HK1069607B - Method for selectively electroplating a strip-shaped, metal support material - Google Patents

Description

Method for the local electroplating of a strip-shaped metal substrate

Technical Field

The invention relates to a method for continuously and locally electroplating a strip-shaped metal substrate, in particular a base strip with pre-stamped contacts.

Background

In the method disclosed in DE19934584a1, the substrate is first completely painted by painting or dipping in paint. The lacquer is then removed by a laser at those locations where the contact material should be plated.

In this known method, only a coating layer of non-uniform thickness can be disadvantageously obtained by both painting and dipping. This problem becomes acute for three-dimensional substrates because the paint then builds up very thickly at the corner corners. In addition, the complete lacquer layer absolutely necessary for the process can only be obtained if the lacquer layer is comparatively thick. This leads to long work times when the material of the site to be plated is removed with a laser, or a high-power laser must be used. Since the lacquer layer on the region to be electroplated has to be completely removed, the laser beam has to be adjusted in order to also remove the lacquer layer on the thickest region. This in turn leads to the laser beam damaging the substrate at the location where the layer thickness is small. A further disadvantage of the known method is that even very small areas are electroplated, a lot of lacquer is required in order to completely coat the substrate with a layer of lacquer. The extremely accumulation of paint becomes more difficult in order to obtain the thicker layers of paint required for a complete paint layer and especially in the case of three-dimensional substrates. It is also considered that the lacquer material required for this method is relatively expensive.

Disclosure of Invention

It is an object of the present invention to further develop the known method such that it allows a faster transport of the strip-shaped substrate along the electroplating line and with very low requirements for the coating composition.

To this end, the invention provides a method for the continuous partial electroplating of a strip-shaped substrate of metal,

a) in an electrophoretic coating unit, a part of the band-shaped substrate is coated with at least one paint stripe using an electrophoretic paint,

b) removing the paint from those parts of the at least one paint strip which are to be electroplated by means of a laser,

c) in the electroplating operation, a metal layer is plated on the paint removing part in the at least one paint strip through local electroplating,

d) the at least one paint strip is then removed.

The advantage of the process according to the invention is that, in electrophoretic coating, a complete coating layer can be obtained with a significantly thinner coating layer, the coating layer having a very stable layer thickness. In this way, damage to the substrate can be effectively prevented when the lacquer layer is removed by means of laser treatment. In addition, very thin layers of paint can be removed more quickly and with less power, which allows for rapid substrate travel. The deposition of the electrophoretic paint on the substrate proceeds very rapidly, which in turn enables the substrate travel speed to be further increased. This advantage can be enhanced by applying only a partial layer of paint, such as a paint stripe or stripes. These lacquer strips are applied only in those regions where the cover plating is to be applied. Thus, in addition to saving expensive paint, the paint can be removed more quickly at the end of the treatment.

Even in the case of three-dimensional substrates, this electrocoating step results only in a thin uniform paint layer, so that the paint layer can also be subjected to a partial electroplating operation. Since the paint removal operation by the laser action can be controlled practically at will, a spot-like plated layer can be obtained in addition to the strip-like plated layer.

The strip-shaped substrate is preferably passed through a cleaning and/or activation and/or rinsing unit before painting in order to provide optimum initial conditions.

Advantageously, a plurality of lacquer strips are applied to the same or to both sides of the band-shaped substrate with the same or different widths. In this case, the width of the paint strip can be precisely adjusted by the electrodeposition coating method, so that the minimization of the required paint can be obtained by optimizing the strip width.

The layer thickness of the lacquer strips is adjusted depending on the applied voltage, the paint composition and the speed of travel of the substrate, in particular here the cationic or anionic electrophoretic coating is carried out. By means of this precisely adjusted thickness of the lacquer layer, it is also possible to remove the lacquer layer completely at the desired location by appropriately adjusting the laser beam, wherein damage to the substrate is still prevented.

For electrophoretic painting, the electrodes in the housing of the painting device are suitably shielded from the substrate by a slit diaphragm, the width of the paint strip being adjusted according to the slit width and the distance between the diaphragm and the substrate. By means of the partition plate with multiple slits, a plurality of paint strips can be formed accordingly.

After painting, the substrates are suitably rinsed and dried, in particular in an oven or using uv light. Furthermore, it is appropriate to rinse the substrate after the laser depainting.

The areas from which the lacquer has been removed by the laser are now plated by one or more of the following partial plating methods: the partial immersion in the electroplating bath, the covering of the area outside the at least one paint line by means of a mechanical shield or a belt tool, and the application of the electrolyte by means of etching, desmear or brushing techniques.

Drawings

Embodiments of the invention are illustrated in the drawings and will be described in detail in the following description.

FIG. 1 schematically shows a plurality of stations of a local electroplating plant for carrying out the method according to the invention.

Fig. 2 schematically shows a painting unit for painting a strip of paint of a desired width.

Fig. 3 is an end view of a base strip having three paint stripes on the front and back sides.

Fig. 4 shows the base band shown in fig. 3 in a perspective view.

FIG. 5 shows in end view a stamped base strip having two painted stripes.

Fig. 6 shows the base strip shown in fig. 4 in a perspective view.

Fig. 7 shows in end view a three-dimensional base strip with a strip of lacquer on the protrusion.

Fig. 8 shows the base strip shown in fig. 7 in a perspective view.

Fig. 9 shows in end view a three-dimensional base strip with a lacquer strip.

Fig. 10 shows the base strip shown in fig. 9 in a perspective view.

Fig. 11 shows in end view a base strip with a strip of paint and a shield for partial plating, wherein one strip area of paint has been removed by laser treatment.

Fig. 12 shows the base tape shown in fig. 11 in a perspective view.

Detailed Description

The electroplating device shown in fig. 1 for the partial electroplating of the metal strip is designed as a so-called reel-to-reel installation, in which the metal strip 10 is continuously unwound from a first reel or reel 11 and, after passing through the electroplating device, is again wound as a finished strip onto a second reel or reel 12. In this case, a belt speed of 20m/min or more is possible.

First, the base strip 10 passes through a preparation station 13, where the base strip 10 is cleaned, activated and rinsed.

The base strip 10 then passes through a painting station 14 where partial electrophoretic painting takes place. The painting station 14 may include one or more painting units 15, as shown schematically in FIG. 2. Such a painting unit generally comprises an enclosure, such as an enclosure, which is protected against uncontrolled deposition of paint in undesired areas. For this purpose, the separating walls 17, 18, which are made of teflon or another electrically non-conductive plastic, like the remaining housing part, are arranged in such a way that they shield the uncoated region of the base strip 10 against a plate-shaped anode 19. Since the two partitions 17, 18 form the slot 20, a strip of paint of corresponding width is formed on the base strip 10 by electrophoretic painting of the paint. Further, the anode 19 is made of high-quality steel, but may be plated with titanium.

The illustrated painting unit 15 is designed for anionic electrophoretic painting, for which anionic electrophoretic painting is used. Such a lacquer layer is resistant to plating solutions of acidic media such as nickel, gold or tin and can be dissolved in an alkaline environment. For the purpose of anionic electrophoretic painting, the anode 19 is connected to the positive pole of a source of electroplating voltage, and a contact device 21 is arranged in front of the unit for supplying current to the base strip 19. As an alternative, cationic electrophoretic coating using cationic electrophoretic coating is also possible. Cationic electrodeposition paints are resistant to alkaline media and can be dissolved in acidic environments. The polarity is reversed, that is, a cathode replaces the anode 19.

The painting unit 15 is designed such that the formed paint strip or painted portion is not damaged after the coating process. This is achieved, for example, by means of not shown guide rollers which are arranged in front of and behind the painting unit 15 and which position the substrate precisely in the vertical and horizontal directions so that the area of the painting strip 22 does not touch parts of the housing 16. The distance between the base strip 10 and the separating walls 17, 18 is selected such that, on the one hand, a sufficiently good barrier effect is present, and, on the other hand, no contact points are present.

The paint in the paint tank is supplied to the painting unit 15 through a nozzle. A pump located in the paint tank is connected via a line to the painting unit, where the paint supply can be set or controlled by means of an intermediate throttle, also shown. A filter device may also be provided. The paint delivery pump is constructed so as to prevent electrification by using a less slippery material on all moving parts to be surrounded by paint, since otherwise paint deposition on moving parts that may be electrified and come into contact with paint may occur.

In fig. 3-10 different types of base tape are shown by way of example, which are equipped with differently arranged lacquer strips.

In the base strip shown in fig. 3 and 4, three paint strips 24-26 of different widths are applied to the front and back, either by means of the paint units 15 arranged one behind the other or by means of paint units having a plurality of slots 20 and having spacers and anodes or cathodes arranged on both sides of the base strip 23.

The base strip 27 as shown in fig. 5 and 6 is pre-stamped in such a way that a plurality of contacts have been formed, which can be broken or cut after the machining has been completed. Two paint strips 28, 29 are applied.

To form a plurality of contacts, the base strip 30 is also pre-stamped as shown in fig. 7 and 8, where the contacts have semicircular projections 32 on one side of a fixing strip 31 that secures them together, so that the base strip 30 is in a three-dimensional configuration. A strip of paint 33 is applied to the outer surface of the protrusion 32.

The base strip 34 shown in fig. 9 and 10 is also three-dimensionally shaped with a fixing strip 35 connecting the ends of these contacts 36. These contacts 36 are boxed in the middle region, with a strip of lacquer 37 extending over the central part of the boxed protrusion. In the case of a three-dimensional base tape, as shown in fig. 7-10, the partial lacquer stripe(s) are applied over the entire spatial height.

After applying the one or more paint stripes, the base strip 10 as shown in FIG. 1 is passed through a drying station 38. The drying and thus the partial polymerization is carried out in a furnace of the drying station 38, in which there is a uniform temperature distribution. Alternatively, the paint chips can be dried with UV light and partially polymerized.

Next, the substrate 10 is passed through a laser station 39 for partial removal of the lacquer. This or these lacquer strips are removed by means of the laser beam of the laser 40 at the painted areas which are to be subsequently electroplated. Furthermore, it is possible to remove the lacquer in strips and on individual surfaces by laser machining these surfaces, for example by vibration. Of course, it is also possible to remove the paint in strips several times in one paint strip by means of a laser. The tolerances for stripping and subsequent plating are small and equal to about 50 microns. The laser beam did not damage the substrate and the paint was removed thoroughly. This is ensured by adjusting the laser in terms of energy, wavelength, intensity and period of the pulse. As shown in fig. 11 and 12, a strip 42 is removed from the paint strip 22 applied to the substrate 10 at the laser station 39.

The base strip 10 is now passed through a plating station 43, in which the areas 42 from which the lacquer has been removed by means of the laser are plated. This is achieved by known localized electroplating methods. In this case, as shown in fig. 12, the region of the substrate tape 10 outside the lacquer strip 20 is masked by means of two continuously running belts 44. Here, the speed of the belt 44 is equal to the speed of the base tape 10 traveling, so that the belt 44 operates synchronously accordingly. The free area between the two belts 44 is now wetted with the plating solution by means of a cloth, brush or the like and plated simultaneously. Depending on the desired layer thickness, the electroplating can be carried out in several steps. If the varnish strip is located in an edge region of the base tape 10, the partial plating can be performed by partial immersion in a plating solution. Alternatively, other mechanical shields may be used, wherein desmear techniques and brush coating techniques are other known localized plating methods.

As a final step, in a paint removal station 45, the paint is completely removed by passing the base strip 10 through a suitable aqueous solution. The aqueous solution may be acidic or basic, depending on whether cationic or anionic electrophoretic coating is used.

Of course, various materials such as gold, palladium, silver and zinc may be electroplated onto the base strip 10, the base strip 10 typically being composed of brass, copper or copper alloys. Different plating layers can be stacked, wherein the required steps are performed one after the other for this purpose. The base strip 10 may also have a conventional coating, such as a partial coating without a paint coating, for example.

As mentioned above, the method of the invention may be carried out by a base tape having pre-punched contacts or other elements as shown in fig. 5-10, or the base tape may be full-faced, as shown, for example, in fig. 3, 4, 11 and 12. In the latter case, the stamping operation may also be performed after the plating operation, although this would require more lacquer and plated metal.

Claims (12)

1. A method for the continuous, localized electroplating of a strip-shaped substrate of metal,

a) in an electrophoretic coating unit (14, 15), portions of the band-shaped substrate (10, 23, 27, 30, 34) are coated with at least one coating strip (22, 24-26, 28, 29, 33, 37) by means of an electrophoretic coating,

b) removing the paint from those areas (42) of the at least one paint strip (22, 24-26, 28, 29, 33, 37) which are to be plated by means of a laser (40),

c) in the electroplating operation, a metal layer is applied to the paint removal region (42) in the at least one paint strip (22, 24-26, 28, 29, 33, 37) by local electroplating,

d) the at least one lacquer strip (22, 24-26, 28, 29, 33, 37) is then removed.

2. The method of claim 1, wherein the tape substrate is a tape having pre-punched contacts.

3. The method as claimed in claim 1, characterized in that the band-shaped substrate (10, 23, 27, 30, 34) is subjected to a cleaning and/or activation and/or rinsing process before the painting.

4. A method as claimed in any one of claims 1 to 3, characterized in that a plurality of paint strips (24-26, 28, 29) are applied to the same or to both sides of the band-shaped substrate (23, 27) with the same or different widths.

5. A method as claimed in one of claims 1 to 3, characterized in that the layer thickness of the paint strip is adjusted as a function of the applied voltage, the paint composition and the speed of travel of the band-shaped substrate, whereby a cationic or anionic electrophoretic coating is effected.

6. A method as claimed in one of claims 1 to 3, characterized in that the electrode (19) in a housing (16) of the painting device (14, 15) is shielded against the band-shaped substrate (10) by means of a slit diaphragm (17, 18), the width of the paint strip being adjusted in dependence on the slit width (20) and the distance between said diaphragm (17, 18) and the band-shaped substrate (10).

7. The method as claimed in one of claims 1 to 3, characterized in that the band-shaped substrate (10, 23, 27, 30, 34) is rinsed after painting and dried in an oven (28) or by means of UV light.

8. A method as claimed in any one of claims 1 to 3, characterized in that the stripes and/or the individual plated areas (42) are formed by laser depainting.

9. A method as claimed in any one of claims 1 to 3, characterized in that the band-shaped substrate (10, 23, 27, 30, 34) is rinsed after the laser depainting.

10. A method according to any one of claims 1 to 3, characterized in that the areas (42) where lacquer is removed by means of a laser (40) are plated by one or more of the following partial plating methods: the part is immersed in the electroplating solution, the region outside the at least one paint strip is covered by means of a mechanical shielding (44), and the electrolyte is applied by means of an etching technique, a desmear technique or a brush technique.

11. Method according to one of claims 1 to 3, characterized in that after the electroplating is completed, the at least one lacquer strip (22, 24-26, 28, 29, 33, 37) is completely removed in an alkaline or acidic aqueous solution.

12. The method of claim 10, wherein the mechanical shield (44) is a belt tool.