GB2324805A

GB2324805A - Electroplating

Info

Publication number: GB2324805A
Application number: GB9709412A
Authority: GB
Inventors: Robert Platt
Original assignee: PLATT ELECTROMECK Ltd
Current assignee: PLATT ELECTROMECK Ltd
Priority date: 1997-04-30
Filing date: 1997-04-30
Publication date: 1998-11-04
Also published as: GB9709412D0

Abstract

An electroplating apparatus comprises a bath 2, for receiving electrolyte and means for receiving and mounting an article 18 to be electroplated in the bath, and at least one anode 16 extending over a substantial portion of the vertical length of the bath in the region of the article to be electroplated. A corresponding method is also disclosed. Means may be provided for driving the electrolyte through the bath past the article to be electroplated. Recirculation means for the electrolyte may also be provided. The electroplating material may be copper.

Description

METHOD AND APPARATUS FOR ELECTROPLATING Field of the Invention The present invention relates to methods and apparatus for electroplating, in particular, though not exclusively, to such methods and apparatus for copper electroplating cylinders for gravure rollers.

Backaround to the Invention It is known to locate a cylinder to be electroplated for a gravure roller with its longitudinal axis horizontally disposed partly submerged in an electrolyte with curved anodes disposed about the submerged surface of the cylinder. The cylinder is rotated to ensure its entire surface is coated. By way of example, such an apparatus is disclosed in international patent application publication number WO-A-95/21952. However, such an arrangement does not result in an even coating of the roller in practice.

It is known from United Kingdom patent application publication number GB-A-2,208,873 to provide a component to be electrolytically coated with the axis of the plating surface substantially vertical while passing an angular jet of electrolytic solution over the surface of the component. An anode is provided over a narrow region of the component to be coated. The method and apparatus of GB-A-2,208,873 is specifically intended for electroplating small parts of a whole component. This apparatus does not coat a substantial region of the surface and would appear to be unsuitable for coating rollers in particular.

It is an aim of preferred embodiments of the present invention to obviate or overcome at least one disadvantage of the prior art, whether referred to herein or otherwise.

Sugary of the Invention According to the present invention in a first aspect, there is provided an electroplating apparatus comprising a bath for receiving electrolyte and means for receiving and mounting an article to be electroplated in the bath, and at least one anode extending over a substantial portion of the vertical length of the bath in the region of the article to be electroplated.

Suitably, the apparatus comprises means for driving the electrolyte through the bath past the article to be electroplated. Suitably, the driving means is adapted to drive electrolyte vertically past the article, preferably upwards. Suitably, the apparatus comprises eductors through which the electrolyte is driven. Suitably, the bath is in a tank for holding overflowing electrolyte.

Suitably, the apparatus comprises means for recirculating electrolyte. Suitably, the recirculation means comprises a pump and tubing adapted to take electrolyte from near the bottom of the tank into the bath or from near the top of the tank into the bath.

Suitably, there are a plurality of anodes. Suitably the anodes define a generally cylindrical electroplating region. Suitably, the anodes are evenly spaced.

Suitably, the at least one anode comprises a plurality of metallic pieces in a holder and an opening to the holder whereby further metallic pieces can be inserted in use.

Suitably, the bath has a longitudinal axis and the at least one anode comprises an elongate body having an axis generally parallel to the longitudinal axis of the bath.

Suitably, the at least one anode comprises an elongate, generally straight tube. Alternatively, the at least one anode comprises a ring. Suitably, there are a plurality of anode-rings stacked vertically.

Suitably, the apparatus is for coating a cylindrical body, preferably a roller and more preferably a gravure cylinder roller.

According to the present invention in a second aspect, there is provided a method for electroplating an article, the method comprising the steps of providing an electroplating apparatus according to the first aspect of the invention, at least partly filling the bath with an electrolyte, at least partly immersing an article to be electroplated in the electrolyte, and providing a voltage across the anode and a cathode.

Preferably, the article is completely immersed in the electrolyte.

Suitably, the article is generally circular symmetrical and has a longitudinal axis.

Suitably, the method comprises the steps of driving electrolyte past the article to be electroplated.

Suitably, electrolyte is driven vertically past the article, preferably upwards. Suitably, the article is held substantially stationary relative to the apparatus.

Brief Description of the Drawings The present invention will now be described, by way of example only, with reference to the drawings that follow; in which: Figure 1 is a schematic plan view of parts of an electroplating apparatus according to a first embodiment of the present invention without the cylinder mounting apparatus.

Figure 2 is a schematic cross-sectional illustration of the electroplating apparatus of Figure 1 on the line II-II.

Figure 3 is a schematic sectional side view, similar to Figure 2, but showing the electrolyte pumping arrangement without many of the other items of Figures 1 and 2.

Description of the Preferred Embodiments Referring to Figures 1-3 of the drawings that follow, there is shown an electroplating apparatus according to a first embodiment of the present invention. It is noted that the feature of Figures 2 and 3 are combined in the apparatus. They are shown separately for ease of explanation. The electroplating apparatus comprises an outer tank 2 within which is disposed an inner bath 4.

The inner bath 4 terminates at a height lower than the outer tank 2. The outer tank 2 is generally cuboidal while the inner bath 4 is cylindrical.

A copper based electrolyte 6 fills inner bath 4 and partly fills outer tank 2. The electrolyte consists of the known copper sulphate and sulphuric acid solutions with the usual additive components.

Pumps 8a, 8b and tubing 10 for pumping electrolyte 6 from outer bath 2 into inner bath 4 through twelve 3/4 eductors 12 disposed in a ring. Pump 8a draws electrolyte from the region of the top of the electrolyte level while pump 8b draws electrolyte from the bottom of the outer bath 2 through a filter 14 to eductors 12. Electrolyte 6 overflows from inner bath 4 into outer tank 2. The arrangement is configured to drive 60,000 litres of electrolyte through the system per hour.

In the inner bath 4, are disposed ten 60 mm anode baskets 16 hanging from a copper mounting ring 17. The anode baskets 16 are circular cylindrical elongate tubes, open at one end. The anode baskets 16 are filled with copper chips (not visible) so they can be readily recharged. Each anode basket 16 extends for substantially the entire length of inner bath 4. The longitudinal axis of each anode basket 16 is generally vertical. The anode baskets 16 are disposed in a circle, evenly spaced, about the longitudinal axis of inner bath 4.

In the inner bath 4 within the ring of anode baskets 16, is disposed a gravure roller cylinder 18 to be electroplated. The cylinder 18 is held in position by a universal cylinder clamp 20 (not shown in Figure 1). The cylinder 18 is disposed with its longitudinal axis as near as possible to the longitudinal axis of the inner bath 4.

The cylinder 18 is entirely submerged in the electrolyte 6.

The electrolyte is driven by eductors 12 between the anode baskets 16 and the cylinder 18.

A combined power supply and control unit 22 regulates the current and voltage applied to the apparatus. The cylinder 18 is connected to a cathode 24.

In use, the arrangement of anodes 16 about the cylinder 18 ensures that the rate of coating of the cylinder 18 is substantially constant. The recirculation of electrolyte 6 by pumps 8a, 8b ensures that relatively fresh electrolyte is available throughout.

The cylinder 18 is maintained stationary relative to the coating apparatus while electrolyte is driven past and across its to be coated surface. This is contrary to most electrolytic coating systems in which the cylinder is moved relative to the apparatus. The stationary cylinder 18 helps reduce agitation in the electrolyte 6 so local concentration and dilutions of metal in the electrolyte are reduced.

Using this arrangement it has been found possible to provide a substantially constant coating rate of 20 amps per square decimeter. The combined power, supply and control unit 22 varies the voltage to maintain a substantially constant current density. Where it is desired not to coat the ends of the cylinder, or in the case in which the cylinder is shorter than the anodes, one of more screens can be provided between the anodes and cylinder to prevent or restrict coating.

An anode arrangement of a second embodiment according to the present invention comprises circular torroidal anodes 30 stacked in a spaced column, one on top of the other about a common longitudinal axis.

Other arrangements of anodes will be suitable and apparent to those skilled in the art.

By providing a bath 4 in which the cylinder 18 can be mounted vertically (ie its longitudinal axis substantially vertical), the entire cylinder can be submerged in electrolyte and surrounded by an arrangement of anodes to provide an even coating thickness.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMS:

1 An electroplating apparatus comprising a bath for receiving electrolyte and means for receiving and mounting an article to be electroplated in the bath, and at least one anode extending over a substantial portion of the vertical length of the bath in the region of the article to be electroplated.

2 An electroplating apparatus according to Claim 1, in which the apparatus comprises means for driving the electrolyte through the bath past the article to be electroplated.

3 An electroplating apparatus according to Claim 2, in which the driving means is adapted to drive electrolyte vertically past the article.

4 An electroplating apparatus according to any preceding Claim, in which the apparatus comprises eductors through which the electrolyte is driven.

5 An electroplating apparatus according to any preceding Claim, in which the bath is in a tank for holding overflowing electrolyte.

6 An electroplating apparatus according to any preceding Claim, in which the apparatus comprises means for recirculating electrolyte.

7 An electroplating apparatus according to Claim 6, in which the recirculation means comprises a pump and tubing adapted to take electrolyte from near the bottom of the tank into the bath or from near the top of the tank into the bath.

8 An electroplating apparatus according to any preceding Claim, in which there are a plurality of anodes.

9 An electroplating apparatus according to Claim 8, in which the anodes define a generally cylindrical electroplating region.

10 An electroplating apparatus according to Claim 8 or Claim 9, in which the anodes are evenly spaced.

11 An electroplating apparatus according to any preceding Claim, in which at least one anode comprises a plurality of metallic pieces in a holder and an opening to the holder whereby further metallic pieces can be inserted in use.

12 An electroplating apparatus according to any preceding Claim, in which the bath has a longitudinal axis and the at least one anode comprises an elongate body having an axis generally parallel to the longitudinal axis of the bath.

13 An electroplating apparatus according to Claim 12, in which at least one anode comprises an elongate, generally straight tube.

14 An electroplating apparatus according to Claim 12, in which at least one anode comprises a ring.

15 An electroplating apparatus according to Claim 14, in which there are a plurality of anode-rings stacked vertically.

16 An electroplating apparatus according to any preceding Claim, in which the apparatus is for coating a cylindrical body.

17 An electroplating apparatus according to Claim 16, in which the apparatus is for coating a cylindrical roller.

18 An electroplating apparatus according to Claim 16 or Claim 17, in which the cylindrical roller is a gravure cylinder roller.

19 A method for electroplating an article, the method comprising the steps of providing an electroplating apparatus according to any preceding Claim, at least partly filling the bath with an electrolyte, at least partly immersing an article to be electroplated in the electrolyte, and providing a voltage across the anode and a cathode.

20 A method for electroplating an article according to Claim 19, in which the article is completely immersed in the electrolyte.

21 A method for electroplating an article according to Claim 19 or Claim 20, in which the article is generally circular symmetrical and has a longitudinal axis.

22 A method for electroplating an article according to any one of Claims 19 to 21, in which the method comprises the step of driving electrolyte past the article to be electroplated.

23 A method for electroplating an article according to Claim 22, in which the electrolyte is driven vertically past the article.

24 A method for electroplating an article according to Claim 22 or Claim 23, in which the article is held substantially stationary relative to the apparatus.

25 An electroplating apparatus, substantially as described herein, with reference to and as shown in the accompanying drawings.

26 An electroplating method, substantially as described herein, with reference to the accompanying drawings.