WO1990004272A1

WO1990004272A1 - Method and apparatus for connecting circuit boards and the like

Info

Publication number: WO1990004272A1
Application number: PCT/GB1989/001186
Authority: WO
Inventors: Alan H. Rigby
Original assignee: The Mcmurdo Instrument Co. Ltd.
Priority date: 1988-10-07
Filing date: 1989-10-06
Publication date: 1990-04-19
Also published as: GB8823558D0

Abstract

A two-part electrical connector for connecting a printed circuit board (4) to another board comprises a first part (1) for receiving the circuit board (4) and a second part (3) carrying contacts (2) for connection to the other circuit board. The first part (1) is provided with a cam surface (8) disposed with respect to resilient portions (21) of the contacts (2) to force the contacts into abutment with contact areas on the circuit board (4) when the two parts of the connector are moved into a closed position. The connector parts (1, 3) and the circuit board (4) are provided with interlocking members and recesses to enable the connection and disconnection of the circuit board (4) simply by movement of the board.

Description

Method and Apparatus for Connecting

Circuit Boards and the like

The present invention relates to the field of connectors, in particular connectors for circuit boards and the like.

The methods and types of apparatus described hereafter find application in conjunction with many different devices, such as printed circuit boards, line cards and moulded circuits. The term "circuit board" used below should be understood to cover all of the aforementioned devices as well as any device having a degree of rigidity and bearing electrical contacts.

A wide variety of circuit board connectors have been proposed and the problems involved in their design are well known. One major problem is the need to reconcile the use of minimum insertion force with obtaining maximum contact pressure.

One typical edge connector for circuit boards is formed of a housing having a cavity of generally rectangular cross-section for receiving an edge of a circuit board. A row of contacts is provided on one, or two facing walls of the cavity and the or each row of contacts is biased towards the centre of the cavity. When the edge of the circuit board is inserted into such a connector the biasing of the contacts ensures a good contact pressure, but a high insertion force is required to overcome tangential forces exerted on the board by the contacts.

Whilst low or zero insertion force connectors are known there is a continuing need for high calibre low insertion force connectors, particularly for those which are compact, easy to operate, or which enable circuit boards to be connected together at right angles.

The present invention provides a method of making an electrical connection, comprising the steps of: providing a connector on a first circuit board, which connector is provided with a plurality of contacts at least parts of which are moveable in a direction generally parallel to the plane of the first circuit board; inserting a second circuit board into said connector in a direction transverse to the plane of the first circuit board; and causing the parts of the contacts to be moved under the action of a camming movement whereby to electrically connect the contacts to conductors provided on the second circuit board.

The aforementioned camming movement is in a direction parallel to the insertion direction of the second circuit board and is preferably caused either by the second circuit board being provided with a camming surface, or by the connector being provided with a cap portion having a camming surface moveable relative to the contact carrying portion of the connector, and which is entrained by the inserted second circuit board.

The present invention further provides apparatus for making an electrical connection between a circuit board and at least one contact, comprising: a first member comprising a cam surface; and a second member carrying at least one contact and adapted to receive a circuit board adjacent to said at least one contact; wherein the first and second members are adapted to be moveable relative to one another, the relative movement being such that the cam surface causes movement of said at least one contact.

Embodiments of the invention have the advantage of allowing a low or zero initial insertion force to be used whilst still achieving a high contact pressure on connection of the circuit board. Preferred embodiments of the invention also involve a sliding contact before full connection of a circuit board so as to clean dirt, oxides, and the like from the contacting surfaces.

A particularly preferred embodiment of the invention enables connection to be made simply by pushing a circuit board into a connector without the prior art disadvantage of a high insertion force. Also, disconnection and resetting of a connector according to one preferred embodiment is achieved simply by pulling a circuit board out of the connector.

A further preferred embodiment of the invention incoporporates means for ensuring that the connector will be in a condition to receive a circuit board i.e. will not be in a condition where the cam surface has moved at least one contact into the path of movement the circuit board with the consequential risk of damage to contacts.

Another advantage provided by the particularly preferred embodiment is that it enables a large number of daughter boards to be connected close together on a motherboard; this is particularly useful in telecommunications applications.

Further features and advantages of the present invention will become clear from the following description of embodiments thereof, given by way of example, with reference to the accompanying drawings, in which:

Figure 1 shows a partial longitudinal cross- sectional elevation through a two-part connector according to a first embodiment of the invention, in a first configuration and bearing a circuit board;

Figure 2 shows a transverse cross-section (in elevation) through the connector shown in Figure 1 in a second configuration;

Figure 3 shows a partial longitudinal cross- section similar to that shown in Figure 1 but in a second configuration;^"

Figure 4 shows a longitudinal cross-section of a part of the connector shown in Figure 3, with modified locking device; and

Figure 5 shows a transverse cross-sectional elevation through the part shown in Figure 4.

There follows a detailed description of embodiments of the invention taking the form of two-part connectors for connecting circuit boards at right angles. In the described embodiments, the two parts of the connector, one of which has a camming surface, the other of which houses the contacts, are moveable relative to one another on insertion of the edge of a circuit board, the circuit board entrains one part of the connector and causes that part to move relative to the other part such that the camming surface acts to cam the contacts and the circuit board against each other. Figures 1 , 2 and 3 relate to a first embodiment of a two-part connector according to the invention. In this embodiment electrical connection is made between the connector contacts and conductors on both sides of the circuit board but it will be appreciated that a single sided connector could be produced simply by cutting the connector down the middle.

The connector of Figures 1-3 comprises an outer, cap, part 1 and an inner part 3 which is shaped and dimensioned so as to be capable of being accommodated within the outer part. The outer and inner parts of the connector are moveable relative to one another. Figure 1 shows the connector and a circuit board 4 in transverse cross-section with the inner part 3 partially inserted into the outer part 1.

Figure 2 shows a view similar to Figure 1 but with the inner part 3 fully inserted into the outer part 1.

The outer part 1 is shaped rather like an open-based rectangular box but has flanges at the front and rear edges of its top wall such that in transverse cross-section it is shaped like a fat letter T. A slot 10 is provided in the top wall of the outer part 1 to receive an edge of a circuit board 4. The walls defining the slot 10 taper outwards towards the outer surface of the top wall so as to act as a guide for an inserted circuit board edge.

In the interior of the outer part 1 at least one bar 6 is formed. There may be two bars, one at each end of the outer part or a plurality of bars 'may be provided between the contacts. The bars 6 connect the rear wall to the front wall of the outer part. The profile of the inner surface of the rear wall between the bars 6 is shaped so as to serve as a camming surface 8 (shown in dashed lines in Figure 2). The inner part 3 has a substantially rectangular base portion 30 on the upper surface of which is formed a platform 31. At each end of the base 30 a post 33 is provided for use in a mechanism (to be described later) for latching the inner and outer parts together. Between each of the posts 33 and the respective end of the platform 31 there are formed a pair of guide walls 34a, 34b for use in guiding an inserted circuit board into the correct position for connection.

The connector is provided with contacts 2 located in the base 30 of the inner part 3 in two parallel rows staggered one from the other. Each of the contacts 2 comprises a pin portion 20 extending away from the bottom surface of base 30 and a resilient portion 21 extending away from the top surface of the platform 31 on the base 30. Each contact passes through a bore 23 in the base 30 and a corresponding bore in the platform 31.

The pin sections 20 of the contacts 2 are used to make contact with a second circuit board (not shown) having corresponding holes therein, such that a circuit board 4 inserted in the connector will be substantially at right angles to the second circuit board.

The operation of the first embodiment will now be described with reference to Figures 1 and 2.

Before inserting a circuit board into a connector according to the first embodiment of the invention, the inner part 3 (bearing contacts 2) and the outer part 1 are assembled in the position shown in Figure 1 (ignoring for the time being the circuit board 4 shown in the drawing). With the connector parts in this relative position, the resilient portion 21 of each of the contacts 2 is unstressed and free to adopt a position shown for it in dotted lines in Figure 2. While the connector parts are in this relative position, an edge of a circuit board 4 is introduced into the connector through the slot 10.

The edge of the circuit board 4 experiences substantially no resistance to its entry into the slot 10 but is guided by the tapering sides of the slot into a position roughly parallel to the side walls of the connector parts. The edge of the circuit board enters the connector and continues to move without resistance, being further guided into a position parallel to the connector side walls by the guide walls 34a, 34b and the front wall 32 of the inner part 3, until it strikes the bars 6 of the outer part 1. (This location of the circuit board 4 is shown in Figure 1. ) In this initial phase substantially zero insertion force is required on the circuit board.

Once the edge of the circuit board 4 has struck the bars 6 further inward movement of the circuit board carries the.outer part 1 progressively towards the base 30 of the inner part 3, i.e. the further insertion of the circuit board causes a relative sliding movement between the connector parts. The relative movement between the connector parts results in the camming surface 8 being brought into contact with the resilient portion 21 of each of the contacts 2. Continuing insertion of the circuit board 4 moves the camming surface 8 along the resilient portions 21 causing the resilient portions 21 to move inwards and eventually to come into contact with conductors on the surfaces of the circuit board.

During the last phase of insertion of the circuit board 4 into the connector the surface 8 further constrains the resilient portions of the contacts 2 so that a sliding contact is achieved between the contacts 2 and the conductors of the circuit board; a "wipe" action is accordingly produced which removes dust, oxides and the like from the contacting surfaces (this embodiment produces a 1.5mm contact wipe). The camming action of the surface 8 produces a contact pressure which rises to a maximum when the circuit board has reached its fully inserted position (shown in Figure 2). In this position the bars 6 of the outer part 1 rest on the base 30 of the inner part 3 between the platform 31 and the locking device 36, thus the connector parts are at their position of greatest overlap.

The connector parts may be retained in the positions shown in Figures 1 and 3 respectively (i.e. ready for insertion of a circuit board, and in the position of greatest connector part overlap, respectively) .

Each of the posts 33 on the inner part 3 is provided with a projection 42 and a stop 44 to co¬ operate with a respective one of two flexible latches 40 formed at the ends of the outer part 1. When the connector parts are first assembled the outer part 1 is pushed over the inner part 3 until the flexible latches snap over the stops 44. Thereafter the flat lower surfaces of the stops 44 serve to prevent unlatching occurring back over the stops 44. The projections 42 have sloping upper and lower surfaces so as to allow repeated latching and unlatching to occur over projections 42.

In order to enable the inserted circuit board to be removed from the connector simply by moving the circuit board itself, the connector parts are provided with two co-operating sections one, a pair of fingers 57, 58 provided on the outer part 1 and the other a shaped post 56, provided on the inner part 3. The pair of fingers 57, 58 comprise a relatively rigid finger 57 and a resilient finger 58 depending from the top wall of the outer part 1 and separated by a tapering space. The shaped post 56 is provided on the base of the inner part 3 in a position such as to enter the space between the depending fingers 57, 58 when the connector parts move towards each other forcing the resilient finger 58 to move further away from the rigid finger 57.

The co-operating sections operate such that when a circuit board is inserted into the connector an enlarged head at the end of the resilient finger 58 engages in a notch 39 provided in the side of the circuit board. When an inserted circuit board is to be removed from the connector the circuit board itself may now simply be pulled outwardly of the connector because the resilient finger 58 of the modified locking device cannot disengage from the notch 39 until the shaped post 56 is removed from the space between the depending fingers and so the outer part 1 will move with the circuit board 4. The dimensions of the fingers 57, 58 and the shaped post 56 are chosen so that the contact pressure is released before the finger 58 disengages from the circuit board 4.

Figures 4 and 5 illustrate an alternatively modified locking device which may be incorporated in the embodiments of the invention described above, and identical reference numerals denote identical features in the previous Figures. The alternatively modified locking device incorporates the additional feature of a release mechanism which prevents movement of the outer part 1 relative to the inner part 3 (as described above) other than due to the insertion into the connector of a second circuit board 4 which is of suitable size and shape. Thus the movement of the inner part 3 relative to the outer part 1 cannot occur simply by exerting a force on the outer part 1.

As shown in Figures 4 and 5, the release mechanism is in the form of a resilient arm 66, extending from the inner part 3. The resilient arm 66 has at its free end a generally flat surface 62 lying in a plane parallel to that of the first circuit board and a sloping surface 64, adjacent the surface 62 and lying in a plane which is at an acute angle to that of the first circuit board. As the second circuit board 4 (which is of the correct shape and size is inserted into the connector (in the direction of arrow A), the corner 68 of the leading edge 70 of the second circuit board 4 engages a sloping surface 60 of the resilient finger 58. Motion of the inner part 1 relative to the outer part 3 in the direction of arrow A is prevented during the passage of the corner 68 along the sloping surface 60 since the free end of the resilient finger 58 abuts the surface 62 (which is parallel to the plane of the first circuit board) at the free end of the resilient arm 66, which is attached to the inner part 3 and the only resultant motion during this passage in the rotation of the resilient finger 58 in the direction of arrow B. When the leading edge 70 reaches the plane of the surface 62 the resilient finger 58 has rotated to the position shown by the dashed line in Figure 11, and at this instant the leading edge 70 engages the sloping surface 64 on the free end of the resilient arm 66. During the passage of the leading edge 70 over the surface 64, movement of the inner part 1 relative to the outer part 3 is still prevented a s described above the only resultant motion is the rotation of the resilient arm 66 in the direction of arrow C.

As soon as the leading edge 70 has passed over the surface 64, the free end of the resilient arm 66 becomes clear of both the free end of resilient finger 58 and the leading edge 70 of the second circuit board 4, and the motion of the second circuit board 4, of the outer part 1 relative to the inner part 3 and of the resilient portions 21 of the contacts 2 in response to the camming surface 8 proceeds as described with reference to Figures 1 to 10 (the free end of resilient finger 58 locating in notch 39 to secure the second circuit board 4 within the connector under the resilient bias of resilient finger 58, during the subsequent motion of the second circuit board 4) . When the second circuit board 4 is pulled out of the connector the motion of the parts of the connector is in the opposite sense to and in the reverse order of that described above for the insertion of the second circuit board: resilient arm 66 and resilient finger 58 rotate back to their original positions ready for the insertion of a second circuit board.

■ Two resilient arms are preferably used, one at each end of the connector but a single resilient arm may be provided at one end of the inner part 3.

Further, in place of the resilient arms described above, a resilient member such as a spring may be provided between the inner part 3 and the outer part 1 in the connector, to bias the inner part 3 and the outer part 1 into the open condition, but such an arrangement would increase the insertion force required to insert a circuit board into the connector.

The connector parts described above may be made from a variety of materials, preferably thermoplastics which are known to provide desirable mechanical and electrical characteristics. One material which has been used in practice is polyester 94 V-O glass filled.

Similarly, the contacts may be made from a variety of known materials. Since the embodiments described above can produce a contact pressure of at least 150 gramforce per contact materials suitable for use with high contact pressures, e.g. tin/lead plated phos bronze (PB102) fullhard, may be used. In a reduced contact pressure version of the invention materials such as gold can be used for the contacts.

Various features of the embodiments described above may be altered or dispensed with altogether.

The latching arrangement described above for retaining the connector parts in particular relative positions may be modified, e.g. by removing the stops 44 such that the outer part 1 may be completely removed from the inner .part 3, by replacing each projection 42 by a pair of spaced projections, or by replacing the whole latching arrangement with a different retaining mechanism altogether, such as a manually operated system. Depending upon the application for which the connector is intended it may be appropriate to omit the retaining mechanism.

Similarly, a different arrangement may be used from those described above for securing a circuit board in the connector in the fully inserted position, e.g. a cap could be manually fitted over the free end of the circuit board. Again, the securing arrangement may be dispensed with depending on the intended use of the connector.

Alternative means to those described above may be chosen for guiding an inserted circuit board into the desired position within the connector.

The bars 6 provided in the outer part 1 so as to ensure that the outer part is carried along by the inward movement of an inserted circuit board can be replaced, e.g. by L-shaped arms projecting inwards from the front or rear wall of the outer part 1. In some applications of the connector specific means for entraining the outer part 1 on the inserted circuit board may be omitted, in such a case the circuit board would be inserted and then connector part 1 moved towards part 3.

The pin sections 20 of the contacts 2 as described above are adapted to pass through holes in a circuit board. It is equally possible to use pin sections of greater length, bent outwardly so as to lie along and extend beyond, the lower surface of the connector, which pins could then be lain on and soldered to conductors on a circuit board.

Because of the flexibility of the design parameters for moulded circuits it is possible to incorporate features of the connectors described above into the moulded circuit itself. For example, the camming surface used to bring the contacts into communication with the conductors on the circuit board could be provided on an arm extending from a moulded circuit board and a separate outer part could be dispensed with.

Details of the shape of the connector parts described above can also be varied, e.g. the inner part need not be provided as a male member and the outer part as a female member.

Claims

Claims :

1. An apparatus for making an electrical connection between.a circuit board and at least one contact comprising: a first member having a camming surface; and a second member carrying at least one contact and adapted to receive a circuit board adjacent to said at least one contact; wherein the first and second members are adapted to be moveable relative to one another between first and second positions, the relative movement being such that the camming surface causes movement of said at least one contact into engagement with the circuit board in the second position.

2. Apparatus according to claim 1, wherein: one of the members is provided with at least one abutment surface for abutting the circuit board when the circuit board is inserted into the apparatus with the first and second members in the first position, wherein further movement of the board in the direction of insertion causes said relative movement of the members to said second position.

3 Apparatus according to claim 1 or 2, wherein the apparatus further comprises means, attached to one of the members, for retaining the circuit board when the members are in the second position.

4. Apparatus according to claim 3, wherein: the retaining means comprises a resilient member arranged to co-operate with a recess in the circuit board. 5. Apparatus according to claim 3 or 4, further comprising: locking means for preventing movement of the retaining means when the members are moving between the second position and the first position.

6. Apparatus according to any of the preceding claims, further comprising: first latch means, releasable in response to the motion of the circuit board, for preventing movement of the members from the first position to the second position.

8. Apparatus according to any of the preceding claims further comprising: connection means permitting assembly of the first and second member together and for facilitating relative movement therebetween.

9. Apparatus according to claim 8, wherein the connection means comprises: second latch means, for temporarily latching the members in the second position; and stop means for stopping relative movement of the members in the direction of movement from the second position to the first position when the members reach the first position.

10. A method of making an electrical connection, comprising the steps of: providing a connector on a first circuit board, which connector is provided with a plurality of contacts at least parts of which are moveable in a direction generally parallel to the plane of the first circuit board; inserting a second circuit board into said connector in a direction transverse to the plane of the first circuit board; and causing the parts of the contacts to be moved under the action of a camming movement whereby to electrically connect the contacts to conductors provided on the second circuit board.

11. The method according to claim 10, wherein: the step of causing the parts of the contacts to be moved is achieved by a connector part moving in a direction transverse to the plane of the first circuit board in response to the movement of the second circuit board in said transverse direction.

12. The apparatus substantially as hereinbefore described with reference to Figures 1 to 12 of the accompanying drawings.

13. The method substantially as hereinbefore described with reference to Figures 1 to 12 of the accompanying drawings.