ANTI-MULTIPACTOR COATING DEPOSITED ON AN RF OR MW METAL COMPONENT, METHOD FOR FORMING SAME BY LASER SURFACE TEXTURING

Abstract

Anti-multipactor coating deposited on an RF or MW component, by surface texturing of such a coating by laser.

The invention relates to a formation method by laser ablation, on a metal substrate, of an anti-multipactor coating whose constituent material is chosen from amongst the metals of column 10 or column 11 of the Mendeleev table or an alloy of these metals and whose texture comprises one or more patterns of cavities repeated at regular intervals, the interval pitch between two adjacent cavities being in the range between 0 and 100 m.

Claims

1. A method for forming an anti-multipactor coating on a metal substrate, comprising the following steps: (a) deposition of a coating made of a constituent material chosen from amongst the metals of column 10 or column 11 of the Mendeleev table or an alloy of these metals over at least a part of the surface of the metal substrate, (b) laser treatment of the coating deposited according to the step (a), in such a manner as to obtain a texturing of the deposited coating, with one or more patterns of cavities repeated at regular intervals, the interval pitch between two adjacent cavities being in the range between 0 and 100 m.

2. The formation method according to claim 1, comprising, prior to the step (a), a step for deposition of an adhesion layer for the coating.

3. The formation method according to claim 1, wherein the constituent material of the coating deposited according to the step (a) is chosen from amongst gold, silver, an alloy of silver, preferably an alloy of gold, a gold-nickel or gold-cobalt alloy.

4. The formation method according to claim 1, wherein the step (b) is carried out by means of a femtosecond laser.

5. The formation method according to claim 1, wherein the step (a) is carried out according to an electrochemical surface treatment technique.

6. The formation method according to claim 1, wherein the opening diameter of each cavity is in the range between 2 and 50 m, preferably between 2 and 30 m.

7. The formation method according to claim 1, comprising, prior to step (a), a step of coating the metal substrate with at least one thin layer deposited according to a physical vapour deposition (PVD) technique.

8. The formation method according to claim 7, wherein the thin layer is a gold layer.

9. A radiofrequency (RF) or microwave (MW) component at least a part of the surface of the active part of which is composed of a metal substrate coated with the anti-multipactor coating according to the formation method of claim 1.

10. The radiofrequency (RF) or microwave (MW) component according to claim 9, forming an RF coaxial connector, or an RF switch of the coaxial type or a waveguide.

11. Use of an RF or MW component according to claim 9 for the transmission of signals from or to a satellite.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG. 1 is a photographic reproduction of an anti-multipactor coating according to the invention;

[0046] FIG. 2A is a schematic top view of repeated patterns of cavities of an anti-multipactor coating according to the invention;

[0047] FIG. 2B1 is a schematic longitudinal cross-sectional view of a cavity of an anti-multipactor coating according to the invention;

[0048] FIG. 3 is a display, obtained by 3D laser scanning confocal microscope, of the topography of an anti-multipactor coating with patterns of cavities repeated at regular intervals according to the invention;

[0049] FIG. 4 is a perspective view of a coaxial connector of the TNC type implemented for testing an anti-multipactor coating according to the invention;

[0050] FIG. 5 is a perspective view of a socket implemented for testing an anti-multipactor coating according to the invention;

[0051] FIG. 6 is a perspective view of a connector half-shell implementation for testing an anti-multipactor coating according to the invention;

[0052] FIG. 7 is a perspective view of a connection system comprising two TNC connectors such as shown in FIG. 4, between which a connection socket according to FIG. 5 is connected and surrounded by two connector half-shells according to FIG. 6, the exterior of the socket and the interior of the connector half-shells being covered with an anti-multipactor coating of silver according to the invention;

[0053] FIG. 8 is a perspective view of the connection system according to FIG. 7 such as assembled;

[0054] FIG. 9A is a a scanning electron microscope (SEM) view with a magnification 250 of an anti-multipactor coating of silver according to the invention which covers the exterior of the socket and the interior of the connector half-shells;

[0055] FIG. 9B1 is a a scanning electron microscope (SEM) view with a magnification 1000 of an anti-multipactor coating of silver according to the invention which covers the exterior of the socket and the interior of the connector half-shells;

[0056] FIG. 9C1 is a a scanning electron microscope (SEM) view with a magnification 5000 of an anti-multipactor coating of silver according to the invention which covers the exterior of the socket and the interior of the connector half-shells, this magnification allowing a cavity to be viewed;

[0057] FIG. 9D1 is a a scanning electron microscope (SEM) view with a magnification 7500 of an anti-multipactor coating of silver according to the invention which covers the exterior of the socket and the interior of the connector half-shells, this magnification allowing the cavity in FIG. 9C to be seen with a greater precision;

[0058] FIG. 10 is a perspective view of a connection system comprising two TNC connectors such as shown in FIG. 4 between which a connection socket according to FIG. 5 is connected and surrounded by two connector half-shells according to FIG. 6, the exterior of the socket and the interior of the connector half-shells being covered with an anti-multipactor coating of gold according to the invention;

[0059] FIG. 11A is a a scanning electron microscope (SEM) view with a magnification 550 of an anti-multipactor coating of gold according to the invention which covers the exterior of the socket and the interior of the connector half-shells;

[0060] FIG. 11B is a a scanning electron microscope (SEM) view with a magnification 1000 of an anti-multipactor coating of gold according to the invention which covers the exterior of the socket and the interior of the connector half-shells;

[0061] FIG. 11C is a a scanning electron microscope (SEM) view with a magnification 6000 of an anti-multipactor coating of gold according to the invention which covers the exterior of the socket and the interior of the connector half-shells, this magnification allowing a cavity to be viewed;

[0062] FIG. 11D is a view of a scanning electron microscope (SEM) with a magnification 7500 of an anti-multipactor coating of gold according to the invention which covers the exterior of the socket and the interior of the connector half-shells, this magnification allowing the cavity of FIG. 11C to be seen with a greater precision;

[0063] FIG. 12 is a graph in the form of histograms showing the gain in transmission power provided by an anti-multipactor coating of silver and of gold according to the invention compared with a coating respectively of silver and of gold according to the prior art, obtained by electrochemical surface treatment only, without texturing.

DETAILED DESCRIPTION

[0064] FIG. 1 illustrates an anti-multipactor coating, denoted overall by the reference 1, according to the invention.

[0065] This coating 1 is a layer of silver, gold, or an alloy of one or the other of these metals and its texture comprises one or more patterns of cavities repeated at regular intervals 10.

[0066] A schematic representation of repeated patterns and of cavities 10 is shown in FIGS. 2A to 2B: the cavities 10 are substantially adjoining and each has a circular opening and a general cross-sectional shape substantially in the form of a Gaussian. By way of indicative example, the unitary diameter of the cavities 10 is of the order of 20 m and their depth (height) h is of the order of 4 m.

[0067] The topography repeating at regular intervals of these cavities 10 is clearly visible in FIG. 3.

[0068] In order to obtain the anti-multipactor coating 1 according to the invention over at least a part of the surface of a metal RF or MW component, the inventors have carried out the following steps.

[0069] Step a): a deposition is carried out by surface treatment of the electrochemical deposition type for example of a gold or silver coating, or of an alloy of one or the other of these metals, selectively over the surface of the metal component in question.

[0070] This deposition is of the order of a few m, or even a few tens of m. For example, the thickness of deposition may be in the range between 1 and 15 m for silver and 1 and 7 m for pure gold.

[0071] Step b): a laser treatment of the deposited coating is carried out, in such a manner as to obtain a texturing of the deposited coating, with one or more patterns of cavities repeated at regular intervals.

[0072] The laser used is preferably a femtosecond laser. Each cavity 10 is created by a pulse produced by the laser, with a duration of a few fs to 100 fs.

[0073] In order to test the effectiveness of the anti-multipactor coating 1 according to the invention, the inventors have carried out trials on an RF test vehicle, a part of the metal components of which is coated with the said coating.

[0074] The connection system used 5 during the trials comprises two coaxial connectors 4 of the TNC type, such as shown in FIG. 4, between which a socket 3 shown in FIG. 5 is connected and around which two connector half-shells 4, as shown in FIG. 6, are assembled defining an annular space around it.

[0075] The connection system 5 assembled and in an operational configuration is shown in FIG. 8.

[0076] In each of the examples considered hereinafter, the conditions of the trials were as follows: [0077] socket 3 made of copper beryllium (CuBe.sub.2) and connector half-shell 4 made of aluminium; [0078] frequency of the signal transmitted by the connection system 5: 1 GHz; [0079] annular space between the exterior of the socket 3 and the interior of the cylinder defined by the two assembled connector half-shells 4: 2 mm; [0080] power of transmission of the signal: until the multipactor discharge is obtained.

[0081] Example 1: The exterior of the socket 3 and the interior of the connector half-shells 4 is coated with an anti-multipactor coating 1 made of silver and textured according to the invention, i.e. according to the steps a) and b) of the method described hereinabove.

[0082] Comparative example 1: The exterior of the socket 3 and the interior of the connector half-shells 4 are coated with a silver coating 1 but without any texturing, i.e. according to the step a) only of the method described hereinabove.

[0083] Example 2: The exterior of the socket 3 and the interior of the connector half-shells 4 are coated with a gold anti-multipactor coating 2 and textured according to the invention, i.e. according to the steps a) and b) of the method described hereinabove.

[0084] Comparative example 2: The exterior of the socket 3 and the interior of the connector half-shells 4 are coated with a gold layer 2 but without any texturing, i.e. according to the step a) only of the method described hereinabove.

[0085] Comparative example 3: The socket 3 and the connector half-shells 4 have no coating.

[0086] The measurements of power of the signal were made according to the standard cited in the reference hereinafter.

[0087] The results of the trials are shown in FIG. 12 and summarized in Table 1 hereinbelow.

TABLE-US-00001 TABLE 1 Example Power (W) Example 1 390 Comparative example 1 105 Example 2 750 Comparative example 2 153 Example 3 80

[0088] It is observed that the best result is obtained with a gold coating 1 textured according to the invention, with a gain by a factor of the order of 4.9 with respect to a coating that is gold plated only, which is already considerable, and a gain by a factor of the order of 9.38 compared with metal components with no coating, which is very significant.

[0089] A silver coating 1 textured according to the invention, for its part, provides a gain by a factor of around 2.95 with respect to a coating which is silver plated only.

[0090] Other variants and advantages of the invention may be implemented without however straying from the scope of the invention.

[0091] For example, although, in the example illustrated, the anti-multipactor coating according to the invention is deposited on a socket forming a central contact of an RF connection system, the invention is also applicable to any other electrically-conductive part of an RF or MW device, notably for high-power transmission, of a switch, such as a coaxial switch or a waveguide switch.

[0092] The invention is not limited to the examples that have just been described; features of the examples illustrated may notably be combined together within variants not shown.

LIST OF THE DOCUMENTS CITED

[0093] [1] Sattler et al. Modeling micro-porous surfaces for secondary electron emission control to suppress multipactor, Journal of Applied Physics, American Institute of Physics, Vol. 122, N 5, 7 Aot 2017. [0094] [2] Wang et al. A novel method to improve the power capabilities of microwave components, 2013 European Microwave Integrated Circuit Conference; European Microwave Association, 6 Oct. 2013. [0095] [3] ECSS-E-20-01A (REV-1), SPACE ENGINEERING: MULTIPACTION DESIGN AND TEST (1 Mar. 2013)