CONNECTING PIN FOR PULL-OUTS AND METHOD FOR MANUFACTURING

Description

[0001] The invention relates to a connecting pin, in particular a metal pin, preferably for a feedthrough, in particular a metal fixing material feedthrough, preferably for devices that are exposed to high pressures, preferably igniters of airbags or belt tensioners, a feedthrough with such a connecting pin and a method for manufacturing such a connecting pin.

[0002] Connecting pins for feedthroughs, in particular metal-fixing material feedthroughs, are known in various designs from the prior art, e.g. AT 513 238 B1.

[0003] Metal-fixed feedthroughs are vacuum-tight fusions of fixative materials, particularly glass, glass-ceramics, or plastics, within metals. The metals act as electrical conductors. Reference is made, for example, to US Patents 5,345,872 and 3,274,937. Such feedthroughs are widely used in electronics and electrical engineering. The material used for fusion, especially glass, serves as an insulator. Typical metal-fixed feedthroughs are constructed such that metallic inner conductors are fused into a pre-formed sintered glass part, with the sintered glass part or glass tube being fused into an outer metal part containing the so-called base body, which is formed from a ring- or plate-shaped element. Ignition devices are among the preferred applications of such metal-fixed feedthroughs.These are used, among other things, for airbags or seatbelt tensioners in motor vehicles. In this case, the metal fixing material feedthroughs are part of an ignition device. The complete ignition device comprises, in addition to the metal fixing material feedthrough, an ignition bridge, the explosive, and a metal cover that tightly encloses the ignition mechanism. Either one, two, or more than two connecting pins, particularly metallic pins, can pass through the feedthrough. In a particularly preferred embodiment with one metallic pin, the housing is grounded; in a preferred two-pole embodiment, it is grounded to one of the pins.

[0004] Metal fixing material feedthroughs, particularly for airbag igniters or seatbelt tensioners, have become known from US 2006 / 0222881 A1, US 2004 / 0216631, EP-A-1 455 160, US 2007 / 0187934 A1 and US-A-1 813 906, which are characterized by the fact that the through-hole for the connecting pins, in particular the metal pins, is punched out of the base body. In the manufacture of the base bodies, according to US 2007 / 0187934 A1, the openings are driven through the entire thickness of the base body by means of the punching process from a strip material with a thickness in the range between 1 mm and 5 mm, preferably 1.5 mm and 3.5 mm, in particular between 1.8 mm and 3.0 mm, most preferably between 2.0 mm and 2.6 mm.

[0005] The connecting pin, in particular the metal pin in the fixing material, is inserted or glazed into the entrance opening punched into the base body over the entire thickness of the base body, which lies in the area mentioned above.

[0006] Furthermore, the through-hole in the bushings with more than one pin is arranged off-center according to US 2007 / 0187934 A1.

[0007] Stamping from sheet metal according to US 2007 / 0187934 A1 has a number of disadvantages. One disadvantage is that stamping from strip material, such as a sheet of the base body, results in a large amount of material waste.

[0008] German patent application DE 10 2006 056077 A1 discloses an ignition device for a pyrotechnic protective device, which has a sheath for fixing the position of the current passage of the metal pin and means for preventing relative movement between the sheath and the metal pin. As in US patent application US 2007 / 0187934A1, the base body of DE 10 2006 056077 A1 is also stamped from a sheet, for example, a strip of material, which results in a large amount of material waste. Furthermore, as in US patent application US 2007 / 0187934A1, the passage openings were arranged off-axis.

[0009] EP 1 491 848 A1 discloses a current feedthrough with a centrally located through-hole for a pin-shaped conductor. The manufacturing method of the through-hole is not described and it extends over the entire thickness of the base body.

[0010] US Patent 8,978,557 B2 discloses an annular, plate-shaped element for a seatbelt tensioner and / or airbag igniter, having a clearance area where the through-hole is created by punching. The through-hole component with the annular, plate-shaped element includes two metal pins, but US Patent 8,978,557 B2 does not specify how the metal pins are manufactured.

[0011] DE 10 2017 123 278 A1 discloses a base body for feedthrough elements comprising a metallic base body, at least one through-opening for receiving a functional element in a fixing material, in particular an electrically insulating one, and at least one conductor which is electrically conductively connected to the base body by a solder joint. The solder joint comprises a metallic solder material, wherein the metallic solder material covers a surface area of ​​the base body and thus forms a solder area on a surface of the base body. The base body has a microstructure, at least in the solder area, which comprises at least depressions in the surface of the base body.

[0012] DE 10 2012 009 765 A1 discloses an igniter for a gas generator of a vehicle safety system with at least two contact pins or connecting pins that are spatially separated from each other by an electrically insulating material, wherein each contact pin is provided with a chlorine-free gold coating. The gold layer can be applied in an electroplating process, whereby chlorine scavengers are introduced into a cleaning solution used in an upstream cleaning step.

[0013] Neither DE 10 2017 123 278 A1 nor DE 10 2012 009 765 A1 discloses how the conductors or contact pins are manufactured.

[0014] In particular, with metal fixing material feedthroughs with two connecting pins, especially metal pins and an off-center through-hole, the off-center through-hole leads to a weakening of the glazing.

[0015] In the prior art, connecting pins, particularly metal pins for feedthroughs, especially glass-to-metal feedthroughs, were provided with a rounded section, a so-called radius, at least at one end. The rounding, especially the radii of the connecting pins, was generally produced by vibratory finishing. For example, Al₂O₃ or silicon carbide (SiC) or other abrasives from vibratory finishing blocks were used as the vibratory finishing medium. A disadvantage of this method of rounding with vibratory finishing media was that small particles of the vibratory finishing medium became embedded in the pin surface. These particles, which settled on the surface after processing, then led to defects in the coating itself during surface plating, for example, nickel plating.These defects then became the starting point for corrosion, which spread as far as the base of the penetration, e.g., in the case of metal-fixing material penetrations. Furthermore, a specified rounding could not be reliably achieved.

[0016] The object of the invention is therefore to avoid the disadvantages of the prior art and to provide a connecting pin, in particular a metallic connecting pin for feedthroughs, especially metal-fixing material feedthroughs, which avoids these disadvantages.

[0017] According to the invention, this is achieved by a connecting pin, in particular a metal pin, for feedthroughs, in particular glass-to-metal feedthroughs, according to claim 1.

[0018] Avoiding vibratory finishing particles ensures that defects in the surface of the connecting pin are suppressed and / or prevented. The advantage of surfaces without or largely free of defects is that no defects occur in coatings, such as nickel and / or gold plating applied to the pin. If the surface is largely free of defects, a continuous surface coating can be applied more easily.

[0019] A specialist would be deterred from rounding using machining and / or machining processes without the use of vibratory finishing materials, because such processes would be too complex and time-consuming compared to material removal or rounding with vibratory finishing materials.

[0020] It is particularly preferred if the radius R of the rounding and / or the rounding section is in the range of 0.45·D to 0.55·D, preferably approximately half the diameter D of the cylindrical section. This results in particularly good contact and low contact resistance.

[0021] It is particularly preferred if the end surface has a diameter F of less than 0.3 mm, cylindrical part of 1.0 mm ± 0.1 mm.

[0022] In a first embodiment of the invention, it is provided that the non-cutting processes, in particular forming processes, include, for example, upsetting, rolling, embossing, pressing, hammering, or even pressing. For the machining processes, turning, milling, or grinding are possible methods.

[0023] In a particularly preferred embodiment, the connecting pin has a pin surface. After the rounding is introduced by a chip-forming and / or chipless process, the pin surface, which is free or largely free of impurities, in particular Al₂O₃, SiC, is provided with a coating, in particular a nickel coating. In the present application, "free or largely free of impurities" means that less than 2%, preferably less than 1.5%, in particular less than 1%, more preferably less than 0.5%, and most preferably less than 0.1% of the total pin surface is contaminated, in particular with a ceramic material such as Al₂O₃, SiC, which could lead to defects in the coating.Due to the absence of contamination according to the invention, particularly with vibratory finishing particles that can become embedded in the pin, the coating applied to the pin surface is free or largely free of defects. Corresponding to the impurities, this means that less than 2%, in particular less than 1.5%, preferably less than 1%, particularly preferably less than 0.5%, and most preferably less than 0.1% of the total pin surface exhibits defects.

[0024] Vibratory finishing stones used in the prior art for machining pin surfaces had a content of 45-65% aluminum oxide and 25-45% silicon oxide, resulting in Al₂O₃ contamination of 3.2% to 6.5% of the total pin surface. In the case according to the invention, where the surface is machined and thus the rounding is achieved without vibratory finishing particles solely by a machining or machining process, the contamination of the total pin surface is less than 2%, most preferably less than 1.5%, particularly less than 1%, preferably less than 0.5%, and most preferably less than 0.1%.

[0025] The near-complete absence of defects is particularly advantageous when the coating thicknesses applied to the metal pin are small. The coating thicknesses on the metal pin range from 0.1 µm to 10 µm. It is especially preferred that the thickness of the nickel layer applied to the metal pin is in the range of 2 to 8 µm, preferably 4 to 6 µm. The thickness of the gold layer is preferably in the range of 0.5 to 5 µm, preferably 0.8 to 1.5 µm. The total thickness of the coating, consisting of the nickel and gold layers, preferably ranges from 4.5 µm to 7.5 µm. With such thin coatings, a largely defect-free surface, as provided by the invention, is essential for a coating in which defects are suppressed.

[0026] It is particularly preferred if the rounding and / or the rounded section with radius R, which is to be introduced into the end section using a machining or machining process, is specified, in particular by a specification. The described connecting pins are usually inserted into connector systems. To provide the lowest possible contact resistance, especially in a connector system, and to ensure a reliable contact, it is particularly preferred if the specification is such that the radius R corresponds to a hemisphere or a hemispherical body in the end region of the connecting pin.

[0027] In a further preferred embodiment, the end region of the connecting pin has a planar area with a width, located particularly in the middle of the pin axis, to which the rounded section with radius R adjoins. The planar area is essentially characterized by a diameter F of its end surface.

[0028] Preferably, radius R corresponds approximately to half the diameter D of the cylindrical connecting pin. It is particularly preferred that the radius R is in the range of 0.4·D ≤ R ≤ 0.65·D, and especially in the range of 0.45·D ≤ R ≤ 0.55·D. Particularly preferred is a connecting pin designed such that, in the case of a pin with a 1 mm diameter, the rounded section of the end merges into the cylindrical section with diameter D after 0.65 mm. In contrast, in the case of a connecting pin or pin rounded with vibratory finishing particles and with a diameter of 1 mm, the cylindrical part with the specified diameter D is only reached after more than 0.7 mm. The advantage of rounding or introducing the radius using a chip-forming or chipless method according to the invention is that the radii can be produced according to a predetermined specification, which allows for a shortened transition area to the cylindrical section of the connecting pin.This is possible because the radius can be adjusted using the chipless or non-chipless process, which was not possible with previous methods, as vibratory finishing does not allow for influencing the shape of the rounding, particularly the radius. Thus, the profile of a smoothly ground pin always exhibits a barrel-shaped profile, meaning the transition from the radius to the cylindrical pin has a longer profile that extends beyond the radius. This can negatively impact the contact reliability of the connector pin, especially when it is inserted into a plug system.

[0029] The connecting pin is cylindrical with a diameter D of, for example, 1 mm. At the end of the cylindrical connecting pin, it transitions into a rounded section, ideally a hemispherical cap with a radius R. Ideally, this radius R corresponds to half the diameter of the cylindrical section, or lies within the range of 0.4·D ≤ R ≤ 0.65·D, which, according to the invention, can only be achieved by a machining or non-machining process, e.g., by forming. With a machining or non-machining process, the radii can be specified according to the specifications, which is not possible with rounding using vibratory finishing particles.

[0030] Because the vibratory finishing particles are not massaged into the surface of the connecting pin, it is possible to produce a closed surface coating after the radius has been manufactured, which is largely free of defects and therefore significantly reduces the risk of corrosion on surface-coated pins.

[0031] In addition to the connecting pin according to the invention, in particular in the form of a metal pin, the invention also provides a feedthrough, in particular a metal-fixing material feedthrough, according to claim 11. Preferably, the feedthrough has an opening through which the connecting pin is guided in a glass or glass-ceramic material.

[0032] In addition to the connecting pin and the feedthrough, the invention also specifies a method according to claim 13.

[0033] The invention will be described in more detail below with reference to the drawings, without limitation thereto.

[0034] They show: Fig. 1: a connecting pin according to the invention; Fig. 2: the end section of a connecting pin according to the invention with rounding; Fig. 3: an exemplary embodiment with a connecting pin; Fig. 4a-4b: representation of a connecting pin according to specification ( Figure 4a ) and manufactured with vibratory finishing particles ( Figure 4b ).

[0035] Figure 1 Figure 1 shows an example of a connecting pin according to the invention. The connecting pin 1 comprises in the figure shown. Figure 1The illustrated embodiment has three regions. A first, essentially straight region, designated by reference numeral 3. A curved region, designated by reference numeral 5, and an end region or end section, designated by reference numeral 7. According to the invention, the end sections 10.1, 10.2 of the pin 1 are rounded using a machining and / or non-cutting process, wherein the radius R of the rounding is predetermined. The radius R can be, for example, 0.5 mm, and the diameter D of the connecting pin 1 mm. Using the machining and / or non-cutting process, it is then possible to set the predetermined radius, which is preferably half the diameter of the cylindrical part of the connecting pin. The connecting pins are obtained by cutting them from a wire section. The non-straight, i.e., curved, section 5 of the pin is inclined at 45° relative to the straight region 3 and the end section 7. The diameter D of the pin is, for example, 0.5 mm.Between 0.5 and 2.5 mm. Pins with a diameter smaller than 0.5 mm are also possible.

[0036] In Figure 2 The diagram shows the end section with the rounded end. The rounded section, which is ideally conical but not necessarily so, has a radius R. The radius is in the range of 0.25 mm to 1.0 mm. The rounded section has a side length that is also within the range of the radius, i.e., between 0.25 mm and 1.0 mm. For example, the height of the rounded end up to the transition into the cylindrical section can be 0.5 mm. The diameter of the pin would then be approximately 1.0 mm.

[0037] After the rounding is performed using a chipless and / or machining process according to specifications (i.e., radii, diameter, height of the area into which at least one end section with the specified rounding is applied), the connecting pin can be coated on its surface. Typically, a nickel layer is first applied to the connecting pin as corrosion protection. This is followed by a gold layer. The thickness of both the nickel and gold coatings is in the micrometer range, preferably in the range of 0.1 µm to 10 µm. A palladium coating can also be used instead of gold. The nickel and gold coating provides a reliable connection with low contact resistance.Since the chip- and / or chipless method according to the invention for introducing the radius keeps the pin surface largely free of contaminants, such as vibratory finishing media, the coating applied to the connecting pin, for example made of nickel, has no defects, which results in the connecting pin remaining largely corrosion-free. In this application, "free" or "largely free" of contaminants means that less than 2%, in particular less than 1.5%, preferably less than 1%, most preferably less than 0.5%, and most preferably less than 0.1% of the pin surface is contaminated, for example, with vibratory finishing particles. Undesirable vibratory finishing particles are, in particular, particles of a ceramic material, such as Al₂O₃ or SiC. Particles of other materials, such as iron particles, are less damaging with regard to defects and are therefore tolerable.This results in low contact resistance. In particular, the absence of a vibratory abrasive prevents defects that would otherwise lead to corrosion. This corrosion, in turn, increases contact resistance and ultimately leads to a loss of electrical conductivity over time.

[0038] In Figure 3 The use of a connecting pin according to the invention, in particular a metal pin, in a feedthrough is shown. Figure 3 Shows a feedthrough 100, in particular a metal fixing material feedthrough for equipment exposed to high pressures.

[0039] The opening 100, comprising an annular element 106 with an opening, is clearly visible. A clearance area 105 is also shown. A through-opening 20, with a thickness DR, is punched out of the remaining material of the annular element 106. In this case, the through-opening has a conical profile 200. While in the illustrated embodiment the conicity extends over the entire length of the through-opening, in an alternative embodiment the conicity can extend only over a portion of the length of the through-opening. This means the through-opening then has two sections: a conical section followed by a non-conical section. The conical section can then be produced, for example, by forming or shaping, and the non-conical section by punching.

[0040] The ring- or plate-shaped element 106 serves as a base for a metal-fixing material feedthrough with a total of two connecting pins 50, 52 according to the invention. While the connecting pin, preferably a metal pin 50, is guided through a fixing material 60, here a glass material, which can also be a glass-ceramic or ceramic material, from the front to the back of the ring- or plate-shaped base body 106, the second connecting pin, in particular a metal pin 52, serves as a grounding pin. For this purpose, the second metal pin 52 is directly connected to the ring- or plate-shaped body 106. Both the connecting pin, in particular metal pin 50, and the connecting pin, in particular metal pin 52, are curved. The curve of both metal pins is designated 54 and 56, respectively, and is clearly visible.

[0041] The connecting pin, in particular metal pin 50, can also be provided with means 62 on the metal pin 50 itself, which engage in the glass plug and thus prevent the metal pin from being pushed out of the glass plug 60, in which the metal pin is encased, even under high pressures.

[0042] The encapsulation of the connecting pin, in particular a metal pin 50, into the fixing material 60 is carried out by melting. Once the connecting pin, in particular a metal pin, has been melted into the fixing material 60, the glass plug, together with the metal pin, is inserted into the through-opening 20. Subsequently, the glass plug, together with the ring- or plate-shaped element, i.e., the base body, is heated so that, after cooling, the metal of the ring- or plate-shaped element shrinks onto the fixing material, here the glass material, as already occurred during the production of the glass plug, in which the connecting pin, in particular a metal pin, is inserted into the glass plug. The connecting pin, in particular a metal pin 52, which serves as ground, is conductively connected to the plate-shaped element, for example by brazing. The solder joint is designated 70.All related metal pins are rounded at their end sections 72 according to the invention by machining and / or non-machining processes. This prevents any contamination of the surface of the connecting pins, especially metal pins, so that the connecting pins can be coated without defects. The coated connecting pins exhibit low contact resistance. Since defects are avoided, a subsequent coating, for example with Ni or Au, with a largely defect-free, closed surface is possible. The closed surface, in turn, ensures that corrosion can be largely prevented.

[0043] In Fig. 4a and 4b Rounded pins produced according to the inventive method and rounded pins produced using vibratory finishing particles are shown.

[0044] Figure 4ashows a connecting pin manufactured according to the invention and a predetermined specification. Figure 4a The manufactured connecting pin is a connecting pin in which the cap 110 was produced by cold forming. The cap is a cap with an end surface F whose surface is perpendicular to the pin axis A, and to which a rounded section with a radius of R = 0.65 mm adjoins. The cross-section of the rounded section geometrically corresponds to a circular segment, and the diameter D of the cylindrical part of the pin is 1 mm. In the illustrated embodiment, the diameter of the end surface F is 0.1 mm. Ideally, the radius R would be identical to half the diameter D of the cylindrical part of the pin 1, i.e., 0.5 mm. However, the range 0.4 ≤ R ≤ 0.65D for the radius is still considered to be within the limits of the invention. Another preferred embodiment corresponds to the formula R = D / 2 - Durchmesser von F / 2 ,

[0045] where F is the diameter of the end face. If the diameter D of the cylindrical area is 1 mm and the diameter F is 0.1 mm as in Fig. 4a In the example shown, R is preferably 0.45 mm. The invention particularly advantageously allows the diameter of the end surface F to be less than 0.4 mm, and in particular less than 0.3 mm.

[0046] While the cold-formed connecting pin exhibits a rounding of the end section with a predetermined radius R and a cap with circular segment-shaped rounding sections, this is done as in Figure 4b The desired rounding is not achieved with a connecting pin where the rounding is produced using vibratory finishing particles. The rounded section is particularly hyperbolic. Again, the connecting area of ​​the pin is designated with the reference numeral 1100. The cylindrical part of the connecting pin has a diameter D = 1 mm. As shown in Figure 4bThe profile of the pin is clearly barrel-shaped, i.e., the transition from the connection area 1100 to the cylindrical part is 0.65 mm, in contrast to 0.65 mm according to Figure 4a With a connecting pin manufactured in this way, the diameter is 0.9 mm and is therefore significantly longer. This results in a much higher contact resistance than in the case of the design according to [reference to design]. Figure 4a It can also be observed that the end surface has a relatively large diameter. This results in a sharp transition to the rounded section, on which coatings adhere poorly or are easily scraped off.

[0047] The invention thus provides a rounded end of a connecting pin that can be manufactured according to specifications, in particular without surface contamination and with a geometrically defined contact area, especially for insertion into a connector system. This results in low contact resistance and very good long-term contact properties.

Claims

1. Connection pin (1), in particular a metal pin, for feedthroughs, in particular glass-metal feedthroughs (100), having at least one first, elongated, cylindrical section (3) with a diameter D, as well as at least one adjoining end section (7), wherein the end section (7) has a rounding and / or a rounding section with a radius, and the rounding and / or the rounding section has at least the shape of a circular segment with radius R, wherein the radius R is a radius according to a specification, in particular a predetermined specification, and is obtained by means of a cutting process and / or a non-cutting process, and the connection pin (1) has a pin surface, and the pin surface in the cylindrical section, in particular the entire pin surface, is largely free or as far as possible free or free of impurities consisting of vibratory grinding particles, preferably of Al2O3, SiC, wherein the radius R of the rounding and / or the rounding section is in the range of 0.4D to 0.65D, and wherein the end section has an end face F, the surface of which is arranged substantially perpendicular to the pin axis A, and to which the rounding section with radius R adjoins and forms the transition to the outer circumferential surface of the cylindrical section (3), wherein the end face (F) has a diameter of less than 0.4 mm and wherein the connection pin has a closed surface coating.

2. Connection pin according to claim 1, characterized in that the radius R of the rounding and / or the rounding section is in the range of 0.45-D to 0.55-D, preferably approximately half the diameter D of the cylindrical region.

3. Connection pin (1) according to claim 1 or 2, characterized in that the end face (F) has a diameter of less than 0.3 mm, in particular with a diameter D of 1.0 mm ± 0.1 mm.

4. Connection pin according to one of claims 1 to 3, characterized in that the non-cutting process comprises forming processes, in particular upsetting, rolling, stamping, pressing, squeezing, hammering.

5. Connection pin according to one of claims 1 to 3, characterized in that the cutting process comprises turning, milling, grinding.

6. Connection pin according to one of claims 1 to 5, characterized in that less than 2%, in particular less than 1.5%, preferably less than 1%, in particular less than 0.5%, preferably less than 0.1% of the total pin surface has impurities consisting of vibratory grinding particles, preferably of Al2O3, SiC.

7. Connection pin according to one of claims 1 to 6, characterized in that the pin surface comprises a coating, in particular a nickel coating and / or a gold coating, preferably with a layer thickness in the range of 0.1 µm to 10 µm.

8. Connection pin according to claim 7, characterized in that the coating is a nickel coating and the layer thickness of the nickel coating is in the range of 2 to 8 µm, preferably 4 to 6 µm, and / or the coating is a gold coating and the layer thickness of the gold coating is in the range of 0.5 to 5 µm, preferably 0.8 to 1.5 µm.

9. Connection pin according to one of claims 7 to 8, characterized in that the coating is largely free of defects.

10. Connection pin according to one of claims 1 to 9, characterized in that the radius R is in the range of 0.25 mm to 1.0 mm and / or the diameter D is in the range of 0.5 mm to 2.0 mm.

11. Feedthrough (100), in particular metal-fixing material feedthroughs, preferably for devices that are exposed to high pressures, having at least one connection pin, characterized in that the connection pin is a connection pin according to one of claims 1 to 10.

12. Feedthrough according to claim 11, characterized in that the feedthrough (100) comprises an opening (20), wherein the connection pin is preferably guided through the opening (20) in a glass or glass material (60).

13. Method for manufacturing a connection pin, preferably a metal pin, for a feedthrough, in particular a glass-metal feedthrough, comprising the following steps of: - providing a connection pin blank made of a wire material with at least one end section; - introducing a rounding and / or rounding section with radius R, according to a specification, into the end section of the wire material by means of a cutting and / or non-cutting process, resulting in the rounded end section of the connection pin, wherein - the connection pin (1) has a pin surface and, after the rounding and / or rounding section with radius R has been introduced using a cutting and / or non-cutting process, the pin surface in the cylindrical section, in particular the entire pin surface, is largely free or as far as possible free or free of impurities consisting of vibratory grinding particles, preferably Al2O3, SiC, and - the radius R of the rounding and / or the rounding section is in the range of 0.4D to 0.65D, wherein D is the diameter of the cylindrical region, and wherein the end section has an end face F whose surface is arranged substantially perpendicular to the pin axis A and to which the rounding section with radius R adjoins and forms the transition to the outer circumferential surface of the cylindrical section (3), wherein the end face (F) has a diameter of less than 0.4 mm; - wherein the connection pin is provided with a closed surface coating after the radius has been produced.

14. Method according to claim 13, characterized in that the connection pin is provided with a coating that is largely free of defects, preferably a nickel and / or gold coating.