early detect stubborn contaminants that can only be removed by abrasive manufacturing methods. Additionally, the entire manufacturing chain must be viewed under the principles of contamination avoidance and prevention. Dirt that never reaches the components in the first place does not need to be later removed with extensive effort. Supplemented by a targeted selection of operating and auxiliary materials, as well as assembly and commissioning under cleanroom conditions (≤ ISO7), it is ensured that no unwanted molecular residues remain in the vacuum chamber after fine cleaning.

Furthermore, during the design of vacuum process technology, care must be taken to prevent unwanted backflows into the chamber interior during operation.

Another crucial step to optimize UHV performance is the so-called "Bakeout" process. Heating the vacuum system to ≥ 120 °C for at least 24 hours promotes the desorption of unwanted molecules, which are then expelled from the vacuum system by the vacuum pumps. Bakeout also shortens pump-down times because it efficiently removes residual water remaining on the vacuum surfaces. Similarly, pre-heating vacuum internal components before assembly has proven effective, as it minimizes the component outgassing rate driven by diffusion and desorption processes during vacuum operation.

With this solid vacuum expertise, Streicher Maschinenbau has commissioned a fully automated UHV vacuum system weighing 28 tons with an internal volume of 27 m³ under cleanroom conditions, achieving an ultimate pressure of 3.5 × 10⁻¹¹ mbar. Even better vacuum performance was limited by the permeation effects of the FKM sealing material, which was used, among other things, for sealing the 4 x 4 meter large door. Additionally, considering the good RGA results, the project schedule was prioritized, and a bakeout was omitted, which would have further reduced the water peak in the RGA spectrum and could have achieved an even better ultimate pressure.

The residual gas analysis (RGA) is a widely used nondestructive testing method in the vacuum industry for quantifying and determining the chemical composition of volatile and less volatile molecular compounds.

With these approaches, the company demonstrates how cutting-edge technologies and solid expertise can be utilized to meet the demands of ultra-high vacuum technology. This makes a significant contribution to the further development of precision and efficiency in industrial applications.