DE8701205U1 - Spring contact pin for test devices - Google Patents

Description

5842 - 6 -

Feinmetall GmbH 7033 Herrenberg

Spring contact pin for test devices

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The invention relates to a spring contact pin according to the preamble of claim 1.

Such test devices , for which such spring contact pins are intended, are used to test the test objects for electrical faultlessness. Each spring contact pin usually has to contact many thousands, often even millions of test objects.

Test devices of this type are known and generally have a test adapter or similar with a large number of spring contact pins used to make contact with circuit boards or other test objects to be tested, see e.g. Krüger "Test equipment for testing circuit boards for watches", Yearbook of the German Society for Chronometry", Vol. 30, 1979, pp. 269-276.

Known spring contact pins of this type (DE-OS 28 52 686 ;

Krüger, see above) have a sleeve in which a cylindrical compression spring is inserted, which spring-loads a piston of the contact element that is arranged to slide in the sleeve and is supported on a base piece that is firmly inserted in the sleeve. This contact element has a rod that is arranged coaxially to the piston, on which a contact head is firmly arranged, which is intended to come into contact with the test objects to be contacted. Such spring contact pins are relatively expensive to manufacture. After inserting the piston, the sleeve must be slightly flanged inwards at the end next to the piston so that the piston is not pushed out of the sleeve by the pre-tensioned helical compression spring.

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This flanging is relatively labor-intensive. This contact element also causes relatively high costs Due to its extremely small diameter/ since the sleeves of such spring contact pins can only have very small maximum diameters of generally 1.5 mm at most. In contrast, these spring contact pins are designed to be relatively long, e.g. usually around 1 to 5 cm, in order to ensure sufficiently strong axial self-suspension and sufficiently high contact forces, which should usually be more than 100 cN.

It is therefore an object of the invention to create a spring contact pin of the type mentioned in the preamble of claim 1, which can be produced more cost-effectively and which does not require a flanging process during production.

This object is achieved according to the invention by a spring contact pin according to claim 1.

No flanging process is required when producing this spring contact pin. The coil spring of the contact element, which can form the contact element alone or together with a contact head arranged on it, can also be produced cost-effectively in one operation together with the coil compression spring by winding, since this coil spring and the coil compression spring form a single, one-piece spring. It is also very advantageous that the coil spring outside the sleeve can be bent out of its straight direction to the side without bending, which has a positive effect when contacting test objects, for example when the contact element is used to contact hole edges arranged eccentrically to it.

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serves, the free contact end of this contact element then centers itself in the hole and thereby optimally secure contact is achieved. The hole edge of the test object is also evenly loaded and there is no longer any risk of damage to the known spring contact pins with pistons: If the contact tip of the contact element of such a previously known spring contact pin with piston strikes the hole edge of a circuit board or the like eccentrically, this contact element cannot move radially and therefore tries to tilt the piston in the sleeve, resulting in high friction, which can sometimes even lead to the piston jamming. This means that there is a risk of damage to the contact element to the point of breaking and it can also lead to overloading of the contacted hole edge of the circuit board or the like. These disadvantages can therefore be avoided in a simple manner by the invention.

The spring contact pin according to the invention also consists of relatively few parts. In the simplest case, it consists only of the sleeve and the helical compression spring and coil spring forming a one-piece spring, i.e. only of two parts. In this case, it can be expediently provided that the rear end of the helical compression spring is fixedly arranged in the sleeve, which can be achieved, for example, by welding or soldering or by holding it in a form-fitting manner in the sleeve. However, it is also possible to have a support in the sleeve for the rear end of the helical compression spring.

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which advantageously has a rod with which it engages coaxially with the helical compression spring in order to hold it.

The sleeve can conveniently be just one tube, i.e. both

IG side. The mouth of the sleeve through which the helical spring penetrates does not need to be flanged inwards , but can have at least the same clear inside diameter as the preferably circular cylindrical area of the sleeve in which the helical compression spring and the relevant area of the helical spring are located. Another advantage is that the front end of the sleeve can be bent outwards to form a flange _, which is easy to manufacture and enables this sleeve to be inserted into a receiving hole in a plate of the test adapter in such a way that it sits on this plate with the flange and thus does not require any additional fastening to this plate. This is not possible with the previously known spring contact pin according to DE-OS 28 52 886 .

The rear end of the sleeve can be the direct connection end of the spring contact pin or it can also be provided that a separate connection end is inserted on the sleeve or in the sleeve, e.g. a wire, a plug or the like.

In many cases it can also be expedient for the sleeve to have a base or an inner flange at its rear end which completely or largely closes it . The helical compression spring can then sit on this base or this inner flange.

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I The coil spring is so stiff and/cder by a

I inserted into it a rod, preferably a shaft

i of a contact head of the contact element is stiffened,

I 5 that its area protruding over the sleeve in the resting state 1 in the operating position of the contact pin

"; is straight and in alignment with the sleeve so that

When testing test specimens, they point exactly at the intended contact point of the respective test specimen

; ₁₀ The intended operating position of the spring contact pin is normally vertical.

I The coil spring of the inventive

I spring contact pin so stiff and/or by a

I ic the inserted rod, preferably a shaft of a

i contact head of the contact element is stiffened so that its

I over the sleeve protruding area through the

\ Contacting test items acting on them

I forces are not bent but remain straight

I 20 or when contacting eccentric bores

I edges of test specimens can bend slightly without

j. to bend so that they can withstand the forces exerted on them by the test subjects.

* always withstands axial forces without buckling and thus

i to the helical compression spring.

i ( 2b according to a structurally particularly simple embodiment

\ the invention can be provided that the interior of the

*' Coil spring is free from any other parts.

; The inherent stiffness of the coil spring is then

so large that it does not bend during operation and 30 in the operating position in the unloaded state is straight

and is in alignment with the sleeve. However, in an equally advantageous embodiment,

" should be provided, as mentioned, by a shaft

a contact head, which shaft preferably extends into the sleeve, or a

other rod inserted into it.

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Spring contact pins according to the invention can preferably have the following dimension sorting:

The ratio of the length of the area of the unloaded coil spring protruding beyond the sleeve to the maximum outer diameter of the coil in this area should preferably be at least 4:1, particularly preferably at least 5:1.

The outer diameter of the coil of the helical spring can preferably be at least 0.4 mm and/or preferably a maximum of 2 mm, particularly advantageously 0.8 - 1.2 mm.

The length of the area of the coil spring that protrudes beyond the sleeve in its unloaded state can be preferably a maximum of 8 mm and/or preferably at least 2 mm, particularly expediently 4 - 6 mm.

The spring wire forming the helical spring and the helical compression spring, which can preferably have a constant circular cross-section, can preferably be a maximum of 0.18 mm and/or preferably at least 0.07 mm, particularly expediently 0.08 - 0.15 mm.

The outer diameter(s) of the cylindrical region(s) of the sleeve can preferably be a maximum of 2.5 mm and/or preferably at least 0.5 mm, particularly expediently 0.6 - 1.4 mm.

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The length of the spring consisting of the helical compression spring and the helical spring (total spring) can preferably be at least 1 cm and/or preferably a maximum of 6 cm, particularly expediently 1.5 to 5 cm.

Q The wall thickness of the sleeve may preferably be a maximum of 0.25 mm, particularly suitably 0.1 to 0.2 mm.

The length of the screw compression spring may preferably be at least 0.8 cm, preferably 1 to 5 cm.

The length of the spring contact pin can preferably be at least 1 cm and/or preferably a maximum of 8 cm, particularly suitably 1.5 to 6 cm.

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The drawing shows examples of implementation. They show:

Fig. 1 is a broken longitudinal section through a spring contact pin according to an embodiment of the invention,

Fig. 2 shows a broken longitudinal section through a spring contact pin according to a further embodiment of the invention, 15

Fig. 3 a variant of a detail of the spring contact pin according to Fig. 1,

The spring contact pin 10 shown in Fig. 1

consists of a tubular, thin, rotationally symmetrical sleeve 11p, the outer diameter of which can preferably be max. 1.5 mm, but in general can be considerably smaller, for example smaller than 1 mm, a one-piece insert piece 12, a one-piece spring 13 and a one-piece contact head 14. The sleeve 11 is one-piece and is inserted into two support plates 15, 16 of a test adapter (not shown in further detail) that serve to hold it, together with many other identical spring contact pins 10, whereby other contact pins can also be inserted into this test adapter if necessary, for example pneumatic contact pins. A helical spring 21 forming a section of the spring 13 and the contact head 14 together form the contact element of this spring contact pin 10, which is spring-supported by means of a helical compression spring 20 forming the remaining area of the spring 13.

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The elongated region 17 of the sleeve 11 containing the spring 13 is, as shown, cylindrical with the exception of the upper edge flange 30, i.e. essentially cylindrical, preferably circular cylindrical. The sleeve then extends slightly to a short cylindrical lower end region 17'.

The contact pin 10 is used to contact test objects, e.g. circuit boards or the like. The contact head 14 is pressed onto the points of the test object to be contacted by it in order to electrically connect this point to a test device of the test device connected to the test adapter, which tests the test objects for electrical faultlessness. This contact head 14 can have any suitable

¹ ^ design. In this embodiment it has a conical tip 19, but it can also have other suitable designs, for example be provided with cutting edges, be needle-shaped or the like.

This contact head 14 is placed on the spring 13, which will now be described in more detail.

f. The wire made from a single round wire - if necessary, a

Profile wire with a non-circular, e.g. rectangular profile can be provided - wound spring 13 consists of two differently wound sections. Its longitudinal section 2Q forms a cylindrical helical compression spring, which can be compressed axially to a high degree, in that its windings do not touch each other, but rather have so much distance a from each other in the relaxed state that the desired spring travel and the spring force required for contacting the test object are achieved when the compression takes place. The section 21 of this spring 13 forms an axially non-compressible cylindrical helical spring, in that its windings in this embodiment

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For example, in the resting state, they rest against one another with or without pre-tension. As shown, the coil spring 21 has approximately the same coil diameter as the coil compression spring 20, so that the overall spring consisting of them is an approximately cylindrical coil spring 13, preferably a cylindrical coil spring. The coil diameter is understood to mean the average coil diameter. With regard to the constant wire cross-section, however, it follows that if the average coil diameters are approximately the same size, then the outer coil diameters (= outer coil diameter) are also approximately the same size. In some cases, it can also be provided that the coils of the coil spring 21 have a small distance from one another, which is smaller than a, so that this coil spring 21 can hold the shaft 23 of the contact head 14. The number of turns/cm (i.e. the number of turns per centimeter of spring length) is therefore greater for the coil spring 21 than for the coil compression spring 20. The ratio Z/D, where S = number of turns/cm and D = outer diameter of the turns, is also significantly greater for the coil spring 21 than for the coil compression spring 20, since D is the same size or almost the same size for the springs 20 and 21, but not Z, since Z is larger for the coil spring 21, preferably significantly larger than for the coil compression spring 20. The inherent rigidity of the coil spring 21 is so great and/or it is so stiffened by the shaft 23 inserted into it with friction that it cannot buckle when testing test objects if the spring 13 is loaded by compressive forces exerted on the contact head in the direction of arrow B and thus also by the weight of the contact head. 14 in ihifei? Unloaded operating voltage is not bent.

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The area 21 of the spring 13 is referred to as a helical spring and the area 20 as a helical compression spring, in order to give these two areas different names. The helical spring 21 leads from the front end of the spring 13, which rests against a collar 22 of the contact head, in the relaxed state of the spring 13 already a short distance axially into the tubular sleeve as shown, so that this helical spring is guided in the sleeve 11 in such a way that its longitudinal axis runs coaxially to the sleeve 11. The

The area of the helical spring 21 located in the sleeve 11 practically forms a piston, since it is guided in the sleeve with a small sliding bearing clearance. Its outer diameter does not change, so that consistently good guidance of this "piston" in the sleeve 11 is guaranteed. This "piston" is not rigid, however, but flexible, and thus provides particularly good adaptation to the sleeve 11 even if the latter should bend slightly. The helical compression spring 20 can have the same outer coil diameter as the helical spring 20 if there is no risk of it pressing against the inner wall of the sleeve 11 in a disturbing manner due to its slight expansion when compressed. If the latter risk exists, its outer coil diameter can be made slightly smaller than the outer coil diameter of the helical spring 21. If the screws

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If the spring 21 does not protrude into the sleeve 11 or only very slightly, then there would be a risk that, as a result of the helical compression spring 20, it could move out of its position in alignment with the sleeve 11 due to its own weight or the weight of the contact head 14 and then it would no longer be possible to make precise contact with the points of the test objects to be contacted by this spring contact pin. On the other hand, however, this helical spring 21 enables, as already explained, that when the contact head 14 eccentrically hits the edge of a hole in a circuit board or the like that is to be contacted, this head 14 can center itself on this hole edge with a corresponding slight bending of the helical spring 21 and, if necessary, of the very thin shaft 23, which is preferably made of elastic metal, without any risk of damaging the spring contact pin.

In the exemplary embodiments, the helical spring 21 is considerably shorter than the helical compression spring 20. The area of length L of the helical spring 21 that protrudes beyond the sleeve 11 in the unloaded state is several times larger than the maximum external diameter D (Fig. 2) of this protruding area. Preferably, L/D can be at least 4:1, particularly expediently at least 5:1.

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In this exemplary embodiment, the contact head 14 has the cylindrical shaft 23, which is inserted into the coil spring 21 and has thereby widened it somewhat, so that the contact head 14 is held frictionally on the coil spring 21. It is particularly advantageous if, as shown, when the coil compression spring 20 is in the relaxed state, this shaft 23 still extends a short distance into the sleeve 11, whereby the shaft 23 can additionally stiffen the coil spring 21 particularly well.

The constant inner diameter of the sleeve 11 in the area of the spring 13 is slightly larger than the outer diameter, i.e. the outer diameter of the coil of the spring 13, such that the spring 13 is guided through the sleeve 11 in its area located within the relevant circular cylindrical area of the sleeve 11, whereby this spring 13, with the exception of its lower, held end, can still slide in the sleeve with a small sliding bearing play even when the helical compression spring 20 is compressed accordingly by the contact of test objects.

The shaft 23 stiffens the coil spring 21 so that it cannot bend even under extreme conditions. The shaft 23 also allows the spring 13 to be wound from particularly thin wire.

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The rear end of the helical compression spring 20 rests on a support which is designed as an annular collar 25 of the insert piece 12. The annular collar 25 rests on an inner shoulder 29 of the sleeve π formed by a reduction in the diameter of the sleeve it and protrudes with a rear, slotted foot 26 into the cylindrical, reduced-diameter rear end region 27 of the sleeve, where it is held in place by friction. On the other side of the annular collar 25 there is a pin-shaped projection 28, onto which the helical compression spring 20 is placed, where it is held in place by friction. This means that the insert piece 12 is held in the sleeve 11 only by friction and the spring 13 is also held on the insert piece 12 only by friction, and the contact head 14 is also held on the coil spring 21 only by friction, so that these parts are detachably connected to one another and can be easily and quickly put together to form the finished spring contact pin and can also be taken apart again, for example to replace a damaged part.

The rear end area 27 of the sleeve 11 can serve as an electrical connection of this spring contact pin 10, for example by connecting a further conductor to it, e.g. soldering it. It is also possible to insert such a further conductor into a hole in the insert piece 12. Other connection options also exist, e.g. inserting a plug into section 27 of the sleeve 11.

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The sleeve 11 is tapered at the front end to a narrow I

Ring flange 3Ö expanded, which rests on the front of the front plate 15 of the test adapter, so that this spring contact pin 10 is thereby supported against the forces acting on it when testing test objects in the direction of arrow B and no other measures are required for this purpose.

This spring contact pin 10 can be manufactured inexpensively, has only a few parts that can be assembled quickly and easily and can also be disassembled into its individual parts if required in order to replace damaged parts. The contact head 14 can also be exchanged for other contact heads. The spring contact pin 10 is designed for use with test objects because of the possibility of the coil spring 21 bending when contacting them.

no longer at risk of damage like the known |

i Spring contact pins with rigid plungers exposed. Also |

in the manufacture of this spring contact pin no 1

I

Flanging on the sleeve. |

The spring contact pin 10 according to Fig. 2 differs from that according to Fig. 1 in that the front end of the coil spring 21 tapers conically at the front end region 34, so that the front end 32 forms the contact tip of this spring contact pin 10, which serves to come into contact with test objects 33, as shown. In order to show this particularly clearly, a test object 33 is shown in dash-dotted lines in Fig. 2, just as it comes into contact with this contact tip 32. The inherent rigidity of the coil spring 21, which is not stiffened by a shaft here, is so great that its area protruding over the sleeve 11 is straight and in alignment with the sleeve 11, at least in the intended operating position of the spring contact pin 10 in the unloaded state, and it has the bending strength sufficient for testing test objects such as 33.

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strength is given so that this protruding area cannot buckle during operation. The fertiliser can also

outer diameter of the constant coil outer diameter area of the coil spring 21 is equal to

or almost equal to the constant outer coil diameter of the helical compression spring 20.

However, it is also possible to attach a separate contact head 14 to the front area of the coil spring 21, as shown in an exemplary embodiment in Fig. 3. In Fig. 3, only the front end area of the spring 13 of the spring contact pin, which is not shown in further detail, is shown.

This contact head 14 in Fig. 3 can preferably also be held only detachably on the coil spring 21, or it can also be firmly connected to the coil spring 21, for example by laser welding.

The spring contact pin 10 shown in Fig. 2 differs from that shown in Fig. 1 in that the insert piece 12 is omitted and in its place the helical compression spring 20 sits directly on the inner shoulder 29 of the sleeve. This helical compression spring can be held here, for example, by soldering or welding it to the sleeve, for example by means of laser welding. Or it can be held in a form-fitting manner by securing the sleeve above its lowest turn from the outside with one or more inward-facing

indentations .39 which hold this spring 13 at the lower end.

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In the embodiment according to Fig. 2, the helical spring 21 alone forms the contact line of this spring contact pin 10. In contrast, in the embodiments according to Figs. 1 and 3, the contact line of the respective spring contact pin is formed by the helical spring 21 and the contact head 14 arranged on it.

It is also possible, in the case of a contact head 14 according to Fig. to insert a rod that stiffens the helical spring 21 in a friction-locking manner, for example from the free end of the helical compression spring 20 or from the free end of the helical spring 21, which is then cylindrical and not conical as shown.

20

The springs 13 can consist of any suitable metallic material, preferably of spring steel, piano wire, stainless steel, nickel-beryllium or copper-beryllium. The wire forming the spring 13 can preferably have a constant circular cross-section, often expediently also a non-circular cross-section, e.g. a rectangular cross-section.

30 35

Claims (1)

- 1 - Protection claims 1. Spring contact pin for contacting the components to be tested !0 electrical or electronic test objects, such as circuit boards, other electrical components or the like, which spring contact pin is electrically conductive and intended for placement on a test device and has a straight, metallic sleeve !5, in which sleeve a metallic, straight helical compression spring is arranged, which serves for the axial springing of a contact element guided in the sleeve, <3as projects beyond the sleeve in the direction of the test objects to be tested and has a free, metallic contact end serving for contacting the respective test object, characterized in that the contact element has a helical spring (21) which is integrally and axially connected to the straight helical compression spring (20), projects beyond the sleeve (11), i.e. is wound from the same wire as the helical compression spring (20), the number of turns/cm of which is greater than the number of turns/cm of the helical compression spring (20) in such a way that the area of the helical spring which projects beyond the sleeve (11) is straight and in alignment with the sleeve (11) in the intended operating position of the spring contact pin (10) in the unloaded state and is given sufficient buckling strength for the testing of test objects by means of correspondingly large Inherent rigidity of this coil spring (21) and/or by a rod (23) inserted into it. - 2 - 2. Spring contact pin according to claim 1, characterized in that the length of the area of the helical spring (21) projecting beyond the sleeve (11) is greater than the maximum diameter of this area, at least in the unloaded state. 3. Spring contact pin according to claim 1 or 2, characterized in that the turns of the helical spring (21) abut one another in the unloaded state of the spring contact pin. 4. Spring contact pin according to one of the preceding claims, characterized in that the helical spring (21) forms the contact element alone. 5. Spring contact pin according to claim 1, 2 or 3, characterized in that a metallic contact head (14) is arranged on the free end region of the helical spring (21), which serves to come into contact with the test objects to be tested, wherein preferably the contact head (14) can have a shaft (23) inserted into the helical spring and held therein preferably by friction, or a bore into which the helical spring (21) is inserted. &igr;.&iacgr;* i > »4 W « 5842 3 " 6. Spring contact pin according to one of the preceding claims/ characterized in that the sleeve (11) is a tube open on both sides and/or that the sleeve (11) is rotationally symmetrical. 7· Spring contact pin according to one of the preceding claims, characterized in that a support (12) for the helical compression spring is arranged in the sleeve, which preferably has a rod-shaped projection (28) protruding into the helical compression spring (20) to hold it* 8. Spring contact pin according to one of the preceding claims, characterized in that the screw compression spring (20) or the support rests on an inner shoulder (29) of the sleeve formed by a narrowing of the sleeve. Spring contact pin according to one of the preceding claims, characterized in that the turns of the helical spring (21) at the front end region (34) are wound with a radius that decreases in the direction of their free end and the remaining region of the helical spring (21) preferably has a constant turn diameter, which preferably approximately corresponds to the constant turn diameter of _the helical compression spring (20). 10. Spring contact pin according to one of the preceding claims, characterized in that the helical compression spring (20) is attached to the sleeve at its rear end, preferably the rear end of the helical compression spring (20) is soldered or welded to the sleeve or can be held in the sleeve by at least one indentation. ..It I · < &bull; · « 1 I ' rf &bull; »III c ■ « · &bull; 11 I &igr; « « . · ItIiII ' t · t ·· - ⁴ 11. Peder contact pin according to one of the preceding claims, characterized in that at least the area of the coil spring (21) located in the sleeve (11) and the movable area of the a circular cylindrical area of the sleeve _/ with little side play* 12i Spring contact pin according to one of the preceding claims, characterized in that the winding diameter of the helical compression spring (20) is approximately constant over its length, and that the winding diameter of the helical spring (21) is also approximately constant or almost approximately constant over its length and at least the winding diameter of the region of the helical spring (21) located in the sleeve (11) corresponds approximately to the winding diameter of the helical compression spring. 13. Spring contact pin according to one of the preceding claims, characterized in that the front mouth of the sleeve (11) is unconstricted and preferably has an outwardly directed ring flange (30) and/or that the shaft (23) of the contact head (14) extends into the sleeve (11) in the unloaded state of the contact element (14; 21) ^O extends into it And/or that the spring (13) consisting of the helical compression spring (20) and the helical spring (21), if necessary with the exception of the free end region (34) of the helical spring (20), is approximately has a constant outer winding diameter. 35 «» ti
· ■ « i « II «kill »&bull;II 1 1 ·> · ■ Ii · > I &bull; it CS r 5842 14. Spring contact pin according to one of the preceding claims, characterized in that the ratio of the length of the area of the unloaded coil spring (21) projecting beyond the sleeve (11) to the maximum outer winding diameter of this area is at least 4:1, preferably at least 5:1, and/or that the outer winding diameter of the coil spring (21) is a maximum of 2 mm and/or preferably at least 0.4 mm, and/or that the length of the area of the coil spring (21) projecting beyond the sleeve (11) in its unloaded state is a maximum of mm and/or preferably at least 2 mm, and/or that the diameter of the spring wire forming the coil spring (21) and the coil compression spring (20), which preferably has a circular cross-section, is a maximum of 0.18 mm, preferably 0.08 - 0.15 mm, and/or that »3 or the cylindrical areas of the sleeve (11) Outer diameter of maximum 2.5 mm and/or of at least 0.5 mm, particularly expediently 0.6 - 1.4 mm, and/or that the length of the spring (13) consisting of the helical compression spring (20) and the helical spring (21) is at least 1 cm and/or a maximum of 6 cm, particularly expediently 1.5 - 5 cm, and/or that the wall thickness of the sleeve (11) is a maximum of 0.25 mm, preferably 0.1 - 0.2 mm, and/or that the length of the helical compression spring (20) is at least 0.8 cm, preferably 1 - 5 cm, and/or that the length of the spring contact pin (10) is at least 1 cm and/or a maximum of 8 cm, particularly expediently 1.5 - 6 cm.