Method and device for producing a galvanic layer on a substrate surface

Abstract

A method and a device are described for producing a galvanic layer having a defined spatial extent on an electrically conductive substrate surface having any shaped contour at all. In this context, an electrolyte jet from a nozzle is applied to the substrate, and a current flows between the nozzle and the substrate surface essentially via the electrolyte jet. The device is provided with a pump for delivering an electrolyte from an electrolyte reservoir to the nozzle and for producing an electrolyte jet directed at the substrate surface. Moreover, the device has a reactor in which are arranged the substrate to be coated, as well as the nozzle. The substrate and the nozzle are connected to a direct current source, and a configuration of the substrate and of the nozzle in the reactor is variable during the coating process.

Description

BACKGROUND INFORMATION

[0001] The present invention is directed to a method and a device for producing a galvanic layer having a defined spatial extent on an electrically conductive substrate surface.

[0002] Generally, galvanically produced layers which are applied precisely to a limited area of a substrate surface, are described as partial precision layers. The galvanic layers having limited spatial dimensions are produced by selectively influencing a current flow in an electrolyte between an anode and the substrate to be coated, in a generally known way, using screening.

[0003] It is additionally provided in the case of a so-called mask technique, to provide the substrate surface to be coated, for example, with a photosensitive resist, which stops a current flow between the anode and the substrate in this region and prevents a deposition of coating material.

[0004] The known devices in which the galvanic coating processes take place have the disadvantage, however, of being tailored to the geometric form of the particular substrate to be coated, and also of requiring replacement or retrofitting when another substrate or component type is to be coated. The necessity to fix the devices in position in order to produce a galvanic layer on substrates having a specific, spatial form makes the coating process inflexible, and a layer thickness of the partial precision layers is only able to be influenced in its totality by altering the process parameters of the coating process each time.

[0005] This leads disadvantageously to the situation where using devices and methods known in the field for producing a galvanic layer on a substrate surface, for the most part, a contour layer having a constant layer thickness can be applied, a surface contour of the substrate surface being identically replicated by the galvanic contour layer, and a profile layer, which, in its spatial extent, has a variable layer thickness, being only able to be produced with considerable cost for equipment.

[0006] A device and a method for producing galvanic layers on electrically conductive substrates are known from the German DE 197 36 340 A1. The device is provided for producing uniformly unpatterned, as well as patterned galvanic layers, patterned galvanic layers being producible using the described method.

[0007] The device of the DE 197 36 340 A1 has a bath for the electrolyte into which the holder for the substrate and the anode connected to the voltage source, dip. The holder is composed of a cylindrical housing having two open ends and one closure which can be screwed onto the one housing end, thereby sealing it. The interior of the housing is made up of three concentrically disposed cylindrical sections. To ensure adequate movement of the electrolyte over the metal layer or the substrate, an agitator is provided. Alternatively, it can also be provided, however, for the electrolyte to be suctioned out of the housing, thereby producing the desired electrolyte motion for compensating for concentration gradients in the electrolyte.

[0008] To produce a patterned galvanic layer on the electrically conductive substrate surface, a mask pattern of a polymer resist is initially applied to the one-sided metallized, dielectric substrate surface, photolithographically or using excimer laser ablation. The mask pattern is identical to the negative of the patterned galvanic layer to be produced. A mesh for producing a patterned galvanic layer of a uniform thickness is placed between the agitator and the substrate surface.

[0009] However, this device known from the related art has the disadvantage that, prior to producing a patterned galvanic layer, it is necessary to prepare the substrate to be coated, i.e., its surface, or the area surrounding the substrate, i.e., the device itself, in accordance with the layer to be produced. This preparation corresponds to the application of a photoresist or the placement of appropriate screening to guide the current field within the electrolyte. However, such process-preparation production steps entail considerable outlay and increase the production costs related to the coated substrates and/or components.

SUMMARY OF THE INVENTION

[0010] In contrast, the method according to the present invention having the features of claim 1 has the advantage that galvanic layers, formed as contour or profile layers, are able to be applied to an electrically conductive substrate surface having any shaped contour at all, without entailing costly process-preparation production steps.

[0011] This is achieved in that an electrolyte jet is applied to the substrate surface, a current flows between a nozzle and the substrate essentially via the electrolyte jet, and a configuration of the nozzle and of the substrate surface is variable during the coating process, so that to fabricate patterned contour galvanic layers, as well as patterned profile galvanic layers, measures are not needed to mask the components or the substrate surfaces, or an arrangement of screens or meshes is not needed, since a coating is provided essentially only in the region of the substrate surface where the electrolyte jet impinges.

[0012] Applying the method according to the present invention which constitutes a "jet coating technique", a coating of substrates, that is, to a large degree, independent of components, and a rapid adaptation to new conditions is possible, through which means, in comparison to known coating techniques, such as, for example, the mask technique and/or the screen technique, the jet coating technique exhibits a substantially greater flexibility.

[0013] The device according to the present invention having the features of claim 17 has the advantage that any desired contour of a substrate to be coated, or its surface may be simulated, without retrofitting the device, and nearly every desired form of a galvanic layer may be applied to the substrate.

[0014] For this, the device for producing a galvanic layer having a defined spatial extent on an electrically conductive substrate surface having any shaped contour at all, is provided with a pump for delivering an electrolyte from an electrolyte reservoir to a nozzle and for producing an electrolyte jet directed at the substrate surface, and with a reactor in which are arranged the substrate to be coated, as well as the nozzle, and with a direct current source which is connected to the substrate and the nozzle. Moreover, an arrangement of the nozzle and/or of the substrate during the coating process in the reactor is variable, so that the electrolyte jet or the nozzle is able to be guided similarly to a pin with respect to the substrate surface. Thus, the galvanic layer is able to be applied with a specific contour or with a specific profile to the desired regions of the substrate surface.

[0015] Moreover, it is advantageous that substrates having any desired surface contour, such as rotationally symmetric bodies, substrates having grooves or depressions, but also flat plates, are able to be provided with a galvanic layer in a simple manner. In this context, it is particularly advantageous that a change in the substrate type does not necessitate retrofitting the device according to the present invention, since any surface contour at all is able to be covered by the nozzle. In the present connection, the term "substrate type" is to be understood as a variable geometric form of the substrate to be coated.

[0016] Further advantages and refinements of the present invention are derived from the description, the drawing, and the claims.

BRIEF DESCRIPTION OF THE DRAWING

[0017] An exemplary embodiment of the device according to the present invention for producing a galvanic layer on a substrate surface is shown in a schematically simplified version in the drawing and is elucidated in more detail in the following description. in which:

[0018] FIG. 1 shows a method flow chart of a device or system for producing a galvanic layer on a substrate surface;

[0019] FIG. 2 a nozzle and a substrate, an electrolyte jet which constitutes a free jet being applied to the substrate;

[0020] FIG. 3 the nozzle and the substrate according to FIG. 2, the electrolyte jet being an immersion jet;

[0021] FIG. 4 a schematic representation of a substrate, on which a locally limited galvanic layer is applied, a superposition of galvanically produced individual spots being represented in the right illustration; and

[0022] FIG. 5 a comparison of a profile layer applied to a substrate and a contour layer applied to a substrate.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

[0023] FIG. 1 shows a device 1 for producing a galvanic layer having a defined spatial extent on an electrically conductive substrate surface 2 which has a pump 3 for delivering an electrolyte 4 from an electrolyte reservoir 5 to a nozzle 6 and for producing an electrolyte jet 7 directed to substrate surface 2. In addition, device 1 has a reactor 8 in which are placed substrate 9 to be coated as well as nozzle 6, substrate 9 and nozzle 6 each being connected to a direct current source 10.

[0024] Reactor 8 has a protective container 11 and a substrate holder 12 or workpiece holder configured in the protective container. In addition, between nozzle 6 and pump 3, a valve 13 is provided for controlling a delivery quantity of electrolyte 4. In parallel to a connection line 14 between pump 3 and valve 13 is a line 15 which, starting from electrolyte reservoir 5, leads into connection line 14 upstream from valve 13 and is provided with a further valve 16. Thus, the delivery quantity of electrolyte 4 to nozzle 6 is adjustable by way of valve 13 and additional valve 16, as well as by way of the conveying capacity of pump 3.

[0025] Protective container 11 is connected via a further connection line 17 to electrolyte reservoir 5, further connection line 17 being blockable via a shutoff valve 18 and being provided for recirculating electrolyte 4 into electrolyte reservoir 5.

[0026] To ensure a proper functioning of device 1, electrolyte reservoir 5 is equipped with a device 19 for tempering electrolyte 4, so that the coating process is substantially independent of the ambient temperatures. Situated underneath reactor 1 and electrolyte reservoir 5 is a catch pan 20 used to collect electrolyte flows escaping from the closed system in the case of possible leakage from reactor 8, electrolyte reservoir 5, and the line system of device 1, and to avoid contaminating the environment with electrolytes potentially containing substances harmful to health and the environment.

[0027] Device 1 is designed to be able to operated in a so-called free-jet operation or in a so-called immersion jet operation.

[0028] During the free-jet operation of device 1 in accordance with the representation in FIG. 2, nozzle 6 situated in protective container 11 and substrate 9 are not immersed in electrolyte 4. Electrolyte jet 7 emanating from nozzle 6 is applied in empty protective container 11 as a free jet to substrate 9. In this context, the diameter of electrolyte jet 7 corresponds to the nozzle diameter and only increases slightly in size with increasing distance from nozzle 6. In the area of an impact point 21 on substrate surface 2, electrolyte 4 on substrate surface 2 flows away "to the outside", i.e., radially outwardly from electrolyte jet 7, and collects in the bottom area of protective container 11. From there, electrolyte 4 flows via further connection line 17 back into electrolyte reservoir 5, shutoff valve 18 being opened.

[0029] During immersion jet operation of device 1, shutoff valve 18 is closed, so that electrolyte 4 is accumulated in protective container 11, and is fed back via an output 22 to electrolyte reservoir 5. This means that in the immersion jet operation of device 1, substrate 9, as well as nozzle 6 are immersed in electrolyte 4, i.e., protective container 11 is completely filled with electrolyte 4, and electrolyte jet 7 is formed as flow threads in electrolyte 4. In this context, electrolyte jet 7 widens with increasing distance from nozzle 6, i.e., its diameter increasingly enlarges. From an impact region 21 on substrate surface 2, electrolyte jet 7 flows off radially, directed toward substrate surface 2.

[0030] The course of electrolyte jet 7 during free-jet operation, as well as during immersion-jet operation of device 1, is shown greatly schematized in FIGS. 2 and 3, respectively. It proceeds from these basic representations that the impact region of electrolyte jet 7 in the free-jet operation of device 1 has a smaller diameter than in the immersion-jet operation.

[0031] In the context of the method according to the present invention for producing a galvanic layer having a defined spatial extent on a substrate surface having any shaped contour at all, nozzle 6 is essentially directed at an electrically conductive, i.e., metallic surface of substrate 9. Electrolyte 4 flows as a liquid jet through nozzle 6 and meets with substrate surface 2 to be coated, i.e., a workpiece surface. In this context, nozzle 6 is designed as an electrode, so that electric current is able to flow via electrolyte 4, i.e., electrolyte jet 7, to substrate 9, and a metal deposition is effected on a narrowly restricted area around impact region 21, i.e., the impact point of electrolyte jet 7.

[0032] The coating point is primarily described as spot 25, the diameter of this spot 25 being determined by the flow shape, the nozzle diameter of the electrolyte jet, the flow velocity of electrolyte jet 7, as well as by the distance between nozzle 6 and substrate 9. Here, the flow shape of electrolyte 4 is to be understood as whether electrolyte 4 is applied to substrate surface 2 in the form of an immersion jet or a free jet.

[0033] A change in or enlargement of the vertical distance of nozzle 6 from substrate surface 2 effects that the layer profile becomes increasingly flatter, and the diameter of spot 25 increases, this trend being more pronounced in free-jet operation than in immersion-jet operation.

[0034] A height of spot 25 or of the coating is adjusted as a function of a time during which the current flows between nozzle 6 and substrate surface 2. A further parameter of the coating process which influences the height of spot 25 is the magnitude of the applied current intensity, a greater amperage effecting an intensified deposition, the height of spot 25 being greater, and the diameter of spot 25 remaining essentially the same.

[0035] In a schematized representation, FIG. 4 shows substrate 9 which is coated with a spot 25. To produce a flat expansion of a galvanic layer on substrate surface 2, a plurality of individual spots 25 are arranged in a series. To produce a profile layer, a plurality of spots 25 are superposed, this being referred to as superposition.

[0036] To implement a superposition, it is provided to move the workpiece to be coated or substrate 9 and/or nozzle 6 during the coating process, so that a contour layer or a profile layer may be produced in a simple manner on substrate 9. In this manner, the need is eliminated for a conventional mask and screen technique to selectively coat a substrate surface. Moreover, preparatory production steps, such as applying a resist layer to substrate surface 2, or retrofitting a coating device are eliminated.

[0037] By moving substrate 9 or nozzle 6, a vertical distance between them may be altered, for example to form a profile layer 23, as depicted in FIG. 5, on substrate surface 2. Furthermore, the nozzle and/or substrate 9 may be moved to change impact region 21 of the electrolyte jet on substrate surface 2, so that a contour layer having a uniform layer thickness may be produced on the substrate surface.

[0038] Of course, deviating herefrom, it is within the discretion of one skilled in the art to execute the individual movements of nozzle 6 and of substrate 9 in combination. This means that the vertical distance between nozzle 6 and substrate surface 2, and also impact region 21 of electrolyte jet 7 on substrate surface 2 are suitably changed. Thus, a galvanic layer may be precisely applied to substrate surface 2 and with a defined spatial extent, and with any shaped contour at all. A contour layer 24 of this kind is shown in the right representation of FIG. 5, contour layer 24 having a constant layer thickness, and the surface contour of substrate 9 being identically replicated by contour layer 24.

[0039] To move nozzle 6 and substrate 9, a positioning unit is provided for nozzle 6, and for substrate 9 or substrate holder 12. The positioning unit is not shown here in greater detail in the drawing and may be designed as a robot, similarly to resist technology. By designing device 1 in this manner, it is possible for the nozzle to be driven into grooves or other depressions in substrate surface 2 and, there, for a galvanic layer having the desired contour or desired profile to be produced. One possible application case is, for instance, coating components of a valve. It is conceivable in this context, on a seat area of a valve tappet, to place a ring at the crown rim, so that this ring rests only at the rim and not in the entire area of the crown at the valve seat.

[0040] Using the present jet-coating technique, which provides for depositing a metal layer in the form of a spot 25 as the result of impact of electrolyte jet 7 on substrate surface 2, it is possible to produce galvanic layers having any desired pattern delineation at all as a contour or profile layer on a substrate surface, since the coating in impact region 21 in the form of spot 25, even in the free-jet operation of device 1, does not come in contact with air or oxygen. In this manner, a passive surface layer is prevented from forming on the already applied metal layer, because a liquid film or an electrolyte film flows permanently over spot 25. For this reason, it is possible to build up further spots on a deposited spot 25 or to place them next to it, the individually applied spots, among themselves, forming a permanent bond.

[0041] Various series of measurements have revealed that, in the free-jet operation of device 1, high elevated spots 25 formed with a small diameter are produced on substrate surface 2. In the immersion-jet operation of device 1, flatter spots 21 having a larger diameter are produced on substrate surface 2, since the greater flow resistance of electrolyte 4 surrounding electrolyte jet 7, causes it to widen with increasing distance from nozzle 6.

Claims

What is claimed is:

1. A method for producing a galvanic layer having a defined spatial extent on an electrically conductive substrate surface (2) having any shaped contour at all, an electrolyte jet (7) being applied by a nozzle (6) to the substrate surface (2), and a current flowing between the nozzle (6) and the substrate surface (2) essentially via the electrolyte jet (7), a configuration of the nozzle and of the substrate surface being variable during the coating process.

2. The method as recited in claim 1, wherein the electrolyte jet (7) is a free jet.

3. The method as recited in claim 1, wherein the electrolyte jet (7) is an immersion jet.

4. The method as recited in one of claims 1 through 3, wherein parameters of the coating process are provided in such a way that the substrate surface (2) is essentially coated in the impact region of the electrolyte jet (7) on the substrate surface (2).

5. The method as recited in claim 4, wherein a diameter of the coated region (25) is adjusted as a function of the diameter of the nozzle (6), and/or as a function of the flow velocity of the electrolyte (4), and/or as a function of a vertical distance between the nozzle (6) and the substrate surface (2).

6. The method as recited in one of claims 1 through 5, wherein a height of the coating (25) is adjusted as a function of a time during which the current flows between the nozzle (6) and the substrate surface (2), and/or as a function of the current intensity.

7. The method as recited in one of claims 1 through 6, wherein the nozzle (6) and/or the substrate (9) are moved during the coating process.

8. The method as recited in claim 7, wherein the nozzle (6) and/or the substrate (9) are moved to vary the vertical distance between them, the vertical distance being varied, in particular, in such a way that a profile layer (23) is produced on the substrate surface (2).

9. The method as recited in claim 7, wherein the nozzle (6) and/or the substrate (9) are moved to vary the impact region (21) of the electrolyte jet (7) on the substrate surface (2), the impact region (21) being varied, in particular, in such a way that a contour layer (24) is produced on the substrate surface (2).

10. The method as recited in claim 7, wherein the nozzle (6) and/or the substrate (9) are moved to vary the vertical distance between them and to vary the impact region (21) of the electrolyte jet (7) on the substrate surface (2).

11. The method as recited in one of claims 1 through 10, wherein a plurality of electrolyte jets is applied simultaneously to the substrate surface.

12. A device for producing a galvanic layer having a defined spatial extent on an electrically conductive substrate surface (2) having any shaped contour at all, comprising a pump (3) for delivering an electrolyte (4) from an electrolyte reservoir (5) to a nozzle (6) and for producing an electrolyte jet (7) directed to substrate surface (2), a reactor (8) in which are placed the substrate (9) to be coated as well as the nozzle (6), and a direct current source (10) which is connected to the substrate (9) and the nozzle (6), a configuration of the nozzle (6) and/or of the substrate (9) in the reactor (8) being variable.

13. The device as recited in claim 12, wherein the reactor (8) has a protective container (11) and a substrate holder (12) configured in the protective container (11).

14. The device as recited in claim 12 or 13, wherein a valve (13) for controlling a delivery quantity of the electrolyte (4) is provided between the nozzle (6) and the pump (3).

15. The device as recited in claim 13 or 14, wherein the protective container (11) is connected to the electrolyte reservoir (5), and this connection is blockable via a shutoff valve (18).

16. The device as recited in claim 15, wherein in a free-jet operation, the shutoff valve (18) is opened, and, in an immersion-jet operation, the shutoff valve (18) is closed, during the immersion jet operation, the electrolyte (4) is accumulated in the protective container (11), and is fed back via an output (22) to the electrolyte reservoir (5).

17. The device as recited in one of claims 12 through 16, wherein the electrolyte reservoir (5) is equipped with a device (19) for tempering the electrolyte (4).

18. The device as recited in one of claims 13 through 17, wherein the nozzle (6) and/or the substrate holder (12) are provided with a controlled positioning device for guiding the nozzle (6) and/or the substrate holder (12) during the coating process.