GB2208873A

GB2208873A - Electroplating internal and external cylindrical surfaces

Info

Publication number: GB2208873A
Application number: GB8819906A
Authority: GB
Inventors: Brian Vincent Sumner; Neal Barry
Original assignee: SB PLATING Ltd
Current assignee: SB PLATING Ltd
Priority date: 1987-08-21
Filing date: 1988-08-22
Publication date: 1989-04-19
Also published as: GB8719816D0; GB8819906D0; EP0375713A1; WO1989001536A1

Abstract

Apparatus for, and a method of electro-plating an area of an internal substantially cylindrical surface of a component is disclosed, which is characterised by the use of an annular jet of electrolytic solution being directed over the surface of the component to be plated. For example, a jig (32) defines a plating zone (50) in which the component is adapted to be mounted with the axis of plating surface substantially vertical. A plug (54) is adapted to close the end of the surface, and is mounted on a stem (52) around which is disposed a tubular conduit (60) which terminates at one end thereof in the axial vicinity of the end of component. The conduit forms with the stem an annular nozzle (63) for the electrolytic solution. The stem carries an anode (56). A cathode (70) renders the component electrically cathodic with respect to the anode.

Description

ELECTRO-PLATING TECHNIQUES This invention relates to electro-plating techniques and particularly to a method of and apparatus for electro-plating selective areas of internal and external surfaces.

It is often desirable to be able to electreplate selective areas of components because the material deposited may be a valuable rnetal such as gold and the area requiring significant plating may only be a small part of the whole component.

In batch electro-plating, where individual components are held in a static lattice in a treatment bath, there are three basic requirements to ensure efficient and even covering of the deposited metal on each of the components to be plated.

The first is that the components should be closely spaced with respect to one another so that each component receives substantially the same covering of rnetal. If the distribution of components is loose those at the ends or edges of the lattice tend to have an average coating thickness less than those in the centre.

Secondly, the anode should be accurately positioned with respect to each component so that each receives the attention of a similar electric field and that that field is arranged to ensure an even deposit of rnetal over all of the surface to be plated. Without such accurate positioniny, the edges of components tend to be the focus of the electric field and thus receive the greatest density of deposited rnetal.

Thirdly, if a depletion zone develops around the component or any part of it, then there will be insufficient metal ions to ensure an even and thick deposit of metal on the component. There should thus be high mechanical agitation in the electrolytic solution around the component so that a significant depletion zone does not develop.

It is an object of the present invention therefore, to provide a method and apparatus for electro-plating areas of internal and external surfaces which meet at least some and ideally all of these requirements.

While the principles of the present invention are primarily concerned with batch processes, nevertheless they may also find application in continuous processes where components are passed sequentially through a treatment process carried for instance on a ribbon or other conveyor.

Suitable surfaces are cylindrical, either internally or externally, but this term should be construed as encompassing many different shapes of generally similar cross section. Examples include the male and female surfaces of pin and socket connectors for electrical applications, bearing surfaces1 and screw threads. However, areas of other shaped surfaces may be selectively electro-plated in accordance with the invention.

According to one aspect of the present invention there is provided a method of selectively electro-plating an area of an Internal or external substantially cylindrical surface of a substrate1 which method is characterised in that it comprises the steps of emitting an annular stream of eletrolytic solution from a nozzle, arranying an anode adjacent the surface to be plated and providing means to render the substrate cathodic with respect to the anode1 an object being positioned inside the annular stream to maintain its annularity in a plating zone between the substrate and the anode.

The method may be applied to internal or external areas of the surface of the substrate. Areas of a plurality of substrates may be electro-plated simultaneously by mounting each substrate in a lattice framework, connecting each to a common cathode, and providing an anode adjacent each area of each substrate to be plated. An annular stream or jet of electrolytic solution is directed over each area to be plated, submerging each such area and its associated anode in the solution.

Apparatus to put into effect said method and to electro-plate an area of an internal substantially cylindrical surface of a component, characterised in that it comprises a jig defininy a plating zone and in which the component is adapted to be mounted with the axis of said internal surface substantially vertical, and a plug adapted to close the end of said surface, said plug being mounted on a stern around which is disposed a tubular conduit which terminates at one end thereof in the axial vicinity of the end of said surface and forming with said stem an annular nozzle said stem further carrying an anode and said conduit being arranged to be supplied with electrolytic solution under pressure such that on evolving from said nozzle the solution washes said surface, means being provided to render the component electrically cathodic with respect to the anode.

Preferably said stem is also tubular and said anode is in the form of a wire carried within the stem to the vicinity of said surface whereupon the anode exits through an aperture in the stem and is wound around the stem or connected to a preformed anode disposed on the stem.

The stem may also provide an exhaust route for gas evolved in the electro-platiny process by a passaye being formed in the pluy to connect the closed, upper end of said surface with the inside of the stern. The plug also serves to centralise the anode with respect to the component.

The tubular conduit preferably passes through a drain gallery which is adapted to receive electrolytic solution draininy from said plating zone.

The other end of said conduit preferably opens into a pressure gallery adapted to contain electrolytic solution under pressure. The stem preferably passes through said pressure gallery and opens at its lower end into a supplementary drain gallery.

Apparatus to put into effect said method but to electro-plate an external substantially cylindrical surface area of a component, is characterised in that it comprises a jig on which the component is adapted to be mounted and plugged with the axis of said external surface substantially vertical, a tubular conduit being formed around said jig which terminates at one end thereof in the axial vicinity of the end of said surface and foriiiiny with said jig an annular nozzle, an anode being formed around said component and said conduit being arranged to be supplied with electrolytic solution under pressure such that on evolving from said nozzle the solution washes said surface, means being provided to render the component electrically cathodic with respect to the anode.

In another aspect, there is provided apparatus to put into effect said Illethod to selectively electroplate an area of an Internal or external surface of a substrate1 which apparatus is characterised in that it comprises a nozzle adapted to emit an annular stream or jet of electrolytic solution1 means for mounting the substrate as a cathode with said area to be selectively electro-plated exposed to the nozzle, an anode adjacent the area, means for providing an electrolytic solution to the nozzle, whereby an annular stream of solution is emitted therefrom, and an object which is positioned inside the annular stream to maintain its annularity in a plating zone between the substrate and the anode, the anode and the area to be plated being so located relative to the nozzle that the anode and the area to be plated are submeryed in the solution when the annular stream of solution is emitted from the nozzle.

The nozzle can be a continuous annular nozzle, or may cornprise a ring of discrete jets, which may in turn be circular orifices or slots. The annular stream or jet produced by the nozzle ~ may be directional, ie asymmetrical, non-uniform, converyent and/or diveryent. The annular stream or jet rnay also be non-circular; in particular1 it rnay be conformed to the shape of the area of the surface to be electro-plated.

The object in the central area of the nozzle, within the annular stream, may be provided with means for aligning the nozzle with the substrate.

Where an internal surface of the substrate is to be plated, the anode may be mounted, directly or indirectly, on the object, surrounded by the annular stream or jet.

The invention is further described hereinafter with reference to the accompanying drawinys in which: Fig 1 is a section through apparatus according to one aspect of the invention for electro-plating the internal surfaces of cylindrical components; Fig 2 is a section through apparatus according to another aspect of the invention for electro-plating the external surfaces of cylindrical components; and, Fig 3 is a section through another eriibodiinent of the apparatus shown in Fig 1.

In the drawings two components 10, 20 are shown which could be connectors for optic fibres or coaxial cables or any electrical connector or any cylindrical device. Optic fibre connectors are generally constructed frorn brass but which, to ensure yood electrical connection, require plating with a non-corroding material such as gold. While the whole components rnay require just a flash coating of gold (say 0-2 Inicrons thickness) to provide adequate corrosion resistance, a niore substantial coating (between say 2-5 and 50 microns thickness) is required on mating surfaces 12, 22 of the two components 10, 20.This is because of the rnechanical wear which takes place when the two components are coupled and uncou*Jled and also where the most secure electrical contact is required. Thus the areas of the two components which require this extra coating are cross-hatched in the drawings.

It will be noted that in the case of connector 10 of Fig 1, this area is part of the internal cylindrical surface thereof, while for connector 20 of Fig 2 this area is part of the external cylindrical surface thereof. It should be noted that while plain cylindrical surfaces are shown in the accolilpanyiny drawings, the invention extends to connectors which have a Illore complicated shape such as by haviny spring elenlents to retain the connectors toyether once mated with one another.

With specific reference to Fig 1, the connector 10 is shown positioned in a jiy 32 of an electro-plating apparatus 30. Several such jigs and associated components described further below inlay be formed in a lattice on the apparatus 30.

The jiy 32 has rnouth 34 adapted to receive the connector 10 up to a flange 14 provided on the connector. The jiy 32 is formed on a stack of yalleries comprising drain gallery 36, pressure gallery 38 and supplemental drain gallery 40 defined by walls 42, 44, 46 and 48. The jig 32 and wall 42 define between then a plating zone 50. Into this zone extends a tubular stein 52 which is Inounted at its lower end in the wall 46 and opening into supplemental drain gallery 40. At its other end1 the stem 52 carries a pluy 54 which is a close fit inside the connector 10 and effectively plugs it.The pluy 54 also serves to centralise the stern 52 with respect to the connector 10, which is important because the stem 52 carries anode 56 in the form of a length of, preferably platinuiii, wire.

The wire 56 passes frorn the gallery 40 (where it is connected to any other wires enianatiny from siiiiilar steins and ultimately to a source of positive electric potential) up the length of the stern 52 to exit through an aperture 58 in the side of the stem. The wire 56 is then wound around the stein several turns or is connected to a preformed anode (not shown).

A tubular conduit 60 is Inounted in walls 42, 44 and opens into the platiny zone 50 above and the pressure gallery 38 below. The tube 60 is sealed in the walls 42, 44 by any suitable means such as by two O-rinys 62, 64 in order to isolate it frnrii the drain gallery 36. Carried through the tube 60 is the stem 52 which together thus define an annular jet 63 at the opening of the tube 60 in the plating zone 50.

In operation of the plating apparatus 30, the gallery 38 is filled and pressurised with electrolytic solution so that solution wells up the tube 60 s,Jillins out of the annular jet 63 to fill the plating zone 50. Solution in the plating zone 50 then drains into the drain gallery 36 through passages 66 forrned in the wall 42 around the tube 60 where it is recovered and recycled. The pressure of solution in the gallery 38 and the size and nuinber of the passages 66 are chosen so that the plating zone 50 fills with solution.

The plug 54 is provided with several vents 68 which allow gas trapped within the confines of the connector 10 to be bled off down the stein 52.

Any excess solution also spilling through the vents 68 is collected via the stem 52 in the supplemental gallery 40 where it is also recycled.

When all the connectors 10 of an array are positioned in the jigs 32 of a,.,varatus 30, a block electrode 70 is placed on top to contact the connectors so that each, once the block 70 is connected to a neyative electric potential, forms a cathode.

With this arrangement of an anode 56 centrally and axially located with respect to each cathodic connector 10, and with fresh electrolytic solution continuously washiny the internal surfaces 12 of each connector 10, particularly even electro-plating of the surface 12 can be achieved.

Any gas evolved during the electrolytic process is bled off via the vents 68. The external surface of the connector 10 has no access to fresh solution which in this region is thus quickly depleted of metal ions, and in any event, the electric field in this region is negligible. Thus the primary concern of only plating that area of the connector 10 which requires plating is achieved by the apparatus 30. If the relilaining surfaces of the connector require flash slating this can be achieved in a conventional barrel bath, either before or after plating in apparatus 30.

With reference to Fig 2, apparatus 130 differs frorii a,;,Jaratus 30 of Fig 1 only in detail governed by the geoiiietry and plating requirerrients of the connector 12 and retains the essential character of annular jet slating de;iionstrated by apparatus 30.

Here, the apparatus 130 includes a jig 132 in the forin of a pin upstanding frol,l wall 146 and passing through aperture 163 in wall 142.

The jiy 132 has an annular shoulder 133 on which the end of connector 12 is Inounted. Before being so iiiounted a mask 135 is placed around flange 114 of connector 12. The apparatus 130 has two galleries comprising pressure gallery 138 and drain gallery 136. In this situation no supplemental gallery is required.

An anode plate 156 is mounted in the gallery 136 and is provided with an aperture 153 surrounding the connector 12. An electrode block 170 is positioned above connector 12 when each is in place on an array of jigs 132. The anode plate 156 could be replaced by a network of wire if preferred.

In operation, the gallery 138 is filled and pressurised with electrolytic solution until it fountains through annular jet 163 and fills gallery 136 up to the level shown. Solution rising above this level spills over a weir (not shown) and is recycled. When the anode 152 and electrode block 170 are connected to an electric potential, platiny is effected in the region 22 of the connector 12. The mask 135 prevents the fornlation of a ineniscus line around the connector 12 and accurately locates the upper limit of plating on the connector.

The annular jet 163 illay be inclined if the aperture 163 in the wall 142 and the jiy pin 132 are appropriately shaped so as to direct niore acutely the electrolytic solution onto the surface 22 of the connector 20.

The internal surface of the connector 20 has no access to fresh solution which in this region, if any seeps around the jig in 132, is thus quickly depleted of metal ions, and in any event, the electric field in this region is negligible. Thus the primary concern of only platiny that area of the connector 20 which requires plating is also achieved by the apparatus 130.

If the rernaininy surfaces of the connector require flash plating this can be undertaken as with connector 1Q in a conventional barrel bath1 either before or after plating in apparatus 130.

Fig 3 illustrates another einbodiiiient of the apparatus 30 shown in Fig 1.

Here apparatus 230 dispenses with the tube 60 of Fig 1 and instead a flanye 260 is provided on wall 242. This requires the gallery irtiinediately below wall 242 to be a pressure gallery 238 and the drain passages 266 to open into connectiny tubes 267 which pass through gallery 238 to open into the gallery 236 below.

Thus electrolytic solution is supplied to gallery 238 under pressure such that it wells up through annular jet 263 formed by said flange 260 and stein 252. Platiny zone 250 is filled with solution which drains through passages 266 aiid tubes 267 to drain gallery 236. Since the stern 252 also opens into this gallery, the supplemental gallery of Fig 1 is also dispensed with. otherwise apparatus 230 is the same as apparatus 30 of Fig 1 and provides the saine advantages of even electro-plating.

While the invention has been described with reference to specific elements and coiribinations of elements, it is envisaged that each elenient may be colnbirled with any other or any combination of other elelnents. It is not intended to linlit the invention to the particular combinations of elements suggested. Furtherlnore, the foregoing description is not intended to suggest that any eleiiient mentioned is indispensable to the invention, or that alternatives Inay not be employed. What is defined as the invention should not be construed as liiiiitiny the extent of the disclosure of this specification.

Claims

1. A method of selectively electro-plating an area of an internal or external substantially cylindrical surface of a substrate, which method comprises the steps of emitting an annular stream of eletrolytic solution from a nozzle, arranginy an anode adjacent the surface to be plated and providing means to render the substrate cathodic with respect to the anode, an object being positioned inside the annular stream to maintain its annularity in a plating zone between the substrate and the anode.

2. A method as claimed in claim 1 in which the sectional shape of the annular stream is arranged to correspond with the sectional shape of the substrate and so that the solution flows over the surface to be plated.

3. A method as claimed in claim 1 or 2 in which a plurality of substrates are electro-plated simultaneously by mounting each substrate in a lattice framework, rendering each cathodic and providing an anode adjacent each area of each substrate to be plated, said annular stream or jet of electrolytic solution being directed over each area to be plated.

4. A method of electro-plating the external surface of the substrate as claimed in claim 1, 2 or 3 in which the object in the annular stream is the substrate itself.

5. A method of electro-plating the internal surface of the substrate as claimed in claims 1, 2 or 3 in which the object in the annular stream is a stern having a plug at its end which serves to centralise the stem with respect to the substrate.

6. Apparatus to put into effect the method claimed in claim 1 to electro-plate an area of an internal substantially cylindrical surface of a component, which apparatus comprises a jig defining a plating zone and in which the component is adapted to be mounted with the axis of said internal surface substantially vertical, and a pluy adapted to close the end of said surface, said pluy being mounted on a stein around which is disposed a tubular conduit which terminates at one end thereof in the axial vicinity of the end of said surface and forming with said stem an annular nozzle, said stein further carrying an anode and said conduit being arranged to be supplied with electrolytic solution under pressure such that on evolving from said nozzle the solution washes said surface, means being provided to render the component electrically cathodic with respect to the anode.

7. Apparatus as claimed in claim 6 in which said stem is a tube and said anode is in the form of a wire carried within the stern to the vicinity of said surface whereupon the anode exits through an aperture in the stem and is wound around the stem or connected to a preformed anode disposed on the stem.

8. Apparatus as claimed in clairn 7 in which the stem provides an exhaust route for yas evolved in the electroplating process by a passage being formed in the plug to connect the closed, upper end of said surface with the inside of the stem.

9. Apparatus as claimed in any of claims 6 to 8 in which the pluy serves to centralise the anode with respect to the coiiiponent.

10. Apparatus as claimed in any of claims 6 to 9 in which the tubular conduit passes through a drain gallery which is adapted to receive electrolytic solution draining frorn said plating zone, and opens into a pressure gallery adapted to contain electrolytic solution under pressure.

11. Apparatus as claimed in claim 10 in which the stem passes through said pressure gallery and opens at its lower end into a supplementary drain gallery.

12. Apparatus as claimed in any of claims 6 to 9 in which the tubular conduit is forrned by a wall on which said jig is disposed, the tubular conduit comprising an annular space between the stem and an aperture in said wall through which said stem extends, said wall enclosing a pressure gallery adapted to contain electrolytic solution under pressure.

13. Apparatus as claimed in claim 12 in which the stem is rnounted in the base of said pressure gallery and opens on the other side of said base into a drain gallery.

14. Apparatus as claimed in claim 13 in which a passaye through the pressure gallery connects said plating zone with said drain gallery.

15. Apparatus to put into effect the method claimed in claim 1 to electfo-plate an external substantially cylindrical surface area of a coiiiponent, which apparatus comprises a jig on which the component is adapted to be mounted and plugged with the axis of said external surface substantially vertical, a tubular conduit being formed around said jig which teriiiinates at one end thereof in the axial vicinity of the end of said surface and forininy with said jig an annular nozzle, an anode being formed around said component and said conduit being arranged to be supplied with electrolytic solution under pressure such that on evolving from said nozzle the solution washes said surface, means being provided to render the component electrically cathodic with respect to the anode.

16. Apparatus as claimed in claim 15 in which said conduit is formed by a wall separating a pressure gallery, adapted to be supplied with electrolytic solution under pressure, from a drain gallery, said jig being mounted in the pressure gallery and extendiny through an aperture in said wall to form said conduit between the jiy and wall.

17. Apparatus as claimed in claim 16 in which the jig is provided with a shoulder to seat the component in the reyion of said conduit.

18. Apparatus as claimed in claim 17 in which the jig serves to central ise the component with respect to the anode.

19. Apparatus as claimed in any of claims 6 to 18 in which more than one jig is provided in the apparatus to enable plating of more than one component at a time.

20. Apparatus to put into effect the method claimed in claim 1 to selectively electroplate an area of an internal or external surface of a substrate, which apparatus comprises a nozzle adapted to emit an annular strearll or jet of electrolytic solution, means for mounting the substrate as a cathode with said area to be selectively electro-plated exposed to the nozzle, an anode adjacent the area, means for providing an electrolytic solution to the nozzle, whereby an annular stream of solution is remitted therefrorn, and an object which is positioned inside the annular stream to iiiaintain its annularity in a plating zone between the substrate and the anode, the anode and the area to be plated being so located relative to the nozzle that the anode and the area to be plated are submerged in the solution when the annular stream of solution is ernitted frorn the nozzle.

21. Apparatus as claimed in claim 20 in which the nozzle is a continuous annular nozzle.

22. Apparatus as claimed in claim 20 in which the nozzle is formed by a riny of discrete jets.

23. Apparatus as claimed in claim 21 or 22 in which the jet produced by the nozzle is directional.

24. Apparatus as claimed in clairri 23 in which the jet produced by the nozzle is directed towards the area to be electro-plated.

25. Apparatus as claimed in any of clairiis 20 to 24 in which the jet is non-circular in section and is conforined to the sectional shape of the area of the surface to be electro-plated.

26. Apparatus as clainied in any of claiiiis 20 to 25 for electro-plating the internal surface of the substrate, in which the object inside the annular strearn is a stem haviny a plug for aligning the nozzle with the substrate.

27. Apparatus as claimed in any of claims 20 to 25 for electro-platiny the external surface of the substrate, in which the object inside the annular stream is the substrate itself.

28. A method of, and apparatus for, electro-plating selective areas of substrates substantially as hereinbefore described with reference to the accolilpanying drawinys.