GB2307799A - Printed circuit board interconnection apparatus - Google Patents

Abstract

An apparatus is located between two circuit boards 1, 2 and comprises at least one pair of electrically connected portions 11, 12 in which one portion 11 connects to one circuit board 1 and the other portion 12 to the other circuit board 2. The circuit boards 1, 2 become interconnected when pressure is applied between the circuit boards. The circuit boards 1, 2 may be in the same plane and the apparatus may be placed between the opposing edges of the circuit boards 1, 2 with the pressure being applied in a direction within said plane and perpendicular to said opposing edges. The said portions 11, 12 may be parts of a single resilient component 10. A printed circuit board frame arrangement with a dividing wall which includes members which can readily be converted to provide isolated connection means between circuit boards, which are placed in said frame arrangement, is also disclosed (figs. 5 - 7).

Description

ELECTRICAL APPARATUS This invention relates to electrical apparatus.

In particular, it relates to electrical apparatus comprising two or more printed circuit boards on which some of the circuits are required to be electrically interconnected.

Presently, when adjacent printed circuit boards (PCBs) of an electrical apparatus are required to be electrically connected it is necessary to use a further component to connect the two boards. This is shown in Figure 1 which illustrates two circuit boards 1,2 mounted within a frame 3. The circuit boards are electrically interconnected by means of a component 4 which includes an insulating body 5 typically of plastics or resin which bridges the two boards. Conductive legs 6 extend from body 5 and are electrically connected to appropriate circuits 7 on the boards to interconnect them.

Such an approach necessitates a further component being added to the boards and the nature of this component means that it is vulnerable to dislodging or breaking electric connections when the boards are stressed, or with vibration of the apparatus for example.

Heat expansion and contraction of the boards can also be a problem and cause disconnection to occur.

The present invention arose in an attempt to provide an improved method and assembly for electrically connecting adjacent circuit boards.

According to the present invention there is provided electrical apparatus comprising a first circuit board, a second circuit board and electrical interconnection means between the first and second boards which include at least one pair of connected electrically conductive portions which are connected so that one of said portions makes electrical contact with the first board and the other portion makes electrical contact with the second board, the portions being partially or wholly supported, and electrical connection thereby made, by pressure between the two boards.

Preferably, the projections are part of a single piece having a first portion extending toward said first board and a second portion extending toward said second board.

According to the present invention in a second aspect there is provided a method a method of forming electric connections between adjacent circuit boards, comprising positioning a component between two circuit boards, the component having at least one pair of electrically conductive projections; electrically contacting the first projection to the first board and the second projection to the second board and causing an axial force to be applied to at least one of the boards to wholly or partially support the component.

Preferably, part of the plate is then cut away to leave the projections in place while insulating the connections from unwanted electrical connections.

The plate may further comprise means for applying a spring force to at least one of the boards.

The force may be provided by the electrically contacting portions or by other portions.

By employing such a spring force the panel may form part of a frame which can hold one or more of the boards in place as is described more fully in the applicants co-pending patent application reference K1736GB, which is incorporated herein by reference.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a previously proposed electrical apparatus; Figure 2 shows a pair of circuit boards interconnected by an apparatus embodying the present invention; Figure 3 shows an interconnection means; Figure 4 shows a side view of the two boards and the interconnection means; Figure 5 shows a dividing panel; Figure 6 shows the dividing panel of Figure 5 in relation to two circuit boards; and Figure 7 shows the apparatus of Figure 6 after an electrical isolation step has been performed.

Referring to Figures 2 to 4, there is shown an electrical arrangement according to an embodiment of the invention. In this arrangement, two circuit boards 1,2, typically printed circuit boards, are mounted adjacently but spaced apart by a pair of resilient electrically conductive members 10. The members are typically of metal but may be of other conductive material. The members comprise two legs 11,12 and may also include a stem 13 from which the legs depend. As shown in Figure 4, which is a side view, a first one 12 of the legs extends generally forwardly whilst the other leg 11 extends generally rearwardly. The legs have some resilience so that if legs 11 and 12 are pushed towards each other in Figure 4 they will tend to move back into their displaced position.As shown in Figure 4, member 10 is held in place in situ by leg 12 pushing against board 1 and leg 11 pushing against board 2. The boards are physically separated by a distance depending upon the resilience and shape of member 10 and any axial force applied to the ends non-adjacent of the boards.

Member 10 is electrically conductive and, as shown in Figure 4, leg 12 contacts a conductive track 14 on board 1 whilst leg 11 contacts a conductive track 15 on board 2. Thus, electrical signals may pass from track 14 through member 10 to track 15 on the other board and vice versa if appropriate. The natural resilience of the member 10 when it is in a compressed state, ensures that good contact is made at all times with the track boards without a physical solder connection being necessary, although additional soldered connections may be made between the respective legs and tracks if desired.

Two such members 10 are shown in Figure 2. In practice, only one may be required or more than one.

Instead of having only two legs as shown, each member may have three or more legs where a more complex pattern of tracks is to be connected. The legs should bend respectively forwards or backwards depending upon which particular track or board they are to contact. It is of course important that at least one of the legs does point forward and at least one does point backwards to enable electrical contact between the two boards. Where more than two legs are provided, insulating portions may be provided within member 10 such that signals from adjacent tracks are kept electrically insulated from one another.

This may be means of plastic of other insulating parts of the member 10 which electrically isolate and insulate groups of cooperating legs from each other.

Figure 5 shows one example of an apparatus which may be applied between adjacent circuit boards to enable means such as members 10 to be positioned. The figure shows a panel member 16 which is of an electrically conductive material such as a metal. It is often desired in electrical apparatus to mount circuit boards between panel members to separate the circuit boards and also to provide means for mounting the boards within the circuit.

In this regards, the panel 16 includes pair of lugs 17 which are cut out of the panel as shown such that they are only connected to it by a stem portion 18. Lugs 17 extend forwardly from the panel shown in figure (ie out of the page) so that in use a board such as 1 or 2 is held in place by a resilient force applied by one or both of lugs 17. A method of supporting boards using members such as 17 and solder connections is described in co-pending application K1736GB. The electrically connecting members 10 as shown in Figure 3 are provided in the panel of Figure 5 within a rectangular cut out 19. Portions 10 are joined to the remainder of the panel within this cut-out 19 by stem 13. They are thus only connected to the panel at point 13 and are otherwise insulated from each other.

In the panel shown in Figure 5, optional notches 20 are provided at the top edge of panel 16. These notches 20 are to enable a portion of the panel to be cut or otherwise broken off to insulate and thereby electrically isolate the members 10 when they are positioned between circuit boards.

Figure 6 shows the panel of Figure 5 lying between two circuit boards shown in dashed lines. It is seen that the adjacent edges of both circuit boards 1 and 2 lie towards panel 16 such that they contact lugs 17 and members 10. It will be appreciated that leg 11 of each of the members 10 extends rearwardly and leg 12 extends forwardly (although this may of course be reversed).

Thus, the leading edge of panel 1 contacts leg 12 and the adjacent edge of panel 2 contacts leg 11. These are aligned with tracks to be electrically connected on the respective boards so that board 1 is electrically connected with board 2 through members 10.

After the circuit boards have been secured into place and contact made between the respective members 10 and electrical tracks on the boards, part of the top portion of panel 16, between notches 20, may be removed.

This may either be done by cutting in a straight line between the lower edges of each of the notches or, since the panel is deliberately weakened, by bending the part of the panel between the notches. This will cause that part 21 of the panel to be removed as shown in Figure 7. As is clearly shown in the figure, the removal of this part of the panel effectively isolates members 10 which are thereby held in place only by the action of boards 1 and 2. This may be eg by a compressive force. As a result, electrical signals may pass between a first cooperating pair of tracks on the respective boards along a first member 10a and be electrically isolated from signals passing between a second set of tracks through the second member lOb.

This technique may be extended to more complex connection structures utilizing the same general principals.

Claims (12)

1. Electrical apparatus comprising a first circuit board, a second circuit board and electrical interconnection means between the first and second boards which include at least one pair of connected electrically conductive portions which are connected so that one of said portions makes electrical contact with the first board and the other portion makes electrical contact with the second board, the portions being partially or wholly supported, and electrical connection thereby made, by pressure between the two boards.

2. Apparatus as claimed in Claim 1, wherein the portions are part of a single component having at least a first portion extending towards the first board and at least a second portion extending toward the second board, the portions providing a resilient outward force that wholly or partially supports the components.

3. A method of forming electric connections between adjacent circuit boards, comprising positioning a component between two circuit boards, the component having at least one pair of electrically conductive projections; electrically contacting the first projection to the first board and the second projection to the second board and causing an axial force to be applied to at least one of the boards to wholly or partially support the component.

4. A method as claimed in Claim 3, wherein the axial force is provided by an outward force from one or both portions.

5. A method as claimed in Claim 3 or Claim 4, wherein the axial force is applied by an additional projection on the component.

6. A method as claimed in any of Claims 3 to 5, wherein the component is a plate having at least two projections formed in it and bent outwards in opposite directions.

7. A printed circuit board frame into which printed circuit boards are mounted, the frame including at least one electrically conductive dividing wall between two compartments arranged to receive a respective printed circuit board, the dividing wall having partially cut out therefrom an electrical connector positioned adjacent a conductor on each of the two printed circuit boards to effect an electrical connection therebetween, the connection between the connector and the remainder of the dividing wall being readily severable to electrically isolate the connector from the dividing wall.

8. A method of interconnecting printed circuit boards comprising the step of providing two adjoining walled compartments, partially cutting out from the dividing wall between the two compartments a connector, mounting a printed circuit board in each of the two compartments, using the connector to electrically interconnect the two printed circuit boards, and completely severing the connector from the dividing wall to electrically isolate the connector from the dividing wall.

9. A method according to Claim 8, wherein the method of electrically connecting the connector to the printed circuit boards includes effecting soldered joints.

10. A method as claimed in any of Claims 3 to 6, wherein after connection is made, part of the component is removed to leave the electrically interconnecting portions in place while insulating them from undesired electrical connection.

11. Electrical apparatus substantially as hereinbefore described, with reference to, and as illustrated by, Figures 2 to 7 of the accompanying drawings.

12. A method of connecting electrical circuit boards substantially as hereinbefore described, with reference to, and as illustrated by, Figures 2 to 7 of the accompanying drawings.