GB2245770A - Compliant pins - Google Patents

Abstract

A compliant pin having a shank (10) has a radially projecting, resiliently deformable portion (24) and an aperture passing through the shank in the vicinity of the resiliently deformable portion. The pin permits non-damage engagement with apertures (26) in a pin-receiving substrate (28) and has good electrical and mechanical properties. The resiliently deformable portion may be formed either by punching an aperture in an undeformed shank and then compressing the shank longitudinally, or by providing the shank with a radial projection and punching an aperture in the shank in the vicinity of the projection. There may be more than one projection associated with each aperture, and there may be more than one resiliently deformable region. <IMAGE>

Description

DESCRIPTION COMPLIANT PINS The present invention relates to compliant pins, and in particular, but not exclusively, to compliant pins which afford electrical connection in electronic circuit substrates.

The constantly increasing market pressure to miniaturise electronic equipment and the requirements to increase reliability have necessitated the use of multilayer substrates (e.g. typically epoxy or cermic laminates) with through-plated holes. So-called compliant interconnection pins have been developed which may be inserted into the holes without damaging either themselves or the plated holes, yet which provide sufficient anchorage for a subsequert soldering operation or pressure contacts to the thro#gh-plating where removable connections are required. Compliant pins have thus replaced the traditional interference fit pins in these applications.

However, the problem with conventional compliant pins is that the compliant mechanism can restrict their use to stand-off (-.e. one sided) applications, and furthermore the compliant mechanism only enables use with relatively large diameter pins, generally greater than lmm in diameter.

It is an object of the present invention to provide a compliant pin which permits no-damage engagement with through-plated holes in a multilayer substrate, at an economical cost, in relatively small holes, and in the required leadthrough configuration, all without detriment to the electrical and mechanical integrity or its no-damage retention in the substrate.

In accordance with a first aspect of the present invention, a compliant pin comprises a shank having c radially projecting, resiliently deformable portion hiving an aperture passing through the shank.

By punching an aperture in the shank, the material arrnd the aperture may thereby be rendered deformable. The aperture can be designed so that the conductance of the pin is not restricted by the retention mechanism i.e. the cross-sectional area of the pin remains c:nstant along the length of the pin.

Additionally the slt provides a flux vapour ventilation path or the pin soldering operation which produces a very reliable bubble free solder joint.

Typically the pin can be made of brass or beneficially from spring material uc as phosphor bronze or beryllium copper. Par,ictlarly using the latter multiple insertions are possible and thus the use of the invention can be extended to miniature connector applications where the pin is effectively a sprung male contact or for example the slotted pin can be used as the lead through termination in lead through devices such as RFI suppression filters.

In one embodiment, an aperture is provided in the shank, and the pin is then compressed longitudinally, thereby deforming the material around the aperture radially outwardly to form the resiliently deformable portion.

In another embodiment, the pin is provided with a projection and the aperture is formed in the vicnity of the projection to cause the projection to become resiliently deformable.

The pin may be provided with an enlarged head portion to limit its projection through an aperture, or may be headless.

The pin shank may be provided with a plurality of radially projecting, resiliently deformable portions, longitudinally spaced along the shank. The portions may have a common aperture, or each portion may be provided with its own aperture.

In accordance with a second aspect of the present invention, a method of forming a compliant pin comprises punching a through aperture in the shank of the pin and deforming the shank longitudinally in the region of the aperture to provide a resiliently deformable, radially projecting region.

In one embodiment, a plurality of intersecting apertures is provided, and preferably the apertures intersect at right angles. In a preferred embodiment, the apertures are in the form of slot.

In accordance with a third aspect of the present invention, a method of forming a compliant pin comprises punching a through aperture in a region of the pin having a radially outward projection, thereby making the pin resiliently deformable in the region of the projection.

In accordance with a fourth aspect of the present invention, an apparatus for forming an aperture in the shank of a pin comprises a die having an aperture adapted for receiving and retaining the shank of a pin, a connecting passage connecting the shankreceiving aperture with the exterior of the die, and a punch displaceable through the said connecting aperture to form an aperture in the shank of a pin located in the shank receiving aperture.

By way of example only, specific embodiments of the present invention will now be described, with reference to the accompanying drawings, in which: Fig. 1 is a side view of a pin after the first stage of manufacture of a compliant pin in accordance with the present invention; Fig. 2 is a perspective view of a punch and die arrangement in accordance with the present invention, for forming the pin of Fig. 1; Figs. 3 and 3a are side views of a first embodiment of compliant pin in accordance with the present invention, situated in an aperture of first and second substrates which are shown partly cut away; Fig. 4 is a side view of a second embodiment of compliant pin in accordance with the present invention, located in an aperture in a substrate, partly cut away; Fig. 5 is a side view of the embodiment of compliant pin of Fig. 4 located in a tubular filter capacitor;; Figs. 6 and 7 are cross-sectional end elevations through the die of Fig. 2, showing the formation of a further embodiment of compliant pin, in accordance with the present invention; and Figs. 8 and 9 are side views of further embodiments of compliant pin, in accordance with the present invention.

Referring firstly to Fig. 1, a pin comprises a cylindrical pin shank 10 having a circular collar 12 located approximately one third of the way along the length of the shank. The shank of the pin is provided with a through aperture 14 which is rectangular and elongate, and which intersects the longitudinal axis of the shank.

The slot 14 is formed by placing the shank 10 of the pin in a complementarily-shaped aperture 16 in a die D. The die comprises a rigid cudoidal body 18 having a cylindrical aperture 16 passing between its two end faces and extending parallel to the longitudinal axis of the body. A slot 20 is cut into the top and tottom faces of the body and intersects the cylindrical aperture 16. The slot 20 is adapted to receive a punch 22 whose cross section corresponds to that of the slot 14 to be formed in the shank of the pin. The shank of the pin is placed in the aperture 16, and the punch 22 is displaced downwardly.

After treatment in the punch and die combination, the pin emerges as illustrated in Fig. 1.

The pin is then compressed longitudinally, and the presence of the slot 14 causes the metal either side of the slot 14 to buckle outwardly, thereby forming two resiliently deformable leg portions 24, and causing the shape of the slot 14 to change. As illustrated in Fig.

3, the shank of the pin can be inserted through an aperture 26 in a substrate 28 (e.g. a discoidal filter or a planar array), and the resilience of the legs 24 both permits the shank to be pushed through the aperture 24, and retains the pin in position within the aperture. The enlarged head 12 of the pin prevents the pin from passing through the aperture. The resiliently deformable arms 24 also allow removal of the pin from the aperture 26 if desired. Fig. 3a shows the embodiment of Fig. 3 in a different substrate 28' in which the maximum point of deformation is located within, and in contact with, the walls of the aperture 26'.

A second embodiment of the present invention is illustrated in Fig. 4, in which the enlarged head 12 of the pin is dispensed with, and instead two enlarged annular rib portions 30, 32 of generally triangular cross section, are provided in the centre of the shank 10. It should be noted that the enlarged portions 30, 32 are not provided by deforming the shank of the pin, but are present in the undeformed state. A rectangular through slot 34, identical to the slot 14 of the first embodiment, is then formed it the central region of the pin, using the punch and die arrangement of Fig. 2.

The provision of the slot 34 renders the enlarged portions 30, 32 resiliently deformable, so that the pin can be pushed in to an aperture 26 in a substrate 28 as in the first embodiment, where the pin is held in position by the two resiliently deformable portions formed by the enlarged rib portions 30, 32.

The embodiment of Fig. 4 is particularly useful in filtered miniature connectors where space is limited, and where many lead through terminations (connector contacts) must be fitted through discoidal or tubular filter capacitors or monolithic planar arrays of multilayer capacitors. Fig. 5 shows the pin of Fig. 4 located in a tubular capacitor 36. In these latter applications the compliant portion of the pin forms the electrical contact to the internal electrodes or termination of the filter capacitor.

An alternative embodiment of the present invention includes two slots 14, at right angles to each other. As shown in Fig. 6, the first slot is punched in the normal way, and then, as shown in Fig.

7, the pin is rotated through 900 and a second slot is then punched. It is necessary either for the punch to be activated at a very high speed, or alternatively the first slot can be filled with a blank of metal which is removed after the second slot has been formed.

An advantage of the two slots is that the number of contacts to the inside of the hole is increased to four, which would give added stability for the retention of the pin in the hole, compared with the theoretical two contacts with a circular section pin and a single slot.

As illustrated in Figs. 8 and 9, it is possible to have two or more compliant sections formed by spaced apart apertures (e.g. slots 14, 14';34, 34') along the length of the shank of the pin. This can be done either with a headed pin as shown in Fig. 8, or with the unheaded pin having two sets of ribs 28, 29, 28', 29' as shown in Fig. 9. The invention is not restricted to two compliant sections, and any number of compliant sections may be provided.

Although the invention has been described with reference to a pin of circular cross-section, the pin may be of any shape in cross-section, for example, it may be square in cross-section.

Claims (30)

1. A compliant pin comprising a shank having a radially projecting, resiliently deformable portion and an aperture passing through the shank.

2. A pin as claimed in claim 1, wherein the aperture is located in the vicinity of the resiliently deformable portion.

3. A pin as claimed in claim 1 or claim 2, wherein the resiliently deformable portion is formed by providing an aperture in the shank and compressing the pin longitudinally in order to deform the material around the aperture radially outwardly.

4. A pin as claimed in claim 1 or claim 2, wherein the pin is provided with a projection and the aperture is formed subsequently in the vicinity of the projection to cause the projection to become resiliently deformable.

5. A pin as claimed in claim 4, wherein the projection comprises a rib.

6. A pin as claimed in any of claims 1 to 5, further comprising an enlarged head portion to limit the projection of the pin through a receiving aperture.

7. A pin as claimed in any of the preceding claims, comprising a plurality of radially projecting, resiliently deformable portions, longitudinally spaced along the shank.

8. A pin as claimed in claim 7, wherein a plurality of the resiliently deformable portions are provided with a common aperture.

9. A pin as claimed as claimed in any of claims 1 to 7, wherein each resiliently deformable portion is provided with its own aperture.

10. A pin as claimed in any of the preceding claims, comprising a plurality of intersecting apertures passinc through the shank.

11. A pin as claimed in claim 10, comprising two apertures intersecting substantially at right angles to one another.

12. A pin as claimed in any of the preceding claims, wherein the or each through aperture is in the form of a slot.

13. A pin as claimed in any of the preceding claims, wherein the or each aperture is punched into the shank.

14. A pin as claimed in any of the preceding claims, wherein the cross-sectional area of the shank in an undeformed portion thereof is substantially identical to the total cross-sectional area of the shank in the radially projecting, resiliently deformable portion of the shank.

15. A pin as claimed in any of the preceding claims, wherein the pin is made from a pring material.

16. A pin as claimed in any of the preceding claims, wherein the pin comprises brass, phosphor bronze or beryllium copper.

17. A method of forming a compliant pin comprising punching a through aperture in the shank of tl-e pin and deforming the shank longitudinally, in the region of the aperture to provide a resiliently deformable, radially projecting region.

18. A method as claimed in claim 17, comprising punching a plurality of intersecting apertures in the shank of the pin.

19. A method as claimed in claim 18, in which two apertures are provided.

20. A method as claimed in claim 19, wherein the two apertures intersect at right angles.

21. A method as claimed in any of claims 17 to 20, wherein the apertures are in the form of a slot.

22. A method as claimed in any of claims 17 to 21, comprising punching a through aperture in two longitudinally-spaced portions of the shank, and deforming the shank longitudinally in the region of each of the apertures to provide a plurality of resiliently deformable, spaced apart, radially projecting regions.

23. A method of forming a compliant pin, comprising punching a through aperture in a region of the pin having a radially outward projection, thereby making the pin resiliently deformable in the region of the projection.

24. A method as claimed in claim 23, comprising forming through apertures in a plurality of regions of the pin having a radially outward projection thereby providing a plurality of resiliently deformable regions.

25. A method as claimed in claim 23 or 24, comprising punching a through aperture in a region of the pin having a plurality of radially outward projections.

26. An apparatus for forming an aperture in the shank of a pin, comprising a die having a socket adapted to receive and retain the shank of a pin, a connecting passage connecting the shank-receiving socket with the exterior of the die, and a punch displaceable through the said connecting aperture to form an aperture in the shank of a pin located in the shank receiving socket.

27. An apparatus as claimed in claim 26, wherein the connecting aperture and the punch are elongate in cross-section, to enable the punch to form a slot-shaped aperture in the shank of the pin.

28. A compliant pin substantially as herein described, with reference to, and as illustrated in Figs. 1, 3 and 3a, Fig. 4, Fig. 5, Figs. 6 and 7, Fig. 8 or Fig. 9 of the accompanying drawings.

29. A method of forming a compliant pin, substantially as herein described, with reference to, and as illustrated in, the accompanying drawings.

30. An apparatus for forming an aperture in the shank of a pin, substantially as herein described, with reference to, and as illustrated in, Figs. 2, 6 and 7 of the accompanying drawings.