DE102022128363A1 - Method for producing a high-frequency functional structure and high-frequency functional structure - Google Patents

Abstract

The present invention relates to a method for producing a high-frequency functional structure with the steps: providing a base body of the high-frequency functional structure, wherein the base body is produced by an additive process; applying at least one electrically conductive layer to a surface of the base body, wherein the surface of the base body has one or more anchoring elements in regions or completely, which are designed and arranged to improve the adhesion of the electrically conductive layer to the surface compared to an adhesion of the electrically conductive layer to a surface without anchoring elements.

Description

• Bereitstellen eines Grundkörpers der hochfrequenztechnischen Funktions-struktur,
• wobei der Grundkörper durch ein additives Verfahren hergestellt wird;

The present invention relates to a method for producing a high-frequency functional structure comprising the steps:

• Providing a basic body of the high-frequency functional structure,
• wherein the base body is manufactured by an additive process;

Applying at least one electrically conductive layer to a surface of the base body.

One such functional structure is, for example, a waveguide for guiding electromagnetic waves. Electromagnetic waves, in particular high-frequency signals, can propagate either in a space or in waveguide devices. Such waveguide devices provide conductive structures that encompass a spatial area and thus form a spatial path or channel in order to guide the electromagnetic waves or high-frequency signals therein or to manipulate them in space or the frequency range.

When manufacturing high-frequency components, the component is assembled from two halves during production, particularly to create cavities. The cavities thus created, e.g. milled into a metal base body, provide the actual functionality of the high-frequency assembly. These can be, for example, waveguides, so-called hollow conductors, but also filters, resonators, couplers or antennas.

Such high-frequency components can be produced from plastic base bodies. In order to function later, they must be provided with a conductive coating. The state of the art is galvanic or electroless coating with metals. This is also done, for example, in decorative coating (Plating on Plastics (PoP)), where various layer systems are used, for example with Cu, Ni, Cr, Au, Ag, etc. and combinations and/or sequences of these elements.

The electrical conductivity and nature of the component surface that interacts with the electromagnetic wave is essential; in particular, the inner wall forming the cavity must be electrically conductive. Manufacturing the components from metal or electrically conductive base material is not only costly, but also complex, and in particular requires costly CNC milling processes. Against this background, the approach of manufacturing such components from plastic instead and only making them conductive in one or more subsequent steps has already been pursued in the state of the art. Known process proposals here envisage chemical processes such as galvanic or electroless coating of the base body surface with metals.

The metallization of plastics, especially photopolymers, presents technical challenges, particularly with regard to the adhesion of the metal layer to the surface of the plastic. In principle, metallic layers have poor adhesion to photopolymers. The adhesion of the deposited metal layer can also be inadequate on other plastics, especially 3D-printable or 3D-printed plastics that have a low surface roughness, for example with R _q < 20 µm.

According to the state of the art, bodies made of photopolymers are therefore subjected to a complex process of sulfonation of the surface to be metallized in order to achieve better adhesion of the metallic layer to the surface.

Coating processes using hexavalent chromium are also well known. However, due to the harmfulness of hexavalent chromium, these coating processes are subject to severe legal restrictions or bans.

In addition, pickling with hexavalent chromium, for example using chromium-sulfuric acid, results in a significant increase in surface roughness, which is ultimately at least one of the mechanisms that promote adhesion.

With regard to the previously known processes, there is a desire to further simplify the coating process in order to improve the adhesion strength in particular.

Against this background, the present invention is based on the object of providing such an improved method.

This object is achieved by the method having the features of independent claim 1. Advantageous developments of the invention are the subject of the dependent claims.

Accordingly, the invention provides that the surface of the base body has one or more anchoring elements in regions or in its entirety, which are designed and arranged to prevent the adhesion of the electrically conductive layer on the surface from adhesion. to improve the adhesion of the electrically conductive layer on a surface without anchoring elements.

Particularly preferred is an embodiment of the method in which the base body is monolithic, i.e. manufactured in one piece and consists of only one material, preferably produced by an additive process, the electrically conductive layer is applied wet-chemically and a further electrically conductive layer is applied by a galvanic process, wherein the functional structure is preferably a hollow conductor or waveguide, in particular a slotted one. The galvanic process preferably smoothes the surface of the layer, in particular the functional surface.

However, the functional structure can also be a component composed of several parts, one or more parts of which were manufactured by a method according to the invention.

For example, the adhesion, in particular the adhesive strength of the coating on the base body, can be tested by a scratch test according to ISO 20502:2016-11 , by a Rockwell penetrant test according to EN ISO 26443:2016-09 or according to VDI 3824-4, by a cross-cut test according to EN ISO 2409:2020-12 , by a cross-cut test and/or a cross-cut test according to EN ISO 16276-2:2007-08 , by a tear-off test according to EN ISO 4624 or by a similar test method. The test may also be carried out by applying a fabric adhesive tape and tearing it off, feeling or measuring the tear-off force.

Preferably, improved adhesion is understood to mean that at least one of the test methods mentioned produces a better result or a better test value when testing the adhesion of a layer applied to a surface of a base body with anchoring elements compared to testing the adhesion of a layer applied to a surface of a base body without anchoring elements.

The anchoring elements preferably increase the surface area on which the layer is applied and/or the anchoring elements preferably form positive connections between the base body and the layer. This improves the physical or chemical adhesion and/or the mechanical adhesion of the layer to the base body.

Preferably, it is provided that the anchoring element(s) comprise or are depressions penetrating into the surface and/or elevations protruding from the surface and/or have undercuts and/or are generated by the roughness of the surface.

The surface preferably has flat areas and areas that are provided with anchoring elements. An undercut of an anchoring element, which is designed in particular as a depression, is preferably understood to mean that a line extending from the undercut and perpendicular to the flat area penetrates the base body. The undercut thus forms a type of barb through which the layer is positively connected to the base body.

The anchoring elements can have any shape. For example, the anchoring elements can be arranged in a kind of marbling.

The depressions and/or elevations may have the shape of hills, spikes or the like.

A conceivable geometry for an anchoring element with an undercut is, for example, a recess that has a conical cross-section, whereby the recess is widened in the depth direction.

Other conceivable geometries for an anchoring element are cylinders, triangles, tetrahedrons, blocks, trapezoidal blocks, spheres or sphere-like shapes as well as any desired free forms.

It is also conceivable that the geometry of the anchoring elements changes during production compared to the target geometry. This can lead to distortions or increases. Nevertheless, the anchoring elements primarily serve the purpose of increasing the adhesive strength. Adhesion and adhesive strength are preferably understood as synonyms.

The spatial extension of the anchoring elements, preferably in the direction of the surface, is directed towards surfaces that interact with an electromagnetic wave, preferably according to the wavelength Lambda_0 = c_0/f, of the electromagnetic wave and/or according to the wavelength guided in the waveguide Lambda_g=2*pi/Beta, where Beta is the phase coating of the waveguide. Beta = 2*pi*fl(c0*sqrt(epsr)) sqrt(1 -(f_c/f) ² ) with f_c=c0/(2*w) with w=width of the waveguide.

The anchoring elements each have an extension, preferably in the direction of propagation of the electromagnetic wave, which is less than the whole, in particular less than half, preferably less than a quarter of the wavelength of the electromagnetic wave.

On non-HF relevant surfaces, it is conceivable to significantly increase the spatial dimensions of the anchoring elements.

It is conceivable that several anchoring elements are arranged evenly or unevenly distributed on the surface, wherein the anchoring elements have the same shape or at least one anchoring element has a different shape.

It is conceivable that the anchoring elements are produced by a 3D printer.

In other words, there can be a different surface density, i.e. the number of anchoring elements per unit area, of the anchoring elements on the surface.

The surface density can be changed depending on the desired frequency range of an electromagnetic wave transmitted through the functional structure. The higher the application frequency, the higher the surface density can be and the smaller the extension of these anchoring elements in the direction of the surface can be.

A surface density of more than one anchoring element per square centimeter, in particular of more than one anchoring element per square millimeter, is advantageous and/or the surface density is preferably a maximum of 100,000, preferably 40,000, in particular 10,000 anchoring elements per square millimeter.

The surface density can also be less than 100 or less than 10 anchoring elements per square millimetre.

It is conceivable that the anchoring elements are created during the manufacture of the base body or are attached to or inserted into the base body after manufacture.

In a particularly preferred variant of the method, the surface provided with anchoring elements remains a continuous surface. The anchoring elements are thus preferably surrounded by a surface that defines the function of the component.

This preferably enables basic manufacturability that is largely independent of the orientation in the 3D printing build space, whereby the quality of the surface can still vary without the individual anchoring elements being supported.

Furthermore, the outermost areas of the surface that determines the function of the RF component preferably remain of high quality, since the roughness there is not unnecessarily increased, for example by aggressive chemical pickling.

It is conceivable that the electrically conductive layer is applied to the surface having at least one anchoring element using a wide variety of methods, such as PVD, CVD, sputtering, inkjet, aerosoljet, nanojet, roll-to-roll printing, screen printing, physical application using inks or pastes or varnishes, chemical processes using wet chemical deposition or galvanic deposition.

In particular, the electroless and galvanic deposition of metal layers are advantageous.

It is conceivable to arrange the anchoring elements on any 3D-printed surface in order to increase the adhesive strength of a metal layer deposited on it.

Preferably, however, the base bodies are RF components, in particular RF components that have been designed based on slotted waveguide technology. A slotted waveguide is preferably a waveguide in which openings are provided in the outer wall that do not lead to radiation. This is the case when the openings are small compared to the guided wavelength and/or do not intersect the current density associated with the wave in the waveguide on the conductive wall perpendicular to its flow direction.

In an advantageous embodiment, it is provided that the electrically conductive layer is applied by means of a preferably electroless, wet-chemical process, preferably by wetting a part or the entire surface of the base body with a dispersion containing microparticles and/or nanoparticles, wherein the microparticles and/or nanoparticles preferably contain nickel, copper, silver, gold, zinc, tin, chromium, palladium and/or platinum.

Preferably, the electrically conductive layer is applied by one of the following methods: PVD, CVD, sputtering ring, inkjet, aerosoljet, nanojet, roll-to-roll printing, screen printing, physical application using inks or pastes or varnishes, chemical processes using wet chemical deposition or galvanic deposition.

Particles with an average particle size D50 of less than 1 µm can be referred to as nanoparticles and particles with an average particle size D50 of greater than or equal to 1 µm can be referred to as microparticles. Nanoparticles can have an average particle size D50 of 10 nm to 300 nm, preferably 10 nm to 100 nm. Microparticles can have an average particle size D50 of 1 µm to 100 µm, preferably 1 µm to 5 or 10 µm. The particle size preferably refers to the equivalent diameter of the respective particles.

The electrically conductive layer is preferably a layer that contains metal. The electrically conductive layer can also be electrically non-conductive after application and/or become electrically conductive after application.

The base body can determine the shape of the functional structure.

The particles preferably consist of one or more metals or comprise one or more metals.

The particles can be plastic-coated.

In the context of this invention, electrical is the generic term for electrical and/or electronic.

Preferably, when producing a functional structure for electrical components, it is proposed to first create a base body that determines the shape of the functional structure. The material for producing the base body is preferably electrically non-conductive, but for carrying out the process, an electrically conductive or semi-conductive material could just as well be used to produce the base body.

The necessary electrically conductive coating of the base body is preferably achieved by wetting at least part, preferably the entire surface of the base body with a dispersion containing electrically conductive micro- and/or nanoparticles. The dispersion can be an ink with micro- or nanoparticles. The (ink) materials used are preferably those that achieve high conductivities. The dispersion or ink is preferably water-based, and an organic release agent can also be provided. Alternatively or additionally, a solvent can be added. Possible particles are aluminum, silver, gold, tin, zinc or copper particles or a mixture thereof. The dispersion or ink is matched to the surface energy of the base body material used, e.g. plastic, so that sufficient wetting of the surface is promoted. Furthermore, the viscosity of the dispersion or ink material can be matched to the smallest openings in the base body structure, so that wetting by the dispersion is guaranteed.

After the solvent/water has evaporated/evaporated, the surface of the base body is wetted with the ink material and a conductive coating is formed through optional post-treatment, preferably sintering. The new process therefore represents an alternative to chemical, electroless coating. The base body is preferably functionalized, i.e. into an electrical component, by being completely or partially coated with conductive ink material.

In contrast to chemical coating processes, in which a body is placed in a reagent liquid and a chemical reaction occurs between the reagent liquid and the surface of the body, the present process instead relies on a dispersion for coating, which physically wets the base body and forms a conductive coating through post-treatment.

Compared to the chemical coating process, the process according to the invention can achieve a smoother surface structure of the coated base body, which has decisive advantages, especially for components in high-frequency technology. The smoother the surface of the component, the better the subsequent electrical performance of the component. The chemical process of existing processes often leads to a disadvantageous roughening of the body surface due to the necessary pretreatment.

The method according to the invention can be used advantageously, for example, for the production of electrical components, whereby the functional structure of these components is formed by the coated base body. Some of these functional structures require a spatial area enclosed by conductive structures to guide the electromagnetic waves. In this case, the base body is designed with corresponding structures at the locations required for the electrical function, where is required for mechanical or electrical function or only slightly restricts it.

Application and wetting is preferably carried out by completely immersing the base body in an immersion bath containing the corresponding dispersion. In principle, immersing the base body once is sufficient. Better distribution of the dispersion around or through the base body, particularly in an optionally available cavity, is ensured by repeated immersion. An ultrasonic bath containing the dispersion is preferably used. After immersion in the immersion bath, the base body can be shaken briefly to remove excess dispersion.

As an alternative to the immersion bath, the dispersion can also be applied using an aerosol chamber in which the dispersion, atomized into droplets, wets the base body. It is also possible to coat or wet the base body by spraying or pouring the dispersion over it.

It is conceivable that the electrically conductive layer is applied by means of an aerosol or nanojet.

It is also conceivable that the dispersion is applied by flushing.

After the dispersion has been applied, the quality of the coating and its conductivity can be created or improved by thermal post-treatment of the base body surface or the adhering micro- or nanoparticles. This can be done by drying, preferably in a circulating air system, sintering in an oven, UV treatment, the supply of hot air or infrared radiation. Thermal post-treatment can have a positive effect on the electrical conductivity of the applied coating. The subsequent sintering of the micro- or nanoparticles, e.g. in a thermal oven, achieves a high conductivity of the resulting surface coating. The sintering temperature of the ink material is matched to the glass transition temperature of the plastic used so that it is not damaged.

It may be provided that no thermal post-treatment, in particular no drying, of the base body takes place.

It can also be advantageous if a surface pretreatment of the base body is carried out before the application of the dispersion, in particular to achieve surface cleaning or activation for optimized adhesion of the coating.

During the coating process, particularly when placing it in a corresponding immersion bath, it is crucial that the corresponding dispersion can reach all the inner wall surfaces to be coated. To promote fluid circulation, it can therefore also be advantageous to design the base body in such a way that base body material is only present where it is needed for mechanical or electrical function or only restricts this to a small extent, i.e. to build certain walls of the base body only there from the outset or to subsequently provide them with recesses. This makes it easier for the dispersion to penetrate into a cavity. Furthermore, the viscosity of the dispersion or ink material used should be matched to the smallest openings in the base body structure so that circulation is guaranteed.

In the case of rectangular hollow bodies or cavities, walls can be designed to be interrupted in accordance with the side walls of a substrate-integrated waveguide (SIW) known from the state of the art, since these openings do not impair the high-frequency or electrical function, which is also known from the state of the art. For example, the narrow walls of the cavity are slotted, while the wide walls of the rectangular hollow body can be designed without corresponding openings.

In a further advantageous embodiment, it is provided that the electrically conductive layer is applied by means of a wet-chemical process, preferably by means of electroless deposition of nickel, copper, silver, gold, tin, zinc, etc. on the surface having at least one anchoring element.

Furthermore, in an advantageous embodiment, the conductive layer applied without current on a surface having at least one anchoring element is then extended with at least one further metallic layer by an electrochemical and/or galvanic process. The galvanically deposited metallic layer replicates the surface and the anchoring elements, and the latter remain recognizable after the galvanic coating.

In a further advantageous embodiment of the method, it is provided that the electrolessly applied conductive layer is applied to a substrate having at least one anchoring element. The surface is then extended with at least one further metallic layer using an electrochemical and/or galvanic process. The galvanic layer is deposited in such a way that the anchoring elements are closed or completely covered by this layer.

A further advantageous embodiment of the method provides that the galvanic deposition of one or more metallic layers is carried out in such a way that an effective smoothing of the outermost surfaces is achieved, as described in the EN 10 2021 128 881 A1 This reduces losses for electromagnetic waves.

As already mentioned above, the base body can be made of an electrically non-conductive material. Ceramic or plastic are particularly suitable. The plastic can be polyamide, preferably PA6, PA 11 or PA12. The plastic can in particular be a photopolymer. Polyurethanes or acrylates can be contained in the plastic material. It can also be provided that the base body is a hollow body and its inside is coated with the electrically conductive layer.

Preferably, the method comprises the further step of applying at least one further electrically conductive layer to the base body by means of a galvanic or wet-chemical process.

Applying another electrically conductive layer once or several times preferably leads to a functional smoothing of the surface of the layer.

A functionally smooth surface is preferably understood to mean that the layer is designed in such a way that the function of the layer is not impaired. If the function of the layer is to conduct electromagnetic waves, a surface of a layer that is functionally smooth for the wave conduction function is designed in such a way that the wave conduction is not influenced by the anchoring elements.

The anchoring elements or the microstructure can therefore also be optically visible on a surface that is functionally smooth for the waveguide function. The surface provided with anchoring elements can be referred to as a microstructure.

The smoothing of the surface or microstructure is preferably carried out to reduce electromagnetic losses or to reduce the attenuation of an electromagnetic wave that is transmitted through the functional structure.

In an advantageous embodiment, it is provided that the layer or layers cover the anchoring elements after the application of the layer or layers in such a way that the layer has a preferably functional, smooth, flat and/or continuous surface, wherein the anchoring elements are preferably visible, partially visible or invisible.

The anchoring elements may still be partially recognizable in their shape.

A recess as an anchoring element can, for example, be filled with the layer in such a way that a recess is still visible. However, the recess can also be filled with the layer in such a way that the layer completely fills the recess and thus makes it invisible.

A depression as an anchoring element can, for example, be overgrown by a layer deposited on top of it, whereby the depression is filled, for example in the manner of a seal. However, an overgrowing layer can also be deposited so that a hollow space remains.

A further advantageous embodiment of the method provides for anchoring elements protruding above the surface, for example small towers, which are covered by the electrically conductive layer in such a way that they disappear under the layer.

A continuous surface ensures that the material can be manufactured even in overhanging areas and the surface preferably has the same shape as before the layer was applied. In particular, the intended high-frequency functionality of the surface is retained because the anchoring elements do not interact, or do not interact significantly, with electromagnetic waves.

It is conceivable that the anchoring elements are only arranged on surfaces of the base body that have an electrical function.

It is also conceivable that the anchoring elements are only on surfaces of the base body that do not have a high-frequency function or only or also on surfaces of the base body that have a high-frequency function, in particular on the inner sides of a preferably slotted waveguide or are arranged on the radiating surfaces of an antenna.

In a further advantageous embodiment of the method, the anchoring elements are distributed and shaped in a way that is tailored to the functions of the surface. This means that surfaces that do not have high frequency (HF) functionality can have anchoring elements in a much more pronounced form, for example in the form of large and/or deep caverns. On the surfaces that have HF functionality, anchoring elements that are adapted to the frequency and application, for example with a smaller spatial extent, can be introduced. However, it is also conceivable that the surfaces with HF functionality are designed entirely without anchoring elements.

In an advantageous embodiment, it is provided that the functional structure is designed to conduct an electromagnetic wave, wherein the anchoring elements each have an extension, preferably in the propagation direction of the electromagnetic wave, which is less than the whole, preferably less than half, preferably less than a quarter, of the wavelength of the electromagnetic wave.

The size of the anchoring elements, preferably in the direction of extension of the surface, can be based not only on the wavelength but also on the surface density. It is conceivable that at least one anchoring element is placed per square centimeter. Surface densities of at least one anchoring element per square millimeter are particularly advantageous.

It is conceivable that areas of the outermost layer are smoothed, in particular by means of galvanic smoothing or smoothing of the plastic body before applying the layer.

It is conceivable that the additive process includes SLS, SLA, DLP, multijet, 2-photon printing, aerosol jet, inkjet, nanojet, FDM, SLM and/or EBM.

Preferably, the base body is made at least partially or completely from ceramic, plastic, in particular a photopolymer, or metal and/or that the base body is a hollow body, the inside of the hollow body being coated with the electrically conductive layer and/or that the base body is designed or produced in one piece or in multiple parts. The base body can also be made partially or completely from a material for selective laser sintering.

In an advantageous embodiment, it is provided that the base body is produced by an additive process, in particular by 3D printing, selective laser sintering or stereolithography, multijet or by a casting process, in particular by injection molding.

The anchoring elements are preferably produced during the manufacture of the base body and are not separately attached to or inserted into the base body. This is particularly conceivable when the base body is manufactured using an additive process. In principle, however, it is also conceivable to attach or insert the anchoring elements separately to the manufacture of the base body. It is also conceivable that the anchoring elements are prepared by 3D printing and then formed in a downstream process step.

It is preferably provided that the functional structure is or comprises a high-frequency line, in particular a preferably slotted waveguide, or an antenna, in particular a horn or helix antenna, or a filter or a resonator or a coupler or another passive RF part or component of a solar system, a solar cell, a touchscreen, a smart glass, a wearable or an LED or a molded interconnect device (MID) or mechatronic integrated device (MID).

The invention also relates to a high-frequency functional structure which was partially or completely produced by means of a method according to the invention, with at least one electrically conductive layer on a surface provided with anchoring elements of a base body produced by an additive method.

It is conceivable that the anchoring element(s) comprise or are depressions penetrating into the surface and/or elevations protruding from the surface and/or have undercuts and/or are created by the roughness of the surface.

It is conceivable that the layer or layers cover the anchoring elements in such a way that the layer has a, preferably functional, smooth, flat and/or continuous surface, wherein the anchoring elements are preferably visible, partially visible or invisible.

It is conceivable that the anchoring elements are only attached to surfaces of the base body that do not have a high-frequency function or only or also to surfaces of the base body that have a high-frequency function. sen, in particular on the inner sides of a, preferably slotted, waveguide or on the radiating surfaces of an antenna.

The features described herein are, mutatis mutandis, preferably features of the product as well as of the method. In other words, the features of one of claims 1 to 17 can also be the subject of the functional structure according to one of claims 18 to 20.

At this point, it should be noted that the terms "a" and "an" do not necessarily refer to exactly one of the elements, although this is a possible embodiment, but can also refer to a plurality of the elements. Likewise, the use of the plural also includes the presence of the element in question in the singular and, conversely, the singular also includes several of the elements in question. Furthermore, all features of the invention described herein can be combined with one another as desired or claimed in isolation from one another.

• 1: eine perspektivische Ansicht einer Ausführungsform einer erfindungsgemäßen Funktionsstruktur.
• 2: eine perspektivische Ansicht einer Oberfläche einer Ausführungsform einer erfindungsgemäßen Funktionsstruktur.
• 3: eine perspektivische Ansicht einer Oberfläche einer Ausführungsform einer erfindungsgemäßen Funktionsstruktur.
• 4: eine perspektivische Ansicht einer Oberfläche einer Ausführungsform einer erfindungsgemäßen Funktionsstruktur.
• 5: eine Schnittansicht einer Ausführungsform einer erfindungsgemäßen Funktionsstruktur.
• 6: eine perspektivische Ansicht einer weiteren Ausführungsform einer erfindungsgemäßen Funktionsstruktur.
• 7: eine perspektivische Ansicht einer weiteren Ausführungsform einer erfindungsgemäßen Funktionsstruktur.
• 8: eine perspektivische Ansicht einer weiteren Ausführungsform einer erfindungsgemäßen Funktionsstruktur.
• 9: eine Schnittansicht einer weiteren Ausführungsform einer erfindungsgemäßen Funktionsstruktur.
• 10: ein Diagramm für das Übertragungsverhalten einer erfindungsgemäßen Funktionsstruktur.

Further advantages, features and effects of the present invention will become apparent from the following description of preferred embodiments with reference to the figures in which identical or similar components are designated by the same reference numerals.

• 1 : a perspective view of an embodiment of a functional structure according to the invention.
• 2 : a perspective view of a surface of an embodiment of a functional structure according to the invention.
• 3 : a perspective view of a surface of an embodiment of a functional structure according to the invention.
• 4 : a perspective view of a surface of an embodiment of a functional structure according to the invention.
• 5 : a sectional view of an embodiment of a functional structure according to the invention.
• 6 : a perspective view of another embodiment of a functional structure according to the invention.
• 7 : a perspective view of another embodiment of a functional structure according to the invention.
• 8th : a perspective view of another embodiment of a functional structure according to the invention.
• 9 : a sectional view of a further embodiment of a functional structure according to the invention.
• 10 : a diagram for the transfer behavior of a functional structure according to the invention.

In 1 an exemplary base body 10 of a high-frequency functional structure according to the invention is shown.

The 1 The base body 10 shown is a test body for measuring the adhesion of an electrically conductive layer on the base body 10 and is therefore provided with a bore 2. Of course, the invention is not limited to such base bodies 10 in the form of test bodies.

Through the bore 2, the base body 10 provided with a metallic coating can be fixed to a base and then various test procedures can be carried out on it to check or estimate the adhesion, in particular the adhesive strength of the coating on the base body 10.

In the 2 to 4 increasingly enlarged sections of the surface of the base body 10 are now shown. The largest magnification of the surface of the base body 10 shows 4 .

For example 4 it can be seen that the surface of the base body 10 is provided with depressions. The depressions 1 are arranged in a regular pattern on the surface of the base body 10, but can also be arranged irregularly. Likewise, the depressions 1 can have the same or different shapes. Several depressions 1 with one shape and further depressions 1 with a different shape can also be arranged. The depressions 1 can therefore have any shape.

In 5 the cross-section of the depressions 1 can be seen. The depressions 1 are circular on the surface and widen conically towards the depth. The depressions 1 therefore have an undercut compared to the surface. The depressions 1 are thus designed like caverns.

In 6 a base body 10 for a slotted waveguide or hollow conductor for conducting electromagnetic waves is shown. The base body has two flanges and a channel for wave conduction.

In the 7 and 8th Now increasingly enlarged sections of the base body 10 are shown The largest magnification of the surface of the base body 10 shows 8th .

On a surface of the base body 10 recesses 1 are arranged, as can be seen particularly well from 8th emerges.

Likewise, depressions 1 are arranged on a surface parallel to this surface, as can be seen from 9 The depressions 1 are circular on the surface and widen conically in the depth direction. The depressions 1 therefore have an undercut compared to the surface. The depressions 1 are thus designed like caverns.

The two surfaces with the recesses are connected to each other by two slotted walls 3, which creates a channel for wave guidance. The walls have slots, which is where the term slotted waveguide comes from.

The printed surface does not represent a sharp boundary between dielectric, e.g. air and metal, but can be described as a gradual transition for the penetrating electromagnetic field.

This material transition corresponds to the cumulative frequency function of the surface profile, as can be seen from 10 emerges.

In the diagram on 10 The abscissa shows the depth of the depressions in nm and the ordinate shows the normalized conductivity, the magnetic field and the power loss density. The solid curves are the respective measurement curves without depressions and the dashed lines are the respective measurement curves with depressions. Curves 100 represent the conductivity, curves 200 the magnetic field and curves 300 the power loss density.

The creation of mechanical roughness by introducing caverns of any shape mainly leads to a change in this function in the area after the middle surface (depth > 0). Due to the low penetration depth of the electromagnetic field, the area in front of the middle surface is essentially relevant for the transmission behavior. In this case, the mechanical roughness created in this way only results in a minimal influence on the electromagnetic field and almost unchanged power loss density, which consequently does not lead to any deterioration in the transmission properties in the application.

The anchoring elements can have dimensions of less than 10 nm or less than 1 µm to about 2-3 µm, in particular less than 10 µm.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 102021128881 A1 [0070]

Cited non-patent literature

• EN ISO 20502:2016-11 [0017]
• EN ISO 26443:2016-09 [0017]
• EN ISO 2409:2020-12 [0017]
• EN ISO 16276-2:2007-08 [0017]
• EN ISO 4624 [0017]

Claims (20)

Method for producing a high-frequency functional structure with the steps: providing a base body of the high-frequency functional structure, wherein the base body is produced by an additive process; applying at least one electrically conductive layer to a surface of the base body, characterized in that the surface of the base body has one or more anchoring elements in regions or completely, which are designed and arranged to improve the adhesion of the electrically conductive layer to the surface compared to an adhesion of the electrically conductive layer to a surface without anchoring elements. Procedure according to Claim 1 , characterized in that the anchoring element(s) comprise or are depressions penetrating into the surface and/or elevations protruding from the surface and/or have undercuts and/or are produced by the roughness of the surface. Procedure according to Claim 1 or 2 , characterized in that a plurality of anchoring elements are arranged evenly or unevenly distributed on the surface, wherein the anchoring elements have the same shape or at least one anchoring element has a different shape. Method according to one of the preceding claims, characterized in that the anchoring elements are produced by a 3D printer. Method according to one of the preceding claims, characterized in that the surface density of the anchoring elements on at least one region of the surface is greater than one anchoring element per square centimeter, preferably more than one anchoring element per square millimeter and/or wherein the surface density is preferably a maximum of 100,000, preferably 40,000, in particular 10,000 anchoring elements per square millimeter. Method according to one of the preceding claims, characterized in that the anchoring elements are produced during the manufacture of the base body or are attached to or introduced into the base body after manufacture. Method according to one of the preceding claims, characterized in that the electrically conductive layer is applied by means of a preferably electroless, wet-chemical process, preferably by wetting a part or the entire surface of the base body with a dispersion containing microparticles and/or nanoparticles, wherein the microparticles and/or nanoparticles preferably contain nickel, copper, silver, gold, zinc, tin, chromium, palladium and/or platinum. Method according to one of the preceding claims, characterized in that the electrically conductive layer is applied by means of one of the following methods: PVD, CVD, sputtering, inkjet, aerosoljet, nanojet, roll-to-roll printing, screen printing, physical application by means of inks or pastes or varnishes, chemical methods by means of wet chemical deposition or galvanic deposition. Method according to one of the preceding claims, characterized in that the method comprises the further step: applying at least one further electrically conductive layer to the base body by means of a galvanic or wet-chemical process. Method according to one of the preceding claims, characterized in that the layer or layers, after application of the layer or layers, cover the anchoring elements in such a way that the layer has a preferably functional, smooth, flat and/or continuous surface, wherein the anchoring elements are preferably visible, partially visible or invisible. Method according to one of the preceding claims, characterized in that the anchoring elements are arranged only on surfaces of the base body which do not have a high-frequency technical function or only or also on surfaces of the base body which have a high-frequency technical function, in particular on the inner sides of a, preferably slotted, waveguide or on the radiating surfaces of an antenna. Method according to one of the preceding claims, characterized in that the functional structure is designed to conduct an electromagnetic wave, wherein the anchoring elements each have an extension, preferably in the direction of propagation of the electromagnetic wave, which is less than the whole, preferably less than half, preferably less than a quarter, of the wavelength of the electromagnetic wave. Method according to one of the preceding claims, characterized in that preparation surface of the outermost layer must be smoothed, in particular by means of galvanic smoothing or smoothing of the base body before application of the layer. Method according to one of the preceding claims, characterized in that the additive method comprises SLS, SLA, DLP, multijet, 2-photon printing, aerosol jet, inkjet, nanojet, FDM, SLM and/or EBM. Method according to one of the preceding claims, characterized in that the base body consists at least partially or completely of ceramic, plastic, in particular a photopolymer, or metal and/or that the base body is a hollow body, wherein the inside of the hollow body is coated with the electrically conductive layer and/or that the base body is or was produced in one piece or in multiple parts. Method according to one of the preceding claims, characterized in that the functional structure is or comprises a high-frequency line, in particular a preferably slotted waveguide, or an antenna, in particular a horn or helix antenna, or a filter or a resonator or a coupler or another passive RF part or component of a solar system, a solar cell, a touchscreen, a smart glass, a wearable or an LED or a molded interconnect device (MID) or mechatronic integrated device (MID). High-frequency functional structure which was partially or completely produced by means of a method according to one of the preceding claims, with at least one electrically conductive layer on a surface provided with anchoring elements of a base body produced by an additive process. High frequency technical functional structure according to Claim 17 , characterized in that the anchoring element(s) comprise or are depressions penetrating into the surface and/or elevations protruding from the surface and/or have undercuts and/or are produced by the roughness of the surface. High frequency technical functional structure according to Claim 17 or 18 , characterized in that the layer or layers cover the anchoring elements in such a way that the layer has a, preferably functional, smooth, flat and/or continuous surface, wherein the anchoring elements are preferably visible, partially visible or invisible. High frequency functional structure according to one of the Claims 17 until 19 , characterized in that the anchoring elements are arranged only on surfaces of the base body which do not have a high-frequency technical function or only or also on surfaces of the base body which have a high-frequency technical function, in particular on the inner sides of a, preferably slotted, waveguide or on the radiating surfaces of an antenna.