GB2332209A - Electroplating involving the use of a preliminary coating - Google Patents

Abstract

A method for providing a substantially electrically non-conductive substrate 11 with an electrolytically deposited metallic layer 14, the substrate (11 being associated with a member 12, such as a filament, having a relatively high electrical conductivity, comprises providing the substrate 11 and the member 12 with a coating 13 having a relatively low electrical conductivity and applying an electrical potential to the coating 13 to cause deposition of a metal on the coating 13 to form the metallic layer 14. The member 12 distributes the electrical potential throughout the member 12 to promote deposition of the metal across an area of the coating disposed over the substrate 11. The coating 13 may be graphite, palladium sulfide, polypyrrole, polyaniline, TiO 2-x , PbO 2 or Fe 2 O 3 . The metallic layer 14 may be copper. The member and the substrate may be mechanically engaged with one another to form a textile.

Description

1 ELECTROPLATING METHOD AND ELECTROPLATED ARTICLES 2332209 The invention

relates to a method for providing a substantially electrically non-conductive substrate with an electrolytically deposited metallic layer and an article comprising a substantially electrically non- conductive substrate and an electrolytically deposited metallic layer.

The provision of a substantially electrically non-conductive substrate with an electrolytically deposited metallic layer is often a difficult task.

Thin coatings of electrically conductive materials applied to electrically non-conductive substrates have been widely used as "starters" for subsequent metal electroplating. This strategy has been used, in particular, for making printed circuit boards, where metallic layers are deposited on the walls of holes to connect many layers together, and for providing functional or decorative electroplated metal layers on non-conductors, such as parts moulded from plastics materials.

A well-known process to make such thin starting coatings for subsequent electroplating is the electroless deposition of a 2 metal, for example, nickel or copper. In this process the metal is deposited from a solution containing dissolved salts of the metal and a suitable reducing agent. The substrate is suitably catalyzed. This process has been used for many decades for through-holes plating in printed circuit boards. The process has also been used to manufacture lead-coated plastic grids, which are used as current collectors in lead- acid batteries (as described in DE-A 39 16 713), because other known processes for producing starting coatings do not allow subsequent electroplating to proceed sufficiently rapidly. However the electroless metal coating process is continuously, it can provide uneven metal large volumes of waste chemicals.

r difficult to monitor coatings and it creates Newer processes for electroplating electrically non-conductive substrates have been developed which avoid a preliminary electroless metal deposition step. Electrically conductive starting coatings have been made, for example, with dispersions of carbon (EP 0 200 398 B1, DE 41 41 416 Al) and graphite (US-A 10 37 469, US-A 409 096). Additionally starting coatings can be formed from intrinsically conductive polymers like polypyrrole (DE 38 06 884 Cl) or polyaniline (EP 0 413 109 A2), sulfides of noble metals (EP 0 320 601 A2) or semi-conducting oxides like 3 T'02-xy Pb02 or Fe203.

The above-mentioned carbon and graphite coatings are sufficiently conductive to allow through-hole electroplating in printed circuit boards when the boards they are applied to have dimensions up to 3 mm. However, the use of these coatings on non-conductive substrates with larger dimensions is unsatisfactory because the subsequent electroplating is not sufficiently complete, even or rapid. The use of other nonmetallic starting coatings like conductive polymers or sulfides of noble metals suffer from the same difficulties.

Metal electroplating on starting coatings having a low electrical conductivity is limited by the electrical potential available at a given point of the coating - the potential being needed for the initial metal ion nucleation. When neighbouring points relatively close to the source of electrical potential are provided with the same potential, they start metallizing along a front. The metallizing speed at a place of the coating is limited by the electrical current that can be supplied at that place.

However, the electrical potential transmitted through a starting 4 coating of low electrical conductivity, to a point relatively remote from the source of reductive electrical potential, may be neither sufficient to assure a metal ion nucleation on the surface of the coating, nor to assure a cathodic charge sufficient to protect the starting coating. At these remote points, an oxidizing anodic charge can passivate or even remove the starting coating of low electrical conductivity, leaving an insulating substrate surface with no electroplated metal.

a multi-laver coatina Various strategies have been considered to overcome this problem. Combination of the above-mentioned newer processes, e.g. overcoating a carbon starting coating with graphite (as described in EP 0 583 426 BI), or the deposition of multiple layers to form each layer being dried before the deposition of the next layer, can slightly improve the speed of the subsequent electroplating. This is due to lower electrical resistance of the multi-layer coating. However, such multi-layer coatings are thicker than single layer coatings and have the drawback of limited adhesion on the substrate, leading to the flaking-off of the subsequently electroplated metal layer. Also, the accumulation of layers might change the shape of the substrate or produce an uneven metallized layer. Hence, it is often desirable for a starting coating to be as thin as possible.

The problem of low conductivity could be overcome by dipping only a part of the coated substrate in the electroplating solution, in order to expose to the solution only a region of the coating that has, over its whole area, an electrical potential sufficient to assure metal ion nucleation. However, this process is rather slow, thus not economical.

Another solution that has been considered is to use a voltage greatly in excess of that normally required to cause metal deposition. This provides an electrical potential sufficient to assure a metal ion nucleation at a greater distance from the site of application of the current. However, this exposes the immediate contact with the source of electrical potential to a high current which, in turn, leads to the generation of high heat, finally burning the thin starting coating.

startinn coatinn in According to a first aspect of the invention, there is provided a method for providing a substantially electrically nonconductive substrate with an electrolytically deposited metallic layer, the substrate being associated with a member having a relatively high electrical conductivity, the method comprising providing the substrate and the member with a coating having a 6 relatively low electrical conductivity and applying an electrical potential to the coating to cause deposition of a metal on the coating to form the metallic layer, the member distributing the electrical potential throughout the member to promote deposition of the metal across an area of the coating disposed over the substrate.

According to a second aspect of the invention, there is provided an article comprising a substantially electrically non-conductive substrate, a coating having a relatively low electrical conductivity covering at least part of the substrate and an electrolytically deposited metallic layer on the coating, a member having a relatively high electrical conductivity providing at least one electrical pathway on a side of the coating remote from the metallic layer.

According to a third aspect of the invention, there is provided a process for electrolytic deposition of a metallic layer on an electrically nonconductive material as substrate, in which the substrate is first brought in contact with both:

- a network made of a highly electrically conductive material, and a coating made of a low electrically conductive material, 7 extending over the substrate and the highly electrically conductive material, then a metallic layer is deposited by electroplating on both conductive materials.

The following is a more detailed description of embodiments of the invention, by way of example, in which Examples 1 to 3 are examples of methods according to the invention and;

Figure 1 is a schematic representation, in cross-section, of a first article in accordance with the invention and, Figure 2 is a schematic representation, in cross-section, of a second article in accordance with the invention.

EXAMPLE 1

In this example, polyester network structure (PNS), which is used as a current collector for lead-acid batteries, is firstly provided with a coating of a material of low electrical conductivity and is then provided with an electrolytically deposited metallic layer.

PNS is made with two types of polyester fibres, having respective 8 different melting points, and a copper monofilament. These components are spun and then knitted to build an open mesh textile. The textile is then rigidified through heat-setting (Producer: Hoechst Trevira, Bobingen, Germany).

During the spinning step, a thread (1350 dtex) is made with equal parts of unmodified high tenacity polyethyleneterephtalate (PET) multifilaments and a composite thread made of two 250 dtex filaments composed of PET modified with 12.5% isophtalic acid, around which a copper monofilament (diameter 100 micrometers) is twisted. The modified PET has a lower melting point than the unmodified PET.

The knit produced with the resultant threads is heat-set in an infra-red oven. During this process the modified, low-melting, polyester component reaches its melting point, but the high tenacity component does not melt. On subsequent solidification of the melted polyester, the grid becomes rigid. The copper monofilaments are thus mechanically engaged with the electrically non-conductive PET.

Hence, the PET forms a substantially electrically non-conductive substrate that is associated with the copper monofilaments. The 9 monofilaments contact one another so as to form an electrically conductive network extending substantially throughout the textile.

The rigidified grid produced in this way has meshes of alternating rows of 3 mm by 1 mm and 1 mm by 1 mm, with a thread diameter of 0. 5 mm. The shape of electrodes for batteries (1 3 cm x 15 cm, with a 1. 5 cm wide lug) is cut out from a roll of the rigidified grid.

The grid is provided with a starting conductive carbon coating by the following coating process:

Carbon coating process:

The following steps are carried out in the sequence indicated.

The surface of the grid 5% dodecyIsulfate solution.

2.

is cleaned: 30 sec in The grid is then rinsed with demineralized water (30 sec).

The grid is then dipped in conductive carbon paste (30 sec polyacrylate sold under (7 at room temperature). The carbon paste is prepared with conductive carbon particles sold under the trade mark Printex L6 (10% by weight, Producer: Degussa,AG, D-63403 Hanau Germany), an organic water-soluble binder based on the trade mark Basoplast 400 DS 5% by weight; Producer: BASF, Ludwigshafen, Germany), an anionic detergent sold under the trade mark Aerosol OT 100 (2% by weight; Producer: Cytec Industries B.V., 3208 La Spijkenisse, Netherlands) and deionized water (80.5% by weight).

For preparing the paste to the desired consistency, the detergent and carbon particles are progressively added to lukewarm water (40'C) in an ultrasonic bath and dispersed homogenously during 1 0 minutes, and the paste is stabilized treatment for 10 minutes.

then the binder is added by a further ultrasonic 4. Excess conductive paste is then removed from the grid with a compressed air jet.

Finally the carbon coating is dried in hot air for 30 sec.

1---1 1 The carbon coating formed in this way covers the high and low melting point PET and also the copper multifilaments. Hence, each copper monofilament provides an electrical pathway on the inner side of the carbon coating.

This whole carbon coating process can be performed batchwise (on individual battery electrodes cut from the grid as described above) or in a continuous manner, using a length of the rigidified grid that goes continuously through the different steps of said coating process.

A layer of copper is then electrolytically deposited on the outer side of the carbon coating. To achieve this the carbon coated grid is drawn through an acidic, copper electroplating solution having the following composition, in an electroplating bath:

INGREDIENT AMOUNT Copper sulfate (CuSO, 5H20) 75 g/l Sulfuric acid (H2SO4), chem. pure 110 ml/l Sodium chloride, chem. pure 0.1 g/l Levelling agent, Copper Gleam 2001 Carrier 10 ml/l Brightener, Copper Gleam 2001 Additiv 2.5 ml/l Producer: Lea Ronal, Littau, Switzerland 1 2 The solution is heated to 24-27'C and has a pH of 1.5-2.5.

The anode baskets are kept filled with electrolytic copper pellets. The carbon-coated grid is brought in contact, by the 15 em side, with the negative pole of a continuous current generator while the grid is immersed in the electroplating solution. The positive pole of the generator is brought in contact with the anode basket. A potential of 4.7 volts is applied by the generator, to produce a metal electrodeposition current of 40 amperes. After 1 minute, the elect rodepos i ted copper covered the whole surface of the grid in a continuous metal coating, providing an electrical resistance of 0.090 ohms/square.

During this process, the electrical potential applied to the carbon coating is distributed by the copper monofilaments throughout the network formed by the copper monofilaments. As copper has a high conductivity very little decrease in the potential occurs between the copper monofilaments located closest to the point of application of the potential and the monofilaments furthest from the point of application. The distribution of the potential by the monofilaments throughout the 1 13 grid promotes electrolytic deposition of copper over the whole area of the carbon coating.

By comparison, the same electroplating process applied to a similar carbon-coated grid, prepared in the same way but from which the copper monofilaments have been omitted, needs more than 40 minutes to cover the whole surface of the grid with a layer of copper.

Before being used for battery current collectors, the electroplated grid (prepared from PNS including copper monofilaments) may be further electroplated with copper (so that each collector has 8g of copper when the collector has the dimensions indicated above) and then with lead.

EXAMPLE 2

A second type of polyester network structure (PNS), used as a see-through electromagnetic shielding, is currently made with high tenacity fibres and copper monofilament. The fibres and the monofilament are spun to form a thread which is knitted to build an open mesh textile (Producer: Hoechst Trevira, Bobingen, 14 Germany). The spun thread (1350 dtex) is made with unmodified high tenacity polyethyleneterephtalate (PET), around which a copper monofilament (diameter 100 micrometers) is twisted. The mesh openings of the textile are the same as in Example 1. This PNS is however not heatset or otherwise rigidified. Rolls of this textile of more that 100 meters length and 0.30 meters width can be obtained.

Hence, the PET forms a substantially electrically non-conductive substrate that is associated with the copper monofilaments. The monofilaments contact one another so as to form an electrically conductive network extending substantially throughout the textile.

A starting conductive carbon coating is built over this textile or knit according to the process described in Example 1. Each copper filament then provides an electrical pathway on the inner side of the carbon coating.

A length of this coated textile (0.30 meters wide) is then electroplated in an acidic nickel solution (Producer: Lea Ronal, Littau, Switzerland) in an electroplating bath. The length is passed continuously through the bath such that 20 meters of the band is immersed in the solution at any one time. The immersed portion of the band is maintained in contact with multiple metallic rollers that are loaded with a cathodic potential of 5 volts. Again the copper monofilaments act to distribute the electrical potential throughout the network formed by the monofilaments so as to promote the electrolytic deposition of nickel over the whole area of the outer side of the carbon coating.

At a speed of 2 meters per minute and a total electroplating current of 900 amperes, the whole surface can be covered with a layer of nickel, having a weight of 28g/square meter of PNS.

EXAMPLE 3

A 21 cm by 30 cm Polyester-Terephtalate sheet forming an electrically nonconductive substrate (Cellpack, Wohlen, Switzerland) is laminated on one side with a polyester co-polymer heat-settable sheet (Xiro, Schmitten, Switzerland), onto which copper threads (100 4m diameter) are fixed. In this way, the substrate is associated with the threads. The copper threads lie parallel to one another with a spacing of 5 mm between one another. If required, a network can be made by providing further copper threads extending across and contacting the parallel threads.

16 A starting conductive carbon coating is built over this composite foil according to the process described in Example I On the laminated side of the substrate the carbon coating extends over and contacts the copper threads and the heat-settable sheet. Hence, each copper thread provides an electrical pathway on the inner side of the coating.

A series of sheets of this coated material are then electroplated in an electroplating bath containg an acidic copper solution (described in Example 1). The sheets are passed continuously through the bath (immersed length: 20 meters), while being maintained in contact with multiple metallic rollers that are loaded with a cathodic potential of 5 volts. Again the copper threads distribute the electrical potential to promote electrolytic deposition of copper over the full area of the outer side of the carbon coating at the laminated side of the substrate.

At a speed of 2 meters per minute and a total electroplating current of 900 amperes, the whole surface is covered with a layer of copper having a weight of 28g/square meter of foil.

17 EXAMPLE 4

Threads (1000 dtex) are made with 3 parts of unmodified high tenacity polyethyleneterephtalate (PET) multifilaments and one part of PET modified with 12.5% isophtalic acid. These threads are chopped into strands of 50 mm. Copper monofilament (diameter 80 micrometers) is chopped into strands of 15 mm. length and blended with the PET strands, in a ratio of 5 PET to 1 copper (by weight).

This blend of strands is spread on a transportation band, heated in an infra-red oven and passed through heated calender rolls, to provide a 250 micrometer thick non-woven felt. The different copper strands cross over and contact each other, forming an electrically conductive network. The low melting point PET moiety of the PET strands acts as an adhesive that bonds together the non-modified PET and the copper strands, forming a nonwoven textile. The copper network extends substantially throughout the non-woven textile. Hence, the PET forms a substantially electrically nonconductive substrate that is associated with the copper strands.

A starting conductive carbon coating is deposited on this textile according to the process described in Example 1. Each copper 1 18 strand then provides an electrical pathway on the inner side of the carbon coating.

A length of this coated textile is then electroplated with copper to reach a weight of 32g copper/square meter of fabric, according to the process described in Examples 1 and 3. Again the network formed by the copper strands acts to promote the electrolytic deposition of copper over the whole area of the outer side of the carbon coating.

The methods of Examples 1 to 4 are particularly useful for making electromagnetic shielding screens and current collectors.

Figure 1 shows, in cross-section, a small portion of a composite article 10 made by a method similar to the method of Example 1. The article comprises a plurality of substantially electrically non-conductive filaments 11, which may comprise natural or synthetic fibres or the like, mixed with electrically conductive filaments 12 which may comprise copper or stainless steel wires or the like. Hence, the non-conductive filaments 11 form a nonconductive substrate associated with the conductive filaments. The non-conductive filaments 11 and the conductive filaments 12 are covered by a continuous or substantially continuous 1:

19 coating 13 of a material having a low electrical conductivity. The coating 13 may comprise carbon, palladium sulfide or the like. The coating 13 is preferably 0.05 to 0.25 Am thick, most preferably 0.10 um thick.

The coating 13 is, in turn, covered by a metal layer 14, formed by electroplating. The metal layer 14 may comprise any electroplateable metal, for example, nickel, copper, lead, zinc, The metal layer 14 may consist of, for 1 alloy or two or more metals in the metal layer 14 may consist over copper; lead alloyed with or copper alloys. The metal nonconductive and conductive renders the article 10 highly titanium, silver or gold. example, a single metal, a meta respective layers- For example, of or comprise: a nickel layer tin, antimony and/or bismuth; layer 14 serves to bind the filaments 11, 12 together and electrically conductive.

Hence, each conductive filament 12 provides an electrically conductive pathway on a side of the coating 13 (the inner side) remote from the metallic layer 14.

Figure 2 shows, in cross-section, a second composite article 15 formed by a method similar to the method of Example 3. The article 15 comprises a substantially electrically non-conductive substrate 16 in the form of a sheet. The substrate16 may comprise natural or synthetic polymers or the like and is coated on one side with an adhesive layer 17 which may comprise heat settable polymers or the like. Electrically conductive filaments 18, 19, which may comprise copper or stainless steel wires or the like, are partially embedded in the adhesive layer 17 so as to associate them with the substrate 16. In some areas of the second article 15, the conductive filaments 18 are arranged parallel to one another, separated by a relatively large, even spacing. In other areas of the second article 15, the conductive filaments 19 are grouped more closely to one another to obtain a selective electrically conductive reinforcement. The conductive filaments 18, 19 and the adhesive layer 17 are covered by a continuous coating 20 of a material having a low electrical conductivity. The material of the coating 20 may comprise carbon, palladium sulfide or the like.

The coating 20 is preferably 0.05 to 0.25 /im thick, most preferably 0.10 kim thick.

This coating 20 is, in turn, covered by a metal layer 21, formed by electroplating. The metal layer 21 can comprise any electroplateable metal, for example, nickel, copper, lead, zinc, 1 21 titanium, silver or gold. The metal layer 21 may consist of, for example, a single metal, a metal alloy or two or more metals in respective layers. For example, the metal layer 21 may consist of or comprise: a nickel layer over copper; lead alloyed with tin, antimony and/or bismuth; or copper alloys.

Hence, each conductive filament 18, 19 provides an electrical pathway on a side of the coating 20 remote from the metallic layer 21.

The metal layer 21 renders the second article 15 highly electrically conductive on one of its faces. In those areas where the conductive filaments 19 are grouped more closely, the metal layer 21 is thicker (indicated at 22 in Figure 2) than in those areas where the conductive filaments 18 have a relatively large spacing (especially when the filaments 18, 19 are composed of copper and the metal layer 21 consists of copper).

The conductive filaments 12 connect spaced regions of the coating so as to form electrical pathways between the spaced regions having lower electrical resistances than the portions of the coating lying intermediate the spaced regions- 22 It will be appreciated that the invention may be embodied in different ways to those described above. In particular, instead of associating the substantially electrically non-conductive substrate with a relatively high conductive filament or thread, other members of different configurations having a relatively high electrical conductivity compared to that of the coating 13, 20 may be used. The configuration and position of the member relative to the substrate will be suitable for distributing the electrical potential throughout the member to promote deposition of metal across a desired area of the coating 13, 20 disposed over the substrate 11, 16.

23

Claims (1)

1. A method for providing a substantially electrically nonconductive substrate with an electrolytically deposited metallic layer, the substrate being associated with a member having a relatively high electrical conductivity, the method comprising providing the substrate and the member with a coating having a relatively low electrical conductivity and applying an electrical potential to the coating to cause deposition of a metal on the coating to form the metallic layer, the member distributing the electrical potential throughout the member to promote deposition of the metal across an area of the coating disposed over the substrate.

2. A method according to claim 1, wherein said coating is nonmetallic and said provision of said coating comprises nonelectrolytic deposition of said coating.

3. A method according to claim 2, wherein the coating comprises: carbon, e.g. graphite; a noble metal sulfide, e.g. palladium sulfide; an intrinsically electrically conductive polymer, e.g. polypyrrole or polyaniline; or a semi-conducting oxide, e.g. T'02-x or PbO, or Fe20J- 24 4. A method according to any preceding claim, wherein said deposition of said metal comprises deposition of copper from a solution comprising copper ions.

5. A method according to any preceding claim, wherein the member comprises an elongate member having a relatively high electrical conductivity, said elongate member contacting the coating substantially along the length of the elongate member, the elongate member distributing the electrical potential along the length of the elongate member to promote deposition of the metal on an area of the coating disposed adjacent the elongate member and over the substrate.

6. A method according to claim 5, wherein the member comprises a plurality of elongate members, each elongate member having a relatively high electrical conductivity and contacting the coating substantially along the length of the elongate member, the elongate members together forming a network, the network distributing the electrical potential throughout the network to promote deposition of the metal on an area of the coating disposed ad)acent the elongate members and over the substrate.

A method according to claim 5 or claim 6, wherein the or each elongate member is a metal filament, thread or wire.

8. A method according to claim 7, wherein the or each elongate member is composed of copper.

9. A method according to any one of claims 5 to 8, wherein the substrate and the or each elongate member are mechanically engaged with one another and form a textile.

10. A method according to any one of claims 5 to 8, wherein the substrate has a surface and the or each elongate member is attached to the substrate by an adhesive layer covering the surface, the coating extending over the adhesive layer.

11. An article comprising a substantially electrically nonconductive substrate, a coating having a relatively low electrical conductivity covering at least part of the substrate and an electrolytically deposited metallic layer on the coating, a member having a relatively high electrical conductivity providing at least one electrical pathway on a side of the coating remote from the metallic layer.

An article according to claim 1 1, wherein the coating is 26 non-metallic.

An article according to claim 12, wherein the coating comprises: carbon, e.g. graphite; a noble metal sulfide, e.g. palladium sulfide; an intrinsically electrically conductive polymer, e.g. polypyrrole or polyaniline; or a semi-conducting oxide, e.g. T'02-., or Pb02 or Fe203' 14. An article according to any one of claims 1 1 to 13, wherein the metallic layer comprises copper.

15. An article according to any one of claims 11 to 14, wherein the member comprises at least one elongate member having a relatively high electrical conductivity, the at least one elongate member providing said pathway.

16. An article according to claim 15, wherein the substrate and the at least one elongate member are mechanically engaged with one another and form a textile.

17. An article according to claim 15, wherein the substrate has a surface and the at least one elongate member is attached to the substrate by an adhesive layer covering the surface, the coating I- 27 extending over the adhesive layer.

18. Process for electrolytic deposition of a metallic layer on an electrically non-conductive material as substrate, in which the substrate is first brought in contact with both:

- a network made of a highly electrically conductive material, and a coating made of a low electrically conductive material, extending over the substrate and the highly electrically conductive material, then a metallic layer is deposited by electroplating on both conductive materials.

19. Process according to claim 18, in which the electrically conductive material is distributed in a manner.

highly uniform 20. Process according to claim 18, in which the highly electrically conductive material is distributed in a non-uniform manner.

21. Process according to claims 19 or 20, in which the highly electrically conductive material is a metal, preferably copper.

1 i 28 22. Process according to claims 19 or 20, in which the low electrically conductive material comprises conductive particles, preferably carbon black.

23. Process according to claims 19 or 20, in which the low electrically conductive material is a conductive polymer, preferably polypyrrole.

24. Process according to claims 19 or 20, in which the low electrically conductive material is a metallic layer of minimum 10 ohms per square, made of oxides of metals or a very thin layer of plain metal.

25. Process according to claims 19 or 20, in which the electrically nonconductive substrate is a synthetic fibre which forms a textile, preferably a knitted textile.

26. Process according to claim 25, in which the highly electric conductive material is a copper wire, knitted with the fibre.

27. Process according to claims 19 or 20, in which the electrically nonconductive substrate is a sheet of natural or synthetic material, preferably polyester, to which the highly 29 electrically conductive material is fixed with an adhesive.

28. Process according to claims 26 or 27 in which the highly conductive conductor is distributed in a non-uniform density across the nonconductive substrate in order to obtain a selective reinforcement of metallic layer deposited by electroplating.

29. A method for providing a substantially electrically nonconductive substrate with an electrolytically deposited metallic layer substantially as hereinbefore described with reference to any one of examples 1 to 3.

30. An article comprising a substantially electrically nonconductive substrate and an electrolytically deposited metallic layer substantially as hereinbefore described with reference to Figure I or Figure 2.