Method for producing a functional structure, and functional structure

Abstract

The invention relates to a method for producing a functional structure, having the steps of: providing a main part of the functional structure; and applying at least one metal layer onto a surface of the main part, wherein the surface of the main part has one or more anchoring elements at least in some regions which are designed and arranged so as to improve the adhesion of the metal layer to the surface in comparison to an adhesion of the metal layer to a surface without anchoring elements.

Description

[0001] Method for producing a functional structure and functional structure

[0002] The present invention relates to a method for producing a functional structure comprising the steps:

[0003] Providing a basic body of the functional structure;

[0004] Applying at least one metallic layer to a surface of the base body.

[0005] One such functional structure is, for example, a waveguide for guiding electromagnetic waves. Electromagnetic waves, especially 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 for guiding the electromagnetic waves or high-frequency signals within it or for manipulating them in space or the frequency domain.

[0006] In the manufacture of high-frequency components, the component is assembled from two halves, particularly to create cavities. The resulting cavities, milled into a metal base body, for example, provide the actual functionality of the high-frequency assembly. These can be waveguides, so-called hollow conductors, but also filters, resonators, couplers, or antennas.

[0007] Such high-frequency components can be manufactured from plastic base bodies. For their subsequent functionality, they must be coated with a conductive layer. The state of the art is electroplating or electroless plating with metals. This is also used, for example, in decorative coating (Plating on Plastics (PoP)), where various layer systems, such as Cu, Ni, Cr, Au, Ag, etc., and combinations and / or sequences of these elements, are used.

[0008] The electrical conductivity and quality of the component surface, which interacts with the electromagnetic wave, are essential; in particular, the inner wall forming the cavity must be electrically conductive. Manufacturing components from metal or an electrically conductive base material is not only costly but also complex, particularly necessitating costly CNC milling processes. Against this background, the prior art has already pursued the approach of manufacturing such components from plastic instead and making them conductive only in one or more subsequent steps. Known process proposals for this include chemical processes such as galvanic or electroless plating of the base body surface with metals.

[0009] 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. Metallic layers generally exhibit poor adhesion to photopolymers. This also applies to other plastics, particularly 3D-printable or 3D-printed plastics that have a low surface roughness, for example, with R q If the thickness of the deposited metal layer is < 20 pm, the adhesion of the deposited metal layer may be insufficient. Therefore, according to the state of the art, photopolymer bodies are subjected to a complex sulfonation process of the surface to be metallized in order to achieve better adhesion of the metallic layer to the surface.

[0010] Coating processes using hexavalent chromium are also known. However, due to the harmfulness of hexavalent chromium, these coating processes are subject to severe legal restrictions or prohibitions.

[0011] In addition, pickling with hexavalent chromium, for example using chromic sulfuric acid, results in a significant increase in surface roughness, which is ultimately at least one of the mechanisms that promote adhesion.

[0012] With regard to the previously known processes, there is a desire for further simplification of the coating process in order to improve, in particular, the adhesion strength.

[0013] Against this background, the present invention is based on the object of providing such an improved method.

[0014] 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.

[0015] Accordingly, the invention provides that the surface of the base body has at least in some regions one or more anchoring elements which are designed and arranged to improve the adhesion of the metallic layer to the surface compared to an adhesion of the metallic layer to a surface without anchoring elements.

[0016] The metallic layer can also be electrically conductive. A particularly preferred embodiment of the method is one in which the base body is monolithic, i.e., manufactured in one piece and consists of only one material, preferably by an additive process. The metallic layer is applied wet-chemically, and a further metallic layer is applied by a galvanic process. 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.

[0017] However, the functional structure may also be a component composed of several parts, one or more of which were manufactured by a method according to the invention.

[0018] For example, the adhesion, in particular the adhesion strength of the coating to the substrate, can be tested or estimated by a scratch test according to DIN EN ISO 20502:2016-11, by a Rockwell penetrant test according to DIN EN ISO 26443:2016-09 or according to VDI 3824-4, by a cross-cut test according to DIN EN ISO 2409:2020-12, by a cross-cut test and / or cross-cut test according to DIN EN ISO 16276-2:2007-08, by a tear-off test according to DIN EN ISO 4624, or by a similar test method. The test can also be performed by applying a fabric adhesive tape and tearing it off, whereby the tear-off force is felt or measured.

[0019] 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 enlarge the surface to 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.

[0020] It is preferably 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 produced by the roughness of the surface.

[0021] The surface preferably has flat areas and areas provided with anchoring elements. An undercut of an anchoring element, which is particularly designed as a recess, preferably means that a line extending from the undercut and perpendicular to the flat area penetrates the base body. The undercut thus forms a kind of barb, through which the layer is positively connected to the base body.

[0022] The anchoring elements can have any shape. For example, the anchoring elements can be arranged in a marbled pattern.

[0023] The depressions and / or elevations may have the shape of hills, spikes or the like.

[0024] A conceivable geometry for an anchoring element with an undercut is, for example, a recess that has a conical cross-section, wherein the recess is widened in the depth direction.

[0025] Other conceivable geometries for an anchoring element include cylinders, triangles, tetrahedrons, blocks, trapezoidal blocks, spheres or spherical shapes, as well as any desired free form. It is also conceivable that the geometry of the anchoring elements may change from the target geometry during production. This can result in 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.

[0026] 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 LambdaJD = c_O / 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 angle of the waveguide. Beta = 2*pi*f / (c0*sqrt(epsr) ) sqrt( 1 -(f_c / f) 2 ) with f_c=c0 / (2*w) with w=width of the waveguide.

[0027] The anchoring elements each have an extension, preferably in the propagation direction 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.

[0028] On non-HF relevant surfaces, it is conceivable to significantly increase the spatial dimensions of the anchoring elements.

[0029] 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.

[0030] It is conceivable that the anchoring elements could be produced using a 3D printer. In other words, the anchoring elements can have a different areal density, i.e., the number of anchoring elements per unit area, on the surface.

[0031] The areal density can be varied depending on the desired frequency range of an electromagnetic wave transmitted through the functional structure. The higher the application frequency, the higher the areal density can be and the smaller the extension of these anchoring elements toward the surface can be.

[0032] An areal 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 wherein the areal density is preferably a maximum of 100,000, preferably 40,000, in particular 10,000 anchoring elements per square millimeter.

[0033] The areal density can also be less than 100 or less than 10 anchoring elements per square millimetre.

[0034] 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.

[0035] 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.

[0036] This preferably enables fundamental manufacturability that is largely independent of the orientation in the 3D printing build space, while still allowing the surface quality to vary without supporting the individual anchoring elements. Furthermore, the outermost areas of the surface that determine the function of the RF component preferably remain of high quality, as the roughness there is not unnecessarily increased, for example, by aggressive chemical etching.

[0037] It is conceivable that the metallic layer is applied to the surface having at least one anchoring element using a variety of methods, such as PVD, CVD, sputtering, inkjet, aerosol jet, nanojet, roll-to-roll printing, screen printing, physical application using inks or pastes or lacquers, chemical processes using wet chemical deposition or galvanic deposition.

[0038] In particular, electroless and galvanic deposition of metal layers are advantageous.

[0039] It is conceivable to arrange the anchoring elements on any 3D-printed surface in order to increase the adhesion strength of a metal layer deposited thereon.

[0040] Preferably, however, the base bodies are RF components, especially RF components designed based on slotted waveguide technology. A slotted waveguide is preferably a waveguide with openings 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.

[0041] In an advantageous embodiment, it is provided that the metallic layer is applied by means of a preferably electroless, wet-chemical process, preferably by wetting part or the entire surface of the base body with a dispersion containing microparticles and / or nanoparticles, wherein the microparticles and / or nanoparticles preferably comprise nickel, copper, silver, gold, zinc, tin, chromium, palladium and / or platinum.

[0042] Preferably, the metallic layer is applied by one of the following methods: PVD, CVD, sputtering, inkjet, aerosol jet, nanojet, roll-to-roll printing, screen printing, physical application by means of inks or pastes or lacquers, chemical methods by means of wet chemical deposition or galvanic deposition.

[0043] Particles with an average particle size D50 of less than 1 pm can be referred to as nanoparticles, and particles with an average particle size D50 greater than or equal to 1 pm 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 pm to 100 pm, preferably 1 pm to 5 or 10 pm. The particle size preferably refers to the equivalent diameter of the respective particles.

[0044] The electrically conductive layer is preferably a layer containing metal. The electrically conductive layer may also be electrically non-conductive after application and / or become electrically conductive after application.

[0045] The basic body can determine the shape of the functional structure.

[0046] The particles preferably consist of one or more metals or comprise one or more metals.

[0047] The particles may be plastic-coated.

[0048] For the purposes of this invention, "electrical" is the generic term for electrical and / or electronic. Preferably, when manufacturing 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 used to manufacture the base body is preferably electrically non-conductive; however, for the purposes of the method, an electrically conductive or semiconductive material could equally well be used to manufacture the base body.

[0049] The metallic 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; an organic release agent can also be provided. Alternatively or additionally, a solvent can be added. Conceivable 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 canThe ink material must be matched to the smallest openings in the base body structure so that wetting by the dispersion is ensured.

[0050] After evaporation / evaporation of the solvent / water, the surface of the base body is wetted with the ink material, and optional post-treatment, preferably sintering, forms a conductive coating. The new process thus represents an alternative to chemical, electroless plating. The base body is preferably functionalized, i.e., transformed 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 introduced into 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 coating dispersion that physically wets the base body and, through post-treatment, forms a conductive coating.

[0051] Compared to the chemical coating process, the process according to the invention can achieve a smoother surface structure of the coated base body, which offers decisive advantages, especially for components used in high-frequency technology. The smoother the surface of the component, the better the component's subsequent electrical performance. The chemical process of existing methods often leads to adverse roughening of the body surface due to the required pretreatment.

[0052] The method according to the invention can be advantageously used, for example, for the production of electrical components, where 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 they are necessary for the mechanical or electrical function or only slightly restrict it.

[0053] Application and wetting is preferably carried out by completely immersing the base body in an immersion bath containing the corresponding dispersion. In principle, a single immersion of the base body is sufficient. Better distribution of the dispersion around or through the base body, particularly in an optionally present 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 briefly shaken 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.

[0054] It is conceivable that the metallic layer is applied using an aerosol or nanojet.

[0055] It is also conceivable that the dispersion is applied by flushing.

[0056] 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 substrate surface or the adhering micro- or nanoparticles. Suitable methods for this include drying, preferably in a circulating air system, sintering in an oven, UV treatment, the addition of hot air, or infrared irradiation. Thermal post-treatment can have a positive effect on the electrical conductivity of the applied coating. For example, the subsequent sintering of the micro- or nanoparticles, e.g., in a thermal oven, achieves a high level of conductivity in the resulting surface coating. The sintering temperature of the ink material is matched to the glass transition temperature of the plastic used to prevent damage.

[0057] It may be provided that no thermal post-treatment, in particular no drying, of the base body takes place.

[0058] It may 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.

[0059] During the coating process, particularly when introduced into a corresponding immersion bath, it is crucial that the corresponding dispersion can reach all of 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 slightly restricts this function. This means that certain walls of the base body can be constructed only there from the outset or they can be subsequently provided with recesses. This simplifies the penetration of the dispersion into a cavity. Furthermore, the viscosity of the dispersion or ink material used should be matched to the smallest openings present in the base body structure to ensure circulation.

[0060] In rectangular hollow bodies or cavities, walls can be designed with interrupted openings similar to the side walls of a substrate-integrated waveguide (SIW), which is known in the prior art, since these openings do not impair the high-frequency or electrical function, which is also known in the prior 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.

[0061] In a further advantageous embodiment, it is provided that the metallic 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.

[0062] Furthermore, in an advantageous embodiment, it is provided that the electrolessly applied metallic layer on a surface having at least one anchoring element is subsequently 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 metallic layer on a surface having at least one anchoring element is subsequently extended with at least one further metallic layer by 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.

[0063] A further advantageous embodiment of the method provides for the galvanic deposition of one or more metallic layers to be carried out in such a way that effective smoothing of the outermost surfaces is achieved, as described in DE 10 2021 128 881 A1. This reduces losses for electromagnetic waves.

[0064] As already mentioned above, the base body can be made of an electrically non-conductive material. Ceramic or plastic have proven particularly suitable for this purpose. 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, the inside of which is coated with the metallic layer.

[0065] Preferably, the method comprises the further step of applying at least one further metallic layer to the base body by means of a galvanic or wet-chemical process.

[0066] Applying another metallic layer once or several times preferably leads to a functional smoothing of the surface of the layer.

[0067] A functionally smooth surface is preferably understood to mean that the layer is designed in such a way that its function is not impaired. If the function of the layer is to conduct electromagnetic waves, a functionally smooth surface of a layer for the waveguiding function is designed in such a way that the waveguiding function is not affected by the anchoring elements.

[0068] The anchoring elements or microstructure can therefore be visually visible even on a surface that is functionally smooth for waveguiding. The surface provided with anchoring elements can be referred to as a microstructure.

[0069] 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.

[0070] 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 coherent surface, wherein the anchoring elements are preferably visible, partially visible or invisible.

[0071] The anchoring elements may still be partially recognizable in their shape.

[0072] For example, a recess used as an anchoring element can 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, thus making it invisible.

[0073] A recess serving as an anchoring element can, for example, be covered by a layer deposited on it, filling the recess, perhaps in the manner of a seal. However, an overgrowing layer can also be deposited, leaving a hollow space. Another advantageous embodiment of the method provides for anchoring elements protruding above the surface, such as small towers, which are covered by the metallic layer in such a way that they disappear beneath the layer.

[0074] A continuous surface ensures manufacturability even on overhanging areas, and the surface preferably retains 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.

[0075] It is conceivable that the anchoring elements are only arranged on surfaces of the base body that have a function.

[0076] It is also conceivable that the anchoring elements are arranged only on surfaces of the base body that have no function or only or also on surfaces of the base body that have a function, in particular on the inner sides of a preferably slotted waveguide or on the radiating surfaces of an antenna.

[0077] In a further advantageous embodiment of the method, the anchoring elements are distributed and shaped according to the functions of the surface. This means that surfaces that do not have high-frequency (HF) functionality can have anchoring elements in a significantly more pronounced form, for example, in the form of large and / or deep cavities. On surfaces that have HF functionality, anchoring elements adapted to the frequency and application, for example, with a smaller spatial extent, can be introduced. However, it is also conceivable for surfaces with HF functionality to be 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.

[0078] The size of the anchoring elements, preferably in the direction of surface extension, can be determined not only by wavelength but also by areal density. It is conceivable that at least one anchoring element is placed per square centimeter. Areal densities of at least one anchoring element per square millimeter are particularly advantageous.

[0079] It is conceivable that areas of the outermost layer are smoothed, in particular by means of galvanic smoothing or smoothing of the base body before the application of the layer.

[0080] It is conceivable that the base body is manufactured by an additive process, whereby additive processes include SLS, SLA, DLP, multijet, 2-photon printing, aerosol jet, inkjet, nanojet, FDM, SLM and / or EBM.

[0081] Preferably, the base body is made at least partially or entirely of ceramic, plastic, in particular a photopolymer, or metal, and / or the base body is a hollow body, the inside of which is coated with the metallic layer, and / or the base body is formed or produced in one piece or in multiple parts. The base body can also be made partially or entirely of a material suitable for selective laser sintering.

[0082] 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.

[0083] The anchoring elements are preferably created during the production of the base body and not separately attached to or incorporated into the base body. This is particularly conceivable when the base body is manufactured using an additive process. However, it is also conceivable to attach or incorporate the anchoring elements separately from the production of the base body. It is also conceivable for the anchoring elements to be prepared using 3D printing and then formed in a subsequent process step.

[0084] It is preferably provided that the functional structure is or comprises an electrical or high-frequency functional structure, a high-frequency line, in particular a preferably slotted waveguide, or an antenna, in particular a horn or helical 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) or a decorative structure.

[0085] The invention also relates to a high-frequency functional structure which has been produced partially or completely by means of a method according to the invention, with at least one metallic layer on a surface of a base body provided with anchoring elements.

[0086] 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.

[0087] 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.

[0088] It is conceivable that the anchoring elements are arranged only on surfaces of the base body that have no function or only or also on surfaces of the base body that have a function, in particular on the inner sides of a preferably slotted waveguide or on the radiating surfaces of an antenna.

[0089] The features described herein are, mutatis mutandis, preferably features of both the product and the method. In other words, the features of any of claims 1 to 17 can also be the subject of the functional structure according to any of claims 18 to 20.

[0090] It should be noted here that the terms "a" and "an" do not necessarily refer to exactly one of the elements, although this represents 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 encompasses 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.

[0091] 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. Herein:

[0092] Fig. 1: a perspective view of an embodiment of a functional structure according to the invention. Fig. 2: a perspective view of a surface of an embodiment of a functional structure according to the invention.

[0093] Fig. 3: a perspective view of a surface of an embodiment of a functional structure according to the invention.

[0094] Fig. 4: a perspective view of a surface of an embodiment of a functional structure according to the invention.

[0095] Fig. 5: a sectional view of an embodiment of a functional structure according to the invention.

[0096] Fig. 6: a perspective view of another embodiment of a functional structure according to the invention.

[0097] Fig. 7: a perspective view of another embodiment of a functional structure according to the invention.

[0098] Fig. 8: a perspective view of another embodiment of a functional structure according to the invention.

[0099] Fig. 9: a sectional view of another embodiment of a functional structure according to the invention.

[0100] Fig. 10: a diagram for the transmission behavior of a functional structure according to the invention.

[0101] Fig. 1 shows an exemplary base body 10 of a high-frequency functional structure according to the invention.

[0102] The base body W shown in Fig. 1 is a test body for measuring the adhesion of an electrically conductive layer to the base body W 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.

[0103] 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.

[0104] Figs. 2 to 4 show increasingly enlarged sections of the surface of the base body 10. The largest magnification of the surface of the base body 10 is shown in Fig. 4.

[0105] From Fig. 4, for example, 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 shape 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 desired shape.

[0106] Fig. 5 shows the cross-section of the depressions 1. The depressions 1 are circular on the surface and widen conically towards the depth. Thus, the depressions 1 have an undercut relative to the surface. The depressions 1 are thus cavern-like in shape.

[0107] Fig. 6 shows a base body 10 for a slotted waveguide or hollow conductor for conducting electromagnetic waves. The base body has two flanges and a channel for wave conduction. Figs. 7 and 8 show increasingly enlarged sections of the base body 10. The largest magnification of the surface of the base body 10 is shown in Fig. 8.

[0108] Recesses 1 are arranged on a surface of the base body 10, as can be seen particularly well in Fig. 8.

[0109] Likewise, depressions 1 are arranged on a surface parallel to this surface, as shown in Fig. 9. The depressions 1 are circular on the surface and widen conically in the depth direction. Thus, the depressions 1 have an undercut relative to the surface. The depressions 1 are thus cavern-like in design.

[0110] The two surfaces with the recesses are connected by two slotted walls 3, creating a channel for waveguiding. The walls have slots, hence the name "slotted waveguide."

[0111] 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.

[0112] This material transition corresponds to the cumulative frequency function of the surface profile, as shown in Fig. 10.

[0113] In the diagram in Fig. 10, the depth of the depressions in nm is plotted on the abscissa, and the normalized conductivity, magnetic field, and power loss density are plotted on the ordinate. 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 cavities of any shape primarily leads to a change in this function in the region after the middle surface (depth > 0). Due to the shallow penetration depth of the electromagnetic field, the region in front of the middle surface is essentially relevant for the transmission behavior.In this case, the mechanical roughness thus generated results in only a minimal influence on the electromagnetic field and almost unchanged power loss density, which consequently does not lead to any deterioration of the transmission properties in the application.

[0114] The anchoring elements can have dimensions of less than 10 nm or less than 1 pm to about 2-3 pm, in particular less than 10 pm.

Claims

Patent claims Method for producing a functional structure with the steps: providing a basic body of the functional structure; Applying at least one metallic layer to a surface of the base body, characterized in that the surface of the base body has, at least in some regions, one or more anchoring elements which are designed and arranged to improve the adhesion of the metallic layer to the surface compared to adhesion of the metallic layer to a surface without anchoring elements. Method 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 generated by the roughness of the surface. Method 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 areal 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, wherein the areal 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 production of the base body or are attached to or incorporated into the base body after production. Method according to one of the preceding claims, characterized in that the metallic layer is applied by means of a preferably electroless, wet-chemical process, preferably by wetting the surface or the base body with a dispersion containing microparticles and / or nanoparticles, wherein the microparticles and / or nanoparticles preferably comprise nickel, copper, silver, gold, zinc, tin, chromium, palladium, and / or platinum. Method according to one of the preceding claims, characterized in that the metallic layer is applied using one of the following methods: PVD, CVD, sputtering, inkjet, aerosol jet, nanojet, roll-to-roll printing, screen printing, physical application using inks or pastes or lacquers, chemical methods using wet chemical deposition or electroplating. Method according to one of the preceding claims, characterized in that the method comprises the further step: Applying at least one further metallic 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 that have no function or only or also on surfaces of the base body that have a 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 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. Method according to one of the preceding claims, characterized in that regions of the outermost layer are 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 base body is produced by an additive process, wherein the additive process 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 metallic layer and / or that the base body is formed 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 an electrical or high-frequency functional structure, a high-frequency line, in particular a preferably slotted waveguide, or an antenna, in particular a homing or helical 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, smart glass, a wearable or an LED or a molded interconnect device (MID) or mechatronic integrated device (MID) or a decorative structure. Functional structure that was partially or completely produced by means of a method according to one of the preceding claims, with at least one metallic layer on a surface of a base body provided with anchoring elements. Functional structure according to claim 17, characterized in that the anchoring element(s) comprise or are depressions penetrating the surface and / or elevations protruding from the surface and / or have undercuts and / or are generated by the roughness of the surface. Functional structure according to claim 17 or 18, characterized in that the layer or layers cover the anchoring elements such that the layer has a preferably functionally smooth, flat and / or continuous surface, wherein the anchoring elements are preferably visible, partially visible, or invisible.Functional structure according to one of claims 17 to 19, characterized in that the anchoring elements are arranged only on surfaces of the base body which have no function or only or also on surfaces of the base body which have a function, in particular on the inner sides of a, preferably slotted, waveguide or on the radiating surfaces of an antenna.

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