EP2262929B1 - Method for the electrochemical coating of a substrate by brush plating and device for carrying out said method - Google Patents

Abstract

The invention relates to a method for the electrochemical coating of a substrate (15) by brush plating. This is to take place with an electrolyte in that particles are dispersed, which are embedded into the developing layer (16). According to the invention, it is proposed to add the particles to the carrier (12) for the electrolyte by way of a separate conduit system (22). The electrolyte is added by way of a conduit system (21). Advantageously, in this way it is achieved that an agglomeration of the particles in the electrolyte can be prevented because only a short time passes between when the particles are fed and the layer (16) is formed. Also claimed is a device for electrochemical coating, comprising two conduit systems (21, 22) provided for this purpose.

Description

The invention relates to a process for the electrochemical coating of a substrate by brush plating, in which an electrolyte in which particles are dispersed is applied to the substrate using a transfer agent, wherein a metallic layer is formed on the substrate, in whose matrix the particles are installed.

A method of the type mentioned can be, for example, the JP 01301897 A remove. In order to prepare a layer in which particles are dispersed, it is proposed according to this document to use a brush plating process. Brush plating is to be understood as meaning an electrochemical coating method in which the substrate to be coated is not immersed in an electrolyte, but the electrolyte is applied to the substrate with a carrier called a brush or "brush". There is no need to use a brush in the narrower sense. Instead, the transmitter must have the properties of being able to transfer the electrolyte to the substrate on account of predominantly capillary effects. For this purpose, for example, a brush is suitable because capillary channels are formed between the individual bristles, which are suitable for transporting the electrolyte. Other structures which are suitable for the transfer of the electrolyte are, for example, sponge-like, ie open-pored, inherently elastic materials.

In order to allow an effective coating, the transmitter is fed by a channel system with electrolyte, which is in fluid communication with the capillary channels of the transmitter. The main advantage compared to classical electrochemical coating, in which the substrate is immersed in the electrolyte, is that a high material throughput is possible by constantly feeding electrolyte. Accordingly, correspondingly high deposition currents can be converted, for example, during galvanic coating, which is why a faster layer structure is possible. In contrast to electrolyte baths, constant flow of the electrolyte during brush plating prevents a stationary state in the electrolyte due to a limited diffusion speed, which limits the coating speed.

Of course, it is also known to incorporate particles in electrochemically produced layers that have been coated in an electrochemical bath. For example, it is according to the US 2007/0036978 A1 It is known to incorporate CNT (this abbreviation is used below for carbon nanotubes or carbon nanotubes) in electrochemically deposited layers. However, here is another limiting factor for the installation of CNT given that they can be dispersed only limited in the electrochemical bath. Preparation of stable dispersions, ie dispersion which remain stable for longer than 24 hours, poses problems. Although it is possible to stabilize the dispersion by the use of wetting agents, but these are then at least partially deposited in the layers. With the incorporation of CNT in electrochemical layers but, for example, an improvement in the conductivity is desired. The presence of wetting agents, the priority remain on the surface of the CNT, but limits the desired effect of incorporation of CNT into the metallic matrix of the electrodeposited layer.

US2003 / 234181 A1 discloses a method of electroplating a substrate by brush plating wherein an electrolyte in which particles are dispersed is applied to the substrate using a transfer.

The object of the invention is therefore to specify a method for the electrochemical coating of substrates by means of brush plating, in which comparatively high incorporation rates of particles can be realized.

This object is achieved with the method mentioned in the fact that the transmitter is fed via two fluidly independent feed systems, namely a first conduit system for the electrolyte, in which the concentration of particles compared to the required concentration is at least reduced, or no particles are present, and a second conduit system for the particles, with which particles are added to the electrolyte, until in this the required concentration of particles is reached. The inventive method advantageously ensures that no stable dispersion of particles in the electrolyte has to be produced. Rather, the fact is used that the brush plating is the time that elapses until the fed into the transmitter electrolyte reaches the surface to be coated of the substrate is very short. In addition, the electrolyte is passed over the capillary channels formed by the transmitter, which aggravate agglomeration in the electrolyte. Therefore, unwanted agglomeration of particles during the short time to coating of the substrate from the constituents of the electrolyte is very unlikely. This has the advantage that it is also possible to use particles, such as CNT, which in themselves are difficult to disperse in the available electrolytes. Another way to make sense of this circumstance is to use the particles comparatively high concentrations, which are normally no longer stable as a dispersion in the electrolyte concerned, can be added. As a result, the rate of incorporation of particles in the forming layer can be increased. Thus, the process window, which is available for the formation of electrochemical layers with dispersed particles, advantageously larger.

Another advantage of Brush Platings is that the transfer medium is in contact with the substrate during the film formation process. As a result, a dendritic layer growth is counteracted because the forming layer is immediately compacted. Incorporation of CNT would otherwise favor the formation of dendrites, with negative effects on the quality of the coating.

According to a particular embodiment of the invention, it is provided that the required concentration of particles in the electrolyte is at a value which is above a critical value for stability of the dispersion. The advantages of a resulting increased incorporation rate of particles in the forming layer have already been explained.

Another embodiment of the invention provides that the particles are supplied in the second alloy system as a dispersion. In this case, a gas (formation of an aerosol), a liquid (formation of a suspension) or a solid (formation of a solid mixture) can likewise be used as dispersion medium. When using a solid, a powder is preferably formed from larger particles than the particles to be dispersed in the layer to be formed, which are easier to handle and meter or can be produced. But also the promotion and dosage of the particles to be incorporated into the trainee layer as a powder is possible. However, the use of dispersions has the advantage that handling is generally simplified. As the liquid dispersion medium, the electrolyte itself is also preferably used. Thus, the electrolyte fed through the first conduit system and the electrolyte fed through the second conduit system differ only in the concentration of dispersed particles. The electrolyte in the first conduit system, which makes up the major part of the mass flow rate, is advantageously not provided with a larger quantity of particles, so that handling is advantageously simplified. In particular, with multiple use of the electrolyte, so the capture of the electrolyte after brush plating and recycling the same in the stock from which the first line system is fed, it may be that small amounts of particles are present in this electrolyte. However, these do not cause the already mentioned problems of agglomeration, since upon reaching a critical concentration, the particles already precipitate in the collecting container after brush plating and therefore are not returned to the reservoir. On the other hand, the comparatively small amount of electrolyte which is fed through the second conduit system can be mixed for a short time before its use, so that a long-term stability of this suspension is not required. Alternatively, as a liquid dispersion medium, a liquid can be used in which the dispersion of the respective particles is simplified. However, this dispersing agent must not affect the coating process of the brushing board in an undesirable manner. This must be taken into account in the selection accordingly. If a liquid or else a solid is supplied as the dispersion medium, then these can advantageously be selected such that the dispersant evaporates or sublimates at the temperatures prevailing during the brushing. In this way, it is removed from the brush plating process before it can be incorporated into the forming coating. It may be necessary to provide a suitable catching device which prevents the gaseous dispersion medium from escaping into the environment. As a result, any health risks can be avoided or the dispersant can be used for re-dispersion formation.

According to another embodiment of the method, it is provided that the particles are prevented from agglomerating by the action of an energy, in particular ultrasound, in the second line system. As a result, supercritical dispersions can advantageously also be used, since the danger that the dispersed particles are already agglomerating in the second conduit system can be reduced by the introduction of energy. In particular, when using ultrasound this can also be introduced into the transmitter, so that agglomeration of the particles is prevented in this area. As a result, they can be installed individually in the matrix of the forming layer.

A further advantageous embodiment of the invention is obtained when the particles are nanoparticles, in particular CNT. When using nanoparticles can be advantageous to produce particularly fine layer structures on the component to be coated. In addition, the above-described mechanisms of preventing agglomeration of nanoparticles prior to incorporation into the layer are particularly useful use effectively. In particular, the incorporation of CNT in a metallic matrix without the use of the function of the coating disturbing wetting agents is advantageously possible.

Furthermore, the invention relates to a device for electroplating a substrate by brush plating, comprising a liquid-permeable carrier for an electrolyte on a substrate to be coated and a first conduit system for the electrolyte, which has outlets on the transmitter.

Such a device is already mentioned in the beginning JP 01301897 A described. The device for brush plating is therefore designed roller-shaped, with a sponge-like roller is used as the transmitter. Inside this roller, the conduit system is provided, which has the shape of an elongated cylinder which extends in the center of the transmitter. This tubular conduit system has a plurality of holes which open into the material of the transmitter.

The object of the invention is also to specify a device for electrochemical coating of a substrate by brush plating, with which can be produced relatively effectively electrochemical layers are dispersed in the particles.

This object is achieved with the said device in that this device has a second conduit system which can be fed independently of the first conduit system, which opens into the first conduit system or the transmitter and which is in engagement with a generator for ultraschaft. As a result, a possibility is provided according to the invention, the Particles to be incorporated in the coating to be formed, to be supplied separately to the device. Depending on whether this second conduit system opens into the first conduit system, or opens directly into the carrier, it is possible according to the invention to feed the particles which are to be incorporated into the coating only shortly before carrying out the coating process into the coating electrolyte. This advantageously avoids formation of a dispersion consisting of the coating electrolyte and the particles to be incorporated. This results in the possibility, in particular, of incorporating particles into the electrochemically forming layer whose dispersion in the electrolyte as dispersant is problematic. For example, as already mentioned, it is also possible to avoid the use of wetting agents which can adversely affect the coating result.

According to one embodiment of the invention, it is provided that the first line system and the second line system are combined in a line module, which communicates with its outlets with the transmitter in contact. In this way, it is possible to advantageously produce a particularly compact device in which the paths which the electrolyte and the particles have to cover are kept short. As a result, advantageously agglomeration of the particles in the electrolyte can be avoided as far as possible. In addition, the device advantageously has a simple structure, so that, for example, the transmitter can be easily changed.

The second line system is engaged with a generator for ultrasound. The generator is thereby engaged with the second line system that the through The generator generated ultrasound affects at least in the second line system. The ultrasound advantageously effects that particles which are conveyed in the second line system do not agglomerate. For example, a powder of particles conveyed in the second line system can also be kept flowing by means of the ultrasound. More detailed information on how the ultrasound generator can be applied in the pipeline system, for example, the DE 10 2004 030 523 A1 remove.

In addition, it is advantageous if the junctions of the second conduit system are provided in the first conduit system or in the transmitter with metering valves, in particular piezo valves. This embodiment of the invention can be implemented by the information of the mentioned DE 10 2004 030 523 A1 be taken into account. By using the piezo valves advantageously a very accurate dosage of the particles to the electrolyte is possible, even if they are handled as a powder.

It is particularly advantageous if the excitation by ultrasound does not only act on the second line system but also on the first line system and / or on the transmitter. In this way it can be avoided that any particles still present in the electrolyte agglomerate or agglomerate the particles after they have been introduced into the electrolyte. In addition, the mixing of the electrolyte with the particles is promoted by the influence of the ultrasound in the transmitter.

Figur 1

schematisch den Ablauf eines Ausführungsbeispiels des erfindungsgemäßen Verfahrens unter Anwendung eines Ausführungsbeispiels der erfindungsgemäßen Vorrichtung,

Figur 2

schematisch ein anderes Ausführungsbeispiel der erfindungsgemäßen Vorrichtung als isometrische Ansicht und

Figur 3

ein Leitungsmodul, wie es in einem anderen Ausführungsbeispiel der erfindungsgemäßen Vorrichtung zum Einsatz kommen kann, als Querschnitt.

Further details of the invention will be described below with reference to the drawing. The same or corresponding drawing elements are in each case provided with the same reference numerals and are only explained several times, how differences arise between the individual figures. Show it

FIG. 1

1 schematically the sequence of an embodiment of the method according to the invention using an embodiment of the device according to the invention,

FIG. 2

schematically another embodiment of the device according to the invention as an isometric view and

FIG. 3

a line module, as it can be used in another embodiment of the device according to the invention, as a cross section.

A device 11 according to the invention has a transmitter 12 and a line module 13, to which the transmitter 12 is connected. The transmitter is a brush that can be placed on the surface 14 of a substrate 15. As will be explained in more detail below, the device can be used to produce a layer 16 on the substrate 15 in which particles are dispensed.

For the purpose of producing the layer 16, the substrate 15 is placed in a collecting container 17. Furthermore, the substrate 15 and the device 11 are connected to a voltage source, wherein the substrate is connected as a cathode. From an electrolyte reservoir 19, an electrolyte is fed into the transmitter 12. This contains ions of the coating material, which will form the metallic matrix (not shown in more detail) of the layer 16. In addition, from a particle reservoir 20, which is a highly concentrated Contains suspension of the particles to be incorporated into the layer 16, introduced into the transmitter 12.

The line module 13 has a first conduit system 21 for the electrolyte and a second conduit system 22 for the particles. These are independent of each other, d. h., That the first conduit system through the electrolyte reservoir 19 and independently of the second conduit system 22 can be fed from the particle reservoir 20. In the transmitter, it then comes to a mixture of the electrolyte with the particles, which is preferably used as a dispersant for the particles, a liquid having the composition of the electrolyte.

In order to form a layer 16, the device 11 is now pulled over the surface 14 in the indicated direction (arrow). Thereby a constant flow of particles and electrolyte is maintained. The applied voltage leads to a comparatively rapid formation of the layer 16, wherein excess electrolyte, mixed with the particles, is collected in the collecting container 17. From this leads a return line 23 to a separator 24, where the particles are again separated from the electrolyte. The electrolyte, which now contains only insignificant amounts of particles, is returned to the electrolyte reservoir 19, and the particles, which are concentrated in the liquid of the electrolyte start, are returned to the particle reservoir 20. Now, the coating process with the recovered electrolyte or the recovered particles can be continued. It should be noted that the taking place on the surface 14 substance turnover in the formation of the layer 16 in a manner not shown must be replaced.

The device 11 according to FIG. 2 is suitable for coating a wire 25, which thus acts as a substrate 15 according to FIG. The device is therefore also tubular. First, the transmitter 12, which is an open-pore, sponge-like structure, cylindrical and has in the central axis a through hole for the wire 25. The device can be guided back and forth in the direction of the indicated arrows on the wire.

In order to allow a coating, the line module 13 is arranged in a ring around the transmitter 12, d. h., That the conduit module forms a tubular sleeve. This is supplied via the first line system 21 with electrolyte. Here, a central nozzle is used, wherein the electrolyte is passed through the transmitter 12, in this case also comes into contact with the wire 25 and exits at the ends of the tubular sleeve of the line module 13.

Furthermore, the second line system 22 is embodied in the wall of the line module 13 and has a plurality of orifices 26 for feeding the particles into the transmitter 12. These orifices are evenly distributed over the length of the conduit module and also over its circumference. Here, the fact is taken into account that the diffusion of the particles in the transmitter 12 is restricted in comparison to the electrolyte and therefore a uniform distribution in the transmitter 12 is conveyed by a larger number of orifices 26.

The introduction of the particles into the second conduit system 22 via not shown connection modules 27. These also each have a generator 28 for ultrasound. These generators 28 are dimensioned so that the ultrasonic waves in the entire line module 13 propagate. The ultrasound counteracts agglomeration of the particles in the second conduit system 22.

In FIG. 3 is a section of the device shown, you can see the interaction of the line module 13 and the transmitter 12. The transmitter 12 in turn consists of a sponge-like, elastic, open-pored structure, wherein the pores 29 can be seen. The line module has the first line system 21, which forms outlets 30, which adjoin the transmitter 12. From the outlets, the electrolyte can be forced into the pores 29.

Unlike the embodiment according to FIG. 2 the second line system 22 is arranged parallel to the first line system 21. The mouths 26 of the second conduit system do not lead into the transmitter 12, but into the first conduit system 21. Thus, there is a mixing of the electrolyte with the particles already in the first conduit system, which has the advantage that here still necessary for mixing diffusion processes can run relatively undisturbed. The path which the electrolyte dispersion produced in this way must still travel in the transmitter is short, so that neither segregation nor agglomeration of the particles can occur.

In the second conduit system, the particles may preferably be conveyed as powder. In order to prevent agglomeration, the generators 28 are arranged directly in the second line system 22. These can be formed for example by piezo crystals. Furthermore, a metering of the powder present in the second line system 22 can be facilitated by providing metering valves 31 at the mouths 26. These can be designed as piezo valves be. By using the piezo technology can be advantageously realize a very compact design of the line module. Therefore, the paths in the first and second conduit systems can be kept short to preclude agglomeration of particles to the surface to be coated.

Claims (9)

1. Process for the electrochemical coating of a substrate (15) by brush plating, in which process an electrolyte, in which particles are dispersed, is applied to the substrate (15) using a carrier (12), wherein a metallic layer (16), in the matrix of which the particles are incorporated, forms on the substrate (15),
   characterized
   in that the carrier is fed via two fluidically independent supply systems, namely via

   • a first conduit system for the electrolyte, in which the concentration of particles is at least reduced compared to the required concentration, or no particles are present, and

   • a second conduit system for the particles, by means of which particles are added to the electrolyte until the required concentration of particles is achieved therein.
2. Process according to Claim 1,
   characterized
   in that the required concentration of particles in the electrolyte is at a value above a critical value for stability of the dispersion.
3. Process according to either of the preceding claims,
   characterized
   in that the particles are supplied in the second conduit system as a dispersion.
4. Process according to one of the preceding claims,
   characterized
   in that the particles are conveyed in the second conduit system as a powder.
5. Process according to either of Claims 3 and 4,
   characterized
   in that agglomeration of the particles is prevented by the action of an energy, in particular ultrasound, in the second conduit system.
6. Process according to one of the preceding claims,
   characterized
   in that the particles used are nanoparticles, in particular carbon nanotubes.
7. Device for the electrochemical coating of a substrate (15) by brush plating, comprising

   • a carrier (12) through which liquid can pass for applying an electrolyte to a substrate (15) to be coated, and

   • a first conduit system (21) for the electrolyte, which has outlets (30) on the carrier (12),

   wherein the device has a second conduit system (22), which can be fed independently of the first conduit system and issues into the first conduit system (21) or into the carrier (12),
   characterized
   in that the second conduit system (22) engages with a generator (28) for ultrasound.
8. Device according to Claim 7,
   characterized
   in that the first conduit system (21) and the second conduit system (22) are combined in a conduit module, which is in contact with the carrier (12) by way of its outlets (30).
9. Device according to one of Claims 7 to 8,
   characterized
   in that the points at which the second conduit system (22) issues into the first conduit system (21) or into the carrier (12) are provided with metering valves (31), in particular piezo valves.

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