Method for depositing a metal material on a ceramic or mineral substrate using an application device

Abstract

The invention relates to a method for depositing a metal material (14) on a ceramic or mineral substrate (6) using an application device (1). A high-energy beam from an energy source (2) arranged on the application device (1) is directed onto a surface (5) of the ceramic or mineral substrate (6). With the aid of the application device (1), the metal material (14) is applied to a region of the surface (5) of the ceramic or mineral substrate (6). The metal material (14) is melted, at least in portions, by the high-energy beam, and therefore, after the metal material (14) has solidified, the metal material (14) is deposited in the form of a material application on the surface (5) of the ceramic or mineral substrate (6). The high-energy beam impinging on the surface (5) of the ceramic or mineral substrate (6) defines a working region (7), and the position of the working region (7) on the surface (5) can be modified by a relative displacement of the surface (5) of the ceramic or mineral substrate (6) and the laser device (3). In the working region (7), an indentation (13) is made in the surface (5) of the ceramic or mineral substrate (6), and the material is applied into the indentation (13).

Description

[0001] Method for depositing a metallic material on a ceramic or mineral substrate using an application device

[0002] The invention relates to a method for depositing a metallic material on a ceramic or mineral substrate using an application device, wherein a high-energy beam is directed onto a surface of the ceramic or mineral substrate from an energy source arranged on the application device, wherein the metallic material is applied to a region of the surface of the ceramic or mineral substrate with the aid of the application device, wherein the metallic material is at least partially melted with the high-energy beam, so that after the metallic material has solidified, the metallic material is deposited as a material deposit on the surface of the ceramic or mineral substrate, wherein the high-energy beam impinging on the surface of the ceramic or mineral substrate defines a working area,wherein the position of the working area on the surface can be changed by a relative displacement of the surface of the ceramic or mineral substrate and the energy source.

[0003] Laser cladding is an established process for depositing or applying a metallic material to the surface of a metal substrate. The conventional process uses a deposition device with a laser system. The surface of the metal substrate is melted locally at the point of impact by a laser beam emitted by the laser device and directed onto the surface. A fine-grained metallic material is fed into the local melt thus created. The material is fed in by means of an inert carrier gas. The metal powder thus fed to the local melt is also melted by the laser beam or the heat of the existing melt on the substrate.After the molten metallic material solidifies, a bond is formed between the metallic material and the metal substrate. This process can be repeated at various points on the metal substrate or over a contiguous area of ​​the surface by a relative movement of the metal substrate and / or the application device.

[0004] However, this conventional process has disadvantages when applying a metallic material to a non-metallic substrate, such as a ceramic or mineral substrate. Due to the different chemical and physical properties inherent in the material classes, it is challenging to create a bond between metal and ceramic using a laser beam, for example. Due to the generally high melting points of ceramics, which can often be in the range between 2000 and 3000 °C, melting is complex, particularly since the required temperatures are sometimes above the boiling point of the metallic materials used. Thus, evaporation of the applied metallic material would make material deposition impossible. Furthermore, ceramics and metallic materials have different coefficients of expansion, which for ceramics are in the range of 4 to 13 10 -6 K -1and for metallic materials between 1 and 30 10 -6 K -1 . When heated, the ceramic's tendency to brittle fracture results in the problem of cracks and fractures forming in the ceramic substrate, particularly during rapid heating and cooling processes such as those encountered when using laser radiation. The large and rapid heat induced and the low thermal conductivity of the ceramic create stresses in the ceramic. Since ceramic has very little formability even at higher temperatures, it is difficult for it to relieve these thermal stresses, unlike metallic materials. If these stresses exceed the material hardness, they lead to fracture. These effects cause the component to fail and are irreparable. A further problem lies in the poor wettability of the ceramic with molten metals due to the so-called "balling effect".

[0005] Various processes are known from the state of the art to overcome the problems mentioned. Firstly, application via physical vapor deposition (PVD) is the most commonly used process. In this process, an active metal such as a metal alloy or a pure metal is transferred into the gas phase and then deposited on the ceramic surface as an adhesion promoter, so that a thin metal layer is created. The actual metallic material can then be applied to this thin metal layer, which acts as an adhesion promoter. This process takes place under vacuum or inert gas conditions. Furthermore, the surface of the ceramic substrate must be laboriously cleaned before application in order to enable suitable bonding to the ceramic substrate. Metallization using PVD processes 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 available process chamber.

[0006] Also known is so-called aerosol jet printing (AJP). In this process, the metallic material is applied as an aerosol. The aerosol is generated in an ultrasonic or pneumatic atomizer and applied to the substrate at high pressure together with a carrier gas. The disadvantage of this process is that only layers in the micrometer range can be applied, and layer thicknesses in the millimeter range cannot yet be achieved.

[0007] It is therefore considered to be the object of the present invention to offer an alternative to the methods known from the prior art, which can offer significant economic and technical advantages.

[0008] The object is achieved in that a depression is made in the work area on the surface of the ceramic or mineral substrate, the material being applied into the depression. By applying the metallic material to the depression, reliable adhesion of the metallic material to the ceramic or mineral substrate can be achieved. Advantageously, the method according to the invention allows geometric freedom, which also makes it possible to coat 3D geometries. Furthermore, isolated, individual areas can be selectively coated without the need for masking or other preparatory work, as is known in the prior art methods. The method also makes it possible to produce a firmly adhering, electrically conductive metal coating on ceramic or mineral substrates without additional flux and at high application rates.Unlike processes such as DVD, no process chamber that can be flooded with a protective gas or evacuated is required. Applications include implants in medical technology as well as components in the automotive and aerospace sectors. Furthermore, circuit boards for high-performance LED installations, for example, can be created. The process can also be used in the production and development of energy storage devices.

[0009] The depression can be created, for example, by removing substrate material from the surface of the substrate. The depression is advantageously a region of the substrate whose surface is concave and, for example, forms an elongated channel or is spherical cap-shaped. The shape of the depression can advantageously be very different, does not have to be symmetrical and can run in different directions over the surface and also have different cross-sectional areas. The depression can advantageously also reach to the edge of the substrate, so that the depression extends over a side edge of the substrate.

[0010] The metallic material molten by the high-energy radiation can flow in liquid form into the recess in the surface of the ceramic or mineral substrate. After solidification, it is mechanically bonded to the wall and bottom of the recess and adheres there. This significantly improves and increases the adhesion of the metallic material to the ceramic or mineral substrate, in contrast to direct application of the metallic material to a planar surface.

[0011] The introduced recess can also enable a stable material-locking connection of the metallic material to the ceramic or mineral substrate through diffusion processes and ultimately through reactions at the atomic level - which lead to bonds.

[0012] It is possible for the metallic material to be applied as a fine-grained powder in the manner of classic laser deposition welding, or the deposition can be carried out as a wire fed via the deposition device or arranged in the recess, which is melted by the introduced energy.

[0013] A ceramic substrate is understood to be a substrate made of a ceramic material. A ceramic material is a material that is synthesized from non-metallic, inorganic substances at elevated temperatures, thereby acquiring its characteristic properties such as its high melting point, low electrical conductivity, and brittleness. These include, for example, oxides, nitrides, and silicates. Furthermore, glass ceramics, which have an amorphous phase in addition to a polycrystalline phase, are also considered ceramics in the broadest sense. Glasses can also be used.

[0014] A mineral substrate is understood to be a generally crystalline substance of varying chemical composition, such as granite, formed by geological processes.

[0015] Advantageously, the invention provides that the material deposit is formed exclusively from the metallic material. In this way, the desired material properties of the material deposit can be specified by a suitable selection of the metallic material. Thus, the substrate is not melted, or at most only superficially, when the metallic material is heated, 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, the surface being selectively ablated by the laser beam directed onto the surface, so that the recess on the surface is created by the material removed. The use of a laser beam represents a cost-effective and effective way of creating the recess in the surface of the ceramic or mineral substrate. High-power laser devices such as solid-state lasers - including diodes or fiber lasers - but also classic CO2 lasers can be used as the laser device. The high power of the laser radiation striking the surface can loosen and selectively ablate individual layers or particles from the surface. The recess can be formed as a result of the ablation.Depending on the specific power and cross-section of the laser beam, the desired geometric shape of the recess can be controlled. The ablation and thus the removal of heated material from the ceramic or mineral substrate also prevents heat-induced stresses that could transfer to the ceramic or mineral substrate and damage it.

[0017] Through the relative movement of the ceramic or mineral substrate and the application device, the depression can be repeated at different locations on the ceramic or mineral substrate or even over a continuous area of ​​the surface. In this way, trench- or furrow-like structures, as well as any other geometric structure, can be created 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 beam emitting source. This can be particularly advantageous if the metallic material, for example, is introduced into the recess as a wire and melted using an energy source such as an electron beam.

[0019] According to an advantageous implementation of the inventive concept, the depression made in the surface of the ceramic or mineral substrate is a V-shaped depression with an acute angle. The depression preferably has a V-shaped geometry so that the molten metallic material can flow easily into the depression. After solidification, the metallic material can be flush with the surface, resulting in a depression with a triangular cross-section. In an alternative embodiment, the metallic material can also form a raised area on the surface, resulting in a substantially "cake-shaped" cross-section. Furthermore, the metallic material can also only partially fill the depression after solidification.

[0020] In addition to a V-shaped recess, the recess can also have configurations other than a V-shape, in particular a U-shaped configuration. Furthermore, configurations of the recess with a rectangular, trapezoidal, or other polygonal cross-section are also within the scope of the invention. The recess can also have undercuts.

[0021] The said depression enables the molten metallic material to flow into the depression and at the same time enables optimized wetting of the surface by the metallic material. Advantageously, the invention provides that the molten metallic material introduced into the depression has a contact angle 0 < 90 °. The contact angle refers to the angle that a drop of liquid on the surface of a solid makes to this surface. This angle can be described by Young's equation. In the present case, the molten metallic material applied to the surface of the ceramic or mineral substrate can be regarded as a liquid and the ceramic or mineral substrate as a solid.

[0022] The size of the contact angle between the liquid and the solid is a function, among other things, of the interaction between the two phases at their contact surface. The wetting of the surface by the liquid droplet can be described as a function of the cohesive forces within the droplet and the adhesive forces of the liquid droplet with respect to the surface. If the cohesive forces within the liquid droplet outweigh the adhesive forces between the liquid droplet and the surface, the liquid droplet will assume the shape of a sphere and only touch the surface at a small contact area.

[0023] In the case of a liquid metal on a ceramic or mineral substrate surface, cohesive forces far outweigh adhesive forces, resulting in a sphere with a contact angle 0 > 90° on a planar surface. The following applies: the smaller the contact angle, the larger the contact area. To ensure the best possible bond and thus the largest possible contact area of ​​the liquid droplet on the ceramic or mineral substrate, the contact angle should preferably be 0 > 90°.

[0024] The depression forms a geometric shape on the surface of the substrate. By designing this depression according to the invention, for example with a V-shaped design with an acute angle, the contact angle of the metallic material flowing into the depression or molten there is reduced to below 90°, thereby optimising the wettability of the surface of the depression. Thus, by artificially reducing the contact angle through the geometric design of the depression, optimal bonding of the metallic material to the ceramic or mineral substrate can be achieved. As already mentioned, the depression can also have designs other than a V-shape, as long as the selected design creates a suitable angle between the opposing surfaces in an upper region of the groove.

[0025] The small contact angle and thus the largest possible bonding of the two phases is retained even after the metallic material has hardened, whereby a continuous bond can be achieved with as few bubbles or cavities as possible.

[0026] It is also possible, and provided according to the invention, that an adhesion promoter is used to improve the adhesion between the applied metallic material and the ceramic or mineral substrate. An adhesion promoter can, for example, be a metal or a metal alloy that is applied directly to the surface of the ceramic or mineral substrate. Its properties are preferably selected such that it has an optimal bond to the ceramic or mineral substrate on the one hand and to the metallic material applied to the adhesion promoter on the other. In this way, the bond between the metallic material and the ceramic or mineral substrate can be improved. The adhesion promoter is also applied into the recess.

[0027] For this purpose, the adhesion promoter preferably has a small contact angle so that optimal bonding can be achieved. In the case of metallic adhesion promoters, the bond between the adhesion promoter and the metallic material applied to it can also be strengthened by a positive connection in the form of a metallic bond, and in particular by the formation of an alloy at the interface between the two metals.

[0028] The bonding agent can also be adapted to the low thermal expansion coefficient of the ceramic or mineral substrate to facilitate the bonding process. Ductile alloying elements can be used for this purpose, which can compensate for the thermally induced stresses due to the different thermal expansion coefficients in the interface.

[0029] Copper or titanium, for example, can be used as an adhesion promoter. It is preferably provided that the removal of an area of ​​the surface by the laser beam and the application of the metallic material are carried out at the same time. This makes it possible for the process chain for applying the metallic material - if necessary the prior application of the adhesion promoter - to be carried out in a single process step. For this purpose, a mixture of an inert carrier gas and a fine-grained metallic material can be fed in, similar to laser cladding. The metallic material molten, for example by the laser radiation, can thus also be melted by the laser beam or the heat of the ceramic or mineral substrate and flow into the recess before solidification.

[0030] Furthermore, it is possible and provided according to the invention that the production of the recess takes place in a separate step before the application of the metallic material. For this purpose, the recess can be machined in a separate process step by means of laser radiation directed onto the surface, while in a second subsequent process step the metallic material is introduced into the recess and melted. For this purpose, a device with a laser device can be used to create the recess, or the creation takes place by means of the application device

[0031] The recess can also be created by an etching process using an etching compound or by other mechanical methods. Furthermore, the ceramic or mineral substrate can also be provided with the desired recesses during production, for example, by using suitable molds.

[0032] In an advantageous embodiment of the invention, the laser beam generates a working area of ​​between 0.2 and 3 mm. This allows recesses to be formed with a single application of metallic structures over a large area. The dimensions of the recess are essentially determined by the area of ​​the working area and thus by the cross-section of the laser beam and the power of the laser beam.

[0033] In an advantageous implementation of the inventive concept, an application device with a powder nozzle is used to generate a coaxial, continuous powder gas jet. The powder nozzle can have a circumferential annular gap surrounding the emitted laser beam, or multi-jet nozzles can be used, which have several discrete powder nozzles arranged so that the injected metal powder meets at a common focus.

[0034] Advantageously, the invention provides for a metal oxide and / or a nitride and / or a silicate to be used as the ceramic substrate. Aluminum oxide AI2O3 can preferably be used as the ceramic substrate.

[0035] Advantageously, the invention optionally provides for copper and / or titanium and / or aluminum and / or vanadium and / or silver and / or iron and / or gold and / or an alloy thereof to be used as the metallic material. Titanium or a titanium alloy such as T1-6A1-4V can preferably be used as the metallic material.

[0036] Advantageously, the invention provides that the metallic material is electrically conductive and that the material deposit is electrically conductive, with an electrical resistance of the material deposit corresponding to an electrical resistance of the metallic material. In this way, highly conductive conductor tracks can be applied to the non-conductive substrate.

[0037] Advantageously, the invention provides that the ceramic or mineral substrate is electrically non-conductive. In this way, for example, circuit arrangements made of the metallic material can be arranged on the substrate and are electrically insulated from one another by the substrate.

[0038] Further advantageous embodiments of the method for depositing a metallic material on a ceramic or mineral substrate using an application device are illustrated in the following drawing. It shows:

[0039] Figure 1 shows a method according to the invention for depositing a metallic material on a ceramic or mineral substrate using an application device, wherein a laser beam is directed onto the surface of the ceramic or mineral substrate, Figure 2 shows the method from Figure 1, wherein the surface of the ceramic or mineral substrate is selectively removed so that a depression is created,

[0040] Figure 3 shows the process from step 2, in which a metallic material is applied into the resulting depression,

[0041] Figure 4 shows a comparison of a contact angle between a liquid drop on a planar surface and a liquid drop in the depression,

[0042] Figure 5 shows a circuit board produced by the method according to the invention with applied conductor tracks made of the metallic material, and

[0043] Figure 6 is a sectional drawing along section line VI-VI of Figure 5.

[0044] Figures 1 to 3 schematically show a variant of the method according to the invention for depositing a metallic material on a ceramic or mineral substrate using an application device.

[0045] Figure 1 shows an application device 1 with an energy source 2 in the form of a laser device 3. With the aid of the 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. The laser beam 4 directed onto the surface 5 defines on the

[0046] Surface a working area 7 . The application device 1 further has a powder nozzle 8 arranged on the application device 1, with which a continuous powder gas jet 9 of a carrier gas and a finely distributed metallic material is guided 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 onto the surface 5 heats the ceramic or mineral substrate 6 within an effective range 11 .

[0047] Due to the high power density of the laser beam 4, the surface 5 of the ceramic or mineral substrate 6 in the working area 7 is ablated piece by piece and removed from the surface 5. By removing the material 12, crack formation caused by the effect of heat, which could lead to the failure of the ceramic or mineral substrate 6, can be prevented. By dissolving out the material 12, a depression 13 is machined out on the surface 5 of the ceramic or mineral substrate 6. Figure 2 shows the method step of forming the depression 13.

[0048] Metallic material 14 introduced into the recess 13 through the powder nozzle 8 is melted by the incident laser radiation 4 and flows into the recess 13, solidifies there, and forms a material deposit in the recess 13. This process step is illustrated in Figure 3.

[0049] The advantage of the method according to the invention is illustrated in a schematic view in Figure 4. On the left-hand side, the application of a molten metallic material 14 as a liquid droplet onto a planar ceramic or mineral substrate 6 is illustrated. The wetting of the surface 5 by the liquid droplet depends on the cohesive forces within the liquid droplet and the adhesive forces of the liquid droplet with respect to the surface. If, as in the case of a metallic material 14, the cohesive forces within the liquid droplet outweigh the adhesive forces, the liquid droplet will assume the shape of a sphere and will only touch the surface at a small contact area 15. In this case, the contact angle θ 16 - the angle that a liquid droplet on the surface of a solid forms with the surface - is greater than 90°.

[0050] Due to the V-shaped geometry of the depression 13 with an acute angle, however, the contact angle 0 16 of a liquid drop in the depression 14 is always less than 90 °C, thereby achieving complete wetting of the side areas and the bottom area of ​​the depression 13. The contact angle 0 16 of a liquid drop in the depression according to the invention is shown on the right-hand side of Figure 3.

[0051] Figure 5 shows a circuit board 17 produced by the method according to the invention with applied conductor tracks 18 made of the metallic material 14, while Figure 6 shows a sectional drawing of the circuit board 17 along the section line VI-VI in Figure 5. The V-shaped recesses 13 can be seen there. LIST OF REFERENCE SYMBOLS

[0052] 1 application device

[0053] 2 Energy source

[0054] 3 Laser device

[0055] 4 laser beam

[0056] 5 Surface of the ceramic or mineral substrate

[0057] 6 Ceramic or mineral substrate

[0058] 7 Work area

[0059] 8 Powder nozzle

[0060] 9 Powder gas jet

[0061] 11 Powder gas path

[0062] 11 Effective range

[0063] 12 material removed from the surface

[0064] 13 Deepening

[0065] 14 metallic material

[0066] 15 Contact surface between metallic material and the surface of the ceramic or mineral substrate

[0067] 16 contact angles

[0068] 17 Circuit board

[0069] 18 conductor track

Claims

PATENT CLAIMS 1. Process for depositing a metallic material (14) on a ceramic or mineral substrate (6) with an application device (1), wherein a high-energy beam is directed onto a surface (6) of the ceramic or mineral substrate (5) from an energy source (2) arranged on the application device (1), wherein the metallic material (14) is applied to a region of the surface (6) of the ceramic or mineral substrate (5) with the aid of the application device (1), wherein the metallic material (14) is at least partially melted with the high-energy beam, so that after the metallic material (14) has solidified, the metallic material (14) is deposited as a material deposit on the surface (5) of the ceramic or mineral substrate (6), wherein the high-energy beam impinging on the surface (5) of the ceramic or mineral substrate (6) defines a working area (7),wherein the position of the working area (7) on the surface (5) is variable by a relative displacement of the surface (5) of the ceramic or mineral substrate (6) and the energy source (2), characterized in that a depression (13) is formed in the working area (7) on the surface (5) of the ceramic or mineral substrate (6), wherein the material is applied into the depression (13).

2. Method according to claim 1, characterized in that the material deposit is formed exclusively from the metallic material (14).

3. Method according to claim 1 or claim 2, characterized in that the energy source (2) is a laser device (3) emitting a laser beam (4), wherein the surface (5) is selectively ablated by the laser beam (4) directed onto the surface (5), so that the recess (13) on the surface (5) is formed by the ablated material (12).

4. Method according to one of the preceding claims, characterized in that the depression (13) introduced into the surface (5) of the ceramic or mineral substrate (6) is a V-shaped depression with an acute angle.

5. Method according to one of the preceding claims, characterized in that the metallic material (14) introduced into the recess (13) and melted thereon has a contact angle (16) 0 < 90°.

6. Method according to one of the preceding claims, characterized in that an adhesion promoter is used to improve the adhesion between the applied metallic material (14) and the ceramic or mineral substrate (6).

7. Method according to one of the preceding claims, characterized in that the removal of a region of the surface (5) by the laser beam (4) and the application of the metallic material (14) is carried out simultaneously.

8. according to one of the preceding claims, characterized in that the production of the recess (13) takes place in a separate step before the application of the metallic material (14).

9. Method according to one of the preceding claims, characterized in that a working area (7) between 0.2 and 3 mm is generated by the laser beam (4).

10. Method according to one of the preceding claims, characterized in that an application device (1) with a powder nozzle (8) is used to generate a coaxial continuous powder gas jet (9).

11. Method according to one of the preceding claims, characterized in that a metal oxide and / or a nitride and / or a silicate is used as the ceramic substrate (6).

12. Method according to one of the preceding claims, characterized in that copper and / or titanium and / or aluminum and / or vanadium and / or silver and / or iron and / or gold and / or an alloy thereof is used as the metallic material (14).

13. Method according to one of the preceding claims, characterized in that the metallic material (14) is electrically conductive and that the material application is electrically conductive, wherein an electrical resistance of the material application corresponds to an electrical resistance of the metallic material (14).

14. Method according to one of the preceding claims, characterized in that the ceramic or mineral substrate (5) is electrically non-conductive.

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