What is a vacuum valve?
A vacuum valve is a device mounted in a supply or exhaust line of a vacuum system. It is usually used to isolate
vacuum areas such as process chambers, or to control
incoming and outgoing gas volumes. Vacuum valves can be operated manually, pneumatically, electropneumatically,
electrically or electromagnetically. Vacuum valves
are an integral part of any vacuum system and vacuum systems are used in a wide variety of industrial production
applications.
What are high-performance vacuum valves?
Certain vacuum processes place particularly high demands on the purity as well as the chemical and physical
stability of the process environment. This applies, for
example, to almost all areas of semiconductor production as well as to many research facilities where vacuum
systems are used. In the field of elementary research, the
ability to deal with extreme conditions such as very high or low temperatures, strong radiation and extremely
high vacuum (XHV) with pressures up to 10-15 mbar – the
limits of what is currently technically feasible and measurable – are often added to these requirements.
Vacuum valves in these applications differ from standard vacuum valves in the following respects:
Minimized Particle Emission
High-performance vacuum valves are optimized not to release particles through their materials for
housing, mechanics or seals by outgassing, nor through
their opening and closing or control movements by friction. This is achieved by special selection and
treatment of the materials used, and by certain design
details that minimize or, in some cases, completely eliminate particle release.
Minimized Motion Pulses
Every valve generates motion pulses through its opening and closing movements. In the case of
automatically driven valves, these can range from slight vibrations
to audible and perceptible hard impacts. These motion pulses can have a negative impact on sensitive
manufacturing processes, e.g. through additional particle
release. In addition to design features, high-performance vacuum valves minimize these impulses
primarily by controlling the motion in so-called motion profiles.
Similar to the way that passenger elevators operate, the closing speed is slowed down shortly before the
closing point is reached in order to prevent "hitting".
These motion profiles can usually be modified so that, for example, they can be adapted to the desired
conditions in terms of closing time and closing frequency.
Neutral Chemical and Physical Behavior
Vacuum valves always change the homogeneity of a vacuum process chamber, in whatever form. This occurs,
partly, as a result of their geometry. Narrowing or
widening in the flow path can change the flow resistance and flow velocity, or dead spaces, such as
travel spaces for valve plate, can promote deposition
processes. This also occurs through the opening and closing motion, which alters flow behavior as well
as the concentration, distribution, mixing and temperature
of process gases. High-performance vacuum valves are optimized to compensate for such influences
wherever possible or to make them controllable. To this end,
a variety of additional techniques are incorporated into the designs that go far beyond the basic valve
functions such as opening and closing or control.
Precisely Reproducible Behavior
High-performance vacuum valves differ from standard solutions primarily in their highly reproducible
behavior. This means that while standard solutions exhibit
fluctuations in each individual opening and closing movement and show deviations from their defined
performance values over the period of use, high-performance
vacuum valves are optimized to always exhibit the same behavior, defined within very narrow limits, over
long intervals of use. This means that they stabilize
vacuum processes and minimize process control complexity.
