GB2069532A

GB2069532A - Method of manufacturing slip rings and to slip rings produced thereby

Info

Publication number: GB2069532A
Application number: GB8005139A
Authority: GB
Original assignee: IDM Electronics Ltd
Current assignee: IDM Electronics Ltd
Priority date: 1980-02-15
Filing date: 1980-02-15
Publication date: 1981-08-26
Also published as: EP0034232A2; EP0034232A3

Abstract

A method of manufacturing a slip ring including the steps of forming a body (2) of plastics material, forming a plurality of grooves (6) in a surface of the body, treating the grooved surface to allow a metal skin (7) e.g. copper, to be deposited thereon by an electro- less plating process, electro-less plating a layer of base metal (7) on the treated surface of the plastics material, including the grooves (6) formed in the plastics body, removing the plated material (8) from between adjacent grooves to define individual tracks of the slip ring and electroplating the plated material to overlay the grooves only with a layer (9) of a noble metal e.g. gold. <IMAGE>

Description

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GB 2 069 532 A 1

SPECIFICATION

Improvements in and relating to a method of manufacturing slip rings and to slip rings produced thereby

5 This invention relates to a method of manufacturing slip rings in which an electroless plating step is included during manufacture to deposit layers of conductive metal including a noble metal, and to slip rings produced by such a 10 method.

An object of the invention is to produce a slip ring which, by eliminating certain high precision techniques involving highly skilled personnel and time-consuming operations, is capable of being 15 produced far more economically than conventional slip rings.

According to one aspect of the present invention there is provided a method of manufacturing a slip ring including the steps of 20 providing a body of plastics material, forming a plurality of parallel grooves in a surface of the plastics body, treating the grooved surface to allow metal to be deposited thereon by an electro-less plating process, electro-less plating a layer of 25 base metal on the treated grooved surface of the plastics body including the grooves thereof removing the plated metal from between adjacent grooves to define individual tracks of the slip ring and electroplating to overlay the base metal in the 30 grooves only with a noble metal.

According to a further aspect of the invention there is provided a method of manufacturing a slip ring including the steps of forming a cavity in a slip ring body of plastics material, 35 forming terminal holes in the body extending between a surface of the body and the cavity, locating terminal pins within the holes and securing the pins in position by filling the cavity with an encapsulating medium, forming V-grooves 40 in said surface in line with the pins and exposing a portion of a pin at the base of each V-groove, electro-less plating a base layer of metal on said surface and on the walls of the grooves, removing said plated metal from between adjacent grooves 45 to define individual tracks of the slip ring and replating to overlay the base metal in the grooves only with a noble metal.

The term 'slip ring' is intended to include discs or cylinders and thus to manufacture a slip ring in 50 accordance with one embodiment of the method of the present invention using the electro-less plating method, a cylinder or disc is cast from plastics material consisting for example of an epoxy base filled resin, and all surfaces are 55 machined to remove the resin rich skin. The plastics material is then cured and the disc or cylinder machined to obtain the required external profile leaving sufficient material to maintain rigidity for subsequent machining operations. 60 A cavity for the terminals is then machined in the body of plastics material and the body drilled with a plurality of holes for the terminals of the rings, each hole having for example, a depth of between 0.6 mm and 0.7 mm and each terminal

65 hole extends from the surface of the body opposite the cavity, through to the cavity.

Copper terminal pins are located within the holes and cemented in position. The length of the terminals should each be for example, 70 to 80% 70 of the ring width and project through the holes in the body of the ring, through the cavity formed in the body and slightly beyond the cavity extending radially or in any other direction. It is important to ensure that the ends of the terminal pins remote 75 from the cavity lie flush with the surface of the plastics material.

The cavity is then filled with an encapsulating medium to fix the terminal pins in position.

With presently manufactured slip rings, square 80 section grooves are machined in the plastics body in line with each terminal pin and the base of each groove is hand-painted with silver paint. It is extremely important to ensure that the paint is applied only to the base of each groove, since 35 when the ring is subsequently placed in a plating bath, if any silver paint has been deposited on the walls of the grooves, copper from the materials of the plating bath will tend to be deposited at the nearest point to the anode of the bath and 90 continue to be deposited from this point in any groove having silver paint on the walls. Since the object of the plating step is to provide a uniform deposit of copper in the groove, it will be appreciated that it is important to ensure that the 95 .silver paint is applied only to the base of the groove. This, obviously, is a highly skilled,

precision operation involving the use of highly skilled personnel and is also obviously time-consuming and accordingly costly, particularly 1 oo since if any silver paint inadvertently appears on the side walls of any groove, it must be meticulously removed manually by means such as a scalpel. The copper deposited in the square section grooves is finally machined to form V-105 shaped grooves.

In the method of manufacture according to the described embodiment of the present invention, the hand-painting step is eliminated by introducing an electro-less plating step and 110 instead of machining square section grooves in the ring, V-grooves are machined in the plastics material in line with each terminal pin, exposing the head of each terminal pin only at the base of each V-shaped groove. The grooved body of 115 plastics material is treated in preparation for plating by an electro-less plating step and placed in the plating bath and a thin layer of copper is deposited uniformly in the V-grooves and betweer adjacent grooves. Peaks of copper may be 120 deposited between the grooves and these peaks are machined away back to the plastics base to define the individual tracks of the ring. The electro-less plating step provides a homogeneous bond between the copper terminal pins and the 125 thin copper skin.

The ring is finally inserted in an electro-plating bath of noble metal e.g. gold where the copper layer in each V-groove is overlaid with the noble metal.

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GB 2 069 532 A 2

The steps of the process are illustrated in the accompanying drawings 1 to 6 in which in Figure 1, the terminal holes 1, are drilled in the plastics base 2 after formation of the cavity 3. After 5 cementing the terminals 4 in position within the holes 1, the terminals 4 are encapsulated within an encapsulating medium 5 which fills the cavity 3, as shown in Figure 2. The V-grooves 6 are machined in the plastics base 2 as shown in 10 Figure 3 exposing the tips of the terminals 4, and the plastics base is treated and then inserted in an electro-less plating bath where a thin copper skin 7 is deposited over the surface of the plastics material and uniformly within the V-grooves 6 as 15 shown in Figure 4. Peaks such as shown at 8 may be formed during plating and as shown in Figure 5, the peaks 8 between the grooves 6 are , machined away to expose the plastics material and define the individual tracks of the ring and in 20 Figure 6, the copper skin 7 in each groove has been overlaid with a noble metal layer 9 e.g. gold in an electro plating bath.

Claims

1. A method of manufacturing a slip ring 25 including the steps of providing a body of plastics material, forming a plurality of parallel grooves in a surface of the plastics body, treating the grooved surface to allow metal to be deposited thereon by an electro-less plating process, electro-less plating 30 a layer of base metal on the treated grooved surface of the plastics body including the grooves thereof, removing the plated mdtal from between adjacent grooves to define individual tracks of the slip ring and electroplating to overlay the base 35 metal in the grooves only with a noble metal.

2. A method of manufacturing a slip ring including the steps of forming a cavity in a slip ring body of plastics material, forming terminal holes in the body extending between a surface of the body

40 and the cavity, locating terminal pins within the holes and securing the pins in position by filling the cavity with an encapsulating medium, forming V-grooves in said surface in line with the pins and exposing a portion of a pin at the base of each V-45 groove, electro-less plating a base layer of metal on said surface and on the walls of the grooves, removing said plating metal from between adjacent grooves to define individual tracks of the slip ring and replating to overlay the base metal in 50 the grooves only with a noble metal.

3. A slip ring produced by the method claimed in claim 1 or 2.

4. A method of manufacturing a slip ring and substantially as hereinbefore described with

55 reference to the accompanying drawings.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1981. Published by the Patent Office, 25 Southampton Buildings, London, WC2A 1AY, from which copies may be obtained.

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