Electrical contact elements for high operating voltages

Abstract

The present invention relates to an electrical contact element for a connector, comprising a metallic substrate 111, 211 and a wear layer 113, 213 applied to the substrate 111, 211. The wear layer 113, 213 is made of an alloy having the following composition by weight: 82-91% nickel, 9-18% phosphorus and 0-1% other alloying elements.

Description

[Technical field]

[0001] The present invention relates to electrical contact elements for connectors suitable for electrical operating voltages above 150V. [Background technology]

[0002] Electrical connectors generally have one or more electrical contact elements and one or more insulators. The contact elements are usually designed as male or female elements. They are made of a substrate that is generally not corrosion resistant. They are often copper alloys. Therefore, to ensure the function of the contact elements over the service life of the connector, thin layers of other metals are applied to the substrate. They can be equipped with intermediate layers and wear layers.

[0003] The intermediate layer can have various purposes: it can improve the adhesion of the wear layer to the substrate, it can create a mechanical equilibrium between the substrate and the wear layer, it can prevent diffusion processes from occurring between the wear layer and the substrate, and it often consists of copper or nickel.

[0004] A wear layer, also called functional layer, is located on the intermediate layer. The wear layer can extend the technically useful life of the contact element, improve electrical transmission and protect the underlying layers from corrosion. It can consist of soft non-inert metals, such as tin or silver. In connectors in the automotive field, for example, silver is widely used as a wear layer. If voltages of more than 150 V occur in the application, the potential forces between the different contact elements can gradually excite metal ions and cause them to migrate from one physical location to another. This metal migration can cause short circuits of the connector and other technical problems. Silver functional surfaces are prone to this type of metal migration at higher voltages. For this reason, functional layers of more expensive noble metals are usually used in applications with operating voltages of more than 150 V. Thus, for example, gold-cobalt alloys or palladium-nickel alloys are used. Summary of the Invention [Problem to be solved by the invention]

[0005] It is an object of the present invention to provide an electrical contact element suitable for use in electrical connectors and suitable for electrical operating voltages above 150 V. However, it must be possible to manufacture it at a lower cost than conventional electrical contact elements and still achieve the reliability and service life of conventional electrical contact elements. [Means for solving the problem]

[0006] This object is solved by an electrical contact element for a connector, which has a metallic substrate or a wear layer applied to the substrate. The wear layer can be applied directly to the metallic substrate or one or more further layers can be arranged between the metallic substrate and the wear layer. The wear layer consists of the following alloy elements: 82-91% by weight nickel, 9-18% by weight phosphorus and 0 to 1% by weight of further alloy elements. Preferably, the layer consists of 82-89% by weight nickel, 11-18% by weight phosphorus and 0 to 1% by weight of further alloy elements. The sum of the alloy elements is 100% by weight. Proportions of up to 1% by weight of further alloy elements in the alloy are accepted, for example as impurities, but are preferably avoided. According to the invention, it has been found that the use of this type of wear layer provides similar good electrical transmission and similar good corrosion protection as can be achieved by wear layers made of, for example, gold-cobalt alloys or palladium-nickel alloys. However, the use of nickel-phosphorus alloys makes it possible in comparison to produce the electrical contact element more cost-effectively.

[0007] In a preferred embodiment of the invention, the wear layer is arranged directly on the substrate, with no further layers between the wear layer and the substrate. In order to ensure good corrosion protection, in this embodiment it is preferred that the wear layer has a thickness in the range of 1.00 μm to 2.50 μm. Particularly preferably, the thickness is in the range of 1.50 μm to 2.00 μm. Since the wear layer used according to the invention provides such good protection against corrosion and such good electrical transmission, these properties cannot be significantly improved by further increasing the layer thickness. On the other hand, when using conventional wear layers of gold-cobalt alloys or palladium-nickel alloys, a layer thickness of, for example, at least 3 μm is usually necessary, together with the simultaneous use of a metallic intermediate layer, in order for the electrical contact element to meet the requirements of corrosion resistance and electrical transmission. The invention therefore not only allows the production of electrical contact elements using less expensive materials, but also allows the reduction of the amount of material by using particularly thin wear layers.

[0008] In another preferred embodiment of the invention, a metallic intermediate layer is arranged between the substrate and the wear layer. Particularly preferably, the intermediate layer is the only layer arranged between the wear layer and the substrate, such that the substrate is directly connected to the intermediate layer and the intermediate layer is directly connected to the wear layer. As in conventional designs of electrical contact elements, the intermediate layer improves the adhesion of the wear layer to the substrate, ensures mechanical compensation between the substrate and the wear layer and prevents diffusion processes between the wear layer and the substrate. In addition, the intermediate layer allows the use of a thinner wear layer compared to the embodiment of the invention in which the wear layer is arranged directly on the substrate. In this embodiment, the wear layer preferably has a thickness in the range of 0.15 μm to 1.50 μm. Particularly preferably, the thickness is in the range of 0.30 μm to 1.00 μm.

[0009] In one embodiment of the contact element, the intermediate layer comprises 99 to 100% by weight of copper and 0 to 1% by weight of further alloying elements. In another preferred embodiment of the contact element, the intermediate layer comprises 99 to 100% by weight of nickel and 0 to 1% by weight of further alloying elements. The sum of the alloying elements is therefore 100% by weight. The proportion of further alloying elements should preferably be as low as possible, although due to impurities their presence cannot be completely excluded.

[0010] The thickness of the intermediate layer is preferably from 1.5 to 4.0 μm, and particularly preferably from 2.0 to 3.0 μm.

[0011] Furthermore, it is preferred that a metallic and / or organic sliding layer is arranged on the wear layer. The sliding layer can improve the sliding properties of the electrical contact elements, especially the female and male elements. In this way, it helps the wear layer to remain functional longer under mechanical frictional stress. On the other hand, it can also optimize the electrical transmission between the electrical contact elements. If the sliding layer contains both metallic and organic components, it is preferred that the metallic part layer is applied directly to the wear layer and the organic part layer is applied to this metallic part layer. The metallic part layer and the organic part layer then together form the sliding layer.

[0012] Particularly suitable metallic materials for the sliding layer are pure gold or gold alloys consisting of the following alloying elements: 98.5 to 100.0% by weight gold, 0 to 0.5% by weight cobalt and 0 to 1.0% by weight further alloying elements, the sum of the alloying elements being 100% by weight.

[0013] Particularly suitable organic materials for the sliding layer are at least one fluoropolymer and / or at least one fatty acid salt. The fluoropolymer can be, for example, perfluoropolyether (PFPE) or polytetrafluoroethylene (PTFE). The fatty acid salt can be, for example, lithium-12-hydroxystearate.

[0014] The thickness of the sliding layer is preferably in the range of 0.05 μm to 0.25 μm. Since a sliding layer of this kind is already sufficient to provide good sliding properties to the electrical contact element, applying the sliding layer to the wear layer does not result in a significant increase in the overall thickness of the coating.

[0015] The wear layer of the electrical contact element according to the invention can be used particularly advantageously when the substrate is made of copper, low-alloy copper alloys or brass. In this case, it consists of the following alloying elements: 50 to 100% by weight of copper, 0 to 45% by weight of zinc and 0 to 5% by weight of further alloying elements. In this case, the sum of the alloying elements is 100% by weight. In this specification, even if the sum of the further alloying elements can be up to 5% by weight, it is preferred that each of the further alloying elements constitutes up to 2% by weight of the total alloy. Furthermore, only the other alloying elements beryllium, chromium, iron, cobalt, magnesium, manganese, nickel, phosphorus, sulfur, silver, silicon, tellurium, titanium, tin and zirconium can be present in the alloy in an amount of up to 2% by weight each, and all other alloying elements not mentioned in this list are preferably present in an amount of up to 1% by weight in each case.

[0016] The electrical contact element according to the invention can be produced with good technological properties without the need to use large amounts of expensive precious metals.

[0017] Exemplary embodiments of the invention are depicted in the drawings and are explained in more detail in the following description. [Brief description of the drawings]

[0018] [Figure 1] 1 shows a schematic longitudinal cross-sectional view of a configuration of two electrical connectors. [Diagram 2] 1 shows a cross-sectional view of a contact area between two electrical contact elements of a comparative example. [Diagram 3] 2 shows a cross-sectional view of the contact areas of two electrical contact elements according to an exemplary embodiment of the present invention. [Figure 4]4 shows a cross-sectional view of the contact areas of two electrical contact elements according to another exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] FIG. 1 shows the schematic structure of a pair of connectors. The first connector 10 has an electrical contact element 11 in the form of a male element. This is surrounded by a first insulator 12 made of plastic. The second connector 20 has a second electrical contact element 21 in the form of a female element. This is surrounded by a second insulator 22 made of plastic. When the two connectors 10, 20 are connected to each other in the manner shown, the second insulator 22 is pressed into the first insulator 12 and the first electrical contact element 11 slides into the second electrical contact element 21. In doing so, it bends apart the tongues of the second contact element 21, which are then fixedly pressed on the first contact element 11 by their spring force. Electrical transmission is then possible in the contact area 30 where the two contact elements 11, 21 come into contact.

[0020] In electrical connectors 10, 20 having contact elements 11, 21 according to the prior art, the structure of contact elements 11, 21 depicted in FIG. 2 is present in contact area 30. First contact element 11 has substrate 111, intermediate layer 112 disposed on substrate, and wear layer 113 disposed on intermediate layer. Second contact element 21 has substrate 211, intermediate layer 212 disposed on substrate 211, and wear layer 213 disposed on intermediate layer 212. Substrates 111, 211, intermediate layers 112, 212, and wear layers 113, 213 each have the composition in weight percent shown in Table 1. [Table 1]

[0021] In this example, the intermediate layers 112, 212 each have a thickness d 112 , d 212and the wear layers 113, 213 each have a thickness d 113 , d 213 The wear layers 113, 213 contact each other in the contact area 30. The large amount of gold-cobalt alloy required for the manufacture of the wear layers results in the electrical contact elements 11, 21 being expensive to manufacture.

[0022] 3 shows the structure of electrical contact elements 11, 21 according to some exemplary embodiments of the invention, which can be used in a pair of connectors 10, 20 according to FIG. 1. In addition to the structure of the electrical contact elements 11, 21, consisting of the base 111, 211, the intermediate layer 112, 212 and the useful layer 113, 213, already depicted in FIG. 2, the contact elements 11, 21 according to these exemplary embodiments of the invention also have sliding layers 114, 214 on their wear layers 113, 213. This results in no contact of the wear layers 113, 213 in the contact area 30, but rather of the sliding layers 114, 214. The thickness of the intermediate layers 112, 212 of the exemplary embodiments of the invention corresponds to that of the intermediate layers 112, 212 of the comparative example, while the exemplary embodiments according to the invention make do with substantially thinner wear layers 113, 213, in each case with a thickness d 113 , d 213 d is only 0.65 μm. This results in a significant material saving compared to the comparative example. In the embodiment according to the invention, the sliding layers 114, 214 each have a thickness d of 0.10 μm. 114 , d 214 Thus, each wear layer 113, 213 together with its respective sliding layer 114, 214 is thinner than the wear layer 113, 213 of the comparative example.

[0023] In a first exemplary embodiment of the present invention, the components of the contact elements 11, 21 have the compositions in weight percent listed in Table 2. [Table 2]

[0024] Thus, the intermediate layer, which is made of pure silver in the comparative example, is made of a nickel-phosphorus alloy in the first exemplary embodiment, resulting in cost savings not only due to less metal being used in the wear layer, but also due to the use of a lower cost alloy.

[0025] The sliding layers 114, 214 are made of the same gold-cobalt alloy as the wear layers 113, 213 of the comparative example. Therefore, the sliding properties of the contact elements 11, 21 of the comparative example and the first exemplary embodiment of the present invention are equally good. However, since the sliding layers 114, 214 are much thinner than the wear layers 113, 213 of the comparative example, most of the expensive gold-cobalt alloy can be eliminated.

[0026] In a second exemplary embodiment of the electrical contact elements 11, 21, the components have the weight percent compositions shown in Table 3. [Table 3]

[0027] In comparison with the first exemplary embodiment, the metallic sliding layers 114, 214 are replaced by organic sliding layers made of PTFE, respectively. It has been found that in the third exemplary embodiment, by omitting expensive noble metals, it is nevertheless possible to achieve excellent sliding properties of the contact elements 11, 21, the electrical transmission of which is nevertheless no worse than that of the electrical contact elements 11, 21 of the comparative example.

[0028] In a third exemplary embodiment of the invention, the intermediate layer 112, 212 is omitted, so that the contact elements 11, 21 have the structure depicted in FIG. 4, with the wear layer 113, 213 being in each case arranged directly on the substrate 111, 211. In each case, in contrast to the previous exemplary embodiment, the thickness d of the wear layer 113, 213 is 113 , d 213 is 1.50 μm. The components of the contact elements 11, 21 have the weight percent compositions listed in Table 4. [Table 4]

[0029] Thus, by using thicker wear layers than in the first and second exemplary embodiments of the present invention, the contact elements 11, 21 can also be manufactured without the use of intermediate layers 112, 212. Although thicker wear layers 113, 213 are used here than in the first two exemplary embodiments, they are still significantly thinner than the wear layers 113, 213 of the comparative examples.

[0030] In a fourth exemplary embodiment of the present invention, just as the sliding layers 114, 214 of the first exemplary embodiment are replaced by PTFE in the second exemplary embodiment, the sliding layers 114, 214 of the contact elements 11, 21 of the third exemplary embodiment are also replaced by organic sliding layers made of PTFE. The components of the electrical contact elements 11, 21 then have the compositions in weight percent shown in Table 5. [Table 5]

[0031] All five described exemplary embodiments of the electrical contact elements 11, 21 according to the present invention allow a cost-effective replacement of the electrical contact elements 11, 21 according to the comparative examples without leading to impairment of the properties associated with the contact elements 11, 21, which are suitable for electrical operating voltages of more than 150 V.

Claims

1. An electrical contact element (11, 21) for a connector (10, 20) having a metallic substrate (111, 211) and a wear layer (113, 213) applied to said substrate (111, 211), said wear layer (113, 213) being made of the following alloy elements: 82 to 91% by weight of nickel, 9 to 18% by weight of phosphorus; 0-1 wt. % further alloying elements, the sum of said alloying elements is 100% by weight; An electrical contact element (11, 21), further comprising an organic sliding layer (114, 214) disposed directly on said wear layer (113, 213) and comprising at least one fatty acid salt.

2. 2. The electrical contact element (11, 21) according to claim 1, characterized in that the wear layer (113, 213) is arranged directly on the substrate (111, 211).

3. 3. Electrical contact element (11, 21) according to claim 2, characterized in that the wear layer (113, 213) has a thickness (d113, d213) in the range of 1.00 μm to 2.50 μm.

4. 2. Electrical contact element (11, 21) according to claim 1, characterized in that a metallic intermediate layer (112, 212) is arranged between the substrate (111, 211) and the wear layer (113, 213).

5. The intermediate layer (112, 212) comprises the following alloying elements: 99 to 100% by weight of copper or nickel, 0-1 wt. % further alloying elements, 5. Electrical contact element (11, 21) according to claim 4, characterized in that the sum of said alloying elements is 100% by weight.

6. 6. Electrical contact element (11, 21) according to claim 4 or 5, characterized in that the intermediate layer (112, 212) has a thickness (d112, d212) in the range of 1.5 μm to 4.0 μm.

7. 7. An electrical contact element (11, 21) according to claim 4, characterized in that the wear layer (113, 213) has a thickness (d113, d213) in the range of 0.15 μm to 1.50 μm.

8. 8. Electrical contact element (11, 21) according to claim 1, characterized in that the sliding layer (114, 214) has a thickness (d114, d214) in the range of 0.05 μm to 0.25 μm.

9. The substrate (111, 211) contains the following alloying elements: 50 to 100% by weight of copper, 0 to 45% by weight of zinc, 0-5% by weight of further alloying elements, An electrical contact element (11, 21) according to any of the preceding claims, characterized in that the sum of said alloying elements is 100% by weight.

Images