JP2003522840A - Method for electroplating articles coated with a conductive polymer - Google Patents

Abstract

(57) [Summary] An object of the present invention is a method for electroplating an article (1) coated with a conductive polymer or a modified polymer, wherein the article has a current density independent of the article to be electroplated. It is an object of the present invention to provide a method capable of simultaneously performing the reduction and the shortening of the electroplating time. According to the invention, as a first step, the article is connected to a power supply (8) by means of a plurality of adjacent contact elements (5), and the points covered by the contact elements are covered with a thin metal coating, and then in a second step. Contact elements are removed and a continuous metallization (10) is formed.

Description

Detailed Description of the Invention

The present invention relates to a method of electroplating an article coated with a conductive or modified polymer. Furthermore, the invention provides a device for implementing this method.

In order to change the surface or surface structure of a flat or three-dimensional article, the electroplating method is a method equivalent to the state of the art even in the case of a non-metal flat surface, and is often actually used. It is a method. Thus, for example, in the manufacture of circuit boards, electroplating provides metallization of the substrate and formation of full contact. Generally, the substrate is made of an insulating material, and most of the surface to be electroplated is coated with a conductive polymer or a modified polymer.

However, plating a metal coating on a large area of an insulating material coated with a conductive polymer or a modified polymer by electroplating usually requires a considerable amount of labor, which is not possible. is there. Due to the fact that the modified polymer has a higher electrical resistivity compared to metallic materials, the current density on the surface of the electroplated article is unevenly distributed, resulting in a uniform strong electric field. Absent. To obtain a continuous metallization layer, either the current density must be increased or the electroplating time must be increased.

In order to avoid the disadvantages associated with increasing electroplating times, it is known in the state of the art to increase the current density. However, excess current density in the contact area destroys the conductive polymer coating. When the conductivity decreases, metal plating by electroplating can no longer be performed. In order to avoid such destruction of the polymeric coating, an appropriately low current density must be selected, but this results in an extended electroplating time and the associated disadvantages.

Therefore, electroplating an article having a conductive polymer coating requires determining and balancing the current density and electroplating time suitable for the article. Thus, in order to obtain a void-free coating, it is necessary to consider the balance between the excess current density on the one hand and the excess electroplating time on the other hand, and thereby redefine the parameters for the article. The large-scale application of this known method in this state of the art is not satisfactory, as it requires very time-consuming adjustments, which would otherwise result in high failure rates.

[0006] To avoid the above disadvantages, a conductive polymer that is separate from the electroplated article and that makes it possible to reduce the current density and at the same time reduce the electroplating time. It is an object of the present invention to disclose a method of electroplating polymeric coated articles.

According to the invention, the article is connected to the power supply by a plurality of adjacent contact elements in the first step of the invention and with a continuous thin metal layer except for the contact sites covered by the contact elements. By coating, this problem is solved. This contact element is removed in the second step, forming a continuous continuous coating.

The present invention further provides for covering an article to be electroplated with a number of adjacent contact elements. This is to create many connections that carry current between the electroplated surface and the power source. The advantage of this is that even at low current densities, there will be enough electric field to electroplate the surface. The conductive polymer coating is connected to a power source to create a nearly uniform electric field that covers the entire surface of the electroplated article.

In the first step of the method disclosed by the present invention, after connecting the contact element to a power source, a thin metal layer is formed on the conductive polymer coating of the electroplated article. This metal layer is unbroken except at the contact points covered by the contact elements. The contact elements are arranged on the surface to be electroplated in such a way that in the first step the plated metal layer extends over the entire surface and forms a continuous metal coating. Due to the large number of contact elements used, plating of the metallization requires a relatively short electroplating time. It is an advantage that the electroplating time does not increase despite the decrease in current density. In contrast, the method of the invention also offers the possibility of reducing the electroplating time despite the reduction in current density. The drawbacks of the methods known in the state of the art, represented by the destruction of polymer coatings by excessive current density or excessive electroplating time, are completely avoided by using the disclosed method of the invention. be able to.

After plating a continuous metal layer except at the points covered by the contact elements, the contact elements are removed in a second step, and the surface area to be electroplated is passed through the metal coating formed in the first step. Energize. A metal plating layer also develops at the contact points covered by the contact elements during the first step, forming a continuous metal coating on the entire surface of the electroplated article. During this second step, a relatively low current density is required as well as a short electroplating time. This is because the metallization formed in the first step covers the surface area, resulting in a generally uniform electric field with a low current density. Moreover, metal coatings are excellent conductors with low resistivity compared to polymer coatings.

The second step is intended to form a continuous and continuous metal coating,
After the completion of the first step, carried out according to the invention in such a way that uncovered contact points are provided with a metal coating, so that the open contact points in this method are
"Closed", a solid metallization is formed in the second step. The second step can also be carried out in such a way that the metal coating formed in the first step continues to grow in order to form a continuous metal coating that also covers the contact points. The second step can also be carried out, for example, using a different electrolyte composition. When carrying out this method, it is important that the connection of the articles to be coated is made by a large number of adjacent contact elements, so that a substantially uniform electric field is formed over its surface. The contact points covered by the contact elements of the surface to be coated can then be closed by the formation of an unbroken metallization in the second step.

According to the method disclosed in the present invention, it is possible to first apply a metal coating to a planar or three-dimensional article having a conductive polymer coating by electroplating, whereby an electric current is applied. Despite the reduced density, only a relatively short electroplating time is required. Thus, the drawbacks of the methods known in the state of the art, that the polymer coating is destroyed by excessive current density and excessive electroplating time, can be avoided.
The electroplating method implemented in accordance with the present invention allows for mass production of electroplated products. The reason is that maximum independence between the electroplated article and the set current density and the selected electroplating time is ensured, and a new electroplating is started. This is because there is no need for costly readjustment of these process parameters each time.

According to one of the features of the invention, the individual contact elements on the surface to be electroplated are
They are placed next to each other in a grid. In this way, both in the first step in which the surface to be coated is connected to the power supply by the contact element and in the second step in which the current is supplied by the metallization formed in the first step, it is evenly distributed over a wide area. It is achieved that the electric field formed is spread over the surface to be electroplated. further,
The metal coating formed in the first step constitutes a continuous conductor. Therefore, it is particularly advantageous if adjacent contact elements are arranged equidistantly.

According to another characteristic of the invention, the contact element carrier is used for the arrangement of contact elements,
It contains several contact elements. On the one hand, the rapid installation of the contact element on the surface to be electroplated is carried out in this way, and on the other hand, the use of the contact element carrier allows a wide range of automation of the method of the invention. The contact element carrier is preferably designed to include a large number of adjacent contact elements whose relative position can be moved for adjustment, so that the contact element carriers as well as the contact element carriers can be adjusted. . Compatible with electroplated articles to ensure that all contact elements on the surface of the electroplated article actually make an electrical connection between the electroplated article and the power source. It is then possible to adjust the contact element. In this way, it is possible to avoid the formation of voids in the metal coating formed.

In a first alternative, a frame carrying contact elements is used as contact element carrier. Such frame-shaped contact element carriers are particularly preferred for electroplating planar articles such as circuit boards. As the present invention suggests, such a frame is rectangular in shape but may have other geometric shapes depending on the application. A number of contact elements are mounted on the frame, which is installed on either all or the individual components forming the frame. It is contacted by the elements of the frame-shaped contact element carrier for the connection between the electroplated surface and the power supply. In this regard, according to another feature of the invention, for large areas, several frames are placed next to each other or on both sides of the electroplated article. Metallizing both sides of a substrate's raw circuit board in a single step is particularly attractive in the case of circuit boards.

According to yet another aspect of the invention, a fixture including a plurality of contact elements.
ure) is used as the contact element carrier. This type of fitting can be used especially for joining three-dimensional articles. It is inserted in a fitting designed for this purpose and is connected to the power supply by means of the contact elements mounted on the fitting.
This method allows seamless electroplating of even geometrically complex shaped articles in one step. Besides designing the contact element carrier as a frame or fitting, it is of course obvious that other shapes are possible. The deciding factor is that the surface of the electroplated article can be covered over a large area by a plurality of contact element carriers with contact elements.

According to another characteristic of the invention, the contact elements are designed such that their relative position can be moved relative to each other on the one hand and to the contact element carrier on the other hand as well. Moreover, depending on the shape of the article, the contact with the article to be electroplated for connection to the power source can be adjusted. Thus, by means of the method of the present invention, not only a well-shaped article surface but also an irregularly shaped complex geometry can be covered with contact elements over the entire area, and the article to be electroplated can be supplied with power. Make sure you can bind to.

According to yet another feature of the invention, a metal grid is used as the contact element carrier. Metal grids are particularly suitable for horizontal use in continuous production facilities. The metal grid consists of a complete conductor so that it is placed on the surface to be electroplated to create a substantially uniform electric field. In this way, the metallization can be formed in a relatively short time and using only low current densities, which basically constitutes the negative (cathode) of the grid. In other words, the areas of the surface to be electroplated that are not covered by the grid are covered by the metal layer. In the second step of this manufacturing method,
The grid is removed and a closed metallization is formed on the surface. In accordance with an advantageous feature of the invention, the grid is in contact with the surface to be electroplated and the article is passed with the electrolyte together with the grid. Therefore, this grid also serves as a conveyor at the same time. In this method, the surface of the article is electroplated by the method of the present invention in view of its short cycle speed, ease of automation, and above all recyclability. A metal grid installed on the article to be electroplated is provided with a counter-anode to ensure that the underlying polymeric coating can be removed without destruction after plating with the initial metal coating, It is another feature of the invention that the metal plated by the metal grid is stripped from the article.

According to yet another feature of the invention, the thickness of the metallization obtained by this method, which is the subject of the invention, can be specified. On the one hand, this can be adjusted by the residence time of the article in the electrolyte, and on the other hand by the coupled current density. In any case, it is possible to form the desired thickness of metallization in the final product.

Further details, features and advantages of the invention are set forth in the following description along with the accompanying drawings.

FIG. 1 shows the production of a circuit board 1 according to the method of the invention. Here, the first of the method
The steps are shown. A substrate 4 made of an insulator and coated with a conductive or modified polymer is inserted into the electrolytic solution 2 substantially perpendicular to the liquid surface 3 of the electrolytic solution. Since the substrate 4 moves almost perpendicularly to the electrolytic solution surface 3, this method can be called a vertical method.

The substrate 4 is connected to the power supply 8 by a plurality of contact elements 5. This is done by a branched wire 9. As schematically shown in FIG. 1, all contact elements 5 are provided on a substrate 4 to be electroplated and are electrically coupled to a power source 8 by means of contact element carriers 7. By way of example, three frame-shaped contact element carriers 7 are shown, each with five contact elements 5. The contact element 5 is
It is connected to each contact element carrier in such a way that they are movable relative to one another and also with respect to the contact element carrier 7. As a result, individual adjustments of the contact elements 5 can be made with respect to the size of the substrate 4 to be electroplated or its geometric shape. When electricity is applied, a substantially uniform electric field is generated based on the plurality of contact elements 5. It extends over the entire surface of the electroplated substrate 4. As a result of the formation of a widespread and uniform electric field, a thin metallization 10 is produced in a short time at a relatively low current density, except for the contact points 6 which are covered by the contact elements 5. By using a plurality of contact elements 5, electroplating can be carried out within a short electroplating time despite the low current density.

FIG. 2 shows the second step in the present invention. Contact point 6 covered with contact element 5
After the metallization 10 has been removed, the contact elements are removed to form an uninterrupted metallization. For this purpose, the metallization obtained in the first step is connected to the power supply 8 by means of electric wires 9. In this method, a substantially uniform electric field is generated, the remaining voids of the metal coating 10 are covered with metal plating, and a seamless metal coating is generated. After the metal coating having a specific thickness is formed, the substrate 4 is taken out of the electrolytic solution 2.

FIG. 3 shows another example of the metal grid 11. It acts as a contact element with a certain extent and is provided with an insulator except at the contact points. In the first step, the article to be electroplated is placed on the grid 11 with the surface to be electroplated facing the grid and transported through the electrolyte 2 in a horizontal fashion. This is shown schematically in FIG. In this figure, the grid 11 is shown as an endless band which also functions as a conveyor. By means of the receiving roll 12, the grid 11 is moved in the transport direction 14 by the drive 13. The grid 11 is, for example, a sliding contact 15
Is connected to the power supply 8. For the production of circuit boards and the like, the base body 4 is mounted on the grid 11 in the mounting position. The mounting position 16 is located outside the electrolytic solution tank 17. The substrate 4 mounted on the grid 11 is transferred in the direction of 14, enters the electrolytic solution tank 17, and is immersed in the electrolytic solution 2. Since the grid 11 moves substantially parallel to the electrolytic solution surface 3, this method is called a horizontal method, in contrast to the vertical method described above. As a result of covering a large area of the surface of the substrate 4 to be electroplated, relatively weak current densities and short electroplating times are required to form the initial metallization. After the formation of this metal coating, the substrate 4 is taken out from the electrolytic solution tank 17 in the direction 14 and the removal position 18
Be transferred to. There, the substrate 4 is removed from the grid 11. To prevent the contact location from being electroplated permanently, the metal plated there can be melted by a counter-anode means. After the completion of the first step and the formation of the metal coating according to FIG. 4, a seamless metal coating is formed in the same manner as the vertical method described above.

5 and 6 respectively show two alternatives of the contact element 5 located on the contact element carrier 7. The contact elements shown in FIGS. 5 and 6 differ in relative mobility in the pulling direction 20. This is achieved by suitable spring elements. The contact elements are each designed as follows: The current contact pin 21 moves radially with respect to the base body 4 (pulling direction 20). An insulator 22 surrounds the contact pin 21 and is attached to the contact element carrier 7 by means of a threaded connector 23. This design has the advantage that the contact element 5 also fits in an uneven plane of the substrate 4. By this method, a plurality of contact elements 5 contacts the base body 4 and ensures that an electrical connection between the base body 4 and the power supply 6 is obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram of the first step of the method of the present invention for manufacturing a circuit board in a vertical manner.

FIG. 2 is a schematic view of the second step of the method of the present invention for manufacturing a circuit board in a vertical manner.

FIG. 3 is a schematic view of a grid used as a contact element carrier.

FIG. 4 is a schematic view of the first step of the method of the present invention for manufacturing a circuit board in a horizontal mode.

FIG. 5 is a schematic sectional view of a contact element according to a first application design.

FIG. 6 is a schematic sectional view of a contact element according to a second application design. DESCRIPTION OF THE SYMBOLS OF THE DRAWINGS 1 Circuit board 2 Electrolyte solution 3 Electrolyte solution level 4 Substrate 5 Contact element 6 Contact point 7 Contact element carrier 8 Power source 9 Electric wire 10 Metal coating 11 Grid 12 Receiving roll 13 Drive device 14 Transfer device 15 Sliding contact 16 Mounting position 17 Electrolyte tank 18 Removal position 19 Counter anode 20 Stroke direction 21 Contact pin 22 Insulator 23 Connection device

─────────────────────────────────────────────────── ─── Continued front page    (81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, I T, LU, MC, NL, PT, SE, TR), OA (BF , BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, G M, KE, LS, MW, MZ, SD, SL, SZ, TZ , UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AG, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, B Z, CA, CH, CN, CR, CU, CZ, DE, DK , DM, DZ, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, J P, KE, KG, KP, KR, KZ, LC, LK, LR , LS, LT, LU, LV, MA, MD, MG, MK, MN, MW, MX, MZ, NO, NZ, PL, PT, R O, RU, SD, SE, SG, SI, SK, SL, TJ , TM, TR, TT, TZ, UA, UG, US, UZ, VN, YU, ZA, ZW

Claims (19)

[Claims] 1. An article is connected to a power supply by a plurality of adjacent contact elements in a first step and coated with a thin metal layer except for the contact pins covered by the contact elements and in a subsequent second step. A method of electroplating an article coated with a conductive or modified polymer, which comprises removing the element to form a continuous metallization. 2. The method according to claim 1, wherein the contact elements are arranged next to each other in a grid pattern on the surface of the article to be electroplated. 3. The method according to claim 1, wherein adjacent contact elements are located equidistant from each other. 4. A method according to claim 1, characterized in that a contact element carrier with a plurality of contact elements is used for the arrangement of the contact elements. 5. A method according to claim 4, characterized in that a frame fitted with contact elements is used as contact element carrier. 6. The use of several frames next to each other and / or on both sides of an electroplated article to cover a large area of the electroplated surface. The method described. 7. Method according to claim 4, characterized in that a rack fitted with several contact elements is used as contact element carrier. 8. The contact element can be adjusted in its relative position with respect to the contact element carrier and is arranged to be connected to a power supply, depending on the geometry of the article. The method described in. 9. The method according to claim 4, characterized in that a metal grid is used as the contact element carrier. 10. The method of claim 9 wherein a grid is placed on the surface of the article to be electroplated and the article is guided with the grid through an electrolyte. 11. The method according to claim 10, wherein the metal layer deposited on the metallic contact points is dissolved by means of a counter-anode. 12. The method according to claim 1, wherein the thickness of the metal coating produced is selectable. 13. One of the claims 1 to 12, characterized in that at least one contact element carrier with a plurality of adjacent contact elements is provided for the connection of the article to be plated with a power supply. A fixture for performing the method described in. 14. A fixture according to claim 13, wherein each contact element is mounted on the contact element carrier in such a way that its position on the contact element carrier is adjustable. 15. Fitting according to claim 13 or 14, characterized in that the contact element carrier is designed in the form of a frame or a rack. 16. A fitting according to claim 13 or 14, characterized in that the contact element carrier is a metal grid on which an article to be electroplated can be mounted. 17. The fitting of claim 16 wherein the metal grid is formed and is an endless belt. 18. The fixture of claim 17, wherein the grate simultaneously functions as an article conveyor. 19. A fixture according to claims 16-18 characterized in that a counter-anode is used to prevent plating at the contact points.