Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
  • H05H1/00—Generating plasma; Handling plasma
  • H05H1/24—Generating plasma
  • H05H1/2406—Generating plasma using dielectric barrier discharges, i.e. with a dielectric interposed between the electrodes
  • H05H1/2443—Generating plasma using dielectric barrier discharges, i.e. with a dielectric interposed between the electrodes the plasma fluid flowing through a dielectric tube
  • H05H1/245—Generating plasma using dielectric barrier discharges, i.e. with a dielectric interposed between the electrodes the plasma fluid flowing through a dielectric tube the plasma being activated using internal electrodes
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
  • H05H1/00—Generating plasma; Handling plasma
  • H05H1/24—Generating plasma
  • H05H1/2406—Generating plasma using dielectric barrier discharges, i.e. with a dielectric interposed between the electrodes
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
  • H05H1/00—Generating plasma; Handling plasma
  • H05H1/24—Generating plasma
  • H05H1/2406—Generating plasma using dielectric barrier discharges, i.e. with a dielectric interposed between the electrodes
  • H05H1/2443—Generating plasma using dielectric barrier discharges, i.e. with a dielectric interposed between the electrodes the plasma fluid flowing through a dielectric tube
  • H05H1/246—Generating plasma using dielectric barrier discharges, i.e. with a dielectric interposed between the electrodes the plasma fluid flowing through a dielectric tube the plasma being activated using external electrodes

Definitions

• the invention relates to a device for generating a plasma jet with at least one discharge tube, through which a process gas flows.
• Such a device with a discharge tube is from the publication by Jungo Toshifuji et al: "Cold arc plasma jet under atmospheric pressure for surface modification", Surface and Coatings Technology 2003, page 302ff and the further publication “Workshop plasma treatment and plasma CVD Coating at atmospheric pressure ", Dresden, November 16, 2004 known.
• the known device has a discharge tube made of dielectric material, wherein a first electrode is solid and arranged to extend centrally in the interior of the discharge tube in the longitudinal direction, and wherein a second electrode comprises the discharge tube.
• the second electrode is formed concentrically, so that the first electrode in the interior, discharge tube and second electrode form a coaxial and concentric cross-sectional structure with an open end face on which the plasma jet is generated.
• the inner, rod-shaped electrode is placed on high voltage, while the outer electrode is grounded. Due to the conditions of the electric field, ignition of the plasma at the tip of the inner, rod-shaped electrode therefore preferably occurs.
• the plasma then spreads in the direction of the process gas flow.
• a diffused plasma jet forms between the tip of the inner electrode and a substrate that can be processed by the plasma jet. It is a "cold" plasma where the temperature of the gas is relatively low, ranging from room temperature to a few hundred degrees C.
• a direct plasma connection ie a flashover
• the plasma is then no longer diffuse and cold, but occurs contracted in thin channels, which have a much higher gas temperature. This can lead to damage to the device and / or the substrate. Furthermore, thermal damage to the gas tube supplying the process gas can occur.
• the object of the invention is therefore to provide a device for generating a plasma jet of the type mentioned, are suppressed in the parasitic discharges in a suitable manner and no flashovers between the first and second electrode can occur. Furthermore, it is an object of the invention to reduce the overall thermal loads of the individual components of the device and the substrate, by achieving that only "cold" plasma is generated.
• the invention is based on the general knowledge that the interior of metallic, standing under an electrical voltage hollow bodies is field-free.
• a hollow cylinder which would be obvious to a person skilled in the art, this would have the disadvantage that at the edges of the hollow cylinder the electric field in its interior would be sufficient, so that under certain circumstances a field sufficient for ignition of the plasma would be present at one undesired one - Location would be present in the gas hose.
• the metallic holder for the gas hose designed in such a way that it conically widened at a certain angle or otherwise, such as step-shaped, so that the axial electric field at the edge of the holder is substantially smaller than in a conventional hollow cylinder constant diameter.
• all edges of the holder are rounded to avoid high electric fields.
• the second, outer, grounded electrode is no longer, as known in the prior art, arranged directly on the discharge tube, but has a certain radial distance.
• an end cap made of a dielectric is attached to the end of the discharge tube. This makes it possible to produce a more intense plasma jet, especially when using noble gases.
• a filter is provided between the gas hose and the discharge pipe.
• a noise due to turbulence is suppressed. This noise occurs in the known from the prior art devices on that the process gas flows directly from the gas supply via a hose o. ⁇ . In the discharge chamber and by the flow around the holder of the inner electrode it comes to a turbulence with associated noise.
• Figure 1 shows a first embodiment of a device according to the invention with a
• Figure 2 shows a second embodiment of such a device
• Figure 3 shows a third embodiment of such a device with an additional
• End cap Figure 4 shows a fourth embodiment of such a device with a modified
• End cap Figure 5 shows a first embodiment of a device according to the invention with several
• Figure 6 shows a second embodiment of such a device
• Figure 7 shows another commercial embodiment of a device according to the invention with a discharge tube.
• the first device according to the invention shown schematically in Figure 1 has a discharge tube 1 made of dielectric material, in the interior of which an inner, rod-shaped, solid electrode 2 is arranged.
• a second electrode 3 comprises the discharge tube 1. This can be done directly or at a radial distance.
• This electrode 3 is particularly advantageously formed concentrically, so that the electrode 2 in the interior, the dielectric discharge tube 1 and the outer electrode 3 form a coaxial and concentric cross-sectional structure with an open end face on which the plasma jet is generated.
• the inner electrode 1 is set to high voltage while the outer electrode 3 is grounded.
• a metallic discharge protection 4 is provided at the end of the discharge tube 1.
• the discharge protection 4 is here at the same time the holder for a gas hose 5, through which the process gas is supplied. The flow direction of the process gas is symbolized by an arrow.
• the discharge protection 4 is also a holder and is used to make contact for a high voltage cable 6.
• a filter 7 is still made of sintered material here. This filter 7 will be explained in more detail below.
• the inner electrode 2, the z. B. consists of tungsten is held by this filter 7 and fixed in its central position in the interior of the discharge tube 1.
• the discharge protection 4 is designed so that the metallic support for the gas tube 5 widens conically at an angle a, so that the axial electric field at the edge of the holder is substantially smaller than would be the case with a constant diameter hollow cylinder of the prior art.
• the angle a depends on the maximum operating voltage and the ratio of the diameter of the gas hose 5 on the one hand and the diameter of the discharge tube 1 on the other hand. It is particularly advantageous to round off all edges of the discharge protection 4, in particular in the region of the holder, in order to avoid high electric fields.
• the filter 7 can, as also shown in the figure 1, in a particular embodiment, for. Example, if it is made of sintered bronze, are used simultaneously as a holder of the inner electrode 2. Furthermore, in the rear region of the filter 7, counter to the flow direction of the process gas, a back pressure, which likewise has an effect on the desired suppression of parasitic discharges, arises because the ignition field strength of the process gas is a function of the prevailing pressure. If you are on the right branch of the so-called Paschen curve, the ignition voltage of a gas increases with increasing pressure.
• FIG. 2 shows a second embodiment of a device according to the invention, in which the discharge protection 4 is designed differently.
• a bore with a diameter d and a depth t is provided in the discharge protection 4.
• a substantially smaller axial electric field is thereby realized at the edge of the holder.
• other embodiments of the discharge protection 4 are conceivable, for example, a stepped expansion instead of an angle a.
• FIG. 3 shows a further embodiment of a device according to the invention. Notwithstanding the prior art here is the outer, grounded electrode 3 is no longer located directly on the discharge tube 1, but at a certain radial distance to this. Furthermore, in this embodiment, a dielectric end cap 8 is attached to the open end of the discharge tube 1. The end cap 8 is z. Example of Teflon or other plastic with appropriate thermal and mechanical stability, but alternatively also ceramic. In a particularly simple manner, the end cap 8 may be secured by screwing to the outer electrode 3.
• FIG. 4 shows a further embodiment of the device according to the invention with a modified, two-part end cap 8.
• the outer part further consists of a dielectric, while additionally an inner metal insert 9 is provided, which is conductively connected to the outer electrode 3.
• This version is particularly suitable for working with molecular gases as a process gas; the inner metallic insert 9 leads to an increase of the electric field in the interior of the discharge tube 1 and thus also to a more intensive plasma jet.
• the outer electrode 3 can also be partially enclosed by a dielectric in some other way or completely enclosed in a dielectric.
• FIG. 5 shows a schematic illustration of an embodiment of the invention with a plurality of discharge tubes 1, a so-called multi-jet arrangement.
• a plurality of parallel discharge tubes 1 which are supplied by a supply channel 10 for the process gas and a gas distribution system 11 each with this process gas.
• the process gas preferably flows through a plurality of discharge tubes and has the lowest flow resistance or is located closest to the feed channel 10.
• Such unevenness of the process gas leakage in the prior art has a negative effect on the uniformity of the surface treatment of a substrate.
• each discharge tube 1 in each discharge tube 1, a filter 7, as already explained above, arranged, whose flow resistance is substantially greater than the flow resistance of the discharge tube 1 itself, so that a uniform supply of each discharge tube 1 with process gas results; this leads to a homogenization of the individual parallel plasma jets.
• FIG. 6 shows a further modified embodiment of such an arrangement, in which, instead of individual filters, a larger, common filter plate 12 is arranged in front of the individual discharge tubes 1.
• FIG. 1 a complete assembly drawing of a commercial device according to the invention is shown in FIG.
• an annular plastic insulator 13 is shown here, which encloses the discharge tube 1.
• a protective tube 14 is disposed of ceramic.
• a protective insulation 15 made of plastic.
• the outer end forms a round metallic housing 16.
• a special electrode holder 17 made of metal as an independent component.
• the device also has a cap 18 made of plastic, to which an end piece 19 made of metal connects.
• a screw 20 is screwed through which both the gas hose 5 and the high voltage cable 6 are guided.
• open end of the device plastic screws 21 are still shown, by means of which the end cap 8 is fixed, here at the outer annular electrode. 3

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Fluid Mechanics (AREA)
• Plasma Technology (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)
• Surgical Instruments (AREA)

Applications Claiming Priority (2)

Publications (2)

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• 2006
  • 2006-03-16 DE DE102006012100A patent/DE102006012100B3/de not_active Expired - Fee Related
• 2007
  • 2007-02-17 JP JP2008558664A patent/JP2009529772A/ja not_active Withdrawn
  • 2007-02-17 KR KR1020077028418A patent/KR20080104225A/ko not_active Application Discontinuation
  • 2007-02-17 WO PCT/EP2007/001386 patent/WO2007104404A1/fr active Application Filing
  • 2007-02-17 DE DE502007000650T patent/DE502007000650D1/de active Active
  • 2007-02-17 CN CNA2007800005747A patent/CN101326863A/zh active Pending
  • 2007-02-17 EP EP07711569A patent/EP1994807B1/fr not_active Not-in-force
  • 2007-02-17 US US12/293,296 patent/US20090155137A1/en not_active Abandoned
  • 2007-02-17 AT AT07711569T patent/ATE429799T1/de active

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