GB2292840A

GB2292840A - Ensuring contact

Info

Publication number: GB2292840A
Application number: GB9417262A
Authority: GB
Inventors: Malcolm Graham Grandis
Original assignee: NFI ELECTRONICS Ltd
Current assignee: NFI ELECTRONICS Ltd
Priority date: 1994-08-26
Filing date: 1994-08-26
Publication date: 1996-03-06
Also published as: GB9417262D0

Abstract

Contact is ensured between components by means of an embossed sheet of plastics. An electrical component 2 is forced against a contact(s) on or lining a pair of plastics sheets 8 by a bubble 12 optionally provided with one or more further embossments 14. The bubble 12 may define a pocket and the sheets are held together by adhesive 10. Alternatively, a component is held against embossments on a single sheet by sandwiched adhesive and by an optional pressing member, or an embossment on a flexible sheet having electrical contact areas on its surface is pressed against contacts of a rigid board by pressing means. <IMAGE>

Description

Electrical components This invention relates to electrical components, and particularly to means for holding them in position on a substrate.

Electrical components such as printed circuit boards (PCBs) are relativelyrigid and have external contact areas to which connections have to be made to place the circuits on the board in circuit with external circuits and power supplies. The usual edge-mounted or other connectors have electroconductive areas which are urged by springs or other devices into long-term contact with the PCB contacts. In order to make the contacts of low and consistent electrical resistance, they are either made of corrosion-resistant material, such as a thin layer of gold, or they are hermetically sealed from atmospheric moisture. These expedients are either expensive or unwieldy, particularly when the electrical contacts have to be made and broken at will.

The present invention aims at providing means for mechanically biasing two electroconductive surfaces together by means of the inherent resilience in a sheet of suitable plastics material.

Accordingly the present invention provides a biased electric component as claimed in the appended claims.

The present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a sectional view through one embodiment of the present invention which uses two sheets of plastics material to encapsulate an electric component; Figure 2 is a sectional view through a second embodiment similar to Fig. 1; Figure 3 is a sectional view through a third embodiment similar to the previous two; Figure 4 is a sectional view through a fourth embodiment which has the component in a pocket; Figure 5 is a sectional view through a fifth embodiment which uses a single sheet of plastics material;; Figure 6 is a view similar to Fig. 5 showing the application of an additional biasing force, and Figure 7 is a sectional view showing the use of the present invention to make contact with a circuit on a flexible substrate.

In the drawings, like components are given the same references.

In that form of the invention shown in Fig. 1, an electric component 2 is housed in a recess 4 embossed in a sheet 6 of suitable plastics material, being held in place by a planar second sheet 8. The two sheets are held together by a layer 10 of an adhesive or like bonding material. The depth of the recess is related to the thickness of the component so that the embossed 'bump' 12 is flexed by its contact with the component, so that the inherent resilience of the bump is used to bias the component into contact with both sheets. In practice, either or both of the sheets would have surface terminals which would come into contact with corresponding contact areas on the surface of component 2. Alternatively, a sheet of contact material (not shown) could be sandwiched between either sheet and the component so that the bump functions solely to apply mechanical pressure.

In that form of the invention shown in Fig. 2, the bump 12 is formed with an inverted smaller bump 14. This effectively divides the biasing force between the two bumps, in that each is distorted by the contact of bump 14 with the component 2. Although the small bump 14 could have any shape in plan, it is preferred to make each circular in plan, so that the area of contact between the bump and the component is small and substantially circular.

Fig. 3 shows a larger component 2 having three areas on its upper (as viewed) surface contacted by bumps 14. The depths of the bumps from their parent sheet may be different, to accommodate the curvature of the domed base of the major bump 12. In this way, when all three bumps 14 contact a planar surface, the biasing forces applied by the bumps are substantially the same as each other.

In the Fig. 4 embodiment, the sheet 6 is of stiffer material than in the earlier forms of the invention. One edge portion of the sheet is formed into a pocket 16, having a bump 14 embossed into it. When the borders of the pocket are bonded to the underlying sheet 8, the resultant pocket is able to have a component inserted into it by being slid along the surface of sheet 6. Although this is not shown in Fig. 4, the component would usually be inserted until it meets a sidewall 18 of the pocket, in which position a specific area of the component has the bump 14 pressing against it.

Fig. 5 shows an embodiment in which only a single sheet 20 of plastics material is used. The sheet has at least two bumps 14 embossed in it at spacings related to the contact areas on the component 2. In the region between two bumps the component is secured to sheet 20 by a blob of adhesive 22. As the adhesive is curing, the component is pushed towards sheet 18 so as to deform the bumps 14 and thus store some energy in them.

When the adhesive has set, the distortion force is removed, causing the resilience of the bumps to try to move the component away from the sheet, which force is taken up by the adhesive. Fig. 6 shows symbolically the application of a biasing force by body 24 either while the adhesive is setting, or constantly, in the case when no adhesive is used.

In that embodiment of the invention shown in Fig. 7, the component 2 takes the form of a large rigid sheet having electrical contact areas on one of its major surfaces. A sheet 6 of flexible plastics material also has electroconductive areas formed on it. The sheet 6 is post-formed with an embossed bump 14 positioned so that its apex is conductive. When the bump has been positioned so that it is in contact with a conductive area of the body 2, a pressure member 24 is applied to its outer surface so as to bias the two areas into firm contact with each other.

At least one plastics sheet trust be made of a material which is able to be embossed, and in which each embossment so formed is strong enough to be distorted by contact with a rigid surface to provide the required biasing force. Suitable materials are plastics resins which are capable of being made into sheets which can be permanently embossed by the application of pressure and/or heat. Examples of suitable resins are: polyesters; polycarbonates; polyamides; polyethylene naphalate, and acrylonitrile/butadiene/styrene copolymers, but this list is not exhaustive and other resins could be used.

It will thus be seen that this invention provides a simple and effective way of applying a mechanical bias to a component, either to hold it in place, or to enhance the electroconductive contact between a conductive bump on a plastics substrate, or a contact area on an intermediate circuit member, and a conductive area on the surface of the component.

Claims

Claims:

1 An electric circuit component comprising a body of rigid material presenting at least one external contact area of electroconductive material, the component being held in contact with a sheet of plastics material by means of energy stored in an embossed area of the or another sheet of plastics material by deforming mechanical contact by the body with the or each embossment.

2 A component as claimed in claim 1, in which at least one embossment has a surface of electroconductive material, and in which that surface is in contact with one of the contact areas on the body.

3 A component as claimed in claim 1 or 2, in which a body of electroconductive material is in position between a bump and a contact area of the body, so that the bump applies force to the conductive surfaces in contact.

4 A component as claimed in any preceding claim, in which the component is housed within an embossment in at least one of two sheets of plastics material having their major surfaces bonded together.

5 A component as claimed in claim 4, in which a major surface of one embossment has at least one smaller embossment in it and directed towards the component body.

6 A component as claimed in any of claims 1 to 3, in which the component body is held to a base layer of a sheet by a body of adhesive bracketed by two bumps, whereby the adhesive holds the body in deforming contact with the bumps.