Electrode assembly and plasma source for generating a non-thermal plasma, and method for operating a plasma source

Abstract

The invention relates to an electrode assembly (5) for generating a non-thermal plasma, comprising a first electrode (7) and a second electrode (9) which are electrically insulated from each other by means of a dielectric element (11) and which are arranged at a distance from each other. The first electrode (7) has a thickness of at least 10 m when seen in the direction of the distance between the electrodes (7, 9), and the second electrode (9) has a thickness of at least 1 m to maximally 5 m or a thickness of at least 5 m to maximally 30 m when seen in the direction of the distance between the electrodes (7, 9). The dielectric element (11) has a thickness of at least 10 m to maximally 250 m.

Claims

1. An electrode arrangement for generating a nonthermal plasma, comprising: a first electrode and a second electrode that are electrically insulated from each other and spaced from each other in a stack direction of the electrodes by a dielectric element, the first and second electrodes being disposed on opposite sides of the dielectric element along the stack direction, wherein the first electrode, in the stack direction, has a thickness of at least 10 m, wherein the second electrode, in the stack direction, has a thickness of at least 1 m to at most 30 m, wherein the dielectric element, in the stack direction, has a thickness of at least 10 m to at most 250 m, and wherein the first and the second electrodes are continuously spatially separated in the stack direction by the dielectric element from each other without interruption along an entire extension of the dielectric element.

2. The electrode arrangement according to claim 1, wherein the second electrode, in the stack direction, has a thickness of at least 1 m to at most 5 m.

3. The electrode arrangement according to claim 1, wherein the first electrode has a dielectric base element on a side facing away from the dielectric element.

4. The electrode arrangement according to claim 1, wherein at least one electrode, selected from the first electrode and the second electrode, has a material including copper, silver, gold or aluminum.

5. The electrode arrangement according to claim 1, wherein the dielectric element has a material including silicon nitride, a silicate, a glass or a plastic.

6. The electrode arrangement according to claim 5, wherein the dielectric element is made of quartz.

7. The electrode arrangement according to claim 5, wherein the dielectric element is made of a polyamide.

8. The electrode arrangement according to claim 1, wherein the first electrode is flat.

9. The electrode arrangement according to claim 1, wherein the second electrode has a comb-like structure, a linear structure with at least one imaginary line, a winding structure, a spiral structure, a meandering structure or a flat structure with at least one recess.

10. The electrode arrangement according to claim 1, wherein the dielectric element has an average surface roughness (Ra) that is less than 5% of the thickness of the element.

11. A plasma source for generating a nonthermal plasma with a voltage source and an electrode arrangement according to claim 1, wherein the voltage source is electrically connected at least to the first electrode.

12. The plasma source according to claim 11, wherein the voltage source is an AC voltage source, and wherein the second electrode is earthed or grounded.

13. The plasma source according to claim 11, wherein the plasma source is configured to generate AC voltage with an amplitude of at least 0.5 kVpp to at most 3 kVpp.

14. The plasma source according to claim 11, wherein the plasma source has a piezoamplifier.

15. The electrode arrangement according to claim 1, wherein the second electrode in the stack direction has a thickness of at least 5 m to at most 30 m.

16. The electrode arrangement according to claim 1, wherein the second electrode has a dielectric cover element on a side facing away from the dielectric element, which dielectric cover element in the stack direction has a thickness of at least 0.2 m to at most 30 m.

17. The electrode arrangement according to claim 16, wherein the dielectric cover element has a material including silicon nitride, a silicate, a glass or a plastic.

18. A method for operating a plasma source, comprising providing an electrode arrangement comprising a first electrode and a second electrode that are electrically insulated from each other and spaced from each other in a stack direction by a dielectric element, the first and second electrodes being disposed on opposite sides of the dielectric element along the stack direction, wherein the first electrode, in the stack direction, has a thickness of at least 10 m, wherein the second electrode, in the stack direction, has a thickness of at least 1 m to at most 30 m, wherein the dielectric element, in the stack direction, has a thickness of at least 10 m to at most 250 m, and wherein the first and the second electrodes are continuously spatially separated in the stack direction by the dielectric element from each other without interruption along an entire extension of the dielectric element; and applying by means of a voltage source an electrical voltage to the electrode arrangement to generate a nonthermal plasma.

19. The method according to claim 18, wherein applying the electrical voltage includes applying an AC voltage with an amplitude of at least 0.5 kVpp to at most 3 kVpp.

20. The method according to claim 18, wherein applying the electrical voltage includes applying an AC voltage having a frequency of at least 20 kHz to at most 90 kHz.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be further explained below with reference to the drawing. In the drawing:

(2) FIG. 1 shows a schematic representation of an exemplary embodiment of a plasma source;

(3) FIG. 2 shows a plurality of different exemplary embodiments of an electrode arrangement with respect to a structure of the second electrode, and

(4) FIG. 3 shows another exemplary embodiment of an electrode arrangement, in particular with regard to a structure of the second electrode.

DETAILED DESCRIPTION

(5) FIG. 1 shows a schematic representation of an exemplary embodiment of a plasma source 1 that is configured to generate a nonthermal plasma. The plasma source 1 has a voltage source 3 that is electrically connected to an electrode arrangement 5. For its part, the electrode arrangement 5 is configured to generate a nonthermal plasma.

(6) It has a first electrode 7 and a second electrode 9, wherein between the first electrode 7 and the second electrode 9, a dielectric element 11 is arranged so that the two electrodes 7, 9 are electrically insulated from each other and spaced from each other by the dielectric element 11. The two electrodes 7, 9 and the dielectric element 11 form a stack, wherein viewed in the stack direction, the dielectric element is arranged on the first electrode 7, and the second electrode 9 is arranged on the dielectric element 11.

(7) Viewed in the stack direction, the first electrode 7 has a first thickness d.sub.1 of at least 10 m, wherein the second electrode 9, also viewed in the stack direction, has a second thickness d.sub.2 of at least 1 m to at most 5 m, or from at least 5 m to at most 30 m. Viewed in the stack direction, the dielectric element has a third thickness d.sub.3 of at least 10 m to at most 250 m.

(8) The electrode arrangement 5 is accordingly designed as a thin layer electrode arrangement and has a very slight thickness overall. This renders it pliable overall so that it can be flexibly adapted to a plurality of different uses, and in particular to a plurality of geometrically different surfaces to be treated. Moreover, the electrode arrangement 5 can be operated at a low voltage, in particular at less than 3 kV.sub.pp, due to its very thin design which increases the electrical safety of the plasma arrangement 1.

(9) The second electrode 9 has a dielectric cover element 13 on a side facing away from the dielectric element 11 that has a fourth thickness d.sub.4 of at least 0.2 m to at most 30 m viewed in the stack direction.

(10) The dielectric cover element 13 is preferably designed as a coating, wherein in particular the second electrode 9 is coated with the dielectric cover element 13, or with the material of the dielectric cover element 13. The dielectric cover element 13 thereby covers the second electrode 9 preferably completely.

(11) The first electrode 7 has a dielectric base element 15 on the side facing away from the dielectric element 11. This is advantageously designed flat and extends along an overall extension of the first electrode 7 and therefore entirely covers it, at the bottom in FIG. 1. Consequently, the dielectric base element 15 very efficiently prevents coronal discharges that could otherwise proceed from the first electrode 7 so that the efficiency of the electrode arrangement 5 is increased by the electric base element 15. A fifth thickness d.sub.5 of the dielectric base element 15 is preferably selected so that on the one hand coronal discharges emitted by the first electrode 7 are reliably avoided, wherein on the other hand, the electrode arrangement 5 is designed pliable overall.

(12) Overall, a stacked electrode arrangement 5 results with the following stack sequence: On the dielectric base element 15, the first electrode 7 is arranged on which the dielectric element 11 is arranged. The second electrode 9, on which the dielectric element 13 is arranged, is arranged thereupon.

(13) The at least one first electrode 7 and/or the at least one second electrode 9 preferably has/have a material that is selected from a group consisting of copper, silver, gold and aluminum. Preferably, at least one of the first and second electrodes 7, 9 consist of the aforementioned materials.

(14) Other conductive materials are possible for the electrodes 7, 9, in particular alloys as well, particularly preferably based on at least one of the aforementioned elements.

(15) The dielectric element 11, the dielectric cover element 13 and/or the dielectric base element 15 preferably has/have a material that is selected from the group consisting of silicon nitride, a silicate, in particular quartz, a glass, and a plastic, in particular polyamide. It is also possible for at least one of the aforementioned elements to consist of one of the aforementioned materials. Other inorganic or organic materials are also possible for the aforementioned elements as long as they have dielectric and in particular electrically insulating properties.

(16) The first electrode 7 is preferably designed flat, in particular as a layer or leaf electrode.

(17) The second electrode 9 is preferably designed structured. In particular, in the exemplary embodiment shown in FIG. 1, it has a plurality of linear partial electrodes 17. The structure of the second electrode 9 can in particular be tailored to a specifically designed use of the electrode arrangement 5.

(18) In particular, the dielectric element 11 and/or the dielectric cover element 13 preferably have an average surface roughness Ra that is less than 5% of the thickness of the respective element. Alternatively or in addition, the dielectric base element 15 preferably has an average surface roughness Ra that is less than 5% of its thickness.

(19) The voltage source 3 is in particular electrically connected to the first electrode 7, wherein an AC voltage can be applied to the first electrode 7. The second electrode 9 is preferably earthed or grounded. In the exemplary embodiment described here, both electrodes 7, 9 are electrically connected by an amplifier 19 to the voltage source 3. The amplifier 19 is preferably designed as a piezoamplifier.

(20) The electrode arrangement 5 is preferably operated with an AC voltage with an amplitude that is at least 0.5 kV.sub.pp to at most 3 kV.sub.pp, preferably at least 1.0 kV to at most 2.5 kV.sub.pp, preferably at least 1.0 kV.sub.pp to at most 2.0 kV.sub.pp, preferably 1.5 kV.sub.pp. The AC voltage preferably has a frequency of at least 20 kHz to at most 90 kHz, preferably at least 30 kHz to at most 80 kHz, preferably at least 40 kHz to at most 70 kHz, preferably at least 50 kHz to at most 60 kHz, and preferably 50 kHz.

(21) FIG. 2 shows a plurality of different exemplary embodiments of the electrode arrangement 5, wherein the first flat electrode 7 and the structured second electrode 9 are schematically portrayed in a plan view.

(22) A second electrode 9 is portrayed in FIG. 2a) that has a comb-like structure with a plurality of straight lines that are arranged parallel to each other, are electrically connected to each other, and extend to the right proceeding from common base element 21 in FIG. 2a).

(23) In FIG. 2b), the second electrode 9 also has a comb-like structure, wherein serpentine partial electrodes extend parallel to each other proceeding from the base element 21. The individual partial electrodes are electrically connected to each other by the common base element 21.

(24) In FIG. 2c), the second electrode 9 also has a linear structure, however in the form of a path running as an angular zigzag line.

(25) In FIG. 2d), the second electrode 9 has the shape of an angular spiral.

(26) In FIG. 2e), the second electrode 9 has the shape of an round spiral, in particular a circular spiral.

(27) Finally, the second electrode 9 in FIG. 2f) has a meandering structure.

(28) FIG. 3 shows a schematic representation of another exemplary embodiment 5 of the electric arrangement, in particular with respect to another possible design of the second electrode 9. Equivalent and functionally equivalent elements are provided with the same reference numbers; reference is therefore accordingly made to the preceding description. In the exemplary embodiment portrayed here, the first electrode 7, viewed in the perspective of the viewer, i.e., perpendicular to the plane of drawing in FIG. 3, is arranged below the second electrode 9, wherein it projects beyond a first outer margin 23 of the second electrode 9 viewed in the perspective of the viewer, i.e., in the plane of drawing in FIG. 3, so that a second outer margin 25 of the first electrode 7 laterally extends beyond the second electrode 9. The dielectric element 11 is not portrayed in FIG. 3 for the sake of clarity. However in the electrode arrangement 5, it is arranged between the first electrode 7 and the second electrode 9 in the stack direction, i.e., perpendicular to the plane of the drawing in FIG. 3, wherein it projects beyond the first outer margin 23 of the first electrode 9 as well is the second outer margin 25 of the first electrode 7.

(29) In the configuration depicted here, in particular with regard to the first outer margin 23 of the second electrode 9 and the second outer margin 25 of the first electrode 7, surface microdischarges can form, in particular in the region of the first outer margin 23 of the second electrode 9 as well. If, in another exemplary embodiment, the first outer margin 23 of the second electrode 9 laterally extends beyond the second outer margin 25 of the first electrode 7, there are no surface microdischarges at the first outer margin 23 of the second electrode 9.

(30) In the exemplary embodiment portrayed here, the second electrode 9 is designed flat and has a plurality of recesses 27 of which only one recess is identified with reference number 27 to improve clarity. The recesses 27 are in particular designed as penetrations in the surface of the second electrode 9. When the electrode arrangement 5 is operating, surface microdischarges form in particular at edges of the recesses 27. It can be seen that the recesses 27 in this case form symbols accessible to human understanding or comprehensible to human understanding, i.e., letters, wherein the recesses 27 together form a word, i.e., the word plasma. Analogously, such recesses 27 in the second electrode 9 can form other words, numbers, combinations of letters and numbers, pictograms, pictures, faces, logos etc.

(31) In particular, the edges of the recesses 27 are preferably at a distance from each other that is at least a 0.5 mm. In this manner, attenuated surface microdischarges can be generated with optimum efficiency at the edges of the recess 27.

(32) Overall, it can be seen that with the electrode arrangement 5 proposed here, the plasma source 1 and the method allow significant miniaturization with great design freedom for a device to generate a nonthermal plasma and/or for plasma treatment, in particular of surfaces, wherein electrical safety of the device is increased, and wherein a treatment distance can always be selected within wide ranges that is always appropriate for a plasma chemistry desired for the specific use.