GB2287586A

GB2287586A - Edge connection for printed circuit boards

Info

Publication number: GB2287586A
Application number: GB9404562A
Authority: GB
Inventors: Hiroshi Harada
Original assignee: Alps Electric Co Ltd
Current assignee: Alps Alpine Co Ltd
Priority date: 1994-03-09
Filing date: 1994-03-09
Publication date: 1995-09-20
Anticipated expiration: 2014-03-09
Also published as: GB9404562D0; GB2287586B

Abstract

Edge connection is formed by modifying a circuit board by the provision of through holes (2) and slots (3) at one or more edges thereof. Conductive pins are located in respective holes, bent to locate in respective slots and further bent to protrude from the board to act as connection pins. The pins may be assembled as fingers (7) extending from a common backplane (4), which backplane is removed after assembly facilitating the assembly. Various forms of edge connection pins arranged to have two separate contact points with the board are also disclosed (Figures 7 and 8). <IMAGE>

Description

EDGE CONNECTION FOR PRINTED CIRCUIT BOARDS This invention relates to edge connection for printed circuit boards. In particular, it relates to pin type connectors mounted on printed circuit boards. These are often termed "terminal pins".

The simplest way of forming terminal connectors is simply to solder one end of a pin to a board, such that the pin is protruding from the board. The pins must be carefully aligned and can easily move out of position or bend.

Figure 1 shows a presently existing pin type edge connector for printed circuit boards (PCBs). A plurality of pins P are electrically connected to, eg, conductive tracks on a printed circuit board B. Each of the pins is mounted in a resin or plastics mounting block which is adhered or otherwise permanently affixed to the board. Part of each of the pins is encapsulated by the block and held securely therein. Thus, the block provides rigidity to the structure and also provides the desired (usually equal) spacing between the pins. Also, the pins are insulated from each other and from other parts of the PCB.

The use of such blocks is widespread but requires careful installation and adhesion of the block onto the PCB. Also, where several groups of connectors are required along a side of a PCB it is required to attach each connector block M separately. If pins of different length or heights are required then it is necessary to use different blocks. Further, once a block has been assembled, if one of the pins is faulty or broken it is necessary to replace the whole block.

According to the present invention there is provided a circuit board including edge connection means comprising a plurality of pins, each being electrically connected to the circuit on the board and being located on the board by at least two portions on the pin, each contacting a different portion of the board.

Preferably, one set of location portions comprises a plurality of spaced-apart slots at said edge, each pin locating in a respective slot.

The location portions may further comprise a plurality of spaced apart through holes towards said edge, wherein each pin has one end mounted at or through a respective hole and electrically connected to the circuit on the board and being bent to locate in a respective slot and further bent to protrude from the edge at the desired angle.

According to the invention there is further provided apparatus for forming edge connection pins for a printed circuit board, the apparatus comprising an elongate electrically conductive member and a plurality of electrically conductive fingers depending from said member whereby in use the fingers are locatable within spaced apart location means at the edge of a circuit board to form connection pins and the elongate member is removed to physically separate the pins.

According to the present invention in a third aspect there is provided a method for forming edge pin connection means on a printed circuit board, wherein the printed circuit board comprises a plurality of plated through holes towards at least one edge of the board and a plurality of slots formed at said edge and means to form the pin edge connector means comprises an electrically conductive member as defined above, wherein the distal edges of one or more of the fingers of the electrically conductive body are mounted through the respective through holes and electrically connected to the circuit on the board, the pins being bent to locate in respective slots and to protrude from the edge at desired angles, the pins then being cut to provide a desired connecting length of the pins which are thereby separated and electrically insulated from one another.

The pins may be further bent to provide bridging over any pre-existing circuit tracks on the board and thereby to electrically isolate the pins from that circuit track.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a prior art pin connector; Figure 2 shows a printed circuit board modified according to the present invention; Figure 3 shows an electrically conductive structure for forming an array of conducting pins; Figure 4 shows the structure of Figure 3 when assembled with respect to the board of Figure 2; Figure 5 shows a side view of Figure 4; Figure 6 shows a structure similar to that of Figure 3 after a group of fingers has been removed; Figure 7 shows an alternative edge connection arrangement; and Figure 8 shows an alternative pin structure.

Referring to Figure 2, a printed circuit board 1, is shown, on which various electrically conductive circuits and tracks are printed. Towards each edge at which edge connection is required a plurality of through holes 2 are formed. Most preferably, these are throughplated holes. They may be prepared by drilling for example followed by a through-plating process with a suitable electrically conductive plating material.

Generally, one hole 2 is required for each edge connection pin. On the edge of the board itself, an equal plurality of slots 3 are formed. Each of these slots is generally in line with a respective one of the through-holes 2.

Typically, the slots may have a depth of around one millimetre and the holes may have a diameter which is also approximately one millimetre. These dimensions may vary, however, depending upon the size of pin connectors required. Generally, the slots in the group will be equispaced, corresponding to the normal pin spacing.

Although not shown in the figure, several groups of holes and corresponding slots may be formed along an edge or more than one edge of the board. Previously, this would require separate mounting blocks (such as M in Figure 1) to be used for each group.

Figure 3 shows a structure for forming the edge connection pins. The structure is of an electrically conductive material such as a metal and comprises a first elongate member in the form of a back strip 4. Depending from strip 4 are a plurality of fingers 5. These are of the cross-sectional dimensions required of the connecting pins and are spaced in a distance apart corresponding to the distance between adjacent slots 3 on Figure 2. Such a structure as in Figure 3 may be formed as a single large piece having a large number of projections or fingers 5 which may then be cut to the required number of fingers.

It will also be apparent that if more than one group of connectors are required it is possible to form a structure as shown in Figure 3 to at least the total length of an edge and to cut away those fingers or groups of fingers which are not required. Thus, if one group of six fingers and one group of four fingers were required then the structure may look something like that shown in Figure 6.

The structure can then be applied as a unitary body to the PCB for the fingers 5 to be mounted therein and all the pins to be formed.

An integral structure such as that shown in Figure 3 is preferable as a starting point since then all the pins can be assembled simultaneously in a single operation. It is, however, possible to insert a series of pins individually in which case each pin is a single elongate electrically conductive member.

To assemble the pin bearing structure 6 to the PCB 1, firstly any fingers 5 which are not required (such as the first five fingers shown in Figure 3) are removed.

The distal ends 7 of the required fingers are inserted from below the board in the figure through respective ones of mounting holes 2. The fingers may be secured by soldering for example, typically on the underside of the board as shown. The circuit track in this example will also be on the underside and different ones of the fingers 5 will be connected to different parts of the circuit track. Each finger is then brought underneath board 1 and bent upwards (in the figure) to locate into a respective slot 3. Slots 3 thereby serve to locate and correctly space each of the fingers. At this point the finger will be generally parallel to the plane of the edge of the board. At a point a desired distance above the top surface T of the board the pins are bent again, generally at a right angle but other angles may be used, such that they protrude in the same manner as pins P in Figure 1.

The pins are then cut to present a desired length of pin for connection and thus mounting member 4 and the cut off portions of fingers 5 are removed and may be discarded or recycled (by melting down and reforming for example). The resulting structure is shown in Figure 4.

As shown in Figure 4, the position, spacing and length of the formed connecting pins 5 is identical to those of the pins P of the prior art. Fingers 5 are of sufficient rigidity that they are located securely by slots 3 and are thus sufficiently rigid to be used as connector pins.

Figure 5 shows a side view of Figure 4. The figure has been exaggerated slightly to show the distal end 7 of a finger protruding slightly from the top surface of a board 1. The pin extends through through hole 2 and is soldered at 8 in place and also to form an electrical connection between the pin and an appropriate track on the board. The figure shows a preferred feature in which the finger is not adjacent to the underside of the board up to the slot but instead a bridge portion 9 is formed. This may be formed by additional bending of the pin. It should be noted that the pin is preferably pre bent to the shape shown in Figures 4 and 5 before insertion into a board 1.

This bridge portion 9 is intended to cause the pin to bridge over a printed circuit track 10 since it is important that the pin is insulated from this track. In prior art systems involving a mounting block M this is accomplished by the mounting block itself being an insulator. The bridge 9 achieves the same effect by ensuring that the pin underside does not contact the track by having air between the track and the pin. If it is desired to make electrical contact between any one of the pins and this track 10 then this may be achieved by a small wire or solder connection for example between the two parts.

It will be appreciated that the rigidity of the pins in the present invention is achieved by the fact that each pin contacts the board at two or more points along its length. In the above embodiment, this is achieved by mounting the pin in a hole and passing it through a slot.

Alternatively, the holes and the slots may be replaced by merely attaching the pin to a board at two points along its length and/or edge, eg by soldering or glueing. This is shown in Figure 7 which shows a plain board 11, without holes or slots. A pin 12 is soldered at one end 13 to the underside of the board and bent around the edge 14 of the board. It may be soldered or glued at this edge. If desired, holes or slots may be provided in the board so that the pin is attached to a plain part of the board only where a hole or a slot is not provided.

The pin assemblies described above require mounting on one side of the board, and bending around the edge of the board. This may be difficult to achieve when the board is adjacent another board, a frame or a mounting box for example. Figure 8 shows a pin assembly which can be mounted to a board from one side only, to overcome the problem. Each pin comprises a terminal piece 15 forming the terminal, edge-connection, part in use, and two depending legs 16 and 17. Leg 16 depends from one end of pin 15 and leg 17 from a point spaced a distance from leg 16. A plurality of pin members 15 may in turn depend from a support member similar to member 4 in Figure 3, so that a plurality of pins can be inserted simultaneously and the support member subsequently detached. Leg 16 may be inserted into one of the holes 2 and leg 17 into slot 3, if a board such as that shown in Figure 2 is used.

Alternatively, the legs may be soldered, glued or otherwise attached into place on an untreated board (ie without holes and/or slots). The spacing between legs 16 and 17 is chosen to conform to the spacing between holes 2 and slots 3 for example.

Further, legs may depend from member 15 if required for any particular purpose.

Claims

1. A circuit board including edge connection means comprising a plurality of pins, each pin being electrically connected to the circuit on the board and being located on the board by at least two portions on the pin, each contacting a different portion of the board.

2. A circuit board as claimed in Claim 1, wherein each pin is physically attached to the board at each location portion.

3. A circuit board as claimed in Claim 1 or Claim 2, wherein one set of location portions on the board comprises a plurality of spaced-apart slots at said edge, each pin locating in a respective slot.

4. A circuit board as claimed in Claim 3, further comprising a plurality of spaced apart through holes towards said edge, wherein each pin has one end mounted at or through a respective hole and electrically connected to the circuit on the board and being bent to locate in a respective slot and further bent to protrude from the edge at the desired angle.

5. A circuit board as claimed in any preceding claim, wherein one or more of the pins are further bent to form a non-contacting bridge over part of the circuit board.

6. A circuit board as claimed in any preceding claim, wherein each pin has two or more legs depending from it, at least two of the legs providing the contact with the board.

7. Apparatus for forming edge connection pins for a printed circuit board, the apparatus comprising an elongate electrically conductive member and a plurality of electrically conductive fingers depending from said member whereby in use the fingers are locatable within spaced apart location means at the edge of a circuit board to form connection pins and the elongate member is removed to physically separate the pins.

8. Apparatus as claimed in Claim 7, wherein each pin is bent in at least one place.

9. Apparatus as claimed in Claim 7 or Claim 8, formed as a single, integral, body.

10. Apparatus as claimed in any one of Claims 7 to 9, wherein each finger has two or more legs depending from it.

11. A method for forming edge connection means on a printed circuit board, comprising applying an apparatus as claimed in any one of Claims 7 to 10, to the board, so that the apparatus contacts the board in at least two places, and removing the elongate member.

12. A method for forming edge pin connection means on a printed circuit board, wherein the printed circuit board comprises a plurality of through holes towards at least one edge of the board and a plurality of slots formed at said edge or edges and means to form the pin edge connector means comprising an electrically conductive member as claimed in any one of Claims 7 to 10, wherein the distal edges of one or more of the fingers of the electrically conductive body are mounted through the respective through holes and electrically connected to the circuit on the board, the pins being bent to locate in respective slots and to protrude from the edge at desired angles, the pins then being cut to provide a desired connecting length of the pins which are thereby separated and electrically insulated from one another.

13. A method as claimed in Claim 12, wherein one or more of the pins are further bent to form a non-contacting bridge over part of on the circuit board.

14. A method as claimed in Claim 12 or Claim 13, wherein the fingers are pre-bent before mounting on the board.

15. A method as claimed in Claim 12 or Claim 13, wherein the fingers are bent during the mounting process.

16. A circuit board substantially as hereinbefore described with reference to, and as illustrated by any of Figures 2 to 8 of the accompanying drawings.

17. A method of forming edge connection on a circuit board, which method is substantially as hereinbefore described with reference to any of Figures 2 to 8 of the accompanying drawings.

18. A structure for forming an array of pin connectors, which structure is substantially as hereinbefore described with reference to, and as illustrated by, Figure 3 or Figure 7 of the accompanying drawings.