GB2130814A - Insulation displacement contact combined with socket for pin - Google Patents

Abstract

An insulation displacement socket (10) comprises an insulation displacement first portion (14), and a second portion secured in a hole (32) in a board (12) and removably receiving a pin (P), e.g. a pin of an integrated circuit or other component. The second portion (18) comprises three integral resilient fingers (40) to engage the pin (P). <IMAGE>

Description

SPECIFICATION Insulation displacement sockets This invention relates to insulation displacement (ID) sockets, namely sockets which can removably receive pins (e.g. of circuit components), which can be secured to boards, and to which insulated wires can be conductively secured by displacement of the wire insulation to establish connections between the wires and pins.

ID sockets are in themselves known in the art.

They provide a highly convenient form of point-topoint wiring on boards. Like wire-wrapping, the use of ID sockets has the advantage that solder is not required to satisfactorily fix wires in place.

However, the insulation displacement technique is superior to wire-wrapping in that it is relatively simple to effect, it generally enables more wires to be attached to a single socket and, possibly most importantly, the wires can generally be removed from and re-secured to the ID part of the socket with a minimum of trouble and damage, typically at least up to about 50 times. An ID socket typically comprises two or more tines defining a slot or slots into which a wire is forced, the edges of the slot or slots piercing or displacing the insulation to establish conductive communication with the core or conductor of the wire and the wire at the same time being releasably secured to the connector by becoming compressed and retained in the slot or slots.The ID socket comprises a portion capable of being secured in a hole in a board, for instance a circuit board, to enable wires to be connected to the board. The portion engageable with the board is capable also of removably receiving a pin, for instance a pin of an electrical component such as an integrated circuit (IC), whereby the IC or other component can be removably secured to the board and conductively connected via an ID socket or sockets to a wire or wires connected to the socket or sockets.

The component secured to the board may be a component having only a few pins, for instance a passive component such as a resistor or capacitor.

More probably, however, the component will be an integrated circuit (IC) or reed relay or the like having rather more pins. As those skilled in the art will appreciate, the pins of ICs and the like are generally of a rectangular (i.e. square or oblong) cross-section. When the pins are inserted in ID sockets, a good conductive connection must of course be made with the pins. This is generally effected by virtue of the pins coming into abutment with conductive contact fingers resiliently urged against the pins. The resilience urging the fingers against the pins results in a contact force having to be overcome when the component is inserted. Naturally, the insertion force should not be so high as to cause excessive difficulty in insertion of the component and/or the risk of damage to the component on insertion.One known form of ID socket is to some extent subject to an insertion force problem. In the known form of socket, there are four contact fingers intended to engage respective ones of the four faces of the pin when the fingers and the pin are in a predetermined relative angular position. The contact fingers are provided in a sleeve mounted within the socket in such a manner that it is axially constrained yet is free to rotate. This construction, apart from being complex and expensive, is subject to the following disadvantage. The angular position of the sleeve bearing the fingers, after assembly of the socket onto a board, is of course random. That is to say, each sleeve will generally not be so oriented that its fingers are correctly positioned to engage the faces of an associated pin which will enter therein with a predetermined orientation.Instead, the sleeve will in general be skewed to some extent with respect to an incoming pin whereby the sleeve must be rotated into its correct position before it can make satisfactory contact with the pin. Such rotation will be provided by a force exerted by the pin on the sleeve when the component is first inserted.

That is to say, on the first insertion, the component pins must not only overcome an axial insertion force caused by the resilience of the fingers but must provide forces to rotate the individual sleeves to orientate them in the correct positions to receive the pins. This lack of orientation means that the insertion force when the component is first inserted is both unpredictable and higher than the insertion force that would be required were the sleeves correctly orientated to receive the pins of a component.

(Also, only two or three point contact, i.e. contact with only to or three of the four fingers, may be achieved so that the contact pressure between the pin and fingers is uncertain). The problems due to random orientation of the fingers can be overcome at least to some extent by pre-orientating them by rotating the sleeve to an appropriate position. For example, if an array of the sockets is fitted in a board to receive an IC or the like, before the IC proper is fitted one can push into the sockets a relieving tool in the form of a dummy IC or jig having pins like that of the IC. Thus, the sleeves are orientated properly subsequently to receive the IC pins whereby the insertion force when the IC is inserted is predictable. However, the use of a relieving tool and the attendant extra steps in manufacture represent an additional cost which, if possible, should be avoided.Moreover, the contact pressure may still be somewhat uncertain.

According to the present invention there is provided an ID socket comprising a first portion capable of having at least one insulated wire conductively secured thereto by displacement of the wire insulation and a second portion capable of being secured in a hole in a board and of removably receiving a pin, wherein the second portion comprises three fingers formed integrally therein and extending into the interior thereof to resiliently engage a pin mounted therein.

Such an arrangement provides a "three-point" connection to pins inserted therein, whether the pins are of circular cross-section or, as is more likely in practice, of rectangular (square or oblong) cross-section. The fact that the fingers are integral (i.e. non-rotatable with respect to the socket) means that, once the socket has been secured in place in the board, the fingers are in effect "preorientated" in a position in which they will make satisfactory three-point contact with the pin.

Accordingly, the insertion force involved in inserting a predetermined component into an array of the ID sockets will be predictable on first insertion and consistent throughout the life of the array in that it will be determined predominantly or wholly by the force needed to overcome the resilient engagement force of the fingers with the pin with a known and desired relative orientation of the pin and fingers. One can therefore take reliable precautions to ensure that an excessive insertion force, which might damage an IC or the like, will not be encountered. Also due to the pre-orientation of the pin and fingers, the contact pressure between the pin and fingers will be predictable and consistent throughout the life of the array. In fact, the present arrangement maximises the ratio of contact pressure to insertion force.That is to say, a maximum contact pressure is provided for a predetermined permissible contact force. Further, the use of integral fingers, as opposed to a structure in which the fingers are mounted on a separate rotatable sleeve, can simplify manufacture.

The invention also provides a board having mounted thereto a predetermined array of ID connectors as set forth above, the sockets all being secured with respect to the board with predetermined orientations to receive a corresponding array of pins (also having predetermined orientations) on a component.

The invention will now be further described, by way of illustrative and non-limiting example, with reference to the accompanying drawings, in which: Figure 1 is perspective view of an ID socket embodying the invention; Figure 2 is a side view of the ID socket of Figure 1, the socket being shown fitted in a circuit board; Figure 3 is an end view of the ID socket, taken from above in Figures 1 and 2 and with a pin stop thereof omitted for the sake of clarity; Figure 4 is an end view of the ID socket, taken from below in Figures 1 and 2 and with the pin stop omitted for the sake of clarity; Figure 5 is an axial sectional view of the ID socket, taken along the iine V-V in Figure 2;; Figure 6 is a schematic view of part of Figure 3 on an enlarged scale, showing the positional relationship between three fingers of the socket and a pin received by the socket and in contact with the fingers; and Figures 7a, 7b and 7c are schematic views corresponding to Figure 6 for explaining the corresponding situation in a known form of ID socket.

The drawings show an insulation displacement (ID) socket 10 secured in place in a circuit board 12 (Figures 2 and 5). The socket 10 comprises a wire receiving portion 14 to which one or more wires W (Figures 1 and 2) may be connected on one face 1 6 of the board 12 and a pin-receiving portion 1 8 into which a pin P (shown in dotted lines) of an electronic component, for instance an integrated circuit (IC), may be inserted from the other face 20 of the board 12.

The entire socket 10 is formed integrally from sheet beryllium-copper or phosphor-bronze. A plurality of the sockets 10 may in fact be supplied still secured to a strip or bandolier (not shown) of such material by necks (not shown) which can be broken or cut, as required, to remove the sockets from the strip or bandolier for use. Such removal may be effected for instance by an automatic insertion machine operative to insert the sockets automatically into the board 12.

The wire-receiving portion 14 comprises a pair of tines 22, 24 defining a longitudinally extending slot 26 having a tapered outer end 28. In use, when the socket 10 is in place in the board 12, one or more insulated wires W can be inserted into the slot 26, in a manner known per se and shown in Figures 1 and 2, so that the edges of the slot 26 displace or pierce the insulation 27 of the wire and effect conductive communication with the core or conductor 29 thereof, the jamming of the wire into the slot 26 also serving to removably secure the wire in place.

The pin-receiving portion 1 8 is of generally cylindrical form and has a slot 30 extending along its entire length whereby its diameter can be altered by deforming it. The nominal diameter of the portion 1 8 is slightly larger than that of a hole or aperture 32 in the board 12 into which it is pushed from the face 1 6 of the board, whereby the resilient deformation of the portion 1 8 effected when it is pushed into the hole 32 tends to hold it in place. To assist in holding it in place, protrusions 34 formed in the portion 1 8 penetrate the material of the board 12 during insertion and anchor the socket therein.Furthermore, stops 36 are formed in the portion 1 8 to ensure that the socket is pushed into the board to precisely the desired position.

Three angularly equally spaced fingers 40 are formed integrally in the portion 1 8 by pressing them out of the sides of the portion 1 8 into the interior thereof. The pins 40 resiliently and conductively engage and form a three-point contact with the pin P of an integrated circuit or other circuit component inserted into the portion 1 8 from the face 20 of the board 12, whether the pin be of circular or - as shown - of rectangular (e.g. square) cross-section. A pin stop 42 is formed where shown, where the pin-receiving portion 1 8 meets the wire-receiving portion 14, to stop the pin P extending beyond the portion 18.

The free end of the portion 1 8 is provided with three inward protrusions 44 to guide an incoming pin P in such a manner as to ensure that it enters into the tapering space between the three fingers 40, to be resiliently held between all three of them, rather than extending into one of the three spaces defined between each pair of adjacent fingers 40.

As can best be seen from Figures 3, 4 and 6, the ID socket is so positioned in the board 12 that the integral fingers 40 are in effect "pre-orientated" to receive an incoming pin P such that one finger engages one face of the pin and the other two fingers engage two corners of the pin to provide "three-point" contact with the pin.

Thus, if an array (e.g. two columns) of the ID sockets are all positioned in the board 1 2 with the same orientation to receive a corresponding array of pins on an integrated circuit or the like, all.of the sockets are correctly pre-orientated with respect to the pins to provide the above-described "threepoint" contact whereby the insertion force for the first insertion will be predictable and the insertion force for the first and subsequent insertions will be the same. The ratio between contact pressure and insertion force is maximised and predictable.

Contrast this with the case of the known arrangement -- mentioned above -- where there are four fingers mounted on a sleeve that is freely rotatable in the socket. Without a speciai step of pre-orientating the socket with respect to the pin, the pin (P) and fingers (F) will generally be relatively orientated (for example as shown in Figure 7a) such that the sleeve has to be rotated somewhat to allow faces of the pin to engage faces of the fingers. The rotation is provided by a force exerted by the pin P on the sleeve when the associated component is first inserted.Therefore, on the first insertion, the component pins must not only overcome the axial insertion force that would be required to deform the fingers F if they and the pins were correctly relatively orientated, but must provide additional respective random forces to rotate the individual sleeves into a correct position. Thus, the insertion force when the component is first inserted is both unpredictable and higher than the insertion force that would be required if the sleeves were all correctly orientated in advance.

Also, even when the rotation of the sleeve has been effected, the nature of the contact made between the pin P and the fingers F - and thus the contact pressure -- is rather less certain than in the case of the socket of Figures 1 to 6. Thus, as shown in Figure 7b and 7c, respectively, the pin P may only make two-point contact (i.e. contact with only two fingers) or three-point contact (i.e.

contact with only three fingers) with the fingers.

As indicated above, the sockets of Figures 1 to 6 are highly suited for use with automatic insertion machinery which removes them from a bandolier and pushed them into a board. They are also further suited to automatic manufacture in that, when fitted to the board, wiring to the ID parts thereof can be effected automatically.

(Wiring -- and also insertion - can however be effected manually if desired.

The invention can of course be performed in other ways than that described above by way of example. For example, the wire receiving portion 14 can be of any of the various forms known in the ID art either for use in ID sockets of the present type or for use to connect to the conductors of a flat multiconductor cable.

Claims (5)

1. An insulation displacement socket comprising a first portion capable of having at least one insulated wire conductively secured thereto by displacement of the wire insulation and a second portion capable of being secured in a hole in a board and of removably receiving a pin, wherein the second portion comprises three fingers formed integrally therein and extending into the interior thereof to resiliently engage a pin mounted therein.

2. An insulation displacement socket according to claim 1 , wherein the three fingers are equally angularly spaced with respect to one another.

3. An insulation displacement socket according to claim 1 or claim 2, wherein the second portion is formed from sheet metal and the fingers are integral with the sheet metal and pressed out from the sheet metal.

4. An insulation displacement socket substantially as herein described with reference to Figures 1 to 6 of the accompanying drawings.

5. A board having mounted thereto a predetermined array of insulation displacement sockets each according to any one of the preceding claims, the sockets all being secured with respect to the board with the fingers thereof in predetermined orientations to receive a corresponding array of pins (also having predetermined orientations) on a component.