Method for the deposition of metallic materials on ceramic or mineral substrates with a coating device

Abstract

The present invention relates to a method for depositing a metallic material 14 on a ceramic or mineral substrate 6 with an application device 1. From an energy source 2 arranged in the application device 1, a high-energy beam is directed toward the surface 5 of the ceramic or mineral substrate 6. Using the application device 1, the metallic material 14 is applied to an area of ​​the surface 5 of the ceramic or mineral substrate 6. The metallic material 14 is melted at least in parts by the high-energy beam, so that after solidification of the metallic material 14, the metallic material 14 is deposited on the surface 5 of the ceramic or mineral substrate 6 as a material application. The high-energy beam impinging on the surface 5 of the ceramic or mineral substrate 6 defines a working area 7, the position of which on the surface 5 can be changed by relative movement of the surface 5 of the ceramic or mineral substrate 6 and a laser device 3. In the working area 7 on the surface 5 of the ceramic or mineral substrate 6, a depression 13 is formed, and material application is performed in the depression 13.

Description

[Technical Field]

[0001] The present invention relates to a method for the deposition of metallic materials on ceramic or mineral substrates by means of a coating device, a high energy beam is directed from an energy source disposed in the coating device onto a surface of the ceramic or mineral substrate; a coating device is used to coat a metallic material onto a surface area of ​​a ceramic or mineral substrate; The metallic material is melted at least in parts by a high-energy beam; Thus, after solidification of the metallic material, the metallic material is deposited on the surface of the ceramic or mineral substrate as a material coating, a high energy beam impinging on a surface of a ceramic or mineral substrate, defining a working region; The position of the working area on the surface can be varied by relative movement of the ceramic or mineral substrate surface and the energy source. [Background technology]

[0002] Laser cladding is an established method for the deposition or application of metallic materials onto the surface of a metal substrate and for the processing of workpieces. In conventional methods, a coating device with a laser device is used for this purpose, in which the surface of the metal substrate is melted locally at the point of impact by a laser beam emitted from the laser device and directed onto this surface. The resulting localized melt is then supplied with particulate metal material, which is transported using an inert carrier gas. The metal powder thus supplied to the localized melt is then melted by a laser beam or by the heat of the existing melt on the substrate. After solidification of the molten metal material, a material-integral bond is formed between the metal material and the metal substrate. This process can be repeated at different locations on the metal substrate or even performed over interlocking areas of the surface by relative movement of the metal substrate and / or the application device.

[0003] This conventional method, however, has drawbacks when applying metallic materials onto non-metallic substrates, such as ceramic or mineral substrates. Due to the different chemical and physical properties inherent in the material classes, it is challenging to produce bonds between, for example, metals and ceramics using a laser beam. The generally high melting point of ceramics, which can be well between 2000 and 3000°C, makes melting time-consuming, especially since the required temperatures partially exceed the boiling point of the metal materials used. Consequently, evaporation of the applied metal material makes any material application impossible. Furthermore, ceramic and metallic materials have different expansion coefficients, which range from 4 to 13×10 for ceramics. ―6 K -1 For metallic materials, 1 10 ―6 K -1 and 30 x 10 ―6 K -1 Between. This results in problems of crack and fracture formation within the ceramic substrate due to the tendency of ceramics to fracture brittle during heating, especially during rapid heating and cooling processes such as those present when using a laser beam. As a result of the large and rapid heat generation and the low thermal conductivity of ceramics, stresses are generated within the ceramic. Unlike metallic materials, ceramics have only very little deformability, even at higher temperatures, so it is difficult to relieve these thermal stresses. If these stresses exceed the material's hardness, they can cause fracture. These effects can then lead to the structural component's failure, which is irreparable. A further problem is the poor wetting of ceramics with molten metals due to the so-called "balling effect".

[0004] Various methods are known from the prior art to be able to overcome the problems mentioned above. On the one hand, application by physical vapor deposition (PVD) is the most commonly used method, in which an active metal, such as a metal alloy or a pure metal, is converted into the gas phase and subsequently deposited on the ceramic surface as an adhesion agent, thus producing a thin metal layer. The actual metal material is then applied to this thin metal layer, which acts as an adhesion promoter, a process that is laborious and carried out under vacuum or protective gas conditions. Furthermore, to ensure proper bonding to the ceramic substrate, the surface of the ceramic substrate must be painstakingly cleaned prior to application. Metallization by physical vapor deposition (PVD) is subject to other limiting factors in addition to surface cleaning. For example, the size of the substrate to be coated also depends on the size of the process chamber used.

[0005] Likewise, so-called aerosol jet printing (AJP) is known. In this case, the application of the metal material is carried out as an aerosol. For this purpose, the aerosol is generated in an ultrasonic or pneumatic atomizer and, together with a carrier gas, is applied to the substrate at high pressure.

[0006] In this case, it is simply a drawback that coatings can only be applied in the micrometer range and conventionally no coating thicknesses can be produced in the millimeter range. Summary of the Invention [Problem to be solved by the invention]

[0007] It is an object of the present invention to provide an alternative to the methods known from the prior art, which alternative can offer clear economic and technical advantages. [Means for solving the problem]

[0008] This object is achieved in that depressions are formed in the working area on the surface of the ceramic or mineral substrate, and the material application is then carried out into the depressions. [Effects of the Invention]

[0009] By applying the metallic material into the recesses, reliable adhesion of the metallic material to the ceramic or mineral substrate can be achieved. Advantageously, the method according to the invention allows for geometric freedom, which also allows for coating of three-dimensional geometries, and in addition, individual isolated areas can be selectively coated without the need for masking or other preparatory work, as is known in prior art methods. This method also makes it possible to produce strongly adhering, electrically conductive metal coatings on ceramic or mineral substrates without additional fluxes and with high application rates. In contrast to methods such as PVD, no process chamber that can be filled or evacuated with protective gas is required. The fields of use can be, for example, implants in medical technology, and components in the automotive sector, as well as in spaceflight and aviation. Furthermore, circuit boards for high-performance LED arrangements can also be realized. This method can also be used in the production and development of energy storage devices.

[0010] The recesses can be made, for example, by abrading substrate material from the surface of the substrate. The depression is advantageously an area of ​​the substrate, the surface of which is concavely shaped and forms, for example, a longitudinally recessed passage or is configured in the shape of a spherical crown. The shaped state of the recesses can advantageously be configured completely differently, they do not necessarily have to be configured symmetrically, and they can extend across the surface in different directions and can have different cross-sectional areas. The recess can also advantageously extend all the way to the edge of the substrate, so that it extends beyond the lateral edges of the substrate.

[0011] The metal material melted by the high-energy beam can flow in liquid form into a depression in the surface of a ceramic or mineral substrate, whereupon, after solidification, the metal material is bonded by mechanical clamping in the wall and bottom regions of the depression and adheres there. This allows the adhesion of the metallic material to the ceramic or mineral substrate to be significantly improved and enhanced as opposed to the direct application of the metallic material onto a planar surface. The formed depressions 13 may likewise enable a stable and material-integral bonding of the metallic material to the ceramic or mineral substrate by diffusion processes and finally - bonding-inducing - reactions at the atomic level.

[0012] In this case, the metal material can be applied as a fine powder, as in conventional laser cladding, or the application can be carried out as a wire that is fed through an application device or as a wire that is placed in the recess and melted by the introduced energy.

[0013] By ceramic substrate is meant a substrate made of a ceramic material, which is a material synthesized at elevated temperatures from non-metallic, inorganic substances and which gives it characteristic properties such as a high melting point, low electrical conductivity, as well as brittleness. For example, oxides, nitrides or also silicates are suitable under this heading. Furthermore, in this context, glass ceramics which also have an amorphous phase as well as a polycrystalline phase are also to be understood in the broadest sense as ceramics. Furthermore, glasses may also be used.

[0014] Under mineral substrate we understand a general crystalline substrate, such as granite, of very different chemical composition, formed by geological processes.

[0015] Advantageously, it is provided in accordance with the invention that the material application is formed exclusively from metallic material. In this way, the desired material properties of the material application can be predetermined by appropriate selection of the metallic material, and the substrate is therefore not melted during heating of the metallic material, or in some cases is melted only superficially, so that no homogeneous melt is formed between the metallic material and the substrate.

[0016] In an advantageous embodiment of the invention, the energy source is a laser device emitting a laser beam, a surface is selectively ablated by a laser beam directed at the surface; It is therefore intended that depressions will be created on the surface by the abraded material. The use of a laser beam then embodies a cost-effective and efficient possibility for forming depressions in the surface of a ceramic or mineral substrate. As laser devices, in this case, laser devices with high power can be used, such as solid-state lasers, such as diode lasers or fiber lasers, but also conventional CO2 lasers. By the high power of the laser beam impinging on the surface, individual layers, or also particles, can be dissociated from the surface and selectively ablated. By ablation, depressions can be formed, and based on the specific respective power and cross-sectional area of ​​the laser beam, the desired geometric shape of the depressions can be controlled. The ablation and consequent removal of heated material from the ceramic or mineral substrate also prevents similarly thermally induced stresses that can transfer into and damage the ceramic or mineral substrate.

[0017] By relative movement of the ceramic or mineral substrate and the applicator, the indentations can be repeated at different locations on the ceramic or mineral substrate, or similarly performed over connected areas of the surface. In this way, groove- or trench-like structures, as well as different respective geometric structures, can be produced on the surface of the ceramic or mineral substrate.

[0018] In addition to using a laser device, the energy source can also be an electron source emitting an electron beam, which is particularly advantageous when the metallic material is introduced into the cavity, for example as a wire, and melted using an energy source such as an electron beam.

[0019] According to an advantageous variant of the invention, it is provided that the depressions formed into the surface of the ceramic or mineral substrate are V-shaped depressions with acute angles. Advantageously, the depression has a V-shaped geometry, so that the molten metal material can flow into this depression in a simple manner, which, after solidification, ends up flush with the surface, thus creating a triangular depression in cross section. In an alternative configuration, the metal material may form ridges on the surface, which essentially results in a "cake-shaped" cross section. Furthermore, the metal material may only partially fill the depressions after solidification.

[0020] In addition to V-shaped depressions, it is also possible for these depressions to have a configuration different from the V-shape, and in this case in particular a U-shaped configuration. Furthermore, depression configurations with rectangular, trapezoidal or other polygonal cross sections are also in accordance with the invention. The depressions then also have undercuts.

[0021] In that case, the aforementioned depression allows the molten metallic material to flow into said depression and at the same time allows an optimized wetting of the surface by the metallic material.

[0022] Advantageously, it is provided according to the invention that the metallic material introduced into the recess and melted has a contact angle θ<90°. By contact angle is meant in this case the angle that a drop of liquid on the surface of a solid material forms with this surface, which angle can then be described by Young's equation. In the case at issue here, the metallic material applied and melted onto the surface of the ceramic or mineral substrate can be considered as the liquid, and the ceramic or mineral substrate as the solid material.

[0023] The magnitude of the contact angle between a liquid and a solid material is then a function of the interaction at the interface between these liquids and solid materials, in particular between both phases. The wetting of a surface by a liquid droplet can then be explained in terms of the dependence between the cohesive forces within the droplet and the adhesive forces of the droplet to the surface. When the cohesive forces within the droplet exceed the adhesive forces between the droplet and the surface, the droplet will assume a spherical shape and contact the surface only over a small contact area.

[0024] In the case of liquid metals on ceramic or mineral substrate surfaces, the cohesive forces far outweigh the adhesive forces, and therefore, on planar surfaces, spheres are formed with a contact angle θ > 90°. It then holds true that the smaller the contact angle, the larger the contact surface.

[0025] To allow the best possible bonding and therefore the largest possible contact surface of the droplet on the ceramic or mineral substrate, the contact angle θ should advantageously be >90°.

[0026] The depressions form a geometric shape on the surface of the substrate, for example a V-shaped configuration with sharp angles, and due to the configuration of the depressions according to the invention, the contact angle of the metallic material flowing into or melted in the depressions is reduced to less than 90°, thereby optimizing the wettability of the depression surface. Accordingly, an optimal bond of the metallic material to the ceramic or mineral substrate can be achieved by artificially reducing the contact angle due to the geometric configuration of the depressions. As already mentioned, the depressions can also have other configurations different from a V-shape, as long as the selected configuration results in an appropriate angle of the opposing surfaces in the upper region of the groove.

[0027] A small contact angle and therefore a bond of as large an area as possible between the two phases remains maintained in this case even after hardening of the metal material, so that a consistent bond can be achieved as far as possible without bubbles or voids.

[0028] It is also possible, and contemplated according to the present invention, that adhesion promoters be used to improve adhesion between the applied metallic material and the ceramic or mineral substrate. The adhesion agent is, for example, a metal or metal alloy that is applied directly to the surface of the ceramic or mineral substrate, preferably selected such that its properties provide optimal bonding to the ceramic or mineral substrate, on the one hand, and to the metallic material applied to the adhesion agent, on the other hand. In this way, the bonding of the metallic material to the ceramic or mineral substrate can be improved. The application of the adhesion promoter then likewise takes place into the recesses.

[0029] To this end, the adhesion agent advantageously has a small contact angle so that optimal bonding can occur. In the case of metallic adhesion agents, furthermore, strengthening of the bond between the adhesion agent and the metal material applied thereto can be achieved by a form-fit bond in the form of a metallic bond and, in that case, in particular by the formation of an alloy at the interface of both metals.

[0030] The adhesion agent may also be adapted to facilitate the bonding process at low thermal expansion coefficients of ceramic or mineral substrates. For this purpose, ductile alloying elements may be used, which are able to compensate for thermally induced stresses due to the different thermal expansion coefficients at the boundary layer.

[0031] As an attachment agent, for example, copper or titanium can be used.

[0032] Advantageously, it is provided that the ablation of the area of ​​the surface by means of the laser beam and the application of the metallic material are carried out simultaneously. This allows the process chain for the application of the metallic material, possibly with the prior application of an adhesion promoter, to be carried out in a single process step. For this purpose, in accordance with laser cladding, a mixture of an inert carrier gas and a particulate metal material can be supplied, for example, the metal material being melted by a laser beam, which can then likewise be melted by the laser beam or by heating a ceramic or mineral substrate, and flow into the cavity before solidification.

[0033] Additionally, it is possible, and contemplated according to the present invention, for the formation of the recesses to occur in a separate step and prior to the application of the metallic material. For this purpose, on the one hand, depressions can be machined in a separate process step using a laser beam directed onto the surface, while in a subsequent second process step a metallic material is introduced into the depressions and melted. For this purpose, devices with laser equipment can be used to create the depressions, or this creation can be carried out using a coating device.

[0034] The depressions can also be produced by etching with etching compounds or by other mechanical methods.It is also possible for the ceramic or mineral substrate to already be provided with the desired depressions during production, for example by using a suitable mold for this purpose.

[0035] In an advantageous configuration of the invention, it is provided that a working area of ​​between 0.2 and 3 mm is generated by the laser beam. This allows the formation of depressions with application of metal structures within large areas. The dimensions of the recess are then essentially determined from the area of ​​the working region and, therefore, from the cross-sectional area of ​​the laser beam as well as from the power of the laser beam.

[0036] In an advantageous variant of the inventive idea, it is provided that an application device with a powder nozzle is used for generating a coaxial continuous powder gas jet. The powder nozzle then comprises a circumferentially extending annular gap, which surrounds the emitted laser beam, or Multiple injection nozzles may also be used, which include a plurality of discrete powder nozzles arranged so that the injected metal powder impinges at a common focal point.

[0037] Advantageously, it is provided according to the invention that metal oxides and / or nitrides and / or silicates are used as ceramic substrates. Advantageously, aluminum oxide Al2O3 can be used as the ceramic substrate.

[0038] Advantageously, it is optionally contemplated that copper, and / or titanium, and / or aluminum, and / or vanadium, and / or silver, and / or iron, and / or gold, and / or alloys thereof may be used as metallic materials according to the invention. Advantageously, titanium or the titanium alloy Ti-6Al-4V can be used as the metallic material.

[0039] Advantageously, in accordance with the invention, it is provided that the metal material is electrically conductive and that the material coating is electrically conductive, the electrical resistance of the material coating corresponding to the electrical resistance of the metal material. In this way, well-conducting conductor tracks can be applied onto a non-conductive substrate.

[0040] Advantageously, according to the invention, it is provided that the ceramic or mineral substrate is non-conductive. In this way, for example, circuit arrangements made of metallic material can be arranged on a substrate, said circuit arrangements being electrically insulated from one another by the substrate.

[0041] Further advantageous embodiments of the method for the deposition of metallic materials on ceramic or mineral substrates by means of a coating device are clarified with the aid of the following figures. [Brief explanation of the drawings]

[0042] [Figure 1] 1 is a diagram of a method according to the invention for depositing a metal material on a ceramic or mineral substrate in an application device, in which a laser beam is directed onto the surface of the ceramic or mineral substrate. [Figure 2] FIG. 2 is a diagram of the method of FIG. 1, in which the surface of a ceramic or mineral substrate is selectively ablated, thus creating depressions. [Figure 3] 1 is a diagram of the method in step 2, where a metal material is applied into the resulting depression. [Figure 4] FIG. 10 is a comparison of the contact angle between a droplet on a planar surface and a droplet in a depression. [Figure 5] 1 is a diagram of a circuit board with applied conductor tracks made of metallic material, produced with the method according to the invention; [Figure 6] FIG. 6 is a cross-sectional view taken along the line VI-VI in FIG. 5. DETAILED DESCRIPTION OF THE INVENTION

[0043] In Figures 1 to 3, variants of the method according to the invention for the deposition of metallic materials on ceramic or mineral substrates in an application device are diagrammatically illustrated.

[0044] FIG. 1 shows an application device 1 having an energy source 2 in the form of a laser device 3 . Using a laser device 3, a laser beam 4 is emitted onto the surface 5 of a ceramic or mineral substrate 6 in the form of a plate, whereby the laser beam 4, directed onto the surface 5, defines a working area 7 on this surface. The application device 1 further comprises a powder nozzle 8 arranged in the application device 1, by means of which a continuous powder gas jet 9 of carrier gas and dispersed metal material is directed along a powder gas path 10 onto the surface 5 of the ceramic or mineral substrate 6 in the region of the working area 7. The laser beam 4 directed against the surface 5 then heats the ceramic or mineral substrate 6 inside the area of ​​action 11 .

[0045] Due to the high power density of the laser beam 4, in the working area 7 the surface 5 of the ceramic or mineral substrate 6 is ablated and removed from the surface 5 piece by piece in this area. The removal of material 12 can prevent heat-induced crack formation that may cause failure of ceramic or mineral substrate 6. The spalling of material 12 creates depressions 13 on surface 5 of ceramic or mineral substrate 6. FIG. 2 shows the steps of the method for forming the recess 13 .

[0046] Metal material 14 introduced into cavity 13 through powder nozzle 8 is melted by the incident laser beam 4 and flows into cavity 13, where it solidifies and forms a material deposit in cavity 13. The steps of this method are illustrated in Figure 3.

[0047] In FIG. 4 the advantages of the method according to the invention are illustrated by means of a schematic perspective. On the left, a coating of molten metallic material 14 as droplets is illustrated on a planar ceramic or mineral substrate 6 . The wetting of the surface 5 by the droplet then depends on the cohesive forces within the droplet and on the adhesive forces of the droplet to the surface. If the cohesive forces within the droplet dominate the adhesive forces, as is the case with metallic material 14, the droplet will therefore take on the shape of a sphere and contact the surface only over a small contact surface 15. In this case, the contact angle θ (reference number 16)—the angle that a drop of liquid on the surface of the solid material forms with the contact surface 15—is greater than 90°.

[0048] On the other hand, due to the V-shaped geometry of the depression 13 with its acute angles, the contact angle θ (reference number 16) of the droplet in the depression 13 is always smaller than 90°, thereby achieving complete wetting of the side and bottom areas of the depression 13. The contact angle θ (reference numeral 16) of the droplet in the recess according to the invention is shown on the right in FIG.

[0049] Figure 5 shows a circuit board 17 manufactured by the method according to the invention, which has applied conductor tracks 18 made of metal material 14, whereas in Figure 6 a cross section of the circuit board 17 is shown along section line VI-VI in Figure 5. The V-shaped depressions 13 can be seen therein. [Explanation of symbols]

[0050] 1 Coating device 2. Energy Sources 3. Laser equipment 4 laser beams 5. Surfaces of ceramic or mineral substrates 6. Ceramic or mineral substrates 7 Working area 8 Powder Nozzle 9 Powder gas jet 10 Powder gas route 11 Area of ​​action 12 Material removed from the surface 13 Recess 14 Metal materials 15 Interface between metallic materials and the surface of ceramic or mineral substrates 16 Contact angle 17 Circuit Board 18 Conductor track

Claims

1. A method for depositing a metallic material (14) on a ceramic or mineral substrate (6) using a coating apparatus (1), A high-energy beam is directed from an energy source (2) located in the coating apparatus (1) towards the surface (5) of a ceramic or mineral substrate (6). Using a coating apparatus (1), a metal material (14) is coated onto a region of the surface (5) of a ceramic or mineral substrate (6). The metallic material (14) is melted by a high-energy beam, at least in parts. Therefore, after the solidification of the metal material (14), the metal material (14) is deposited on the surface (5) of the ceramic or mineral substrate (6) as a material coating. A high-energy beam impacting the surface (5) of a ceramic or mineral substrate (6) defines the work area (7), The position of the working area (7) on the surface (5) can be changed by the relative movement between the surface (5) of the ceramic or mineral substrate (6) and the energy source (2). In the above method, Within a working area (7) on the surface (5) of a ceramic or mineral substrate (6), a recess (13) is formed, and the material is applied into the recess (13). A method characterized by the following:

2. The material coating is formed exclusively from a metal material (14). The method according to feature 1.

3. The energy source (2) is a laser device (3) that emits a laser beam (4), The surface (5) is selectively abraded by the laser beam (4) directed toward this surface (5), Therefore, the scraped material (12) creates a depression (13) on the surface (5). The method according to 1 or 2, characterized by the features described above.

4. The recess (13) formed within the surface (5) of the ceramic or mineral substrate (6) is a V-shaped recess with an acute angle. The method according to 1 or 2, characterized by the features described above.

5. The metal material (14) introduced into the recess (13) and melted has a contact angle (16) θ < 90°. The method according to 1 or 2, characterized by the features described above.

6. To improve adhesion between the coated metal material (14) and the ceramic or mineral substrate (6), an adhesion mediator is used. The method according to 1 or 2, characterized by the features described above.

7. The scraping of the surface (5) area by the laser beam (4) and the application of the metal material (14) are performed simultaneously. The method according to 1 or 2, characterized by the features described above.

8. The formation of the recess (13) is carried out in a separate step, prior to the application of the metal material (14). The method according to 1 or 2, characterized by the features described above.

9. A laser beam (4) generates a working area (7) between 0.2 and 3 mm. The method according to 1 or 2, characterized by the features described above.

10. A coating apparatus (1) having a powder nozzle (8) is used for generating a coaxial continuous powder gas jet (9). The method according to 1 or 2, characterized by the features described above.

11. As the ceramic substrate (6), a metal oxide and / or nitride and / or silicate is used. The method according to 1 or 2, characterized by the features described above.

12. As the metallic material (14), copper, and / or titanium, and / or aluminum, and / or vanadium, and / or silver, and / or iron, and / or gold, and / or alloys thereof may be used. The method according to 1 or 2, characterized by the features described above.

13. The metal material (14) is conductive, the material coating is conductive, and the electrical resistance of the material coating corresponds to the electrical resistance of the metal material (14). The method according to claim 1 or 2, characterized by the above.

14. The ceramic or mineral substrate (6) is non-conductive. The method according to 1 or 2, characterized by the features described above.

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