Process for producing a surface coating

Abstract

A method for producing a product surface coating (O1) comprising at least one layer is described. The method comprises a product production branch in which the product surface coating (O1) is deposited. In order to be able to better analyze at least one layer of the product surface coating (O1), the method further comprises at least one sample production branch for producing a sample surface coating comprising at least one layer, wherein the layer structure of the sample surface coating differs from the layer structure of the product surface coating (O1) with respect to at least one layer, and the sample surface coating comprises at least one layer that is similar to the product surface coating.

Description

[0001] The invention relates to a method for producing a product surface coating having at least one layer according to the preamble of claim 1.

[0002] Surface coatings play an important role in many technical fields, allowing surfaces to be given specific, desired properties. For example, surface coatings can be used to influence the mechanical and / or electrical properties of a surface. Such product surface coatings play a particular role in contact technology, but they can also play an important role in "non-electrical" applications.

[0003] Such a product surface coating has at least one layer, but multi-layer product surface coatings with two, three, or more layers are also known, with these layers overlapping one another to form a "layer sandwich." Such a product surface coating is applied to a base element. A variety of methods are known for this, in particular galvanic deposition, purely chemical deposition (such as galvanic deposition from a bath), and deposition from a plasma. The invention described below is independent of the selected deposition method; however, it should be noted that deposition from a bath, in particular galvanic deposition, is an essential and particularly preferred application. In principle, it is also possible to produce different layers of a product surface coating using different techniques.

[0004] Of course, it is desirable, and sometimes even mandatory, to monitor (i.e., analyze) the resulting product surface coating, for example, with regard to the thickness of the individual layers and / or their composition. This last point is particularly important when a layer contains multiple components (e.g., more than one metal, or at least one metal and one non-metal).

[0005] Destructive and non-destructive methods are known for analysis, with non-destructive methods generally being preferred. A very frequently used and generally suitable method for inspecting / analyzing a produced product surface coating is the X-ray fluorescence method. In this method, ionizing radiation (usually in the form of X-rays) is directed at the sample to be measured, and the characteristic X-ray fluorescence radiation is measured. This method is well-known and established in the industry and need not be described in detail here.

[0006] EP 4 012 074 A1 describes an electrochemical process for producing a coating comprising at least two partial layers forming a layer system. Several embodiments with different layer systems are described.

[0007] Based on this, the present invention has for its object to further develop a method for producing a product surface coating having at least one layer in such a way that the possibilities for quality control are improved, in particular in that individual layers can be precisely analyzed, in particular by non-destructive methods such as X-ray fluorescence measurement.

[0008] This object is achieved by a method having the features of claim 1.

[0009] The method according to the invention naturally initially comprises a product production branch in which the desired product surface coating is deposited. According to the invention, the method further comprises a sample production branch for producing a sample surface coating, which likewise comprises at least one layer. However, according to the invention, the layer structure of the sample surface coating differs from the layer structure of the product surface coating with respect to at least one layer, whereby the sample surface coating has at least one layer that is similar to the product surface coating. "Similar" here means at least that the composition and structure are the same (at least within the tolerances); an identical thickness need not be required in all applications. One could therefore also say that the two layers correspond to one another.

[0010] When carrying out the method, a strip-shaped base element is coated at least in sections, for example using a strip electroplating system. At least two serially arranged cell arrangements are provided, each having at least one cell filled or fillable with a bath. The strip-shaped base element passes through these cell arrangements. The cell arrangements can be put into an active and a passive state in order to be able to adjust the product production branch and the sample production branch. When the method is in its product production branch, the product surface coating is deposited on the strip-shaped base element, thus producing a strip-shaped product section. When the method is in its sample production branch, the sample surface coating is deposited on the strip-shaped base element, thus producing a strip-shaped sample section.

[0011] The sample sections are usually separated from the product sections, since the sample sections are obviously not suitable for further processing and are used exclusively for measurement and / or documentation purposes.

[0012] In most applications, at least the layer that is identical in the product surface coating and the sample surface coating is created in one bath. To achieve similarity between the layers, the chemical composition of the bath during the product production process and during the sample production process must be essentially identical within standard manufacturing tolerances, which particularly applies to the pH value. Furthermore, the temperature of the bath must also be the same within standard tolerances during the product production process and during the sample production process.

[0013] In the case of electroplating, it is generally still necessary that the current supply takes place under the same conditions, meaning, in particular, that the current density is the same in both cases. In most cases, it is also at least preferable that (in the case of cathodic deposition) the anode be the same. In other words, in the case of electroplating (usually cathodic) of a layer that is similar in the sample generation and product generation stages, the deposition should take place under the same conditions. This is particularly (but not exclusively) easy to achieve in a so-called strip electroplating system.

[0014] As just explained, the product surface coating and the sample surface coating must have at least one layer of the same type, while all other layers can fundamentally be different, especially in that the number of layers in the product surface coating and the sample surface coating differs. Both are possible: the product surface coating can have more layers than the sample surface coating, and vice versa. It is also possible to replace a layer in the sample surface coating with a different layer in the same position.

[0015] In this respect, all layers in the sample surface coating, except for the necessarily similar layer, can be freely selected (and also omitted), in particular in such a way that the layer which is similar to the product surface coating can be easily measured, in particular by means of an X-ray fluorescence measurement.

[0016] One could therefore also say that the method according to the invention is a combined product production and sample production method.

[0017] In one embodiment, the product surface coating comprises at least two layers, one of the two layers covering the other layer, and the sample surface coating does not comprise one of these two layers, namely either the covering layer or the covered layer.

[0018] Omitting the covering layer from the sample surface coating can be particularly useful when this layer contains atoms with a high atomic number ("heavy elements" - for example, gold atoms) and the covered layer contains atoms with a relatively low atomic number ("light elements"). This prevents the X-ray fluorescence radiation from the light elements from being absorbed by the heavy elements.

[0019] Omitting the covered layer during sample surface coating can be particularly useful if the two layers consist partly of the same element but differ in their composition, since it is usually not possible to separate the X-ray fluorescence signals of the common element “by layer”.

[0020] In a further embodiment, the product surface coating comprises three layers: a first layer, a second layer covering the first layer, and a third layer covering the second layer, forming a "layer sandwich." If the measurability of the middle layer is to be improved, the first layer, the third layer, or both can be omitted from the sample surface coating, for example, to achieve the advantages described above.

[0021] In one important application, the layer present in both the product surface coating and the sample surface coating is a nickel-phosphorus layer. This application is of great importance because it has been shown that the nickel-phosphorus ratio of such a layer has not been measurable to date, or at least only with great effort, especially when the nickel-phosphorus layer in the product surface coating is deposited on a nickel-containing layer.

[0022] In a further embodiment, the sample surface coating comprises at least one additional layer, which is not present in the product surface coating at least at the position selected in the sample surface coating, and which is at least partially covered by at least one layer that is also provided in the product surface coating. This additional layer can act, in particular, as a barrier layer to shield X-ray fluorescence radiation from underlying layers, or even from the underlying base element. Heavy elements, especially gold or copper, are particularly suitable for forming such a barrier layer.

[0023] In many applications, at least one of the layers, preferably all layers, are deposited from a bath, for example by galvanic deposition.

[0024] An element carrying the sample surface coating - in the case just described, the sample section - is usually analyzed and / or stored for documentation purposes.

[0025] The invention will now be further explained using exemplary embodiments with reference to the figures. The figures show: Fig. 1 a strip electroplating plant including an input coil and an output coil in a highly schematic representation, Fig. 2 a schematic representation of an example of a band-shaped basic element, which in the Fig. 1 shown strip electroplating plant will be coated section by section, Fig. 3 the band-shaped base element 40 from Fig. 2, which is partially immersed in a bath of a cell of the strip electroplating plant, Fig. 4 the basic element Fig. 2 with a surface coating O, which covers part of the surface of the band-shaped base element, Fig. 5 the strip electroplating plant Fig. 1, which is operated to coat a strip-shaped base element section by section, wherein the process carried out with the strip electroplating process is in its product production branch, so that a product surface coating is deposited on the strip-shaped base element, Fig. 6 a highly schematic and not to scale section through the strip-shaped base element with the product surface coating produced on its surface, Fig. 7 the strip electroplating plant Fig. 5, the method performed with it being located in a sample generation branch, Fig. 8 that in Fig. 6 Shown, but with a sample surface coating deposited on the ribbon-shaped base element, Fig. 9 a schematic representation of the performance of an X-ray fluorescence analysis on the sample surface coating from Fig. 8, Fig. 10 the strip electroplating plant from the Fig. 1, Fig. 5 and Fig. 7, where the process carried out with it is located in a different sample generation branch, Fig. 11 the band-shaped base element 40, which is coated with the product surface coating (according to Fig. 6) and Fig. 12 the band-shaped basic element, which is connected to the Fig. 10 generated sample surface coating (analogous to the representation of the Fig. 8).

[0026] The Fig. 1 shows a strip electroplating system 10 including an input coil 2 and an output coil 5, such that, during operation, a strip-shaped base element 40 is conveyed from the input coil 2 through the strip electroplating system 10 and wound onto the output coil 5. When the strip electroplating system is in an active state, the strip-shaped base element 40 is coated at least in sections.

[0027] The strip electroplating system 10 has a plurality of cell arrangements arranged one behind the other, each having at least one cell. In the illustrated embodiment, for the sake of simplicity, each cell arrangement has only one cell. Each cell unit—here, each cell—serves to deposit a layer of electrolyte, as is naturally known. The individual cells can be put into an active state by applying a direct voltage; if the current is switched off, the cell is in a passive state in which no deposition takes place. Alternatively or additionally, a cell can also be put into a passive state by draining the electrolyte from the cell into a storage tank. Such a setup is also possible if deposition takes place not electrochemically, but purely chemically (i.e., without an external power source).Here too, a cell (or a cell arrangement) can be put into the passive state by draining the bath from the cell.

[0028] In the specific embodiment shown, the strip electroplating system 10 comprises a first cell 21, a second cell 22 located downstream of the first cell 21 in the conveying direction, and a third cell 23 located downstream of the second cell 22 in the conveying direction. In addition, an additional cell 24 is provided, located upstream of the first cell 21 in the conveying direction.

[0029] Furthermore, a degreasing station 12, rinsing stations 30 and a separation station 32 at the end of the strip electroplating plant 10 are provided.

[0030] It should first be emphasized that the cell arrangement shown is only an example, but many aspects of the invention can be clearly illustrated using the chosen arrangement.

[0031] In the concretely illustrated embodiment, the strip electroplating system 10 serves to produce a strip-shaped base element 40, as is shown for example in Fig. 2. In the exemplary embodiment shown, the strip-shaped base element 40 is an elongated, punched pre-product with a carrier section 40a and a plurality of pins 40b extending from the carrier section 40a, which are coated at least in sections with a surface coating O in the baths B of the cells (see Fig. 3 and Fig. 4).

[0032] In the specific embodiment shown, the pins are to be coated for later processing with a three-layer product surface coating, which is designated here as O1. The base element 40 can be made of copper, for example, and in the specific embodiment, the product surface coating O1 consists of a first layer L1 of nickel, a second layer L2 covering this layer, which contains nickel and phosphorus, and a third layer L3 of gold, which in turn covers the second layer L2 (see Fig. 6). Accordingly, the bath in the first cell 21 is a nickel bath, the bath in the second cell 22 is a nickel-phosphorus bath, and the bath in the third cell 23 is a gold bath.

[0033] In the illustrated embodiment, the additional cell 24 also contains a gold bath or a copper bath. The function of this will be discussed later.

[0034] The Fig. 5 shows the strip electroplating plant 10 when the coating process carried out with it is in the product production branch in order to carry out the process just described and in Fig. 6 to produce the product surface coating O1 shown. Here, the first cell 21, the second cell 22, and the third cell 23 are in their active state, while the additional cell 24 is in its passive state.

[0035] If one wishes to perform an X-ray fluorescence measurement on the product surface coating shown above with respect to the second layer L2 (the NiP layer), particularly with respect to the ratio between nickel and phosphorus, two problems arise: Firstly, the fluorescence signal from the first layer L1 (the nickel layer) overlaps with the nickel signal originating from the second layer, making it virtually impossible to determine the nickel-to-phosphorus ratio in the second layer L2. Secondly, the third layer L3 (the gold layer) significantly attenuates the X-ray fluorescence signals of nickel and phosphorus; provided the gold layer is thick enough, a fluorescence measurement of the underlying light elements with sufficient accuracy / quality is practically impossible.

[0036] The process used to operate the strip electroplating plant therefore additionally includes at least one sample generation branch, in which a sample surface coating O2 is generated that differs from the product surface coating. Fig. 5, only the second cell 22 is active (see Fig. 7). This, of course, only deposits the second layer L2 (according to the above nomenclature), i.e., the NiP layer. The operating state of the second cell 22 is not changed, so that the (in this embodiment, only) layer of the sample section 44 is similar to the second layer of the product section. The only layer can, of course, be easily measured using X-ray fluorescence (see Fig. 8 and Fig. 9).

[0037] Thus, a band-shaped sample section 44 is temporarily created. The band-shaped base element preferably continues to run continuously without interrupting the transport and without changing the conditions in the second cell 22, so that the second layer L2 (the only layer in the sample section) in the sample section and the product section are essentially identical. The sample section is separated by means of the separation station, since such a sample section naturally does not represent a product suitable for further processing, but serves exclusively for analysis and documentation purposes.

[0038] Regarding the Fig. Figures 10 to 12 describe a second embodiment, in which the same strip electroplating system as described above can be used. Here, too, a three-layer surface coating is to be produced in the product production branch of the process, as described above (see Figures 10 to 12). Fig. 11). In the second embodiment, the band-shaped base element 40 could, in particular, consist of a nickel-containing material, for example, of a nickel-containing steel, which gives rise to the further problem that the band-shaped base element 40 itself could make the measurement of the second layer L2 (i.e., the nickel-phosphorus layer) impossible. To counteract this, in the sample generation branch of this second embodiment, the additional cell 24 is switched to its active state, while the first and third cells remain passive, as in the first embodiment ( Fig. 10). Thus, in sample section 44, a “barrier layer” of, for example, gold or copper (additional layer L z ) generated ( Fig. 12), which has no equivalent in the product section and shields the X-ray fluorescence signal of the ribbon-shaped base element, so that the nickel-phosphorus layer (second layer L2) can be easily examined by X-ray fluorescence analysis.

[0039] These two examples already demonstrate that even in a multilayer coating system, each layer in the sample generation branch of the process can be prepared in such a way that it can be analyzed non-destructively, particularly by X-ray fluorescence. A corresponding sample piece (i.e., a base element or a section of a base element bearing a sample surface coating) is therefore also very well suited for storage for documentation purposes.

[0040] Finally, it should be mentioned that the method according to the invention is suitable for all types of coating processes, since it only matters to produce, in a sample production branch of the method, a sample surface coating which has a layer which corresponds to a layer of the product surface coating (in particular has the same composition), but the layers of the sample surface coating and the product surface coating differ with respect to at least one layer. List of reference symbols 2 input coil 5 Output coil 10 strip electroplating plant 12 Degreasing station 21 first cell (with Ni bath) 22 second cell (with NiP bath) 23 third cell (with Au bath) 24 additional cells (with Au bath) 30 rinsing stations 32 separation station 40 band-shaped basic element 40' strip-shaped base element coated at least in sections 40a support section 40b pin 42 Product section 44 sample section 48 non-band-shaped basic element 51 first tank (with Ni bath) 52 second tank (with NiP bath) 53 third container (with Au bath) 54 additional containers (with Au bath) 60 Source of stimulation 62 X-ray detector B Bath L1 first layer (Ni layer) L2 second layer (NiP layer) L3 third layer L z additional layer O Surface coating O1 Product surface coating O2 sample surface coating

Claims

[1] Method for producing a product surface coating (O1) comprising at least one layer, wherein the method comprises a product production branch in which the product surface coating (O1) is deposited, characterized by that the method further comprises at least one sample generation branch for generating a sample surface coating (O2) having at least one layer, wherein the layer structure of the sample surface coating (O2) differs from the layer structure of the product surface coating (O1) with respect to at least one layer and the sample surface coating has at least one layer which is similar to the product surface coating, and where the deposition of the surface coatings takes place on a band-shaped base element (40) which passes through at least two serially arranged cell arrangements, each with at least one cell (21, 22, 23, 24) filled or fillable with a bath, so that when the process is in its product production branch, the product surface coating (O1) is deposited on the strip-shaped base element (40) and thus a strip-shaped product section (42) is produced, and when the method is in its sample generation branch, the sample surface coating (O2) is deposited on the band-shaped base element (40) and thus a band-shaped sample section (44) is generated. [2] Method according to claim 1, characterized bythat the product surface coating (O1) has at least two layers, one of the two layers covering the other layer, and the sample surface coating (O2) does not have one of these two layers, namely either the covering layer or the covered layer. [3] Method according to claim 2, characterized by that the product surface coating (O1) has three layers (L1, L2, L3), namely a first layer (L1), a second layer (L2) covering the first layer (L1) and a third layer (L3) covering the second layer (L2), and the sample surface coating (O2) does not have at least the first layer (L1) or the third layer (L3), preferably neither the first layer (L1) nor the third layer (L3). [4] Method according to one of the preceding claims, characterized bythat at least one layer which is present in both the product surface coating and the sample surface coating is a nickel-phosphorus layer, wherein the phosphorus content is preferably at least 5 mass percent. [5] Method according to claim 4, characterized by that the nickel-phosphorus layer in the product surface coating is deposited on a nickel-containing layer, preferably on a layer whose nickel content is at least 50 mass percent. [6] Method according to one of the preceding claims, characterized by that the sample surface coating (O2) has at least one additional layer (L z ) which is not present in the product surface coating (O1) and which is at least partially covered by at least one layer which is also provided in the product surface coating. [7] Method according to claim 6, characterized by that the additional layer (Lz ) consists of at least 70 percent gold or copper. [8] Method according to one of the preceding claims, characterized by that all layers are deposited from one bath (B). [9] Method according to at least one of the preceding claims, characterized by that at least one of the layers, preferably all layers, are deposited electrolytically. [10] Method according to at least one of the preceding claims, characterized by that produced sample sections (44) are separated from the product sections (42). [11] Method according to one of the preceding claims, characterized by that an element carrying the sample surface coating is analyzed and / or stored for documentation purposes.

Images