RUBIG plasma generators
The RUBIG plasma generator is the heart of every RUBIG MICROPULS® series system and, as the name indicates, generates plasma. Plasma, the 4th state of matter beyond solid, liquid and gaseous states is produced when very large quantities of energy are added to a gas. This can be achieved either by heat, radiation, or as in the case of the RUBIG generator, using electrical voltage. The recipient wall provides the anode; the components the cathode. On their way from the cathode to the anode, electrons collide with (process gas) molecules. This collision breaks the gas molecules apart, catapulting electrons out of the shell. As these collide with other gas molecules, and the fission process repeats, the residual ionised gas molecules move towards the components and initiate the sputtering process.
 |
 |
The process gases (generally hydrogen, nitrogen, argon or methane) become a successfully ionised, conductive gas as soon as a voltage threshold is exceeded and the plasma is ignited, i.e. corona discharge occurs. Here the generator takes on the role of an inverter. This means it converts standard 400 V AC three-phase AC power, i.e. power current or rotary current into galvanically-separated rectangular pulsed DC. Only once this pulsed output voltage is combined with a pressure range in the maximum of double-digit millibar will plasma ignition take place.
Voltage, current, and frequency can be varied within the following limits:
| Voltage | 0 - 700 V |
| Current | 0 - 300 A |
| Frequency | 125 Hz - 20 kHz |
The system can be operated either in voltage-controlled (current adjusts) or current-controlled (voltage adjusts) mode. The resistance is defined according to the gas mixture, pressure, temperature, and spacings between the charged components and distance to the anode wall. The relevant variable then evens out according to Ohm’s law. In the basic package in addition, in each module it is possible to select monopulse, bipolar, or pure DC operation. The polarity of the output can also be reversed, meaning that the polarity can be set positive or negative, depending on the specification. Since the pulse length and pauses can be adjusted individually both in monopulse as well as bipolar operation, the plasma power can also be set in a targeted manner. This allows RUBIG plasma generators to provide the highest possible degree of process flexibility. These parameters are defined in the visualisation. Here, or in the Arc Function system area, the limit values for Arc Management can also be set. An arc is a discharge between the positively-charged (anode) and negatively-charged (cathode) poles, i.e. a ‘lightning flash’ within the plasma cloud. Damage to the batch is only possible by detecting the arc as quickly as possible. In this respect RUBIG generators provide safety mechanisms which exceed typical industry standards. The integrated Arc Detection System constantly monitors the current and switches off within a three-figure nanosecond range (generally under 300 ns) if the arc moves too far upwards. Detailed logging of the process recording enables exact fault diagnosis, allowing corresponding fine adjustment of the process.
Application areas
In addition to their reliable and energy-efficient performance, RUBIG generators also benefit from a modular design. Their compact design allows them to be integrated rapidly within existing manufacturing lines. Upgrades at a future point in time are also no issue.
RUBIG plasma generators are especially suitable for the following applications:
- Plasma nitriding (with or without subsequent oxidation)
- DLC coating
- PVD coating
- Plasma carburising
- Magnetron sputtering
- Plasma fine cleaning and sterilisation
- Plasma etching
- Pre-treatment of plastics (plasma cleaning, plasma activation)
- Surface treatment of non-conductive materials via alternating pulse operation
- Retrofitting of existing nitriding and coating systems (including other manufacturers)
 |
